2024-03-28T14:36:56Z
https://eprints.whiterose.ac.uk/cgi/oai2
oai:eprints.whiterose.ac.uk:169
2014-06-04T09:03:22Z
7374617475733D707562
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/169/
The measurement of lubricant-film thickness using ultrasound
Dwyer-Joyce, R.S.
Drinkwater, B.W.
Donohoe, C.J.
Ultrasound is reflected from a liquid layer between two solid bodies. This reflection depends on the ultrasonic frequency, the acoustic properties of the liquid and solid, and the layer thickness. If the wavelength is much greater than the liquid-layer thickness, then the response is governed by the stiffness of the layer. If the wavelength and layer thickness are similar, then the interaction of ultrasound with the layer is controlled by its resonant behaviour. This stiffness governed response and resonant response can be used to determine the thickness of the liquid layer, if the other parameters are known.
In this paper, ultrasound has been developed as a method to determine the thickness of lubricating films in bearing systems. An ultrasonic transducer is positioned on the outside of a bearing shell such that the wave is focused on the lubricant-film layer. The transducer is used to both emit and receive wide-band ultrasonic pulses. For a particular lubricant film, the reflected pulse is processed to give a reflection-coefficient spectrum. The lubricant-film thickness is then obtained from either the layer stiffness or the resonant frequency.
The method has been validated using fluid wedges at ambient pressure between flat and curved surfaces. Experiments on the elastohydrodynamic film formed between a sliding ball and a flat surface were performed. Film-thickness values in the range 50-500 nm were recorded, which agreed well with theoretical film-formation predictions. Similar measurements have been made on the oil film between the balls and outer raceway of a deep-groove ball bearing.
2003-04-08
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/169/1/dwyer-joycers1.pdf
Dwyer-Joyce, R.S., Drinkwater, B.W. and Donohoe, C.J. (2003) The measurement of lubricant-film thickness using ultrasound. Proceedings of the Royal Society Series A: Mathematical Physical and Engineering Sciences, 459 (2032). pp. 957-976. ISSN 1471-2946
doi:10.1098/rspa.2002.1018
oai:eprints.whiterose.ac.uk:215
2014-06-06T03:29:19Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/215/
Operating Limits for Acoustic Measurement of Rolling Bearing Oil Film Thickness
Dwyer-Joyce, R.S.
Reddyhoff, T.
Drinkwater, B.
An ultrasonic pulse striking a thin layer of liquid trapped between solid bodies will be partially reflected. The proportion reflected is a function of the layer stiffness, which in turn depends on the film thickness and its bulk modulus. In this work, measurements of reflection have been used to determine the thickness of oil films in elastohydrodynamic lubricated (EHL) contacts. A very thin liquid layer behaves like a spring when struck by an ultrasonic pulse. A simple quasi-static spring model can be used to determine the proportion of the ultrasonic waves reflected. Experiments have been performed on a model EHL contact between a ball and a flat surface. A transducer is mounted above the contact such that the ultrasonic wave is focused onto the oil film. The reflected signals are captured and passed to a PC for processing. Fourier analysis gives the reflection spectrum that is then used to determine the stiffness of the liquid layer and hence its thickness. In further testing, an ultrasonic transducer has been mounted in the housing of a deep-groove ball bearing to measure the film generated at the outer raceway as each ball passes. Results from both the ball-flat and ball bearing measurements agree well with steady-state theoretical EHL predictions. The limits of the measuring technique, in terms of the measurable rolling bearing size and operating parameters, have been investigated.
2004-07
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/215/1/dwyer-joycers2.pdf
Dwyer-Joyce, R.S., Reddyhoff, T. and Drinkwater, B. (2004) Operating Limits for Acoustic Measurement of Rolling Bearing Oil Film Thickness. Tribology Transactions, 47 (3). pp. 366-375. ISSN 1547-397X
http://journalsonline.tandf.co.uk/openurl.asp?genre=article&id=doi:10.1080/05698190490455410
doi:10.1080/05698190490455410
oai:eprints.whiterose.ac.uk:744
2014-06-08T07:05:19Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/744/
Interaction between toothbrushes and toothpaste abrasive particles in simulated tooth cleaning
Lewis, R.
Dwyer-Joyce, R.S.
Pickles, M.J.
There are currently many toothbrush designs on the market incorporating different
filament configurations such as filaments at various angles and different lengths and
made from several different materials. In order to understand how the tooth cleaning
process occurs there is a need to investigate in detail how the abrasive particles in a
toothpaste interact with the filaments in a teeth cleaning contact and cause material
removal from a plaque or stain layer.
The following describes the development of optical apparatus to enable the
visualisation of simulated teeth cleaning contacts. Studies have been carried out using
the apparatus to investigate particle entrainment into the contact and how it differs
with varying bristle configurations. The effects of filament stiffness and tip shape
were also investigated. Various types of electric toothbrushes were also tested.
The studies have shown how particles are trapped at the tips of toothbrush filaments.
Particles, suspended in fluid, approach the filament tips, as they pass through they
may become trapped. Greater particle entrainment into the filament tip contact occurs
with a reciprocating action at low filament loads and deflections than with a sliding
motion. Large particles are less likely to enter tip contacts and are trapped between
tips or under the filament bend at higher loads.
Whether the particles are likely to be trapped and how long they remain so depends
on the filament stiffness and degree of splay on loading and the filament
configuration. The direction the filaments point in, the number of filaments in a tuft,
the spacing of the tufts and the way the filaments splay when deflected all have an
influence on entrainment of particles. Tufts with tightly packed stiff filaments which
deflected together on loading were more effective at trapping particles than more flexible filaments that splayed out on loading as they present more of a barrier to
particle entry and exit from the tip region.
2004-08
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/744/1/lewisr1_Wear_2004_Teeth_Cleaning_Author_Man.pdf
Lewis, R., Dwyer-Joyce, R.S. and Pickles, M.J. (2004) Interaction between toothbrushes and toothpaste abrasive particles in simulated tooth cleaning. Wear, 257 (3-4). pp. 368-376. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2004.01.015
doi:10.1016/j.wear.2004.01.015
oai:eprints.whiterose.ac.uk:752
2014-06-04T10:18:54Z
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696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/752/
Wheel material wear mechanisms and transitions
Lewis, R.
Dwyer-Joyce, R.S.
Olofsson, U.
Hallam, R.I.
In order to develop more durable wheel materials to cope with the new specifications being imposed on wheel wear, a greater understanding is needed of the wear mechanisms and transitions occurring in wheel steels, particularly at higher load and slip conditions. In this work wear assessment of wheel materials is discussed as well as wear rates, regimes and transitions. Twin disc wear testing, used extensively for studying wear of wheel and rail materials, has indicated that three wear regimes exist for wheel materials; mild, severe and catastrophic. These have been classified in terms of wear rate and features. Wear rates are seen to increase steadily initially, then level off, before increasingly rapidly as the severity of the contact conditions is increased. Analysis of the contact conditions in terms of friction and slip has indicated that the levelling off of the wear rate observed at the first wear transition is caused by the change from partial slip to full slip conditions at the disc interface. Temperature calculations for the contact showed that the large increase in wear rates seen at the second wear transition may result from a thermally induced reduction in yield strength and other material properties. Wear maps have been produced using the test results to study how individual contact parameters such as load and sliding speed influence wear rates and transitions. The maps are also correlated to expected wheel/rail contact conditions. This improved understanding of wheel wear mechanisms and transitions and will help in the aim of eventually attaining a wear modelling methodology reliant on material properties rather than wear constants derived from testing.
2004-10
Conference or Workshop Item
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/752/1/lewisr4.pdf
Lewis, R., Dwyer-Joyce, R.S., Olofsson, U. et al. (1 more author) (2004) Wheel material wear mechanisms and transitions. In: 14th International Wheelset Congress, 17-21 October, Orlando, USA. (Unpublished)
oai:eprints.whiterose.ac.uk:757
2014-06-08T07:31:34Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/757/
Mapping rail wear regimes and transitions
Lewis, R.
Olofsson, U.
This paper outlines work carried out to produce maps of rail material wear coefficients taken
from laboratory tests run on twin disc and pin-on-disc machines as well as those derived from
measurements taken in the field. Wear regimes and transitions are identified using the maps
and defined in terms of slip and contact pressure. Wear regimes are related to expected
wheel/rail contact conditions and contact points (rail head/wheel tread and rail gauge/wheel
flange). Surface morphologies are discussed and comparisons are made between field and
laboratory data.
2004-10
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/757/1/lewisr2_Wear_2004_Rail_Wear_Trans_Author_Man.pdf
Lewis, R. and Olofsson, U. (2004) Mapping rail wear regimes and transitions. Wear, 257 (7-8). pp. 721-729. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2004.03.019
doi:10.1016/j.wear.2004.03.019
oai:eprints.whiterose.ac.uk:778
2014-06-07T17:04:04Z
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74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/778/
Combating automative engine valve recession
Lewis, R.
Dwyer-Joyce, R.S.
[INTRODUCTION] Valve recession occurs when wear of the valve or seat inserts in an automotive engine has
caused the valve to sink or recede into the seat insert (as shown in Figure 1). Excessive recession leads to valves not seating correctly and cylinder pressure loss. Leaking hot combustion gases can also cause valve guttering or torching, which will accelerate valve
failure.
Although new valve materials and production techniques are constantly being developed,
these advances have been outpaced by demands for increased engine performance and wear
related problems remain an issue. Dynamometer engine testing is often used to establish
short-term solutions. This is time consuming and does not necessarily reveal the actual causes
of wear.
A long-term approach is required in order to understand fundamental wear mechanisms and the effect of varying engine operating conditions or design changes to the valve train. This information can then be used to develop tools for predicting wear and for solving problems more quickly if they do occur. In this case study, such tools were developed using a combination of component failure analysis, bench test work and wear modelling.
2003-10
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/778/1/lewisr3_Trib_%26_Lube_Tech_2003_Valve_Recession.pdf
Lewis, R. and Dwyer-Joyce, R.S. (2003) Combating automative engine valve recession. Tribology and Lubrication Technology, 59 (10). pp. 48-51. ISSN 0024-7154
oai:eprints.whiterose.ac.uk:779
2014-06-05T19:12:43Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/779/
Ultrasonic characterisation of wheel hub/axle interference fit pressures
Marhsall, M.B.
Lewis, R.
Dwyer-Joyce, R.S.
Demilly, F.
Flament, Y.
Railway wheels are secured onto the axle by means of an interference fit. The wheel is press fitted onto a pre-lubricated axle, and the resulting interference fit induces a contact pressure at the interface. Occasionally railway wheels fail by fatigue, with the initiation point for the failure frequently traced to the interference fit. The aim of this work is to use ultrasonic reflection to non-destructively determine contact conditions in the interference fit.
The rough surface contact at the interference fit interface behaves like a spring. If the contact pressure is high the interface is conformal with few air gaps, the stiffness is then high and the transmission of an ultrasonic wave is permitted. However, when pressure is low more air gaps exist, interfacial stiffness is then reduced and more of the ultrasound is reflected.
Normalised contact pressure was determined from this stiffness. Maps of the interface have been produced which show the contact pressure to peak at the edges of the fit, and to experience a continuous variation about a mean value elsewhere.
2004-10
Conference or Workshop Item
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/779/1/lewisr5.pdf
Marhsall, M.B., Lewis, R., Dwyer-Joyce, R.S. et al. (2 more authors) (2004) Ultrasonic characterisation of wheel hub/axle interference fit pressures. In: 14th International Wheelset Congress, 17-21 October, Orlando, USA. (Unpublished)
oai:eprints.whiterose.ac.uk:780
2014-06-05T08:52:20Z
7374617475733D756E707562
74797065733D636F6E666572656E63655F6974656D
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/780/
Measuring wheel/rail contact stresses using ultrasound
Marhsall, M.B.
Lewis, R.
Dwyer-Joyce, R.S.
Olofsson, O.
Bjorklund, S.
The investigation of contact area and pressure distribution in a wheel/rail contact is essential information required in fatigue and wear calculations to determine design life, regrinding requirements, and maintenance schedules. The aim of this work was to use ultrasound to non-destructively determine wheel/rail contact pressures. Three different contacts were investigated those resulting from; un-used, sand damaged, and worn wheel/rail specimens.
A wheel/rail interface behaves like a spring. If the pressure is high the interface is very stiff, with few air gaps, and allows the transmission of an ultrasonic sound wave. If the pressure is low, interfacial stiffness is low and almost all the ultrasound is reflected.
A spring model was used to determine maps of contact stiffness from wheel/rail ultrasonic reflection data. Pressure was then determined using a calibration experiment. Separate calibrations were performed for each of the three sets of wheel/rail specimens investigated. Measured contact pressure distributions are compared to those determined using analytical and computer bases numerical techniques.
2004-10
Conference or Workshop Item
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/780/1/lewisr6.pdf
Marhsall, M.B., Lewis, R., Dwyer-Joyce, R.S. et al. (2 more authors) (2004) Measuring wheel/rail contact stresses using ultrasound. In: 14th International Wheelset Congress, 17-21 October, Orlando, USA. (Unpublished)
oai:eprints.whiterose.ac.uk:781
2014-06-04T18:16:50Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/781/
A new CAE procedure for railway wheel tribological design
Lewis, R.
Dwyer-Joyce, R.S.
Bruni, S.
Ekberg, A.
Cavalletti, M.
Bel Knani, K.
New demands are being imposed on railway wheel wear and reliability to increase the time between wheel reprofiling, improve safety and reduce total wheelset lifecycle costs. In parallel with these requirements, changes in railway vehicle missions are also occurring. These have led to the need to operate rolling stock on track with low as well as high radius curves; increase speeds and axle loads; and contend with a decrease in track quality due to a reduction in maintenance. These changes are leading to an increase in the severity of the wheel/rail contact conditions, which may increase the likelihood of wear or damage occurring.
The aim of this work was to develop a new CAE design methodology to deal with these demands. The model should integrate advanced numerical tools for modelling of railway vehicle dynamics and suitable models to predict wheelset durability under typical operating conditions. This will help in designing wheels for minimum wheel and rail wear; optimising railway vehicle suspensions and wheel profiles; maintenance scheduling and the evaluation of new wheel materials. This work was carried out as part of the project HIPERWheel, funded by the European Community within the Vth Framework Programme.
2004-10
Conference or Workshop Item
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/781/1/lewisr7.pdf
Lewis, R., Dwyer-Joyce, R.S., Bruni, S. et al. (3 more authors) (2004) A new CAE procedure for railway wheel tribological design. In: 14th International Wheelset Congress, 17-21 October, Orlando, USA. (Unpublished)
oai:eprints.whiterose.ac.uk:878
2014-06-04T20:05:59Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/878/
Wear and Fatigue of Railway Track Caused by Contamination, Sanding and Surface Damage
Dwyer-Joyce, R.S.
Lewis, R.
Gao, N.
Grieve, D.G.
The wheel rail contact operates in an arduous
environment. Damage to the surface of either
component is possible during manufacture, installation,
or operation. The question arises as to how tolerant is
the railway wheel or section of track to surface
indentation or damage.
In this work a twin disc simulation has been used
to relate the level of surface damage (as well as the way
it is generated) to the fatigue life of the surfaces. A
related problem is the presence of solid contamination
on the track. Sand (applied for improved adhesion) or
track ballast material can cause damage to the rail and
wheel surfaces. These mechanisms have been explored
to assess the effect on contact fatigue life and wear. The
disc specimens have been either artificially damaged
(with dents and scratches) or run with particles of sand
or ballast material. The discs were then loaded and
rotated at realistic conditions of contact pressure and
controlled slip.
For normal operation of the contact, either dry or
with water lubrication, surface dents and scratches have
little effect on fatigue life. The normal plastic flow in
the rail surface layer acts to close up dents. The failure
of the disc is then by fatigue cracking across the whole
surface with no particular preference to the dent
location. Alternatively, if the contact is lubricated with
oil then this plastic flow is greatly reduced and the dents
act as stress raisers and fatigue cracks initiate from their
trailing edge.
Sand or ballast particles are crushed as they enter
the wheel/rail contact. The fragments indent the surfaces
and rapidly roughen the contact faces. The surface
indentation is relatively minor, but the presence of
particles increases the level of traction (over the wet
case) and promotes further surface plastic flow. This
can reduce the residual fatigue life of the contact.
Further, high concentrations of sand were shown to
promote a low cycle fatigue process that caused very
high wear by the spallation of material.
The twin disc simulations have shown that, under
conditions similar to that of wheel/rail operation,
surface damage is not a primary cause of fatigue failure.
However, wear is greatly accelerated by the presence of
solid contaminants and some evidence of a low cycle
fatigue process was observed for sanded contacts.
CHARMEC
Ekberg, A.
Kabo, E.
Ringsberg, J.
2003
Book Section
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/878/1/lewisr8CM2003_Contamination_and_Wear.pdf
Dwyer-Joyce, R.S., Lewis, R., Gao, N. et al. (1 more author) (2003) Wear and Fatigue of Railway Track Caused by Contamination, Sanding and Surface Damage. In: Ekberg, A., Kabo, E. and Ringsberg, J., (eds.) 6th International Conference on Contact Mechanics and Wear of Rail/Sheel Systems : CM2003. CHARMEC , Gothenburg , pp. 211-220. ISBN 9163139286
oai:eprints.whiterose.ac.uk:879
2014-06-04T15:29:19Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/879/
Mapping rail wear transitions
Lewis, R.
Olofsson, U.
This paper outlines work carried out to produce maps of
rail material wear coefficients taken from laboratory
tests run on twin disc and pin-on-disc machines as well
as those derived from measurements taken in the field.
Wear transitions are identified using the maps and
defined in terms of slip and contact pressure. Wear
regimes are related to expected wheel/rail contact
conditions and contact points (rail head/wheel tread and
rail gauge/wheel flange). Surface and sub-surface
morphologies are discussed and comparisons are made
between field and laboratory data.
CHARMEC
Ekberg, A.
Kabo, E.
Ringsberg, J.
2003
Book Section
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/879/1/lewisr9CM2003_Rail_Wear_Mapping.pdf
Lewis, R. and Olofsson, U. (2003) Mapping rail wear transitions. In: Ekberg, A., Kabo, E. and Ringsberg, J., (eds.) 6th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems : CM2003. CHARMEC , Gothenburg , pp. 165-174. ISBN 9163139286
oai:eprints.whiterose.ac.uk:880
2014-06-05T19:38:18Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/880/
Integrating Dynamics and Wear Modelling to Predict Railway Wheel Profile Evolution
Lewis, R.
Braghin, F.
Ward, A.
Bruni, S.
Dwyer-Joyce, R.S.
Bel Knani, K.
Bologna, P.
The aim of the work described was to predict wheel
profile evolution by integrating multi-body dynamics
simulations of a wheelset with a wear model.
The wear modelling approach is based on a wear
index commonly used in rail wear predictions. This
assumes wear is proportional to Tγ, where T is tractive
force and γ is slip at the wheel/rail interface. Twin disc
testing of rail and wheel materials was carried out to
generate wear coefficients for use in the model.
The modelling code is interfaced with
ADAMS/Rail, which produces multi-body dynamics
simulations of a railway wheelset and contact conditions
at the wheel/rail interface. Simplified theory of rolling
contact is used to discretise the contact patches
produced by ADAMS/Rail and calculate traction and
slip within each.
The wear model combines the simplified theory of
rolling contact, ADAMS/Rail output and the wear
coefficients to predict the wear and hence the change of
wheel profile for given track layouts.
CHARMEC
Ekberg, A.
Kabo, E.
Ringsberg, J.
2003
Book Section
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/880/1/lewisr10CM2003_Wheel_Profile_Evolution_Prediction.pdf
Lewis, R., Braghin, F., Ward, A. et al. (4 more authors) (2003) Integrating Dynamics and Wear Modelling to Predict Railway Wheel Profile Evolution. In: Ekberg, A., Kabo, E. and Ringsberg, J., (eds.) 6th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems : CM2003. CHARMEC , Gothenburg , pp. 7-16. ISBN 9163139286
oai:eprints.whiterose.ac.uk:881
2014-06-04T19:49:52Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/881/
Wheel/Rail Contact Isolation Due to Track Contamination
Lewis, R.
Dwyer-Joyce, R.S.
Lewis, J.
An experimental study has been carried out to
investigate the effect of sanding on the electrical
isolation of a wheel/rail contact. Sand is applied to the
wheel/rail interface to increase adhesion in both braking
and traction. Train detection, for signalling purposes,
can be by means of track circuits. Signalling block
occupancy is triggered by the wheelset of the train
‘shorting out’ the track circuit. Sand in the wheel/rail
interface means that contact between the wheelsets and
the track may be compromised, inhibiting train
identification.
Static tests were performed using sections cut
from wheels and rail and dynamic tests on a twin disc
machine where rail and wheel steel discs are loaded
together and driven under controlled conditions of
rolling and slip. The electrical circuit used was a
simplified simulation of the TI21 track circuit.
The application of sand was carried out under a
range of mild and severe test conditions. The results
indicated that a transition exists in the amount of sand
applied, below which there is a measurable, but not
severe, change in voltage, but above which the contact
conductance decreases by an order of magnitude. A
model of electrical isolation has been developed
assuming either full disc separation by a sand layer or
partial disc contact with some sand present.
Idealisations inherent in both test methods mean
that they represent a severe case. Given these
limitations, it is likely that the test methods, at their
present stage of development, should be used as a
means to qualitatively assess the relative effects on
electrical isolation of different contaminants.
CHARMEC
Ekberg, A.
Kabo, E.
Ringsberg, J.
2003
Book Section
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/881/1/lewisr11CM2003_Wheel-Rail_Isolation.pdf
Lewis, R., Dwyer-Joyce, R.S. and Lewis, J. (2003) Wheel/Rail Contact Isolation Due to Track Contamination. In: Ekberg, A., Kabo, E. and Ringsberg, J., (eds.) 6th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems : CM2003. CHARMEC , Gothenburg , pp. 221-230. ISBN 9163139286
oai:eprints.whiterose.ac.uk:1611
2014-06-05T09:18:40Z
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https://eprints.whiterose.ac.uk/1611/
Turbulent diffusion in rapidly rotating flows with and without stable stratification
Cambon, C.
Godeferd, F.S.
Nicolleau, F.C.G.A.
Vassilicos, J.C.
In this work, three different approaches are used for evaluating some Lagrangian properties of homogeneous turbulence containing anisotropy due to the application of a stable stratification and a solid-body rotation. The two external frequencies are the magnitude of the system vorticity, chosen vertical here, and the Brunt–Väisälä frequency, which gives the strength of the vertical stratification. Analytical results are derived using linear theory for the Eulerian velocity correlations (single-point, two-time) in the vertical and the horizontal directions, and Lagrangian ones are assumed to be equivalent, in agreement with an additional Corrsin assumption used by Kaneda (2000). They are compared with results from the kinematic simulation model (KS) by Nicolleau & Vassilicos (2000), which also incorporates the wave–vortex dynamics inherited from linear theory, and directly yields Lagrangian correlations as well as Eulerian ones.
Finally, results from direct numerical simulations (DNS) are obtained and compared We address the question of the validity of Corrsin's simplified hypothesis, which states the equivalence between Eulerian and Lagrangian correlations. Vertical correlations are found to follow this postulate, but not the horizontal ones. Consequences for the vertical and horizontal one-particle dispersion are examined. In the analytical model, the squared excursion lengths are calculated by time integrating the Lagrangian (equal to the Eulerian) two-time correlations, according to Taylor's procedure. These quantities are directly computed from fluctuating trajectories by both KS and DNS. In the case of pure rotation, the analytical procedure allows us to relate Brownian asymptotic laws of dispersion in both the horizontal and vertical directions to the angular phase-mixing properties of the inertial waves. If stratification is present, the inertia–gravity wave dynamics, which affects the vertical motion, yields a suppressed vertical diffusivity, but not a suppressed horizontal diffusivity, since part of the horizontal velocity field escapes wavy motion.
Cambridge University Press
2004-01
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/1611/1/nicolleau.f.c1.pdf
Cambon, C., Godeferd, F.S., Nicolleau, F.C.G.A. et al. (1 more author) (2004) Turbulent diffusion in rapidly rotating flows with and without stable stratification. Journal of Fluid Mechanics, 499. pp. 231-255. ISSN 0022-1120
http://dx.doi.org/10.1017/S0022112003007055
doi:10.1017/S0022112003007055
oai:eprints.whiterose.ac.uk:1612
2014-06-14T22:00:48Z
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https://eprints.whiterose.ac.uk/1612/
Study of the development of three-dimensional sets of fluid particles and iso-concentration fields using kinematic simulation
Nicolleau, F.C.G.A.
Elmaihy, A.
We use kinematic simulation (KS) to study the development of a material line immersed in a three-dimensional turbulent flow. We generalize this study to a material surface, cube and sphere. We find that the fractal dimension of the surface can be explained by the same mechanism as that proposed by Villermaux & Gagne (Phys. Rev. Lett. vol. 73, 1994, p. 252) for the line. The fractal dimension of the line or the surface is a linear function of time up to times of the order of the smallest characteristic time of turbulence (or Kolmogorov timescale).
For volume objects we describe the respective role of the Reynolds number and of the object's characteristic size. Using the method of characteristics with KS we compute the evolution with time of a concentration field and measure the fractal dimension of the intersection of this scalar field with a given plane. For these objects, we retrieve the result of Villermaux & Innocenti (J. Fluid Mech. vol. 393, 1999, p. 123) that the Reynolds number does not affect the development of the fractal dimension of the iso-scalar surface and extend this result to volume geometries. We also find that for volume objects the characteristic time of development of the fractal dimension is the large scales' characteristic time and not the Kolmogorov timescale.
Cambridge University Press
2004-10
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/1612/1/nicolleau.f.c2.pdf
Nicolleau, F.C.G.A. and Elmaihy, A. (2004) Study of the development of three-dimensional sets of fluid particles and iso-concentration fields using kinematic simulation. Journal of Fluid Mechanics, 517. pp. 229-249. ISSN 0022-1120
http://dx.doi.org/10.1017/S0022112004000898
doi:10.1017/S0022112004000898
oai:eprints.whiterose.ac.uk:1964
2014-06-05T12:19:37Z
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https://eprints.whiterose.ac.uk/1964/
Interactions between toothbrush and toothpaste particles during simulated abrasive cleaning
Lewis, R.
Dwyer-Joyce, R.S.
Most people clean their teeth using toothpaste, consisting of abrasive particles in a carrier fluid, and a filament based toothbrush to remove plaque and stain. In order to optimise cleaning efficiency it is important to understand how toothbrush filaments, abrasive particles and fluid interact in a tooth cleaning contact.
Work has been carried out to visualise, simulate, and model the processes in teeth cleaning. Laboratory cleaning contacts were created between a toothbrush and a transparent surface. Video and short duration flash photography were used to study the processes by which a toothbrush traps abrasive particles, loads them against the counterface, and removes material. Small abrasive particles tend to be trapped at the contact between the filament tip and the counterface, whilst larger particles are trapped by clumps of filaments or at the contact with the side of a bent filament.
Measurements of brush friction force were recorded during cleaning for a range of operating conditions. The presence of abrasive particles in the cleaning mixture increased the coefficient of friction, but the absolute particle concentration showed a lesser effect. It is surmised that only a few particles carry any load and cause any abrasion; increasing the particle concentration does not directly increase the number of load bearing particles.
Abrasive scratch tests were also carried out, using PMMA as a wearing substrate. The scratches produced during these tests were studied. The microscopy images were used to deduce how the filaments deflect and drag, and how particles are trapped by filaments and scratch the surface. Again, it was observed that few of the brush filaments loaded particles to produce scratches, and that when a filament changes direction of travel the trapped particle is lost.
Results of these studies were used to develop both qualitative and quantitative models of the process by which material is removed in teeth cleaning. The quantitative model contains, by necessity, several empirical factors, but nonetheless predictions compare well with in vitro wear results from the literature. The results were also used to draw some broad conclusions on appropriate brushing techniques for optimum tooth cleaning.
Professional Engineering Publishing
2006-12
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/1964/1/lewisr12_Teeth_Cleaning_Manuscript_revised.pdf
Lewis, R. and Dwyer-Joyce, R.S. (2006) Interactions between toothbrush and toothpaste particles during simulated abrasive cleaning. Proceedings of the Institution of Mechanical Engineers. Part J: Journal of engineering tribology, 220 (8). pp. 755-765. ISSN 1350-6501
http://dx.doi.org/10.1243/13506501JET96
doi:10.1243/13506501JET96
oai:eprints.whiterose.ac.uk:2661
2013-02-08T16:54:42Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543:536865666669656C642E414552
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/2661/
A study on the compressive strength of thick carbon fibre-epoxy laminates
Lee, J.
Soutis, C.
This paper describes an experimental study that examines the effect of specimen size on the axial compressive strength of IM7/8552 carbon fibre/epoxy unidirectional laminates (UD). Laminate gauge length, width and thickness were increased by a scaling factor of 2 and 4 from the baseline specimen size of 10 mm x 10 mm x 2 mm. In all cases, strength decreased as specimen size increased, with a maximum reduction of 45%; no significant changes were observed for the axial modulus. Optical micrographs show that the failure mechanism is fibre microbuckling accompanied by matrix cracking and splitting. The location of failure in most specimens, especially the thicker ones, is where the tabs terminate and the gauge section begins
suggesting that the high local stresses developed due to geometric discontinuity contribute to premature failure and hence reduced compressive strength. Two generic quasi-isotropic multi-directional (MD) lay-ups were also tested in compression, one with blocked plies [45n/90n/-45n/0n]s and the other with distributed plies [45/90/-45/0]ns with n=2, 4 and 8. The material used and test fixture was identical to that of the unidirectional specimens with three different gauge sections (30 mm x 30 mm, 60 mm x 60 mm and 120 mm x 120 mm) to establish any size effects. Strength results showed no evidence of a size effect when the specimens are scaled up using distributed plies and compared to the 2 mm thick specimens. All blocked specimens had similar compressive strengths to the sub-laminate ones apart of the 8 mm specimens that showed a 30% reduction due to extensive matrix cracking introduced during the specimen's cutting process. The calculated unidirectional failure stress (of the 0° ply within the multidirectional laminate) of about 1710 MPa is slightly higher than the average measured value of 1570 MPa of the 2 mm thick baseline unidirectional specimen, suggesting that the reduced unidirectional strength observed for the thicker specimens is a testing artefact. It appears that the unidirectional compressive strength in thicker specimens (>2 mm) is found to be limited by the stress concentration developed at the end tabs and manufacturing
induced defects.
Elsevier Science
2007-08
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/2661/1/soutisc1.pdf
Lee, J. and Soutis, C. (2007) A study on the compressive strength of thick carbon fibre-epoxy laminates. Composites Science And Technology, 67 (10). pp. 2015-2026. ISSN 0266-3538
http://dx.doi.org/10.1016/j.compscitech.2006.12.001
doi:10.1016/j.compscitech.2006.12.001
oai:eprints.whiterose.ac.uk:3379
2013-02-08T16:54:59Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3379/
Development of engineering design tools to help reduce apple bruising
Lewis, R.
Yoxall, A.
Canty, L.A.
Romo, E.R.
A large percentage of apples are wasted each year due to damage such as bruising. The apple journey from orchard to supermarket is very complex and apples are subjected to a variety of static and dynamic loads that could result in this damage occurring. The main aim of this work was to carry out numerical modelling to develop a design tool that can be used to optimise the design of harvesting and sorting equipment and packaging media to reduce the likelihood of apple bruise formation resulting from impact loads. An experimental study, along with analytical calculations, varying apple drop heights and counterface material properties, were used to provide data to validate the numerical modelling. Good correlation was seen between the models and experiments and this approach combined with previous work on static modelling should provide a comprehensive design tool for reducing the likelihood of apple bruising occurring.
Elsevier Sci Ltd
2007-12
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/3379/1/lewisr1.pdf
Lewis, R., Yoxall, A., Canty, L.A. et al. (1 more author) (2007) Development of engineering design tools to help reduce apple bruising. Journal of Food Engineering, 83 (3). pp. 356-365. ISSN 0260-8774
http://dx.doi.org/10.1016/j.jfoodeng.2007.03.005
doi:10.1016/j.jfoodeng.2007.03.005
oai:eprints.whiterose.ac.uk:3520
2013-02-08T16:55:27Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3520/
Wear of a chute in a rice sorting machine
Camacho, J.
Lewis, R.
Dwyer-Joyce, R.S.
In a rice sorting machine, rice grains drop onto and slide down an anodised aluminium chute. The purpose of the chute is to separate the grains and provide a controlled distribution. At the bottom of the chute the grains are examined optically and contaminants or defective grains
are removed from the stream by jets of air. The machine has the ability to sort low quality rice which contains a large element of contaminants such as husk. The husk is extremely
abrasive and this, along with other factors, can lead to a reduction in the life of the chute by wear of the surface.
In this work a failure analysis process was undertaken to establish the nature and causes of the chute surface wear and the mechanisms of material removal. Wear occurs initially at the location where the grains first strike the chute and at subsequent regions down the chute where bounce occurs.
An experimental and analytical examination of the rice motion on impacting the chute was also carried out along with some friction testing of potential replacement chute materials. The evidence gathered during the failure analysis along with the experimental analysis was
used to propose possible material/design improvements.
Elsevier Science SA
2007-09
Article
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/3520/1/lewisr2.pdf
Camacho, J., Lewis, R. and Dwyer-Joyce, R.S. (2007) Wear of a chute in a rice sorting machine. Wear, 263 (1 - 6). pp. 65-73. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2006.11.052
doi:10.1016/j.wear.2006.11.052
oai:eprints.whiterose.ac.uk:3521
2013-02-08T16:55:27Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3521/
Particle motion and stain removal during simulated abrasive
tooth cleaning
Lewis, R.
Barber, S.C.
Dwyer-Joyce, R.S.
Stain removal from teeth is important both to prevent decay and for appearance. This is usually achieved using a filament based toothbrush with a toothpaste consisting of abrasive particles in a carrier fluid. This work has been carried out to examine how these abrasive particles interact with the filaments and cause material removal from a stain layer on the surface of a tooth. It is important to understand this mechanism as while maximum cleaning
efficiency is required, this must not be accompanied by damage to the enamel or dentine substrate.
In this work simple abrasive scratch tests were used to investigate stain removal mechanism of two abrasive particles commonly used in tooth cleaning, silica and perlite. Silica particles are granular in shape and very different to perlite particles, which are flat and have
thicknesses many times smaller than their width.
Initially visualisation studies were carried out with perlite particles to study how they are entrained into a filament/counterface contact. Results were compared with previous studies using silica. Reciprocating scratch tests were then run to study how many filaments have a particle trapped at one moment and are involved in the cleaning process. Stain removal tests were then carried out in a similar manner to establish cleaning rates with the two particle types. Perlite particles were found to be less abrasive than silica. This was because of their shape and how they were entrained into the filament contacts and loaded against a counterface. With both particles subsurface damage during stain removal was found to be
minimal.
A simple model was built to predict stain removal rates with silica particles, which gave results that correlated well with the experimental data.
Elsevier Science SA
2007-03
Article
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/3521/1/lewisr3.pdf
Lewis, R., Barber, S.C. and Dwyer-Joyce, R.S. (2007) Particle motion and stain removal during simulated abrasive tooth cleaning. Wear, 263 (1 - 6). pp. 188-197. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2006.12.023
doi:10.1016/j.wear.2006.12.023
oai:eprints.whiterose.ac.uk:3600
2013-02-08T16:55:38Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3600/
Characterising pressure and bruising in apple fruit
Lewis, R.
Yoxall, A.
Marshall, M.B.
Canty, L.A.
A large percentage of apples are wasted each year due to damage such as bruising. The apple journey from orchard to supermarket is very complex and apples are subjected to a variety of static and dynamic loads that could result in this damage occurring. The aim of this work was to use a novel ultrasonic technique to study apple contact areas and stresses under static loading that may occur, for example, in bulk storage bins used during harvesting. These results were used to identify load thresholds above which unacceptable damage occurs. They were also used to validate output from a finite element model, which will ultimately be developed into a packaging design tool to help reduce the likelihood of apple damage occurring.
Elsevier B.V
2007-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/3600/1/lewisr4pdf.pdf
Lewis, R., Yoxall, A., Marshall, M.B. et al. (1 more author) (2007) Characterising pressure and bruising in apple fruit. Wear, 264 (1-2). pp. 37-46. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2007.01.038
doi:10.1016/j.wear.2007.01.038
oai:eprints.whiterose.ac.uk:3655
2014-06-05T19:35:39Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3655/
Kinematic simulation for stably stratified and rotating turbulence
Nicolleau, F.
Yu, G.
Vassilicos, J.C.
The properties of one-particle and particle-pair diffusion in rotating and stratified turbulence are studied by applying the rapid distortion theory (RDT) to a kinematic simulation (KS) of the Boussinesq equation with a Coriolis term.
Scalings for one- and two-particle horizontal and vertical diffusions in purely rotating turbulence are proposed for small Rossby numbers.
Particular attention is given to the locality-in-scale hypothesis for two-particle diffusion in purely rotating turbulence both in the horizontal and the vertical directions. It is observed that both rotation and stratification decrease the pair diffusivity and improve the validity of the locality-in-scale hypothesis. In the case of stratification the range of scales over which the locality-in-scale hypothesis is observed is increased.
It is found that rotation decreases the diffusion in the horizontal direction as well as, though to a much lesser extent, in the vertical direction.
Elsevier B.V.
2008-01
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/3655/1/nicolleauf1.pdf
Nicolleau, F., Yu, G. and Vassilicos, J.C. (2008) Kinematic simulation for stably stratified and rotating turbulence. Fluid Dynamics Research, 40 (1). pp. 68-93. ISSN 0169-5983
http://dx.doi.org/10.1016/j.fluiddyn.2006.08.011
doi:10.1016/j.fluiddyn.2006.08.011
oai:eprints.whiterose.ac.uk:3658
2014-06-06T10:12:42Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3658/
Turbulence with combined stratification and rotation: Limitations of Corrsin's hypothesis
Nicolleau, F.
Yu, G.
The properties of one-particle and particle-pair diffusion in rotating and stratified turbulence are studied by applying the rapid distortion theory to a kinematic simulation of the Boussinesq equation with a Coriolis term. We discuss the simplified Corrsin hypothesis and restrict the validity of its predictions to pure rotation. We emphasize the existence of two regimes driven by very different physics when rotation is present. Particular attention is given to the locality-in-scale hypothesis for two-particle diffusion in both the horizontal and the vertical directions.
American Physical Society
2007-12
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/3658/1/nicolleauf2.pdf
Nicolleau, F. and Yu, G. (2007) Turbulence with combined stratification and rotation: Limitations of Corrsin's hypothesis. Physical Review E, 76. 066302. ISSN 1550-2376
http://dx.doi.org/10.1103/PhysRevE.76.066302
doi:10.1103/PhysRevE.76.066302
oai:eprints.whiterose.ac.uk:3714
2013-02-08T16:55:53Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3714/
Crack paths under mixed mode loading
Yates, J.R.
Zanganeh, M.
Tomlinson, R.A.
Brown, M.W.
Diaz Garrido, F.A.
Long fatigue cracks that initially experience mixed mode displacements usually change direction in response to cyclic elastic stresses. Eventually the cracks tend to orient themselves into a pure mode I condition, but the path that they take can be complex and chaotic. In this paper we report on recent developments in techniques for tracking the crack path as it grows and evaluating the strength of the mixed mode crack tip stress field.
Elsevier
2008-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/3714/1/robinsonra1_Yates_EFM75.pdf
Yates, J.R., Zanganeh, M., Tomlinson, R.A. et al. (2 more authors) (2008) Crack paths under mixed mode loading. Engineering Fracture Mechanics, 75 (3-4). pp. 319-330. ISSN 0013-7944
http://dx.doi.org/10.1016/j.engfracmech.2007.05.014
doi:10.1016/j.engfracmech.2007.05.014
oai:eprints.whiterose.ac.uk:3743
2013-02-08T16:55:57Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E414353
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/3743/
Comparisons between harmonic balance and nonlinear output frequency response function in nonlinear system analysis
Peng, Z.K.
Lang, Z.Q.
Billings, S.A.
Tomlinson, G.R.
By using the Duffing oscillator as a case study, this paper shows that the harmonic components in the nonlinear system response to a sinusoidal input calculated using the Nonlinear Output Frequency Response Functions (NOFRFs) are one of the solutions obtained using the Harmonic Balance Method (HBM). A comparison of the performances of the two methods shows that the HBM can capture the well-known jump phenomenon, but is restricted by computational limits for some strongly nonlinear systems and can fail to provide accurate predictions for some harmonic components. Although the NOFRFs cannot capture the jump phenomenon, the method has few computational restrictions. For the nonlinear damping systems, the NOFRFs can give better predictions for all the harmonic components in the system response than the HBM even when the damping system is strongly nonlinear.
Elsevier B.V
2008-03
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/3743/1/pengzk3.pdf
Peng, Z.K., Lang, Z.Q., Billings, S.A. et al. (1 more author) (2008) Comparisons between harmonic balance and nonlinear output frequency response function in nonlinear system analysis. Journal of Sound and Vibration, 311 (1-2). pp. 56-73. ISSN 0022-460X
http://dx.doi.org/10.1016/j.jsv.2007.08.035
doi:10.1016/j.jsv.2007.08.035
oai:eprints.whiterose.ac.uk:4068
2008-08-12T15:24:39Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/4068/
High performance cement based materials and holistic design for sustainability in construction (Part I)
Swamy, R.N.
The cement/concrete industry is faced with two major
challenges – an infrastructure crisis, and a sustainability
problem. Both are worldwide issues with tremendous
implications not only for ourselves but also for the
lives of generations to come. The focus of this paper
is to show that a holistic approach to the formulation
and fabrication of concrete materials with emphasis on
durability, ductility, environment and sustainability can
lead to the development of a large number of eco-friendly
and innovative cement-based construction materials
for a wide range of applications in infrastructure
regeneration and reconstruction. Quality of life is the
one single goal that all humanity wants and aspires for,
and a judicious combination of pozzolanic/cementitious
materials, chemical admixtures, fillers, fibres and other
appropriate constituents can meet the insatiable demand
for basic infrastructure facilities and at the same time
contribute to sustainable growth with the least damage
to our environment. The paper illustrates this philosophy
of manufacturing and designing sustainable concrete
materials for durability rather than for strength with
various examples such as fly ash/slag concrete, high
volume fly ash concrete, structural lightweight aggregate
concrete, low energy-cements, and fibre reinforcement.
It is also shown that the philosophy of holistic design
with emphasis on material stability, structural integrity
and ductility can successfully meet the challenges of the
infrastructure crisis and sustainable development of the
concrete industry.
2008-02
Article
NonPeerReviewed
Swamy, R.N. (2008) High performance cement based materials and holistic design for sustainability in construction (Part I). The Indian Concrete Journal.
oai:eprints.whiterose.ac.uk:4082
2013-02-08T16:56:21Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/4082/
A design model for punching shear of FRP-reinforced slab-column connections
Theodorakopoulos, D.D.
Swamy, R.N.
The overall aim of this paper is to develop a unified design method for the punching shear resistance of slab-column connections irrespective of the type of internal reinforcement. In the first part of the paper a design model for the punching shear resistance of concrete slab-column connections reinforced with fibre-reinforced polymers (FRP) is proposed. This design model is based on the authors’ theoretical analysis for such slabs, which considers the physical behavior of the connections under load. The effects of the inherent linear brittle response, the lower elastic modulus and the different bond features, as compared to steel, of the FRP reinforcement are all accounted for in the present study. The proposed model does not incorporate any fitting factors to match the theory to the trend of the available FRP slab test results. The excellent agreement between the predicted and published test results should give confidence to engineers and designers in using FRP as a sound structural reinforcement for slab-column connections.
It is then shown that the proposed design model for FRP slabs and the previous model of the authors for steel reinforced slabs are both identical in nature and structure, thus constituting a unified approach to design for punching shear in slabs. On the basis of the unified model comparison and correlation between an FRP slab and a reference steel reinforced slab, confirmed by the available test results, are presented. The unified model also enables the development of a more rational and reliable equivalent steel reinforcement ratio which can be applied to existing code equations for steel reinforced slabs to estimate the punching resistance of FRP-reinforced slabs.
Elsevier Ltd.
2008-07
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/4082/2/swamyr3.pdf
Theodorakopoulos, D.D. and Swamy, R.N. (2008) A design model for punching shear of FRP-reinforced slab-column connections. Cement and Concrete Composites, 30 (6). pp. 544-555. ISSN 0958-9465
http://dx.doi.org/10.1016/j.cemconcomp.2007.10.003
doi:10.1016/j.cemconcomp.2007.10.003
oai:eprints.whiterose.ac.uk:4617
2013-02-08T16:56:34Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/4617/
Sustainable Concrete for the 21st Century Concept of Strength through Durability
Swamy, R.N.
The world is passing through difficult and troubled times, and we live in a rapidly changing world. The construction industry is facing many challenges – global warming, climate change forces, and the capability to achieve sustainable development and economic progress without damaging our environment. The concrete industry in particular faces further challenges. There is extensive evidence to show that concrete materials and concrete structures all over the world are deteriorating at a rapid rate, and that we are unable to ensure their long-term durable service life performance. To confound this situation, we are also faced with an urgent need to regenerate our infrastructure systems if we are to eradicate poverty and provide a decent Quality of Life for all the peoples of the world. This paper shows that the current emphasis on high strength and very high strength, and the design philosophy of Durability through Strength for concrete materials and concrete structures is fundamentally flawed. It is this misleading concept and vision that is primarily responsible for the lack of durable performance of concrete in real life environments. To change this scenario, this paper advocates that concrete materials must be manufactured for durability and not for strength. It is shown that this concept of Strength through Durability can be achieved through careful design of the cement matrix and its microstructure. If concrete is to be an eco-friendly, and sustainable driving force and construction material for social change, the need is to produce durable concrete with strengths of 30 to 60 to 80 MPa rather than very high strength concrete without an assured durable performance.
2008-04
Article
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/4617/1/swamyPAPER48-8_.pdf
Swamy, R.N. (2008) Sustainable Concrete for the 21st Century Concept of Strength through Durability. Japan Society of Civil Engineers Concrete Committee Newsletter, 13.
http://www.jsce.or.jp/committee/concrete/e/newsletter/newsletter13/Paper1.pdf
oai:eprints.whiterose.ac.uk:4773
2013-02-08T16:56:55Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/4773/
Analytical model to predict the punching shear strenth of FRP reinforced concrete flat slabs
Theodorakopoulos, D.D.
Swamy, R.M.
The use of FRP reinforcement in practice, especially where the corrosion of steel bars is a concern, is very much hampered by the absence of a rational theoretical method of analysis to predict the ultimate strength of structural elements, especially flat slabs and bridge decks, made with FRP-reinforced concrete. This paper aims at evaluating the punching shear capacity of internally, without shear reinforcement, FRP-reinforced slab-column connections. The method is based on a simple analytical model developed by the authors for concrete slabs reinforced with conventional steel. The effects of the FRP elastic modulus, ultimate tensile strength and bond characteristics, which are sufficiently different from those of steel, are incorporated in the existing model. The predictions of the proposed model for FRP-reinforced slabs are then compared with test results obtained from twenty-eight slabs recently reported in the literature. The comparisons show excellent agreement between the predicted and experimental values. It is concluded that the proposed predictive equation presented in this study provides a convenient and reliable framework for the punching strength analysis of slabs reinforced with FRP bars or grids.
American Concrete Institute
2007-05
Article
NonPeerReviewed
Theodorakopoulos, D.D. and Swamy, R.M. (2007) Analytical model to predict the punching shear strenth of FRP reinforced concrete flat slabs. ACI Structural Journal, 104 (3).
http://www.concrete.org/PUBS/JOURNALS/SJHOME.ASP
oai:eprints.whiterose.ac.uk:4951
2013-02-08T16:57:10Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/4951/
Matrix cracking in polymeric composites laminates: Modelling and experiments
Katerelos, D.T.G.
Kashtalyan, M.
Soutis, C.
Galiotis, C.
Composites ability to retain functionality in the presence of damage is a crucial safety and economic issue. Generally the first damage mode in composite laminates is matrix cracking, which affects the mechanical properties of the structure long before its load-bearing capacity is exhausted. In this paper, a detailed analysis of the effect of matrix cracking on the behaviour of cross-ply [0/90]s and unbalanced symmetric [0/45]s glass/epoxy laminates loaded statically in tension is performed. Theoretical predictions of stiffness reduction due to damage are based on the Equivalent Constraint Model (ECM), which takes into account concurrent matrix cracking in all plies of the laminate, although matrix cracking under consideration is developing only within the off-axis ply of the laminates. The longitudinal Young’s modulus predictions are compared to experimentally derived data obtained using laser Raman spectroscopy (LRS). The good agreement between predicted and measured values of the reduced longitudinal Young’s modulus validates the ECM model and proves that its basic assumptions are accurate. Thus, the predictions for all the mechanical properties by the ECM model are within a realistic range, while experimental evidence is required for further validation.
Elsevier B.V.
2008-09
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/4951/1/Soutisc1pdf.pdf
Katerelos, D.T.G., Kashtalyan, M., Soutis, C. et al. (1 more author) (2008) Matrix cracking in polymeric composites laminates: Modelling and experiments. Composites Science and Technology, 68 (12). pp. 2310-2317. ISSN 0266-3538
http://dx.doi.org/10.1016/j.compscitech.2007.09.013
doi:10.1016/j.compscitech.2007.09.013
oai:eprints.whiterose.ac.uk:4952
2013-02-08T16:57:11Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543:536865666669656C642E414552
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/4952/
Measuring the notched compressive strength of composite laminates: Specimen size effects
Lee, J.
Soutis, C.
Large fibre reinforced composite structures can give much lower strengths than small test specimens, so a proper understanding of scaling is vital for their safe and efficient use. Small size (scale) specimens are commonly tested to justify allowable stresses, but could be dangerous if results are extrapolated without accounting for scaling effects. On the other hand large factors are sometimes applied to compensate for uncertainties, resulting in overweight designs. The most important variables of scaling effects on the strength of composites with open holes have been identified from experimental tests as notch size, ply and laminate thickness. In this study, these have been scaled both independently and simultaneously over a large range of combinations. The specimens are fabricated from commercially available (Hexcel Composites Ltd.) carbon/epoxy pre-impregnated tapes 0.125 mm thick (IM7/8552). The material is laid up by hand in unidirectional [04]ns with n = 2, 3, 4, and 8 (i.e., 2, 3, 4 and 8 mm thick) and multidirectional laminates; two generic quasi-isotropic lay-ups, one fabricated with blocked plies [45n/90n/−45n/0n]s and the other with distributed layers [45/90/−45/0]ns with n = 2, 4 and 8 are examined. It is shown that the critical failure mechanism in these laminates is in the form of fibre microbuckling or kinking. The unnotched compressive strength in unidirectional specimens thicker than 2 mm is found to be limited by the stress concentration developed at the end tabs and manufacturing induced defects in the form of ply waviness, fibre misalignment and voids rather than specimen size (scaling). In the open hole specimens, for both lay-ups, the strength reduction observed is due to hole size effect rather than specimen thickness or volume increase. The open hole (notched) compressive strength results obtained compare favourably to predictions by a linear softening cohesive zone fracture model developed in earlier work by the second author.
Elsevier B.V.
2008-09
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/4952/1/soutisc2.pdf
Lee, J. and Soutis, C. (2008) Measuring the notched compressive strength of composite laminates: Specimen size effects. Composites Science and Technology, 68 (12). pp. 2359-2366. ISSN 0266-3538
http://dx.doi.org/10.1016/j.compscitech.2007.09.003
doi:10.1016/j.compscitech.2007.09.003
oai:eprints.whiterose.ac.uk:5404
2013-02-08T16:57:34Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/5404/
Energy dissipation prediction of particle dampers
Wong, C.X.
Daniel, M.C.
Rongong, J.A.
This paper presents initial work on developing models for predicting particle dampers (PDs) behaviour using the Discrete Element Method (DEM). In the DEM approach, individual particles are typically represented as elements with mass and rotational inertia. Contacts between particles and with walls are represented using springs, dampers and sliding friction interfaces. In order to use DEM to predict damper behaviour adequately, it is important to identify representative models of the contact conditions. It is particularly important to get the appropriate trade-off between accuracy and computational efficiency as PDs have so many individual elements. In order to understand appropriate models, experimental work was carried out to understand interactions between the typically small (1.5–3 mm diameter) particles used. Measurements were made of coefficient of restitution and interface friction. These were used to give an indication of the level of uncertainty that the simplest (linear) models might assume. These data were used to predict energy dissipation in a PD via a DEM simulation. The results were compared with that of an experiment.
Elsevier Ltd
2009-01
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/5404/1/wongc1.pdf
Wong, C.X., Daniel, M.C. and Rongong, J.A. (2009) Energy dissipation prediction of particle dampers. Journal of Sound and Vibration, 319 (1-2). pp. 91-118. ISSN 0022-460X
http://dx.doi.org/10.1016/j.jsv.2008.06.027
doi:10.1016/j.jsv.2008.06.027
oai:eprints.whiterose.ac.uk:8489
2013-02-08T16:58:12Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8489/
Analysis of the vibrational mode spectrum of a linear chain with spatially exponential properties
Michelitsch, T.M.
Maugin, G.A.
Nowakowski, A.F.
Nicolleau, F.C.G.A.
We deduce the dynamic frequency-domain-lattice Green's function of a linear chain with properties (masses and next-neighbor spring constants) of exponential spatial dependence. We analyze the system as discrete chain as well as the continuous limiting case which represents an elastic I D exponentially graded material. The discrete model yields closed form expressions for the N x N Green's function for an arbitrary number N = 2,...,infinity of particles of the chain. Utilizing this Green's function yields an explicit expression for the vibrational mode density. Despite of its simplicity the model reflects some characteristics of the dynamics of a I D exponentially graded elastic material. As a special case the well-known expressions for the Green's function and oscillator density of the homogeneous linear chain are contained in the model. The width of the frequency band is determined by the grading parameter which characterizes the exponential spatial dependence of the properties. In the limiting case of large grading parameter, the frequency band is localized around a single finite frequency where the band width tends to zero inversely with the grading parameter. In the continuum limit the discrete Green's function recovers the Green's function of the continuous equation of motion which takes in the time domain the form of a Klein-Gordon equation. (C) 2008 Elsevier Ltd. All rights reserved.
Elsevier
2009-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8489/1/Nicolleau_analysis.pdf
Michelitsch, T.M., Maugin, G.A., Nowakowski, A.F. et al. (1 more author) (2009) Analysis of the vibrational mode spectrum of a linear chain with spatially exponential properties. International Journal of Engineering Science, 47 (2). pp. 209-220. ISSN 0020-7225
http://dx.doi.org/10.1016/j.ijengsci.2008.08.011
10.1016/j.ijengsci.2008.08.011
oai:eprints.whiterose.ac.uk:8587
2013-02-08T16:58:24Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8587/
Twin disc assessment of wheel/rail adhesion
Gallardo-Hernandez, E.A.
Lewis, R.
Loss of adhesion between a railway wheel and the track has implications for both braking and traction. Poor adhesion in braking is a safety issue as it leads to extended stopping distances. In traction, it is a performance issue as it may lead to reduced acceleration which could cause delays.
In this work, wheel/rail adhesion was assessed using a twin disc simulation. The effects of a number of contaminants, such as oil, dry and wet leaves and sand were investigated. These have been shown in the past to have significant effect on adhesion, but this has not been well quantified.
The results have shown that both oil and water reduce adhesion from the dry condition. Leaves, however, gave the lowest adhesion values, even when dry. The addition of sand, commonly used as a friction enhancer, to leaves, brought adhesion levels back to the levels without leaves present. Adhesion levels recorded, particularly for the wet, dry and oil conditions are in the range seen in field measurements.
Relatively severe disc surface damage and subsurface deformation was seen after the addition of sand. Leaves were also seen to cause indents in the disc surfaces.
The twin disc approach has been shown to provide a good approach for comparing adhesion levels under a range of wheel/rail contact conditions, with and without contaminants.
Elsevier
2008-10-30
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8587/2/Lewis_wheel.rail.pdf
Gallardo-Hernandez, E.A. and Lewis, R. (2008) Twin disc assessment of wheel/rail adhesion. Wear, 265 (9-10). pp. 1309-1316. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2008.03.020
10.1016/j.wear.2008.03.020
oai:eprints.whiterose.ac.uk:8594
2013-02-08T16:58:24Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8594/
Friction in a hydraulic motor piston/cam roller contact lined with PTFE impregnated
Lewis, R.
The aim of this work was to test a new PTFE impregnated cloth material for use as a surface layer on the pistons of a hydraulic motor at the interface with the cam roller. Tests were carried out using a standard Bowden & Leben sliding friction tester which indicated that the cloth material gave similar results to the current material (PTFE impregnated sintered bronze) in both dry and lubricated conditions. Actual component tests run on a modified twin disc test machine showed that the cloth performed better in conditions of reduced lubrication. Wear testing would be required to fully assess the feasibility of using the material in a hydraulic motor. (C) 2008 Elsevier B.V. All rights reserved.
Elsevier
2009-03-25
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8594/2/Lewis_Friction.pdf
Lewis, R. (2009) Friction in a hydraulic motor piston/cam roller contact lined with PTFE impregnated. Wear, 266 (7-8). pp. 888-892. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2008.12.009
10.1016/j.wear.2008.12.009
oai:eprints.whiterose.ac.uk:8860
2017-08-26T05:12:20Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8860/
Hardware-in-the-loop simulation of magnetorheological dampers for vehicle suspension systems
Batterbee, D.C.
Sims, N.D.
Magnetorheological (MR) fluids provide an elegant means to enhance vibration control in primary vehicle suspensions. Such fluids can rapidly modify their flow characteristics in response to a magnetic field, so they can be used to create semi-active dampers. However, the behaviour of MR dampers is inherently non-linear and as a consequence, the choice of an effective control strategy remains an unresolved problem. Previous research has developed a method to linearize the damper's force/velocity response, to allow implementation of classical control techniques. In the present study, this strategy is used to implement skyhook damping laws within primary automotive suspensions. To simulate the vehicle suspension, a two-degree-of-freedom quarter car model is used, which is excited by realistic road profiles. The controller performance is investigated experimentally using the hardware-in-the-loop-simulation (HILS) method. This experimental method is described in detail and its performance is validated against numerical simulations for a simplified problem. The present authors demonstrate that feedback linearization can provide significant performance enhancements in terms of passenger comfort, road holding, and suspension working space compared with other control strategies. Furthermore, feedback linearization is shown to desensitize the controller to uncertainties in the input excitation such as changes in severity of the road surface roughness.
Professional Engineering Publishing
2007
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8860/2/simsnd4.pdf
Batterbee, D.C. and Sims, N.D. (2007) Hardware-in-the-loop simulation of magnetorheological dampers for vehicle suspension systems. Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering, 221 (2). pp. 265-278. ISSN 0959-6518
http://dx.doi.org/10.1243/09596518JSCE304
oai:eprints.whiterose.ac.uk:8861
2013-02-08T16:58:43Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8861/
Magnetorheological landing gear: 2. Validation using experimental data
Batterbee, D.C.
Sims, N.D.
Stanway, R.
Rennison, M.
Aircraft landing gears are subjected to a wide range of excitation conditions with conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. In part 1 of this contribution, a methodology was developed that enables the geometry of a flow mode MR valve to be optimized within the constraints of an existing passive landing gear. The device was designed to be optimal in terms of its impact performance, which was demonstrated using numerical simulations of the complete landing gear system. To perform the simulations, assumptions were made regarding some of the parameters used in the MR shock strut model. In particular, the MR fluid's yield stress, viscosity, and bulk modulus properties were not known accurately. Therefore, the present contribution aims to validate these parameters experimentally, via the manufacture and testing of an MR shock strut. The gas exponent, which is used to model the shock strut's nonlinear stiffness, is also investigated. In general, it is shown that MR fluid property data at high shear rates are required in order to accurately predict performance prior to device manufacture. Furthermore, the study illustrates how fluid compressibility can have a significant influence on the device time constant, and hence on potential control strategies.
Institute of Physics
2007-12
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8861/2/simsnd2.pdf
Batterbee, D.C., Sims, N.D., Stanway, R. et al. (1 more author) (2007) Magnetorheological landing gear: 2. Validation using experimental data. Smart Materials and Structures, 16 (6). pp. 2441-2452. ISSN 0964-1726
http://dx.doi.org/10.1088/0964-1726/16/6/047
10.1088/0964-1726/16/6/047
oai:eprints.whiterose.ac.uk:8862
2013-02-08T16:58:43Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8862/
Magnetorheological landing gear: 1. A design methodology
Batterbee, D.C.
Sims, N.D.
Stanway, R.
Wolejsza, Zbigniew
Aircraft landing gears are subjected to a wide range of excitation conditions, which result in conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. This paper presents a design methodology that enables an MR landing gear to be optimized, both in terms of its damping and magnetic circuit performance, whilst adhering to stringent packaging constraints. Such constraints are vital in landing gear, if MR technology is to be considered as feasible in commercial applications. The design approach focuses on the impact or landing phase of an aircraft's flight, where large variations in sink speed, angle of attack and aircraft mass makes an MR device potentially very attractive. In this study, an equivalent MR model of an existing aircraft landing gear is developed. This includes a dynamic model of an MR shock strut, which accounts for the effects of fluid compressibility. This is important in impulsive loading applications such as landing gear, as fluid compression will reduce device controllability. Using the model, numerical impact simulations are performed to illustrate the performance of the optimized MR shock strut, and hence the effectiveness of the proposed design methodology. Part 2 of this contribution focuses on experimental validation.
Institute of Physics
2007-12
Article
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/8862/2/simsnd1.pdf
Batterbee, D.C., Sims, N.D., Stanway, R. et al. (1 more author) (2007) Magnetorheological landing gear: 1. A design methodology. Smart Materials and Structures, 16 (6). pp. 2429-2440. ISSN 0964-1726
http://dx.doi.org/10.1088/0964-1726/16/6/046
doi:10.1088/0964-1726/16/6/046
oai:eprints.whiterose.ac.uk:8871
2014-06-06T07:32:30Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8871/
Analytical prediction of chatter stability for variable pitch and variable helix milling tools
Sims, N.D.
Mann, B.
Huyanan, S.
Regenerative chatter is a self-excited vibration that can occur during milling and other machining processes. It leads to a poor surface finish, premature tool wear, and potential damage to the machine or tool. Variable pitch and variable helix milling tools have been previously proposed to avoid the onset of regenerative chatter. Although variable pitch tools have been considered in some detail in previous research, this has generally focussed on behaviour at high radial immersions. In contrast there has been very little work focussed on predicting the stability of variable helix tools. In the present study, three solution processes are proposed for predicting the stability of variable pitch or helix milling tools. The first is a semi-discretisation formulation that performs spatial and temporal discretisation of the tool. Unlike previously published methods this can predict the stability of variable pitch or variable helix tools, at low or high radial immersions. The second is a time-averaged semi-discretisation formulation that assumes time-averaged cutting force coefficients. Unlike previous work, this can predict stability of variable helix tools at high radial immersion. The third is a temporal-finite element formulation that can predict the stability of variable pitch tools with a constant uniform helix angle, at low radial immersion. The model predictions are compared to previously published work on variable pitch tools, along with time-domain model simulations. Good agreement is found with both previously published results and the time-domain model. Furthermore, cyclic-fold bifurcations were found to exist for both variable pitch and variable helix tools at lower radial immersions.
Elsevier
2008-11-11
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8871/2/JSV-D-07-01187.pdf
Sims, N.D., Mann, B. and Huyanan, S. (2008) Analytical prediction of chatter stability for variable pitch and variable helix milling tools. Journal of Sound and Vibration, 317 (3-5). pp. 664-686. ISSN 0022-460X
http://dx.doi.org/doi:10.1016/j.jsv.2008.03.045
doi:10.1016/j.jsv.2008.03.045
oai:eprints.whiterose.ac.uk:8881
2013-02-08T16:58:39Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8881/
Temperature sensitive controller performance of MR dampers
Batterbee, D.
Sims, N.D.
Magnetorheological (MR) dampers can experience large temperature changes as a result of heating caused by energy dissipation, but control systems are often designed without consideration of this fact. Furthermore, due to the highly nonlinear behavior of MR dampers, many control strategies have been proposed and it is difficult to determine which is the most effective. This paper aims to address these issues through a numerical and experimental study of an MR mass isolator subject to temperature variation. A dynamic temperature dependant model of an MR damper is first developed and validated. Control system experiments are then performed using hardware-in-the-loopsimulations. Proportional, PID, gain scheduling, and on/off control strategies are found to be equally affected by temperature variation. Using simulations incorporating the temperature dependant MR damper model, it is shown that this is largely due to a change in fluid viscosity and the associated movement of the lower clipped optimal' control bound. This zero-volts condition determines how close any controller can perform to the ideal semiactive case, thus all types of controller are affected. In terms of relative performance, proportional and PID controllers perform equally well and outperform the on/off and gain scheduling strategies. Gain scheduling methods are superior to on/off control.
Sage
2009-02-11
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8881/2/JIM093824_Modified_Original.pdf
Batterbee, D. and Sims, N.D. (2009) Temperature sensitive controller performance of MR dampers. Journal of Intelligent Material Systems and Structures, 20 (3). pp. 297-309. ISSN 1045-389X
http://dx.doi.org/10.1177/1045389X08093824
doi:10.1177/1045389X08093824
oai:eprints.whiterose.ac.uk:8882
2013-02-08T16:58:40Z
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74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/8882/
Energy harvesting from the nonlinear oscillations of magnetic levitation
Mann, B.P.
Sims, N.D.
This paper investigates the design and analysis of a novel energy harvesting device that uses magnetic levitation to produce an oscillator with a tunable resonance. The governing equations for the mechanical and electrical domains are derived to show the designed system reduces to the form of a Duffing oscillator under both static and dynamic loads. Thus, nonlinear analyses are required to investigate the energy harvesting potential of this prototypical nonlinear system. Theoretical investigations are followed by a series of experimental tests that validate the response predictions. The motivating hypothesis for the current work was that nonlinear phenomenon could be exploited to improve the effectiveness of energy harvesting devices.
Elsevier
2009-01-09
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8882/2/EnergHarv_MagSuspFinal.pdf
Mann, B.P. and Sims, N.D. (2009) Energy harvesting from the nonlinear oscillations of magnetic levitation. Journal of Sound and Vibration, 319 (1-2). pp. 515-530. ISSN 0022-460X
http://dx.doi.org/10.1016/j.jsv.2008.06.011
doi:10.1016/j.jsv.2008.06.011
oai:eprints.whiterose.ac.uk:8900
2014-09-15T01:35:40Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4154
696E737469747574696F6E3D536865666669656C64
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https://eprints.whiterose.ac.uk/8900/
Thaumasite form of sulfate attack in limestone cement mortars: A study on long term efficiency of mineral admixtures
Skaropoulou, A.
Tsivilis, S.
Kakali, G.
Sharp, J.
Swamy, R.
Concrete and mortar made from limestone cement may exhibit a lack of durability due to the formation of thaumasite. The addition of minerals that improve the concrete durability is expected to slow down the formation of thaumasite. in this work the effect of natural pozzolana, fly ash, ground granulated blast-furnace slag and metakaolin on the thaumasite formation in limestone cement mortar is examined. A limestone cement, containing 15% w/w limestone, was used. Mortar specimens were prepared by replacing a part of limestone cement with the above minerals. The specimens were immersed in a 1.8% MgSO4 solution and cured at 5 and 25 degrees C. The status of the samples after a storage period of 5 years was reported based on visual inspection, compressive strength, mass measurements, ultrasonic pulse velocity measurements and analytical techniques. It is concluded that the use of specific minerals, as partial replacement of cement, inhibits thaumasite formation in limestone cement mortar. (C) 2008 Elsevier Ltd. All rights reserved.
Elsevier
2009-06
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/8900/2/Swamyrn1.pdf
Skaropoulou, A., Tsivilis, S., Kakali, G. et al. (2 more authors) (2009) Thaumasite form of sulfate attack in limestone cement mortars: A study on long term efficiency of mineral admixtures. Construction and Building Materials, 23 (6). pp. 2338-2345. ISSN 0950-0618
http://dx.doi.org/10.1016/j.conbuildmat.2008.11.004
10.1016/j.conbuildmat.2008.11.004
oai:eprints.whiterose.ac.uk:9083
2013-02-08T16:58:53Z
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696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9083/
The influence of laser hardening on wear in the valve and valve seat contact
Slatter, T.
Taylor, H.
Lewis, R.
King, P.
In internal combustion engines it is important to manage the wear in the valve and valve seat contact in order to minimise emissions and maximise economy. Traditionally wear in this contact has been controlled by the use of a valve seat insert and the careful selection of materials for both the valve and the insert. More recently, due to the increasing demands for both performance and cost, alternative methods of controlling the wear, and the resulting valve recession, have been sought. Using the heating effect of a laser to induce localised phase transformations, to increase hardness and wear resistance, in materials has been used since the 1970s, however it is only in recent years that it has been able to compete with more established surface treatment techniques, particularly in terms of cost, as new laser hardware has been developed. In this work, a laser has been used to treat the valve seat area of a cast iron cylinder head. In order to optimise the laser parameters for use on the head, preliminary tests were carried out to investigate the fundamental wear characteristics of untreated cast iron and also cast iron with a range of laser treatments. Previous work has identified the predominant wear mechanism in the valve and valve seat contact as impact on valve closure. Two bespoke test machines, one for testing basic specimens and one for testing components, were used to identify the laser parameters most likely to yield acceptable results when applied to a cylinder head to be used in a fired dynamometer test. © 2009 Elsevier B.V. All rights reserved.
Elsevier
2009-06-15
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9083/2/Slatter1.pdf
Slatter, T., Taylor, H., Lewis, R. et al. (1 more author) (2009) The influence of laser hardening on wear in the valve and valve seat contact. Wear, 267 (5-8). pp. 797-806. ISSN 00431648
http://dx.doi.org/10.1016/j.wear.2009.01.040
doi:10.1016/j.wear.2009.01.040
oai:eprints.whiterose.ac.uk:9084
2013-02-08T16:58:54Z
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696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9084/
Valve recession: From experiment to predictive model
Lewis, R.
Dwyer-Joyce, R.S.
Slatter, T.
Brooks, A.
Increasing demands on engine performance and cost reductions have meant that advances made in materials and production technology are often outpaced This frequently results in wear problems occurring with engine components. Few models exist for predicting wear, and consequently each wear problem has to be investigated, the cause isolated and remedial action taken. The objective of this work was to carry out experimental studies to investigate valve and seat insert wear mechanisms and use the test results to develop a recession prediction tool to assess the potential for valve recession and solve problems that occur more quickly. Experimental apparatus has been developed that is capable of providing a valid simulation of the wear of diesel automotive inlet valves and seats. Test methodologies developed have isolated the effects of impact and sliding. A semi-empirical wear model for predicting valve recession has been developed based on data gathered during the bench testing. A software program, RECESS, was developed to run the model. Model predictions are compared with engine dynamometer tests and bench tests. The model can be used to give a quantitative prediction of the valve recession to be expected with a particular material pair or a qualitative assessment of how parameters need to be altered in order to reduce recession. The valve recession model can be integrated into an industrial environment in order to help reduce costs and timescales involved in solving valve/seat wear problems.
VDI The Association of German Engineers
2004
Article
NonPeerReviewed
text
en
https://eprints.whiterose.ac.uk/9084/2/Slatter2.pdf
Lewis, R., Dwyer-Joyce, R.S., Slatter, T. et al. (1 more author) (2004) Valve recession: From experiment to predictive model. VDI Berichte (1813). pp. 79-93. ISSN 0083-5560
oai:eprints.whiterose.ac.uk:9112
2013-02-08T16:58:53Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9112/
Explicit equations for leak rates through narrow cracks
Beck, S.B.M.
Bagshaw, N.M.
Yates, J.R.
Explicit equations to describe the leak rate of a single phase fluid through a narrow crack under a low pressure gradient have been developed and are presented. Four distinct flow regimes, which change with crack opening displacement, have been previously identified and are the basis of this model. The fluid flow is governed by the pressure gradient and the tortuosity of the crack, which is particularly important when the opening displacement is small. The equations have been developed by considering the pressure forces created when the fluid flows down an idealized zig-zag channel. The nature of the flow, and hence the governing equations, change as the crack aperture increases. The power of this approach is clearly seen when the flow rates predicted using this model are compared both to the flow rates obtained from computational fluid dynamics analysis and those found by experimentation. The agreement between these sets of data is good, showing that the major effects governing the flow rate have been identified and then accounted for.
Elsevier
2005-07
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9112/2/FFEMS.pdf
Beck, S.B.M., Bagshaw, N.M. and Yates, J.R. (2005) Explicit equations for leak rates through narrow cracks. International Journal of Pressure Vessels and Piping, 82 (7). pp. 565-570. ISSN 0308-0161
http://dx.doi.org/10.1016/j.ijpvp.2004.12.005
doi:10.1016/j.ijpvp.2004.12.005
oai:eprints.whiterose.ac.uk:9113
2014-06-04T10:48:39Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9113/
Energy consumption and capacity utilization of galvanizing furnaces
Blakey, S.G.
Beck, S.B.M.
An explicit equation leading to a method for improving furnace efficiency is presented. This equation is dimensionless and can be applied to furnaces of any size and fuel type for the purposes of comparison. The implications for current furnace design are discussed. Currently the technique most commonly used to reduce energy consumption in galvanizing furnaces is to increase burner turndown. This is shown by the analysis presented here actually to worsen the thermal efficiency of the furnace, particularly at low levels of capacity utilization. Galvanizing furnaces are different to many furnaces used within industry, as a quantity of material (in this case zinc) is kept molten within the furnace at all times, even outside production periods. The dimensionless analysis can, however, be applied to furnaces with the same operational function as a galvanizing furnace, such as some furnaces utilized within the glass industry. © IMechE 2004.
Professional Engineering Publishing
2004
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9113/2/becksbm9.pdf
Blakey, S.G. and Beck, S.B.M. (2004) Energy consumption and capacity utilization of galvanizing furnaces. Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering, 218 (4). pp. 251-259. ISSN 2041-3009
http://dx.doi.org/10.1243/0954408042466927
doi:10.1243/0954408042466927
oai:eprints.whiterose.ac.uk:9114
2013-02-08T16:58:53Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9114/
Development of the orifice plate with a cone swirler flow conditioner
Ahmadi, A.
Beck, S.B.M.
Purpose - The sensitivity of orifice plate metering to poorly conditioned and swirling flows are subjects of concerns to flow meter users and manufacturers. The distortions caused by pipe fittings and pipe installations upstream of the orifice plate are major sources of this type of non-standard flows. These distortions will alter the accuracy of metering up to an unacceptable degree. Design/methodology/approach - The design of orifice plate meters that are independent of the initial flow conditions of the upstream is a major object of flow metering. Either using a long straight pipe or a flow conditioner upstream of an orifice plate usually achieves this goal. The effect of cone swirler flow conditioner for both standard and non-standard flow conditions has been carried out in the experimental rig. The measuring of mass flow rate under different conditions and different Reynolds numbers were used to establish a change in discharge coefficient relative to a standard one. Findings - The experimental results using the cone swirler flow conditioner showed that the combination of an orifice plate and cone swirler flow conditioner is broadly insensitive to upstream disturbances. The results clearly show that this flow conditioner can attenuate the effect of both swirling and asymmetric flows on metering to an acceptable level. Originality/value - Previous work on the orifice plate has shown that the concept has promise. The results of using a combination of a cone swirler and orifice plate for non-standard flow conditions including swirling flow and asymmetric flow show this package can preserve the accuracy of metering up to the level required in the standards, providing that a new discharge coefficient is used for the combined swirler and orifice plate.
Emerald Group Publishing Limited
2005
Article
PeerReviewed
text
en
cc_by_nc_4
https://eprints.whiterose.ac.uk/9114/2/Beck_s.b.m._6.pdf
Ahmadi, A. and Beck, S.B.M. (2005) Development of the orifice plate with a cone swirler flow conditioner. Sensor Review, 25 (1). pp. 63-68. ISSN 02602288
http://dx.doi.org/10.1108/02602280510577861
doi:10.1108/02602280510577861
oai:eprints.whiterose.ac.uk:9115
2013-02-08T16:58:53Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9115/
Pipeline network features and leak detection by cross-correlation analysis of reflected waves
Beck, S.B.M.
Curren, M.D.
Sims, N.D.
Stanway, R.
This paper describes progress on a new technique to detect pipeline features and leaks using signal processing of a pressure wave measurement. Previous work (by the present authors) has shown that the analysis of pressure wave reflections in fluid pipe networks can be used to identify specific pipeline features such as open ends, closed ends, valves, junctions, and certain types of bends. It was demonstrated that by using an extension of cross-correlation analysis, the identification of features can be achieved using fewer sensors than are traditionally employed. The key to the effectiveness of the technique lies in the artificial generation of pressure waves using a solenoid valve, rather than relying upon natural sources of fluid excitation. This paper uses an enhanced signal processing technique to improve the detection of leaks. It is shown experimentally that features and leaks can be detected around a sharp bend and up to seven reflections from features/ leaks can be detected, by which time the wave has traveled over 95 m. The testing determined the position of a leak to within an accuracy of 5%, even when the location of the reflection from a leak is itself dispersed over a certain distance and, therefore, does not cause an exact reflection of the wave.
American Society of Civil Engineers
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9115/1/Beck_s.b.m_5.pdf
Beck, S.B.M., Curren, M.D., Sims, N.D. et al. (1 more author) (2005) Pipeline network features and leak detection by cross-correlation analysis of reflected waves. Journal of Hydraulic Engineering, 131 (8). pp. 715-723. ISSN 07339429
http://dx.doi.org/10.1061/(ASCE)0733-9429(2005)131:8(715)
doi:10.1061/(asce)0733-9429(2005)131:8(715)
oai:eprints.whiterose.ac.uk:9116
2013-02-08T16:59:01Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9116/
An integrated approach to modelling the fluid-structure interaction of a collapsible tube
Scroggs, R.A.
Beck, S.B.M.
Patterson, E.A.
The well known collapsible tube experiment was conducted to obtain flow, pressure and materials property data for steady state conditions. These were then used as the boundary conditions for a fully coupled fluid-structure interaction (FSI) model using a propriety computer code, LS-DYNA. The shape profiles for the tube were also recorded. In order to obtain similar collapse modes to the experiment, it was necessary to model the tube flat, and then inflate it into a circular profile, leaving residual stresses in the walls. The profile shape then agreed well with the experimental ones. Two departures from the physical properties were required to reduce computer time to an acceptable level. One of these was the lowering of the speed of sound by two orders of magnitude which, due to the low velocities involved, still left the mach number below 0.2. The other was to increase the thickness of the tube to prevent the numerical collapse of elements. A compensation for this was made by lowering the Young's modulus for the tube material. Overall the results are qualitatively good. They give an indication of the power of the current FSI algorithms and the need to combine experiment and computer models in order to maximise the information that can be extracted both in terms of quantity and quality.
The Japan Society of Mechanical Engineers
2004
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9116/1/Beck_s.b.m_8.pdf
Scroggs, R.A., Beck, S.B.M. and Patterson, E.A. (2004) An integrated approach to modelling the fluid-structure interaction of a collapsible tube. JSME International Journal, Series B: Fluids and Thermal Engineering, 47 (1). pp. 20-28. ISSN 1340-8054
http://dx.doi.org/10.1299/jsmeb.47.20
doi:10.1299/jsmeb.47.20
oai:eprints.whiterose.ac.uk:9117
2013-02-08T16:58:53Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9117/
Experiment and modelling of birefringent flows using commercial CFD code
Tomlinson, R.A.
Pugh, D.
Beck, S.B.M.
It is well-known that certain fluids are birefringent and when flows are viewed in polarised light interference fringes are observed. The fringes are caused by a phase shift in the light passing through the fluid and are proportional to the integral of the maximum shear strains in the fluid. In order to understand what is happening within the three dimensional flow and overcome the difficulties due to this integration, additional computational or experimental information is needed. In this work, a commercially available computer code (Fluent) is used for the first time to model the flows. The flow data are then exported to a spreadsheet where the shear rates are integrated across the field and then banded for graphical output. The results from this are then compared to results generated from birefringent flow experiments and the agreement is found to be good since the modelled fringes show the same patterns as those in the experiment. This novel use of computational and experimental techniques together will allow quantitative analysis of three-dimensional flows in the future. Currently, there are still a lot of empirical variables involved in fitting the computational fringes to the experiment, but the results of this preliminary study show that this is a promising approach to this type of problem.
Elsevier
2006
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9117/1/Beck_s.b.m_3.pdf
Tomlinson, R.A., Pugh, D. and Beck, S.B.M. (2006) Experiment and modelling of birefringent flows using commercial CFD code. International Journal of Heat and Fluid Flow, 27 (6). pp. 1054-1060. ISSN 0142727X
http://dx.doi.org/10.1016/j.ijheatfluidflow.2006.01.007
doi:10.1016/j.ijheatfluidflow.2006.01.007
oai:eprints.whiterose.ac.uk:9118
2014-06-27T22:22:55Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
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7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9118/
Leak detection in pipeline networks using low-profile piezoceramic transducers
Taghvaei, M.
Beck, S.B.M.
Staszewski, W.J.
Detecting leaks in pipeline networks such as water distribution systems is an important, yet difficult task. Various techniques have been developed for leak detection, but so far none has provided a suitable solution for industrial applications, as they have low performance or high cost. An experimental method based on pressure measurements has previously been developed to identify leaks which involve first removing the noise with orthogonal wavelets and then applying cepstrum analysis to identify features in the physical network. This previous work has shown that this approach is capable of both locating the position and estimating the severity of leaks in pipeline networks. This study involves an experiment with a simple fluid filled pipeline network. A solenoid valve is used to introduce a pressure wave into the network. By periodically opening and closing the valve the wave propagates in the fluid. This pressure wave is then sensed by a low-profile piezoceramic transducer. A conventional pressure transducer is also used for comparative studies. The experiment is performed for different pipe lengths and severities of leakage. This work shows that while the piezoceramic transducer is poor at recording accurate pressure histories, it is perfectly acceptable for this type of condition monitoring, being able to identify the position and severity of leaks and other features in the pipeline network.
John Wiley & Sons
2007
Article
PeerReviewed
Taghvaei, M., Beck, S.B.M. and Staszewski, W.J. (2007) Leak detection in pipeline networks using low-profile piezoceramic transducers. Structural Control and Health Monitoring, 14 (8). pp. 1063-1082. ISSN 15452255
http://dx.doi.org/10.1002/stc.187
doi:10.1002/stc.187
oai:eprints.whiterose.ac.uk:9119
2009-08-13T10:27:08Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9119/
From cystic duct to static mixer: A serendipitous journey via flow visualization
Al-Atabi, M.
Chin, S.B.
Beck, S.B.M.
Boucher, R.F.
The cystic duct is a very complicated conduit that connects the gallbladder to the common bile duct. The geometry of the of the cystic duct and its functions, in particular the valves of Heister, in the flow of bile into and out of the gallbladder have always been a subject of speculation. It has been suggested variously that their function is to: impede the flow of bile into the gallbladder, prevent the outflow of bile from the gallbladder, or prevent the collapse of cystic duct.
Presented in this paper is the results of a novel experiment to assess the role of the valves of Heister during both the filling and the emptying phases of the gallbladder. The results suggest that the existence of these valves helps both the filling and the emptying of the gallbladder by providing structural support and preventing the duct from total collapse. A surge of pressure upstream of the cystic duct is observed prior to the opening of the cystic duct which is consistent with previous in-vivo biological observations
IOS Press
2007-04
Article
PeerReviewed
Al-Atabi, M., Chin, S.B., Beck, S.B.M. et al. (1 more author) (2007) From cystic duct to static mixer: A serendipitous journey via flow visualization. Journal of Visualization, 10 (2). pp. 141-144. ISSN 1343-8875
http://iospress.metapress.com/content/y241q25515guk272/
oai:eprints.whiterose.ac.uk:9162
2013-02-08T16:58:54Z
7374617475733D707562
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9162/
The mechanisms of pedestrian slip on flooring contaminated with solid particles
Mills, R.
Dwyer-Joyce, R.S.
Loo-Morrey, M.
Statistics by the UK Health and Safety Executive (HSE) suggest that slips, trips and falls account for up to one in three major workplace accidents. The vast majority of these accidents are the result of contaminant (fluid or solid) within the shoe-floor contact. Though the lubrication mechanisms for liquid contaminants within the contact are well understood, the same cannot be said for particulate contaminants. This paper considers the key parameters controlling friction in a shoe-floor contact contaminated with various particles of different diameters and shape factors and floors with different roughness values (Rz). Experiments were conducted using a Stanley Pendulum Tester, which is the floor friction tester recommended by the HSE. Results suggest that the adhesive friction is significantly affected by particulate contaminants, while the hysteretic component is not. Three lubrication mechanisms identified as sliding, shearing and rolling have been observed depending on floor roughness, particle size and shape factor and have been plotted in a simple map to predict behaviour.
Elsevier Science B.V., Amsterdam.
2009-03
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9162/1/1_trib_int_slipping_paper_-_pre_submit.pdf
Mills, R., Dwyer-Joyce, R.S. and Loo-Morrey, M. (2009) The mechanisms of pedestrian slip on flooring contaminated with solid particles. Tribology International, 42 (3). pp. 403-412. ISSN 0301679X
http://dx.doi.org/10.1016/j.triboint.2008.07.013
doi:10.1016/j.triboint.2008.07.013
oai:eprints.whiterose.ac.uk:9163
2013-02-08T16:58:54Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9163/
Auto-calibration of ultrasonic lubricant-film thickness measurements
Reddyhoff, T.
Dwyer-Joyce, R.S.
Zhang, J.
Drinkwater, B.W.
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.
IOP Publishing Ltd
2007
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9163/1/J_Meas_Sci_2007_pre-submit.pdf
Reddyhoff, T., Dwyer-Joyce, R.S., Zhang, J. et al. (1 more author) (2007) Auto-calibration of ultrasonic lubricant-film thickness measurements. Measurement Science and Technology, 19 (4). Art. No. 045402. ISSN 0957-0233
http://dx.doi.org/10.1088/0957-0233/19/4/045402
doi:10.1088/0957-0233/19/4/045402
oai:eprints.whiterose.ac.uk:9164
2013-02-08T16:58:54Z
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696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9164/
A new approach for the measurement of film thickness in liquid face seals
Reddyhoff, T.
Dwyer-Joyce, R.S.
Harper, P.
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.
Taylor & Francis
2008
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9164/1/4_Reddyhoff_DJ_Harper_face_seal_film_Trib_Trans_2008.pdf
Reddyhoff, T., Dwyer-Joyce, R.S. and Harper, P. (2008) A new approach for the measurement of film thickness in liquid face seals. Tribology Transactions, 51 (2). pp. 140-149. ISSN 10402004
doi:10.1080/10402000801918080
oai:eprints.whiterose.ac.uk:9165
2013-02-08T16:58:54Z
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696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9165/
Viscosity measurement in thin lubricant films using shear ultrasonic reflection
Kasolang, S.
Dwyer-Joyce, R.S.
When a shear ultrasonic wave is incident on a solid and liquid boundary, the proportion that is reflected depends on the liquid viscosity. This is the basis for some instruments for on-line measurement of bulk liquid viscosity. In machine elements, the lubricant is usually present in a thin layer between two rubbing solid surfaces. The thin film has a different response to an ultrasonic shear wave than liquid in bulk. In this work, this response is investigated with the aim of measuring viscosity in situ in a lubricating film. The proportion of the wave reflected at a thin layer depends on the layer stiffness. A shear wave is reflected by the shear stiffness of the thin layer. For a thin viscous liquid layer, the stiffness is a complex quantity dependent on the viscosity, wave frequency, and film thickness. This stiffness is incorporated into a quasi-static spring model of ultrasonic reflection. In this way, the viscosity can be determined from shear-wave reflection if the oil-film thickness is known. The approach has been experimentally evaluated on some static oil film between Perspex plates. Predictions of the spring model gave good measurement up to layer thicknesses of around 15 μm. For thicker layers, the shear stiffness reduces to such an extent that almost all the wave is reflected and the difference associated with the layer response is hard to distinguish from background noise.
Professional Engineering Publishing
2008
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9165/1/5_Kasolang_DJ_shear_us_and_thin_film_viscosity_IMechE_pt_J.pdf
Kasolang, S. and Dwyer-Joyce, R.S. (2008) Viscosity measurement in thin lubricant films using shear ultrasonic reflection. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 222 (3). pp. 423-429. ISSN 13506501
http://dx.doi.org/10.1243/13506501jet382
doi:10.1243/13506501jet382
oai:eprints.whiterose.ac.uk:9167
2013-02-08T16:58:55Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9167/
Ultrasonic oil-film thickness measurement: An angular spectrum approach to assess performance limits
Zhang, J.
Drinkwater, B.W.
Dwyer-Joyce, R.S.
The performance of ultrasonic oil-film thickness measurement in a ball bearing is quantified. A range of different viscosity oils (Shell T68, VG15, and VG5) are used to explore the lowest reflection coefficient and hence the thinnest oil-film thickness that the system can measure. The results show a minimum reflection coefficient of 0.07 for both oil VG15 and VG5 and 0.09 for oil T68 at 50 MHz. This corresponds to an oil-film thickness of 0.4 μm for T68 oil. An angular spectrum (or Fourier decomposition) approach is used to analyze the performance of this configuration. This models the interaction of component plane waves with the measurement system and quantifies the effect of the key parameters (transducer aperture, focal length, and center frequency). The simulation shows that for a focused transducer the reflection coefficient tends to a limiting value at small oil-film thickness. For the transducer used in this paper it is shown that the limiting reflection coefficient is 0.05 and the oil-film measurement errors increase as the reflection coefficient approaches this value. The implications for improved measurement systems are then discussed.
Acoustical Society of America
2007-05
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9167/1/7_Zhang_et_al_Jasa_2007_pre-submit.pdf
Zhang, J., Drinkwater, B.W. and Dwyer-Joyce, R.S. (2007) Ultrasonic oil-film thickness measurement: An angular spectrum approach to assess performance limits. Journal of the Acoustical Society of America, 121 (5). pp. 2612-2620. ISSN 00014966
http://dx.doi.org/10.1121/1.2713676
doi:10.1121/1.2713676
oai:eprints.whiterose.ac.uk:9168
2013-02-08T16:58:55Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9168/
Particle motion and stain removal during simulated abrasive tooth cleaning
Lewis, R.
Barber, S.C.
Dwyer-Joyce, R.S.
Stain removal from teeth is important both to prevent decay and for appearance. This is usually achieved using a filament-based toothbrush with a toothpaste consisting of abrasive particles in a carrier fluid. This work has been carried out to examine how these abrasive particles interact with the filaments and cause material removal from a stain layer on the surface of a tooth. It is important to understand this mechanism as while maximum cleaning efficiency is required, this must not be accompanied by damage to the enamel or dentine substrate. In this work simple abrasive scratch tests were used to investigate stain removal mechanism of two abrasive particles commonly used in tooth cleaning, silica and perlite. Silica particles are granular in shape and very different to perlite particles, which are flat and have thicknesses many times smaller than their width. Initially visualisation studies were carried out with perlite particles to study how they are entrained into a filament/counterface contact. Results were compared with previous studies using silica. Reciprocating scratch tests were then run to study how many filaments have a particle trapped at one moment and are involved in the cleaning process. Stain removal tests were then carried out in a similar manner to establish cleaning rates with the two particle types. Perlite particles were found to be less abrasive than silica. This was because of their shape and how they were entrained into the filament contacts and loaded against a counterface. With both particles subsurface damage during stain removal was found to be minimal. A simple model was built to predict stain removal rates with silica particles, which gave results that correlated well with the experimental data.
Elsevier Science B.V., Amsterdam.
2007-09-10
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9168/1/8_lewis_et_al_stain_removal_wear_2005.pdf
Lewis, R., Barber, S.C. and Dwyer-Joyce, R.S. (2007) Particle motion and stain removal during simulated abrasive tooth cleaning. Wear, 263 (1-6 SP). pp. 188-197. ISSN 0043-1648
http://dx.doi.org/10.1016/j.wear.2006.12.023
doi:10.1016/j.wear.2006.12.023
oai:eprints.whiterose.ac.uk:9169
2013-02-08T16:58:54Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9169/
Acoustic measurement of lubricant-film thickness distribution in ball bearings
Zhang, J.
Drinkwater, B.W.
Dwyer-Joyce, R.S.
An oil-film thickness monitoring system capable of providing an early warning of lubrication failure in rolling element bearings has been developed. The system is used to measure the lubricant-film thickness in a conventional deep groove ball bearing (shaft diameter 80 mm, ball diameter 12.7 mm). The measurement system comprises a 50 MHz broadband ultrasonic focused transducer mounted on the static outer raceway of the bearing. Typically the lubricant-films in rolling element bearings are between 0.1-1.0 μm in thickness and so are significantly smaller than the ultrasonic wavelength. A quasistatic spring model is used to calculate oil-film thickness from the measured reflection coefficient data. An accurate triggering system has been developed to enable multiple reflection coefficient measurements to be made as the contact ellipse sweeps over the measurement location. Experiments are described in which the loading conditions and rotational speed are varied. Lubricant-film thickness distributions measured ultrasonically are described and are shown to agree well with the predictions from classical elastohydrodynamic (EHD) lubrication theory, particularly at high radial loads and low rotary speeds. A range of parameters affecting the performance of the measurement are discussed and the limits of operation of the measurement technique defined. © 2006 Acoustical Society of America.
Acoustical Society of America
2006-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9169/1/10_Zhang_et_al_JASA_pre-submit.pdf
Zhang, J., Drinkwater, B.W. and Dwyer-Joyce, R.S. (2006) Acoustic measurement of lubricant-film thickness distribution in ball bearings. Journal of the Acoustical Society of America, 119 (2). pp. 863-871. ISSN 0001-4966
http://dx.doi.org/10.1121/1.2146109
doi:10.1121/1.2146109
oai:eprints.whiterose.ac.uk:9170
2013-02-08T16:59:38Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9170/
Monitoring of lubricant film failure in a ball bearing using ultrasound
Zhang, J.
Drinkwater, B.W.
Dwyer-Joyce, R.S.
A lubricant-film monitoring system for a conventional deep groove ball bearing (type 6016, shaft diameter 80 mm, ball diameter 12.7 mm) is described. A high-firequency (50 MHz) ultrasonic transducer is mounted on the static outer raceway of the bearing. The transducer is focused on the ball-raceway interface and used to measure the reflection coefficient of the lubricant in the "contact" ellipse between bearing components. The reflection coefficient characterizes the lubricant film and can be used to calculate its thickness. An accurate triggering system enables multiple reflection measurements to be made as each lubricated contact moves past the measurement location. Experiments are described in which bearings were deliberately caused to fail by the addition of acetone, water and sand to the lubricant. The ultrasonic reflection coefficient was monitored as a function of time as the failure occurred. Also monitored were the more standard parameters, temperature and vibration. The results indicate that the ultrasonic measurements are able to detect the failures before seizure. It is also observed that, when us,ed in parallel, these monitoring techniques offer the potential to diagnose the failure mechanism and hence improve predictions of remaining life.
American Society Mechanical Engineers
2006-07
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9170/1/11_Ultrasound__bearing_failures_text_corrected_pre-print%5B1%5D.pdf
Zhang, J., Drinkwater, B.W. and Dwyer-Joyce, R.S. (2006) Monitoring of lubricant film failure in a ball bearing using ultrasound. Journal of Tribology, 128 (3). pp. 612-618. ISSN 0742-4787
http://dx.doi.org/10.1115/1.2197848
doi:10.1115/1.2197848
oai:eprints.whiterose.ac.uk:9172
2013-02-08T16:58:55Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9172/
Characterisation of contact pressure distribution in bolted joints
Marshall, M.B.
Lewis, R.
Dwyer-Joyce, R.S.
The quantification of contact area and pressure distribution in a bolted joint is essential information, as it determines the integrity of the coupling. Current bolted joint design standards are based on analytical solutions of the pressure distribution, which, because of the inherent assumptions, frequently do not accurately represent the real conditions in a joint. This study uses a nonintrusive ultrasonic technique to quantify the contact pressure distribution in a bolted connection. The advantage of this experimental technique is that the effect of actual contact conditions can be determined. An ultrasonic wave is focused onto the clamped interface, and the reflected sound signal recorded. In areas where the contact pressure is high, most of the ultrasound is transmitted, and the reflected sound signal is weak. Whereas, when the contact pressure is low, the vast majority of the ultrasound is reflected back. A parallel experimental calibration is then used to find the relationship between the reflected sound signal and contact pressure. In this way, the pressure distribution in a clamped interface is determined for a series of different bolt torques. Two different interfaces were investigated: the first consisted of two ground surfaces clamped together, and the second a turned profile pressed against a ground surface. The effect of a washer underneath the bolt head was also considered. The turned profile was found to cause the contact to spread; there was also a certain degree of fragmentation leading to higher peak pressures than in the ground interface case. With a washer positioned under the bolt head for the turned case, the clamping performance of the bolt was improved. Good agreement was found when comparing the ultrasonic measurements with previous studies, with respect to the spread of the contact pressure distribution. However, in this study, the peak contact pressure was found to occur away from the edge of the bolt hole, and to be influenced by the edge of the bolt head.
Blackwell Publishing Ltd
2006-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9172/1/15_Marshall_et_al_bolted_joints_Strain_2006_pre-submit.pdf
Marshall, M.B., Lewis, R. and Dwyer-Joyce, R.S. (2006) Characterisation of contact pressure distribution in bolted joints. Strain, 42 (1). pp. 31-43. ISSN 00392103
http://dx.doi.org/10.1111/j.1475-1305.2006.00247.x
doi:10.1111/j.1475-1305.2006.00247.x
oai:eprints.whiterose.ac.uk:9175
2013-02-08T16:58:55Z
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7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9175/
Wear effects and mechanisms of soot-contaminated automotive lubricants
Green, D.A.
Lewis, R.
Dwyer-Joyce, R.S.
A study has been carried out to investigate the influence of soot-contaminated automotive lubricants in the wear process of a simulated engine valve train contact. Previous research on this topic has been mainly performed from a chemical point of view in fundamental studies, with insufficient relevance to real engine conditions, i.e. load and geometry. This study investigates the conditions under which wear occurs through specimen testing. The objective of the work was to understand the wear mechanisms that occur within the contaminated contact zone, to help in future development of a predictive wear model to assist in the valve-train design process. The effects of soot in lubricants have been tested using a reciprocating test-rig specifically designed for this application, where a steel disc is held in a bath of oil and a steel ball (replicating a valve train contact) is attached to a reciprocating arm. The materials, contact geometry and loading conditions are all related to specific conditions experienced within an engine's valve train. The testing was carried out under various contact conditions, using carbon black as a soot simulant. Wear measurements were taken during the tests and wear scar morphology was studied. The results have revealed how varying lubrication conditions changes the wear rate of engine components and determines the wear mechanism that dominates for specific situations.
Professional Engineering Publishing
2006
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9175/1/18_Soot_Wear_draft_corrected.pdf
Green, D.A., Lewis, R. and Dwyer-Joyce, R.S. (2006) Wear effects and mechanisms of soot-contaminated automotive lubricants. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 220 (3). pp. 159-169. ISSN 1350-6501
http://dx.doi.org/10.1243/13506501jet140
doi:10.1243/13506501jet140
oai:eprints.whiterose.ac.uk:9176
2013-02-08T16:58:55Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9176/
Oil film measurement in polytetrafluoroethylene-faced thrust pad bearings for hydrogenerator applications
Dwyer-Joyce, R.S.
Harper, P.
Pritchard, J.
Drinkwater, B.W.
There is a growing trend in the replacement of the babbit facing in thrust pad bearings with a composite polytetrafluoroethylene (PTFE) surface layer. The PTFE-faced bearings have been shown to allow a greater specific pressure, reduce thermal crowning, and, in some cases, negate the need for an oil-lift (jacking) system. These designs of bearing require new methods for the measurement of oil film thickness both to assist in their development and for plant condition monitoring. In this work, an ultrasonic method of oil film measurement is evaluated for this purpose. An ultrasonic transducer is mounted on the back face of the thrust pad. Pulses are generated and transmitted through the pad material, bonding interlayer, and PTFE surface layer. The proportion of the wave that reflects back from the oil film layer is determined. This is then related to the oil film thickness using a series of calibration experiments and a spring stiffness model. In practice, the reflected signal is difficult to distinguish, in the time domain, from other internal reflections from the pad. Signals are compared with reflections when no oil film is present and processing is carried out in the frequency domain. Experiments have been performed on a full size PTFE-faced thrust pad destined for a hydroelectric power station turbine. The instrumented pad was installed in a test facility and subjected to a range of loading conditions both with and without oil lift. Although there were some problems with the robustness of the experimental procedure, oil films were successfully measured and used to study the effect of the oil-lift system on film formation. © IMechE 2006.
Professional Engineering Publishing
2006
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9176/1/20_PTFE_pad_oil_film.pdf
Dwyer-Joyce, R.S., Harper, P., Pritchard, J. et al. (1 more author) (2006) Oil film measurement in polytetrafluoroethylene-faced thrust pad bearings for hydrogenerator applications. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 220 (6). pp. 619-628. ISSN 0957-6509
http://dx.doi.org/10.1243/09576509jpe264
doi:10.1243/09576509jpe264
oai:eprints.whiterose.ac.uk:9177
2013-02-08T16:58:55Z
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74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9177/
An ultrasonic technique for the measurement of elastic properties of soft surface coatings
Dwyer-Joyce, R.S.
Hankinson, N.
The properties of thin layers of materials can be different from those in the bulk form. The response of a coating to any given load and its ability to remain bonded to the substrate will depend on its elastic modulus and Poisson's ratio. In this study a measurement method based on ultrasonic bulk wave reflection was evaluated. As a model system, a thin layer of polyethylene was pressed between two solid steel bodies. The reflection spectra of longitudinal and shear ultrasonic waves were recorded from the coating. The frequencies at which the layer resonates were measured and from this the wave speeds deduced. The Poisson's ratio can be determined from these two wave speeds and if the layer thickness is known the modulus is also available. The tests yielded reasonable values for both. This approach is only suitable if the layer can be made to resonate by the available ultrasonic frequencies; typically this will be the case for thicker coatings (tens of microns). Further, good coupling between the layer material and the steel bodies is necessary so that the interfaces do not themselves act to reflect ultrasound. This is better achieved with a smooth soft coating.
Elsevier Science B.V., Amsterdam
2006-04
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9177/1/21_Trib_Int_2005_-_soft_coating_props.pdf
Dwyer-Joyce, R.S. and Hankinson, N. (2006) An ultrasonic technique for the measurement of elastic properties of soft surface coatings. Tribology International, 39 (4). pp. 326-331. ISSN 0301679X
http://dx.doi.org/10.1016/j.triboint.2005.02.003
doi:10.1016/j.triboint.2005.02.003
oai:eprints.whiterose.ac.uk:9178
2009-08-18T17:19:13Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9178/
Calibration of the ultrasonic lubricant-film thickness measurement technique
Zhang, J.
Drinkwater, B.W.
Dwyer-Joyce, R.S.
This paper describes an experimental apparatus and procedure for the calibration of the ultrasonic lubricant-film thickness measurement technique. It also presents a study of the accuracy of the technique. The calibration apparatus is demonstrated on a three layer steel-mineral oil-steel system. This was chosen to be representative of a typical bearing system which is the industrial application of the technique. In such bearing systems the lubricant-film thickness typically ranges from 0.1 to 100 νm. The calibration apparatus uses a high precision piezoelectric displacement translator to controllably displace one of the steel surfaces relative to the other and hence alter the lubricant-film thickness by a known amount. Through-thickness resonant frequency measurements are then used to accurately measure a thick lubricant film (h > 10 νm). These resonant frequency measurements form the starting point of the calibration. The displacement translator is then used to reduce the lubricant-film thickness into the, more practically interesting, low micron range. In this range the amplitude of the measured reflection coefficient is used via a spring interface model to calculate the lubricant-film thickness. Issues of ultrasonic beam alignment and frequency of operation are discussed. A detailed study of the effect of reflection-coefficient errors on the resultant thickness measurement is presented. Practical guidelines for use of the calibration are then defined and calibration is demonstrated experimentally over the range 0.5-1.3 νm.
IOP Publishing Ltd
2005-09
Article
NonPeerReviewed
Zhang, J., Drinkwater, B.W. and Dwyer-Joyce, R.S. (2005) Calibration of the ultrasonic lubricant-film thickness measurement technique. Measurement Science and Technology, 16 (9). pp. 1784-1791. ISSN 0957-0233
http://dx.doi.org/10.1088/0957-0233/16/9/010
doi:10.1088/0957-0233/16/9/010
oai:eprints.whiterose.ac.uk:9179
2013-02-08T16:58:55Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9179/
The phase shift of an ultrasonic pulse at an oil layer and determination of film thickness
Reddyhoff, T.
Kasolang, S.
Dwyer-Joyce, R.S.
Drinkwater, B.W.
An ultrasonic pulse incident on a lubricating oil film in a machine element will be partially reflected and partially transmitted. The proportion of the wave amplitude reflected, termed the reflection coefficient, depends on the film thickness and the acoustic properties of the oil. When the appropriate ultrasonic frequency is used, the magnitude of the reflection coefficient can be used to determine the oil film thickness. However, the reflected wave has both a real component and an imaginary component, and both the amplitude and the phase are functions of the film thickness. The phase of the reflected wave will be shifted from that of the incident wave when it is reflected. In the present study, this phase shift is explored as the film changes and is evaluated as an alternative means to measure oil film thickness. A quas i-static theoretical model of the reflection response from an oil film has been, developed. This model relates the phase shift to the wave frequency and the film properties. Measurements of reflection coefficient from a static model oil film and also from a rotating journal bearing have been recorded. These have been used to determine the oil film thickness using both amplitude and phase shift methods. In both cases, the results agree closely with independent assessments of the oil film thickness. The model of ultrasonic reflection is further extended to incorporate mass and damping terms. Experiments show that both the mass and the internal damping of the oil films tested in this work have a negligible effect on ultrasonic reflection. A potentially v ery useful application for the simultaneous measurement of reflection coefficient amplitude and phase is that the data can be used to negate the need for a reference. The theoretical relationship between phase and amplitude is fitted to the data. An extrapolation is performed to determine the values of amplitude and phase for an infinitely thick layer. This is equivalent to the reference signal determined by measuring the reflection coefficient directly, but importantly does not require the materials to be separated. This provides a simple and effective means of continuously calibrating the film measurement approach.
Professional Engineering Publishing
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9179/1/25_IMechE_pt_J_phase_paper_2005.pdf
Reddyhoff, T., Kasolang, S., Dwyer-Joyce, R.S. et al. (1 more author) (2005) The phase shift of an ultrasonic pulse at an oil layer and determination of film thickness. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 219 (6). pp. 387-400. ISSN 1350-6501
http://dx.doi.org/10.1243/135065005x34044
doi:10.1243/135065005x34044
oai:eprints.whiterose.ac.uk:9180
2013-02-08T16:58:55Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9180/
Measurement of interface pressure in interference fits
Lewis, R.
Marshall, M.B.
Dwyer-Joyce, R.S.
When components such as bearings or gears are pressed onto a shaft, the resulting interference induces a pressure at the interface. The size of this pressure is important as many components fail because fatigue initiates from press-fit stress concentrations. The aim of the present work was to develop ultrasound as a tool for non-destructive determination of press-fit contact pressures. An interference fit interface behaves like a spring. If the pressure is high, there are few air gaps, so it is very stiff and allows transmission of an ultrasonic wave. If the pressure is low, then interface stiffness is lower and most ultrasound is reflected. A spring model was used to determine maps of contact stiffness from interference-fit ultrasonic reflection data. A calibration procedure was then used to determine the pressure. The interface contact pressure has been determined for a number of different press- and shrink-fit cases. The results show a central region of approximately uniform pressure with edge stress at the contact sides. The magnitude of the pressure in the central region agrees well with the elastic Lamé analysis. In the more severe press-fit cases, the surfaces scuffed which led to anomalies in the reflected ultrasound. These anomalies were associated with regions of surface damage at the interface. The average contact pressure in a shrink-fit and press-fit joint were similar. However, in the shrink-fit joint more uneven contact pressure was observed with regions of poor conformity. This could be because the action of pressing on a sleeve plastically smooths out long wavelength roughness, leading to a more conforming surface.
Professional Engineering Publishing
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9180/1/26_lewis_et_al_Fits_v1A.pdf
Lewis, R., Marshall, M.B. and Dwyer-Joyce, R.S. (2005) Measurement of interface pressure in interference fits. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 219 (2). pp. 127-139. ISSN 0954-4062
http://dx.doi.org/10.1243/095440605x8432
doi:10.1243/095440605x8432
oai:eprints.whiterose.ac.uk:9181
2013-02-08T16:58:55Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9181/
Wear of human teeth: a tribological perspective
Lewis, R.
Dwyer-Joyce, R.S.
The four main types of wear in teeth are attrition (enamel-on-enamel contact), abrasion (wear due to abrasive particles in food or toothpaste), abfraction (cracking in enamel and subsequent material loss), and erosion (chemical decomposition of the tooth). They occur as a result of a number of mechanisms including thegosis (sliding of teeth into their lateral position), bruxism (tooth grinding), mastication (chewing), toothbrushing, tooth flexure, and chemical effects. In this paper the current understanding of wear of enamel and dentine in teeth is reviewed in terms of these mechanisms and the major influencing factors are examined. In vitro tooth wear simulation and in vivo wear measurement and ranking are also discussed.
Professional Engineering Publishing
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9181/1/27_IMechE_J_2005_tooth_wear_review.pdf
Lewis, R. and Dwyer-Joyce, R.S. (2005) Wear of human teeth: a tribological perspective. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 219 (1). pp. 1-18. ISSN 1350-6501
http://dx.doi.org/10.1243/1350650053295394
doi:10.1243/1350650053295394
oai:eprints.whiterose.ac.uk:9182
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9182/
Evaluation of an ultrasonic method for measurement of oil film thickness in a hydraulic motor piston ring
Harper, P.
Dwyer-Joyce, R.S.
Sjodin, U.
Olofsson, U.
The efficiency of a hydraulic motor depends on the lubrication performance of the piston ring. If the film is too thin then wear occurs quickly, if it is too thick then oil is lost into the cylinder and efficiency is reduced. In this paper a technique for oil film measurement based on ultrasonic reflection is investigated. This has the potential to be used non-invasively on real components. An ultrasonic pulse will reflect from a thin film interposed between two solids. The proportion of the pulse that is reflected depends on the stiffness of the intermediate layer. If the acoustic properties of the film material are known, then the stiffness can readily be used to determine the film thickness. This principle has been employed for the piston ring lubrication case. A piston/cylinder test bench has been used to evaluate the ultrasonic method. A focusing piezo-electric transducer is mounted outside the cylinder and ultrasonic pulses reflected back from the inner bore. The variation of these pulses as the piston ring passes underneath is investigated and used to determine oil film thickness. Films in the range 0.7 to 1.3 μm were measured; the thickness did not depend strongly on either ring speed or sealed pressure. Several practical aspects were investigated such as, attenuation in the cylinder material, response time, and transducer resolution. Whilst this study demonstrated that film thickness measurement is feasible, there are a number of practical considerations that require further work, principally the focusing and coupling of the ultrasonic transducer and the response time.
Elsevier Science B.V.
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9182/1/28_Harper_et_al_Piston_Film.pdf
Harper, P., Dwyer-Joyce, R.S., Sjodin, U. et al. (1 more author) (2005) Evaluation of an ultrasonic method for measurement of oil film thickness in a hydraulic motor piston ring. Tribology and Interface Engineering Series, 48. pp. 305-312. ISSN 15723364
http://dx.doi.org/10.1016/S0167-8922(05)80032-X
doi:10.1016/S0167-8922(05)80032-X
oai:eprints.whiterose.ac.uk:9183
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9183/
Ultrasonic reflection from mixed liquid-solid contacts and the determination of interface stiffness
Gonzalez-Valadez, M.
Dwyer-Joyce, R.S.
Lewis, R.
In thin film or boundary lubricated contacts there is a possibility of potentially damaging asperity contact occurring. Whilst there are many models of this contact mechanism, experimental verification of the proportion of solid contact is difficult to achieve. Electrical methods will only indicate that contact has occurred. Whereas, optical methods can be used to determine the proportion of contact, but only when one surface is transparent. In this work the use of ultrasonic reflection is investigated as a means to analyse these types of mixed solid-liquid contacts. A pulse of ultrasound is partially reflected at the contact between two rough surfaces. The proportion of the wave reflected can be readily used to determine the stiffness of the interface. Experimental data has been obtained from grit-blasted surfaces pressed together, both with and without liquid at the interface. The interface stiffness can be modelled by two springs in series, one of them representing the solid contact stiffness, Ksolid and the other the stiffness of the liquid fluid, Kliquid. The variation of these stiffness values with contact pressure has been investigated. At this stage it is not possible to directly determine the proportion of liquid or solid contact from the stiffness. The results however, give qualitative comparisons and information about the approach of the surfaces and hence the mean thickness of the liquid layer at the interface.
Elsevier Science B.V.
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9183/1/29_Gonzalez_et_al_us_mixed.pdf
Gonzalez-Valadez, M., Dwyer-Joyce, R.S. and Lewis, R. (2005) Ultrasonic reflection from mixed liquid-solid contacts and the determination of interface stiffness. Tribology and Interface Engineering Series, 48. pp. 313-320. ISSN 15723364
http://dx.doi.org/10.1016/S0167-8922(05)80033-1
doi:10.1016/S0167-8922(05)80033-1
oai:eprints.whiterose.ac.uk:9184
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9184/
The application of ultrasonic NDT techniques in tribology
Dwyer-Joyce, R.S.
The use of ultrasonic reflection is emerging as a technique for studying tribological contacts. Ultrasonic waves can be transmitted non-destructively through machine components and their behaviour at an interface describes the characteristics of that contact. This paper is a review of the current state of understanding of the mechanisms of ultrasonic reflection at interfaces, and how this has been used to investigate the processes of dry rough surface contact and lubricated contact. The review extends to cover how ultrasound has been used to study the tribological function of certain engineering machine elements.
Professional Engineering Publishing
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9184/1/30_IMechE_J_2005_us_review.pdf
Dwyer-Joyce, R.S. (2005) The application of ultrasonic NDT techniques in tribology. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 219 (5). pp. 347-366. ISSN 1350-6501
http://dx.doi.org/10.1243/135065005x9763
doi:10.1243/135065005x9763
oai:eprints.whiterose.ac.uk:9185
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9185/
The life cycle of a debris particle
Dwyer-Joyce, R.S.
Debris particles exist in most lubrication systems; they are frequently responsible for the early failure of tribological machine elements. Particles come from the surrounding environment, or may be generated within the machine components. As the lubricant circulates, these particles get flushed into the machine elements. Contact pressures are lugh and oil films are small, so that the relatively large particles damage even the hardest gear, bearing, or cam surface. This damage can lead to contact fatigue or wear, and thus premature failure of the whole machine. Further, one failure can result in the generation of further wear debris, often in very great quantities, that then can have a knock-on effect in other parts of the lubricated system. This paper gives an overview of important features of the life cycle of a debris particle; entrainment of debris particles into a contact, resulting surface damage, shortened component life, and debris particle procreation by fatigue and wear. The debris life cycle coincides with the early mortality of the machine element. The methods by which component life, under particulate contaminated conditions, can be determined are reviewed.
Elsevier Science B.V.
2005
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9185/1/31_DJ__debris_life_cycle.pdf
Dwyer-Joyce, R.S. (2005) The life cycle of a debris particle. Tribology and Interface Engineering Series, 48. pp. 681-690. ISSN 15723364
http://dx.doi.org/10.1016/S0167-8922(05)80070-7
doi:10.1016/S0167-8922(05)80070-7
oai:eprints.whiterose.ac.uk:9186
2019-10-09T12:04:33Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9186/
An ultrasonic approach for contact stress mapping in machine joints and concentrated contacts
Marshall, M.B.
Lewis, R.
Drinkwater, B.W.
Dwyer-Joyce, R.S.
The measurement of pressure at a contact in a machine part is important because contact stresses frequently lead to failure by seizure, wear or fatigue. While the interface might appear smooth on a macroscale, it consists of regions of asperity contact and air gaps on a microscale. The reflection of an ultrasonic pulse at such a rough contact can be used to give information about the contact conditions. The more conformal the contact, the smaller is the proportion of an incident wave amplitude that will be reflected. In this paper, this phenomenon has been used to produce maps of contact pressure at machine element interfaces. An ultrasonic pulse is generated and reflected at the interface, to be received by the same piezoelectric transducer. The transducer is scanned across the interface and a map of reflected ultrasound (a c-scan) is recorded. The proportion of the wave reflected can be used to determine the stiffness of the interface. Stiffness correlates qualitatively with contact pressure, but unfortunately there is no unique relationship. In this work, two approaches have been used to obtain contact pressure: firstly by using an independent calibration experiment, and secondly by using experimental observations that stiffness and pressure are linearly related. The approach has been used in three example cases: a series of press fitted joints, a wheel/rail contact and a bolted joint.
Professional Engineering Publishing
2004
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9186/1/32_Marshall_us_stress_maping_J_Strain_Analysis_2004_pre-subm.pdf
text
en
https://eprints.whiterose.ac.uk/9186/2/Marshall%20us%20stress%20maping%20J%20Strain%20Analysis%202004%20pre-submit.pdf
Marshall, M.B., Lewis, R., Drinkwater, B.W. et al. (1 more author) (2004) An ultrasonic approach for contact stress mapping in machine joints and concentrated contacts. Journal of Strain Analysis for Engineering Design, 39 (4). pp. 339-350. ISSN 0309-3247
http://dx.doi.org/10.1243/0309324041223971
doi:10.1243/0309324041223971
oai:eprints.whiterose.ac.uk:9187
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9187/
Interaction between toothbrushes and toothpaste abrasive particles in simulated tooth cleaning
Lewis, R.
Dwyer-Joyce, R.S.
Pickles, M.J.
There are currently many toothbrush designs on the market incorporating different filament configurations such as filaments at various angles and different lengths and made from several different materials. In order to understand how the tooth cleaning process occurs there is a need to investigate in detail how the abrasive particles in a toothpaste interact with the filaments in a teeth cleaning contact and cause material removal from a plaque or stain layer. The following describes the development of optical apparatus to enable the visualisation of simulated teeth cleaning contacts. Studies have been carried out using the apparatus to investigate particle entrainment into the contact and how it differs with varying bristle configurations. The effects of filament stiffness and tip shape were also investigated. Various types of electric toothbrushes were also tested. The studies have shown how particles are trapped at the tips of toothbrush filaments. Particles, suspended in fluid, approach the filament tips, as they pass through they may become trapped. Greater particle entrainment into the filament tip contact occurs with a reciprocating action at low filament loads and deflections than with a sliding motion. Large particles are less likely to enter tip contacts and are trapped between tips or under the filament bend at higher loads. Whether the particles are likely to be trapped and how long they remain so depends on the filament stiffness and degree of splay on loading and the filament configuration. The direction the filaments point in, the number of filaments in a tuft, the spacing of the tufts and the way the filaments splay when deflected all have an influence on entrainment of particles. Tufts with tightly packed stiff filaments which deflected together on loading were more effective at trapping particles than more flexible filaments that splayed out on loading as they present more of a barrier to particle entry and exit from the tip region.
Elsevier Science B.V.
2004-08
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9187/1/33_Wear_2004_Toothbrush_interactions.pdf
Lewis, R., Dwyer-Joyce, R.S. and Pickles, M.J. (2004) Interaction between toothbrushes and toothpaste abrasive particles in simulated tooth cleaning. Wear, 257 (3-4). pp. 368-376. ISSN 00431648
http://dx.doi.org/10.1016/j.wear.2004.01.015
doi:10.1016/j.wear.2004.01.015
oai:eprints.whiterose.ac.uk:9188
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9188/
Wear mechanisms and transitions in railway wheel steels
Lewis, R.
Dwyer-Joyce, R.S.
The need to improve safety and reduce costs means that new specifications are being imposed on railway wheel wear. These mean that more durable wheel steels are required. In order to develop such materials, a greater understanding is needed of the wear mechanisms and transitions occurring in wheel steels. In this work, twin-disc wear testing has been carried out to study the wear characteristics of R8T railway wheel steel. The results have indicated that, compared with previous wheel steels, R8T offers greater wear resistance. Three wear regimes were identified; mild, severe, and catastrophic. Wear rates were seen to increase steadily initially and then to level off, before increasing rapidly as the severity of the contact conditions increased. This paper is concerned with the form of the data and the reasons for the transitions. Analysis of the contact conditions indicated that the first transition in the wear rate was caused by the change from partial slip to full slip conditions at the disc interface. Temperature calculations for the contact showed that the large increase in wear rates seen at the second wear transition may result from a thermally induced reduction in yield strength and other material properties. This improved understanding will help in progressing towards the aim of eventually attaining a wear modelling methodology reliant on material properties rather than wear constants derived from testing.
Professional Engineering Publishing
2004
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9188/1/34_IMechE_J_2004_rail_wheel_transitions.pdf
Lewis, R. and Dwyer-Joyce, R.S. (2004) Wear mechanisms and transitions in railway wheel steels. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 218 (6). pp. 467-478. ISSN 1350-6501
http://dx.doi.org/10.1243/1350650042794815
doi:10.1243/1350650042794815
oai:eprints.whiterose.ac.uk:9189
2013-02-08T16:58:56Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9189/
A method for the measurement of hydrodynamic oil films using ultrasonic reflection
Dwyer-Joyce, R.S.
Harper, P.
Drinkwater, B.W.
The measurement of the thickness of an oil film in a lubricated component is essential information for performance monitoring and control. In this work, a new method for oil film thickness measurement, based on the reflection of ultrasound, is evaluated for use in fluid film journal bearing applications. An ultrasonic wave will be partially reflected when it strikes a thin layer between two solid media. The proportion of the wave reflected depends on the thickness of the layer and its acoustic properties. A simple quasi-static spring model shows how the reflection depends on the stiffness of the layer alone. This method has been first evaluated using flat plates separated by a film of oil, and then used in the measurement of oil films in a hydrodynamic journal bearing. A transducer is mounted on the outside of the journal and a pulse propagated through the shell. The pulse is reflected back at the oil film and received by the same transducer. The amplitude of the reflected wave is processed in the frequency domain. The spring model is then used to determine the oil film stiffness that can be readily converted to film thickness. Whilst the reflected amplitude of the wave is dependent on the frequency component, the measured film thickness is not; this indicates that the quasi-static assumption holds. Measurements of the lubricant film generated in a simple journal bearing have been taken over a range of loads and speeds. The results are compared with predictions from classical hydrodynamic lubrication theory. The technique has also been used to measure oil film thickness during transient loading events. The response time is rapid and film thickness variation due to step changes in load and oil feed pressure can be clearly observed.
Springer Science + Business Media
2004-08
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9189/1/36_Trib_Let_2004_-_Journal_brg_films.pdf
Dwyer-Joyce, R.S., Harper, P. and Drinkwater, B.W. (2004) A method for the measurement of hydrodynamic oil films using ultrasonic reflection. Tribology Letters, 17 (2). pp. 337-348. ISSN 1573-2711
http://dx.doi.org/10.1023/B:TRIL.0000032472.64419.1f
doi:10.1023/B:TRIL.0000032472.64419.1f
oai:eprints.whiterose.ac.uk:9190
2013-02-08T16:58:57Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9190/
Operating limits for acoustic measurement of rolling bearing oil film thickness
Dwyer-Joyce, R.S.
Reddyhoff, T.
Drinkwater, B.
An ultrasonic pulse striking a thin layer of liquid trapped between solid bodies will be partially reflected. The proportion reflected is a function of the layer stiffness, which in turn depends on the film thickness and its bulk modulus. In this work, measurements of reflection have been used to determine the thickness of oil films in elastohydrodynamic lubricated (EHL) contacts. A very thin liquid layer behaves like a spring when struck by an ultrasonic pulse. A simple quasi-static spring model can be used to determine the proportion of the ultrasonic waves reflected. Experiments have been performed on a model EHL contact between a ball and a flat surface. A transducer is mounted above the contact such that the ultrasonic wave is focused onto the oil film. The reflected signals are captured and passed to a PC for processing. Fourier analysis gives the reflection spectrum that is then used to determine the stiffness of the liquid layer and hence its thickness. In further testing, an ultrasonic transducer has been mounted in the housing of a deep-groove ball bearing to measure the film generated at the outer raceway as each ball passes. Results from both the ball-flat and ball bearing measurements agree well with steady-state theoretical EHL predictions. The limits of the measuring technique, in terms of the measurable rolling bearing size and operating parameters, have been investigated.
Taylor & Francis
2004-08
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9190/1/37_trib_trans_2003_ball_bearing_films.pdf
Dwyer-Joyce, R.S., Reddyhoff, T. and Drinkwater, B. (2004) Operating limits for acoustic measurement of rolling bearing oil film thickness. Tribology Transactions, 47 (3). pp. 366-375. ISSN 10402004
http://dx.doi.org/10.1784/insi.46.8.456.39373
doi:10.1784/insi.46.8.456.39373
oai:eprints.whiterose.ac.uk:9191
2016-09-16T13:48:05Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D5052454E
696E737469747574696F6E3D536865666669656C64
696E737469747574696F6E3D4C65656473
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9191/
Turbulent burning rates of methane and methane-hydrogen mixtures
Fairweather, M.
Ormsby, M.P.
Sheppard, C.G.W.
Woolley, R.
Methane and methane-hydrogen (10%, 20% and 50% hydrogen by volume) mixtures have been ignited in a fan stirred bomb in turbulence and filmed using high speed cine schlieren imaging. Measurements were performed at 0.1 MPa (absolute) and 360 K. A turbulent burning velocity was determined for a range of turbulence velocities and equivalence ratios. Experimental laminar burning velocities and Markstein numbers were also derived. For all fuels the turbulent burning velocity increased with turbulence velocity. The addition of hydrogen generally resulted in increased turbulent and laminar burning velocity and decreased Markstein number. Those flames that were less sensitive to stretch (lower Markstein number) burned faster under turbulent conditions, especially as the turbulence levels were increased, compared to stretch-sensitive (high Markstein number) flames.
Elsevier Science B.V., Amsterdam.
2009-04
Article
PeerReviewed
text
en
attached
https://eprints.whiterose.ac.uk/9191/1/1.pdf
Fairweather, M., Ormsby, M.P., Sheppard, C.G.W. et al. (1 more author) (2009) Turbulent burning rates of methane and methane-hydrogen mixtures. Combustion and Flame, 156 (4). pp. 780-790. ISSN 00102180
http://dx.doi.org/10.1016/j.combustflame.2009.02.001
doi:10.1016/j.combustflame.2009.02.001
oai:eprints.whiterose.ac.uk:9192
2015-06-18T17:30:16Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D4C65656473
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9192/
Laminar burning behaviour of biomass gasification-derived producer gas
Serrano, C.
Hernández, J.J.
Mandilas, C.
Sheppard, C.G.W.
Woolley, R.
In the currently reported work, a mixture of H2, CO and N2 (21:24:55 vol%) has been considered as representative of the producer gas coming from gasification of lignocellulosic biomass. Laminar burning velocities have been determined, with simultaneous study of the effects of flame stretch rate and instabilities. Experimentally determined laminar burning velocities derived from schlieren flame images, over a range of equivalence ratios, have been compared with those determined using the CHEMKIN code. Good agreement obtained for 1 bar flames, but significant differences were observed for high pressure cellular flames. Markstein numbers were also derived from the experimental data and corresponding Lewis numbers were calculated. Hydrogen thermo-diffusive effects tended to destabilise lean flames, while the CO content resulted in laminar burning velocity peaking at very high equivalence ratios. The peak burning rate of producer gas proved faster than those of conventional fuels, such as isooctane and methane.
Elsevier Science B.V., Amsterdam
2008-01
Article
NonPeerReviewed
Serrano, C., Hernández, J.J., Mandilas, C. et al. (2 more authors) (2008) Laminar burning behaviour of biomass gasification-derived producer gas. International Journal of Hydrogen Energy, 33 (2). pp. 851-862. ISSN 03603199
http://dx.doi.org/10.1016/j.ijhydene.2007.10.050
doi:10.1016/j.ijhydene.2007.10.050
oai:eprints.whiterose.ac.uk:9193
2016-09-16T13:48:07Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D4C65656473
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9193/
Laser ignition of iso-octane air aerosols
Lawes, M.
Lee, Y.
Mokhtar, A.S.
Woolley, R.
Iso-octane aerosols in air have been ignited with a focused Nd:YAG laser at pressures and temperatures of 100kPa and 270K and imaged using schlieren photography. The aerosol was generated using the Wilson cloud chamber technique. The droplet diameter, gas phase equivalence ratio and droplet number density were determined. The input laser energy and overall equivalence ratio were varied. For 270mJ pulse energies initial breakdown occurred at a number of sites along the laser beam axis. From measurements of the shock wave velocity it was found that energy was not deposited into the sites evenly. At pulse energies of 32mJ a single ignition site was observed. Overall fuel lean flames were observed to locally extinguish, however both stoichiometric and fuel rich flames were ignited. The minimum ignition energy was found to depend on the likelihood of a droplet existing at the focus of the laser beam.
Elsevier Science B.V.
2008-02
Article
NonPeerReviewed
text
en
attached
https://eprints.whiterose.ac.uk/9193/2/woolleyr1.pdf
Lawes, M., Lee, Y., Mokhtar, A.S. et al. (1 more author) (2008) Laser ignition of iso-octane air aerosols. Combustion Science and Technology, 180 (2). pp. 296-313. ISSN 00102202
http://dx.doi.org/10.1080/00102200701739198
doi:10.1080/00102200701739198
oai:eprints.whiterose.ac.uk:9194
2013-09-19T16:17:14Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9194/
Instabilities and soot formation in high-pressure, rich, iso-octane-air explosion flames: 1. Dynamical structure
Lockett, R.D.
Woolley, R.
Simultaneous OH planar laser-induced fluorescence (PLIF) and Rayleigh scattering measurements have been
performed on 2-bar rich iso-octane–air explosion flames obtained in the optically accessible Leeds combustion
bomb. Separate shadowgraph high-speed video images have been obtained from explosion flames under similar
mixture conditions. Shadowgraph images, quantitative Rayleigh images, and normalized OH concentration images
have been presented for a selection of these explosion flames. Normalized experimental equilibrium OH
concentrations behind the flame fronts have been compared with normalized computed equilibrium OH concentrations
as a function of equivalence ratio. The ratio of superequilibrium OH concentration in the flame front to
equilibrium OH concentration behind the flame front reveals the response of the flame to the thermal–diffusive
instability and the resistance of the flame front to rich quenching. Burned gas temperatures have been determined
from the Rayleigh scattering images in the range 1.4⩽ϕ⩽1.9 and are found to be in good agreement with the
corresponding predicted adiabatic flame temperatures. Soot formation was observed to occur behind deep cusps
associated with large-wavelength cracks occurring in the flame front for equivalence ratio ϕ⩾1.8 (C/O⩾0.576).
The reaction time-scale for iso-octane pyrolysis to soot formation has been estimated to be approximately 7.5–
10 ms.
Elsevier Science B.V., Amsterdam
2007-12
Article
PeerReviewed
Lockett, R.D. and Woolley, R. (2007) Instabilities and soot formation in high-pressure, rich, iso-octane-air explosion flames: 1. Dynamical structure. Combustion and Flame, 151 (4). pp. 601-622. ISSN 0010-2180
http://dx.doi.org/10.1016/j.combustflame.2007.08.004
doi:10.1016/j.combustflame.2007.08.004
oai:eprints.whiterose.ac.uk:9195
2016-09-16T13:57:31Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D4C65656473
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9195/
Laminar burning velocities of lean hydrogen-air mixtures at pressures up to 1.0 MPa
Bradley, D.
Lawes, M.
Liu, K.
Verhelst, S.
Woolley, R.
Values of laminar burning velocity, ul, and the associated strain rate Markstein number, Masr, of H2-air mixtures have been obtained from measurements of flame speeds in a spherical explosion bomb with central ignition. Pressures ranged from 0.1 to 1.0 MPa, with values of equivalence ratio between 0.3 and 1.0. Many of the flames soon became unstable, with an accelerating flame speed, due to Darrieus-Landau and thermodiffusive instabilities. This effect increased with pressure. The flame wrinkling arising from the instabilities enhanced the flame speed. A method is described for allowing for this effect, based on measurements of the flame radii at which the instabilities increased the flame speed. This enabled ul and Masr to be obtained, devoid of the effects of instabilities. With increasing pressure, the time interval between the end of the ignition spark and the onset of flame instability, during which stable stretched flame propagation occurred, became increasingly small and very high camera speeds were necessary for accurate measurement. Eventually this time interval became so short that first Masr and then ul could not be measured. Such flame instabilities throw into question the utility of ul for high pressure, very unstable, flames. The measured values of ul are compared with those predicted by detailed chemical kinetic models of one-dimensional flames.
Elsevier Science B.V., Amsterdam
2007-04
Article
PeerReviewed
Bradley, D., Lawes, M., Liu, K. et al. (2 more authors) (2007) Laminar burning velocities of lean hydrogen-air mixtures at pressures up to 1.0 MPa. Combustion and Flame, 149 (1-2). pp. 162-172. ISSN 0010-2180
http://dx.doi.org/10.1016/j.combustflame.2006.12.002
doi:10.1016/j.combustflame.2006.12.002
oai:eprints.whiterose.ac.uk:9196
2016-09-16T13:53:57Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D4C65656473
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9196/
Darrieus-landau and thermo-acoustic instabilities in closed vessel explosions
Al-Shahrany, A.S.
Bradley, D.
Lawes, M.
Liu, K.
Woolley, R.
Experiments involving a spherical explosion bomb are reported, in which Darrieus-Landau thermo-diffusive, D-L,T-D, flame instabilities interacted with primary and secondary, self-excited, thermo-acoustic oscillations. Explosions with central ignition demonstrated that rich i-octane and lean hydrogen-air mixtures generated strong pressure oscillations, a consequence of their negative Markstein numbers. Utilizing dual wall ignitions, the structures of high pressure flames were studied using appropriate optical techniques. The conditions that gave rise to the greatest increase in the rate of combustion were strong initial D-L,T-D, flame instabilities and a high rate of change of the heat release rate, sufficient to generate strong secondary pressure oscillations. These, in turn, generated Rayleigh-Taylor instabilities that further wrinkled the flames. The bomb was equipped with four fans which showed that an rms turbulent velocity in excess of about 0.6 m/s was sufficient to reduce, and almost eradicate, the effect of these instabilities on the flame speed.
Elsevier Science B.V., Amsterdam
2006-12
Article
PeerReviewed
Al-Shahrany, A.S., Bradley, D., Lawes, M. et al. (2 more authors) (2006) Darrieus-landau and thermo-acoustic instabilities in closed vessel explosions. Combustion Science and Technology, 178 (10 & 1). pp. 1771-1802. ISSN 1563-521X
http://dx.doi.org/10.1080/00102200600788734
doi:10.1080/00102200600788734
oai:eprints.whiterose.ac.uk:9197
2016-09-16T13:48:10Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D4C65656473
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9197/
Variation of turbulent burning rate of methane, methanol, and iso-octane air mixtures with equivalence ratio at elevated pressure
Lawes, M.
Ormsby, M.P.
Sheppard, C.G.W.
Woolley, R.
Turbulent burning velocities for premixed methane, methanol, and iso-octane/air mixtures have been experimentally determined for an rms turbulent velocity of 2 m/s and pressure of 0.5 MPa for a wide range of equivalence ratios. Turbulent burning velocity data were derived using high-speed schlieren photography and transient pressure recording; measurements were processed to yield a turbulent mass rate burning velocity, utr. The consistency between the values derived using the two techniques, for all fuels for both fuel-lean and fuel-rich mixtures, was good. Laminar burning measurements were made at the same pressure, temperature, and equivalence ratios as the turbulent cases and laminar burning velocities and Markstein numbers were determined. The equivalence ratio (φ) for peak turbulent burning velocity proved not always coincident with that for laminar burning velocity for the same fuel; for isooctane, the turbulent burning velocity unexpectedly remained high over the range φ = 1 to 2. The ratio of turbulent to laminar burning velocity proved remarkably high for very rich iso-octane/air and lean methane/air mixtures.
Elsevier Science B.V., Amsterdam
2005-07
Article
PeerReviewed
text
en
attached
https://eprints.whiterose.ac.uk/9197/2/woolleyr2.pdf
Lawes, M., Ormsby, M.P., Sheppard, C.G.W. et al. (1 more author) (2005) Variation of turbulent burning rate of methane, methanol, and iso-octane air mixtures with equivalence ratio at elevated pressure. Combustion Science and Technology, 177 (7). pp. 1273-1289. ISSN 1563-521X
http://dx.doi.org/10.1080/00102200590950467
doi:10.1080/00102200590950467
oai:eprints.whiterose.ac.uk:9198
2016-09-16T13:57:25Z
7374617475733D707562
74797065733D61727469636C65
756E69743D4C65656473:4C656564732E46412D46455053:4C656564732E52432D4D454348
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D4C65656473
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9198/
Fundamentals of high-energy spark ignition with lasers
Bradley, D.
Sheppard, C.G.W.
Suardjaja, I.M.
Woolley, R.
An experimental study of laser-induced spark ignition of flammable, gaseous premixtures is reported, with theoretical interpretations. Ignition was in an explosion bomb, equipped with four variable-speed fans that facilitated the study of quiescent and isotropic turbulent conditions. Good optical access enabled the progress of plasma fronts, shock waves, igniting kernels, and propagating flames to be recorded with high-speed schlieren photography. A focused beam from a Q-switched Nd:YAG laser initiated electrical breakdown, with plasma energies between 85 and 200 mJ. Probabilities of breakdown were found for air and isooctane-air mixtures over ranges of pressures and temperatures. Blast-wave theory applied to shock-wave trajectories enabled initial plasma conditions to be inferred. This suggested electron temperatures of over 10 5 K and very high pressures. Calculated values of the absorption coefficient for the laser beam energy show these plasma properties to be commensurate with the observed energy and size. The ensuing rarefaction wave creates toroidal rings at the leading and trailing edges of the plasma. The former decays more rapidly and a third lobe of the kernel is generated that moves towards the laser. In flammable mixtures this enhances the flame spread. Laminar flame speeds are overdriven by this gasdynamic effect, as well as by the high energy of the plasma, to such an extent that the flame speed decays from elevated values as the flame stretch decreases, contrary to the increases that occur with normal flames with positive Markstein numbers. The extent to which turbulence narrows the ignition limits is found experimentally. For mixtures close to the lean flammability limit, strong gasdynamic flows induced by laser ignition can stretch the flames to extinction and narrow the ignition limits. If a flame becomes established, eventually the third lobe disappears as the initial gas dynamic effects decay and are overwhelmed by the imposed flow fields. Nevertheless, the overdrive effects persist for some time and overdriven flames were observed in regimes where normal flames would have quenched.
Elsevier Science B.V., Amsterdam
2004-07
Article
NonPeerReviewed
Bradley, D., Sheppard, C.G.W., Suardjaja, I.M. et al. (1 more author) (2004) Fundamentals of high-energy spark ignition with lasers. Combustion and Flame, 138 (1-2). pp. 55-77. ISSN 0010-2180
http://dx.doi.org/10.1016/j.combustflame.2004.04.002
doi:10.1016/j.combustflame.2004.04.002
oai:eprints.whiterose.ac.uk:9199
2013-02-08T16:58:58Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9199/
The impact of loads on standard diameter, small diameter and mini implants: A comparative laboratory study
Allum, S.R.
Tomlinson, R.A.
Joshi, R.
Objectives: While caution in the use of small-diameter (≤3.5 mm) implants has been advocated in view of an increased risk of fatigue fracture under clinical loading conditions, a variety of implant designs with diameters <3 mm are currently offered in the market for reconstructions including fixed restorations. There is an absence of reported laboratory studies and randomized-controlled clinical trials to demonstrate clinical efficacy for implant designs with small diameters. This laboratory study aimed to provide comparative data on the mechanical performance of a number of narrow commercially marketed implants. Materials and methods: Implants of varying designs were investigated under a standardized test set-up similar to that recommended for standardized ISO laboratory testing. Implant assemblies were mounted in acrylic blocks supporting laboratory cast crowns and subjected to 30° off-axis loading on an LRX Tensometer. Continuous output data were collected using Nexygen software. Results: Load/displacement curves demonstrated good grouping of samples for each design with elastic deformation up to a point of failure approximating the maximum load value for each sample. The maximum loads for Straumann (control) implants were 989 N (±107 N) for the 4.1 mm RN design, and 619 N (±50 N) for the 3.3 mm RN implant (an implant known to have a risk of fracture in clinical use). Values for mini implants were recorded as 261 N (±31 N) for the HiTec 2.4 mm implant, 237 N (±37 N) for the Osteocare 2.8 mm mini and 147 N (±25 N) for the Osteocare mini design. Other implant designs were also tested. Conclusions: The diameters of the commercially available implants tested demonstrated a major impact on their ability to withstand load, with those below 3 mm diameter yielding results significantly below a value representing a risk of fracture in clinical practice. The results therefore advocate caution when considering the applicability of implants ≤3 mm diameter. Standardized fatigue testing is recommended for all commercially available implants.
Blackwell Publishing Ltd
2008-06
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9199/2/3Tomlinson.pdf
Allum, S.R., Tomlinson, R.A. and Joshi, R. (2008) The impact of loads on standard diameter, small diameter and mini implants: A comparative laboratory study. Clinical Oral Implants Research, 19 (6). pp. 553-559. ISSN 0905-7161
http://dx.doi.org/10.1111/j.1600-0501.2007.01395.x
doi:10.1111/j.1600-0501.2007.01395.x
oai:eprints.whiterose.ac.uk:9200
2014-09-15T01:35:37Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9200/
T-stress determination using thermoelastic stress analysis
Zanganeh, M.
Tomlinson, R.A.
Yates, J.R.
T-stress and mixed-mode stress intensity factors have been determined experimentally using thermoelastic stress analysis and using a finite element method. Pure mode I, strong mixed-mode I and II, and interacting cracks have been used as the case studies. A new technique has been proposed to identify the crack tip from thermoelastic images. It has also been shown that using three terms of Williams's stress field formulation to determine the T-stress, yields a more accurate solution than using only the first two terms of the expansion.
Professional Engineering Publishing
2008
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9200/2/tomlinsonra1.pdf
Zanganeh, M., Tomlinson, R.A. and Yates, J.R. (2008) T-stress determination using thermoelastic stress analysis. Journal of Strain Analysis for Engineering Design, 43 (6). pp. 529-537. ISSN 2041-3130
http://dx.doi.org/10.1243/03093247jsa349
doi:10.1243/03093247jsa349
oai:eprints.whiterose.ac.uk:9201
2013-02-08T16:59:00Z
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9201/
Crack paths under mixed mode loading
Yates, J.R.
Zanganeh, M.
Tomlinson, R.A.
Brown, M.W.
Garrido, F.A.D.
Long fatigue cracks that initially experience mixed mode displacements usually change direction in response to cyclic elastic stresses. Eventually the cracks tend to orient themselves into a pure mode I condition, but the path that they take can be complex and chaotic. In this paper, we report on recent developments in techniques for tracking the crack path as it grows and evaluating the strength of the mixed mode crack tip stress field.
Elsevier Science B.V., Amsterdam
2008-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9201/1/2Tomlinson.pdf
Yates, J.R., Zanganeh, M., Tomlinson, R.A. et al. (2 more authors) (2008) Crack paths under mixed mode loading. Engineering Fracture Mechanics, 75 (3-4). pp. 319-330. ISSN 0013-7944
http://dx.doi.org/10.1016/j.engfracmech.2007.05.014
doi:10.1016/j.engfracmech.2007.05.014
oai:eprints.whiterose.ac.uk:9202
2013-02-08T16:58:59Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9202/
Calibration and evaluation of optical systems for full-field strain measurement
Patterson, E.A.
Hack, E.
Brailly, P.
Burguete, R.L.
Saleem, Q.
Siebert, T.
Tomlinson, R.A.
Whelan, M.P.
The design and testing of a reference material for the calibration of optical systems for strain measurement is described, together with the design and testing of a standardized test material that allows the evaluation and assessment of fitness for purpose of the most sophisticated optical system for strain measurement. A classification system for the steps in the measurement process is also proposed and allows the development of a unified approach to diagnostic testing of components or sub-systems in an optical system for strain measurement based on any optical technique. The results described arise from a European study known as SPOTS whose objectives were to begin to fill the gap caused by a lack of standards.
Elsevier Science B.V., Amsterdam
2007-05
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9202/1/4Tomlinson.pdf
Patterson, E.A., Hack, E., Brailly, P. et al. (5 more authors) (2007) Calibration and evaluation of optical systems for full-field strain measurement. Optics and Lasers in Engineering, 45 (5). pp. 550-564. ISSN 0143-8166
http://dx.doi.org/10.1016/j.optlaseng.2006.08.012
doi:10.1016/j.optlaseng.2006.08.012
oai:eprints.whiterose.ac.uk:9203
2013-02-08T16:58:59Z
7374617475733D707562
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756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9203/
Improvement of Fourier Polarimetry for applications in tomographic photoelasticity
Yang, H.
Gibson, S.
Tomlinson, R.A.
The use of the Fourier Polarimetry method has been demonstrated to extract the three characteristic parameters in integrated photoelasticity. In contrast to the phase-stepping method, it has been shown that the Fourier method is more accurate. However, the Fourier method isn't very efficient as it requires that a minimum of nine intensity images be collected during a whole revolution of a polarizer while the phase-stepping method only needs six intensity images. In this paper the Fourier transformation is used to derive the expression for determination of the characteristic parameters. Four Fourier coefficients are clearly identified to calculate the three characteristic parameters. It is found that the angular rotation ratio could be set arbitrarily. The angular rotation ratio is optimized to satisfy the requirements of efficiency and proper data accuracy, which results in data collection about three times faster than the methods suggested by previous researchers. When comparing their performance in terms of efficiency and accuracy, the simulated and experimental results show that these angular rotation ratios have the same accuracy but the optimized angular rotation ratio is significantly faster. The sensitivity to noise is also investigated and further improvement of accuracy is suggested.
Springer Science + Business Media
2006-10
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9203/2/5Tomlinson.pdf
Yang, H., Gibson, S. and Tomlinson, R.A. (2006) Improvement of Fourier Polarimetry for applications in tomographic photoelasticity. Experimental Mechanics, 46 (5). pp. 619-626. ISSN 0014-4851
http://dx.doi.org/10.1007/s11340-006-9112-7
doi:10.1007/s11340-006-9112-7
oai:eprints.whiterose.ac.uk:9204
2013-02-08T16:58:59Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9204/
Thermoelastic investigations for fatigue life assessment
Tomlinson, R.A.
Marsavina, L.
An investigation is presented on the suitability and accuracy of a thermoelastic technique for the analysis of fatigue cracks. The stress intensity factor ranges ΔKI and ΔKII are determined from thermoelastic data recorded from around the tip of a sharp slot in a steel specimen under biaxial load, in order to assess the accuracy of the technique. ΔKI and ΔK II are determined to within 4% and 9% of a theoretical prediction, respectively. The results from a similar test on a fatigue crack under biaxial load are also presented. These show that thermoelastic stress analysis is a rapid and accurate way of analyzing mixed-mode fatigue cracks. A discussion is given on the potential of thermoelastic stress analysis of propagating cracks.
Springer Science + Business Media
2004-10
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9204/2/7Tomlinson.pdf
Tomlinson, R.A. and Marsavina, L. (2004) Thermoelastic investigations for fatigue life assessment. Experimental Mechanics, 44 (5). pp. 487-494. ISSN 0014-4851
http://dx.doi.org/10.1177/0014485104046091
doi:10.1177/0014485104046091
oai:eprints.whiterose.ac.uk:9205
2009-08-24T17:27:04Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6E6F5F646F63756D656E74735F617661696C61626C65
https://eprints.whiterose.ac.uk/9205/
Measuring stress intensity factors during fatigue crack growth using thermoelasticity
Diaz, F.A.
Patterson, E.A.
Tomlinson, R.A.
Yates, J.R.
Thermoelastic stress analysis has been developed in recent years as a direct method of investigating the crack tip stresses in a structure under cyclic loading. This is a consequence of the fact that stress intensity factors obtained from thermoelastic experiments are determined from the cyclic stress field ahead of a fatigue crack, rather than inferred from measurement of the crack length and load range. In the present paper the results of fatigue crack growth tests performed on welded ferritic steel plates are reported. From the results it can be observed that the technique is sensitive to the effects of crack closure and the presence of tensile and compressive residual stresses due to welding.
Wiley-Blackwell
2004-07
Article
NonPeerReviewed
Diaz, F.A., Patterson, E.A., Tomlinson, R.A. et al. (1 more author) (2004) Measuring stress intensity factors during fatigue crack growth using thermoelasticity. Fatigue and Fracture of Engineering Materials and Structures, 27 (7). pp. 571-584. ISSN 8756-758X
http://dx.doi.org/10.1111/j.1460-2695.2004.00782.x
doi:10.1111/j.1460-2695.2004.00782.x
oai:eprints.whiterose.ac.uk:9206
2014-09-15T01:35:29Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E454545
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9206/
Full-field pulsed-magneto-photoelasticity -
a description of the instrument
Gibson, S.
Tomlinson, R.A.
Jewell, G.W.
This paper describes a novel instrument used for the analysis of full-field through-thickness stress distributions using the theory of magneto-photoelasticity (MPE) developed by Aben and Clarke et al. [ , , ]. MPE is an experimental stress analysis technique which involves the application of a magnetic field parallel to an electromagnetic wave propagating through a birefringent model within a polariscope. The effect viewed through the polariscope is then a combination of the model’s birefringence and the Faraday rotation created in the model by the magnetic field. Aben developed this technique especially for use in the measurement of stress profiles where the integrated photoelastic pattern alone yields little information. Clarke et al. developed MPE in order to study toughened glass.
To date, the technique of MPE has been a single-point measurement and this is of limited utility in the investigation of 3D stress in toughened glasses. The pulsed-magneto-polariscope (PMP), described here, enables the full-field application of MPE. This paper contains a description of the novel apparatus, and demonstrations used to validate the performance of a proof-of-concept PMP instrument. The paper also highlights improvements in the application of MPE which are now possible with this new equipment. These improvements include the extension of MPE to larger areas of analysis, 3D stress analysis and the possibility of analysing a general unknown stress distribution.
Professional Engineering Publishing
2006
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9206/2/tomlinsonra10.pdf
Gibson, S., Tomlinson, R.A. and Jewell, G.W. (2006) Full-field pulsed-magneto-photoelasticity - a description of the instrument. Journal of Strain Analysis for Engineering Design, 41 (2). pp. 161-170. ISSN 0309-3247
http://dx.doi.org/10.1243/03093247JSA92
doi:10.1243/03093247JSA92
oai:eprints.whiterose.ac.uk:9207
2014-09-15T01:35:33Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E454545
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9207/
Full-field pulsed magneto-photoelasticity – Experimental Implementation
Gibson, S.
Tomlinson, R.A.
Jewell, G.W.
This paper contains a description of the experimental procedure employed when using a pulsed-magneto-polariscope (PMP) and some initial full-field through-thickness measurements of the stress distribution present in samples containing 3D stresses. The instrument uses the theory of magneto-photoelasticity (MPE), which is an experimental stress analysis technique that involves the application of a magnetic field to a birefringent model within a polariscope. MPE was developed for through-thickness stress measurement where the integrated through-thickness birefringent measurement disguises the actual stress distribution. MPE is mainly used in toughened glass where the through-thickness distribution can reduce its overall strength and so its determination is important.
To date MPE has been a single-point 2D through-thickness measurement and the analysis time is prohibitive for the investigation of an area which may contain high localised stresses. The pulsed-magneto-polariscope (PMP) has been designed to enable the application of full-field 3D MPE [ ]. Using a proof-of concept PMP several experimental measurements were made, these were promising and demonstrate the potential of the new instrument. Further development of this technique presents several exciting possibilities including a tool for the measurement of the distribution of principal stress difference seen in a general 3D model.
Professional Engineering Publishing
2006
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9207/2/tomlinsonra2.pdf
Gibson, S., Tomlinson, R.A. and Jewell, G.W. (2006) Full-field pulsed magneto-photoelasticity – Experimental Implementation. Journal of Strain Analysis for Engineering Design, 41 (2). pp. 171-182. ISSN 0309-3247
http://dx.doi.org/10.1243/03093247JSA93
doi:10.1243/03093247JSA93
oai:eprints.whiterose.ac.uk:9208
2013-02-08T16:58:58Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9208/
On the energy leakage of discrete wavelet transform
Peng, Z.K.
Jackson, M.R.
Rongong, J.A.
Chu, F.L.
Parkin, R.M.
The energy leakage is an inherent deficiency of discrete wavelet transform (DWT) which is often ignored by researchers and practitioners. In this paper, a systematic investigation into the energy leakage is reported. The DWT is briefly introduced first, and then the energy leakage phenomenon is described using a numerical example as an illustration and its effect on the DWT results is discussed. Focusing on the Daubechies wavelet functions, the band overlap between the quadrature mirror analysis filters was studied and the results reveal that there is an unavoidable tradeoff between the band overlap degree and the time resolution for the DWT. The dependency of the energy leakage to the wavelet function order was studied by using a criterion defined to evaluate the severity of the energy leakage. In addition, a method based on resampling technique was proposed to relieve the effects of the energy leakage. The effectiveness of the proposed method has been validated by numerical simulation study and experimental study.
Elsevier Science B.V., Amsterdam
2009-02
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9208/1/Rongong_3_On.pdf
Peng, Z.K., Jackson, M.R., Rongong, J.A. et al. (2 more authors) (2009) On the energy leakage of discrete wavelet transform. Mechanical Systems and Signal Processing, 23 (2). pp. 330-343. ISSN 0888-3270
http://dx.doi.org/10.1016/j.ymssp.2008.05.014
doi:10.1016/j.ymssp.2008.05.014
oai:eprints.whiterose.ac.uk:9209
2013-02-08T16:58:59Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9209/
Strategies for using cellular automata to locate constrained layer damping on vibrating structures
Chia, C M.
Rongong, J.A.
Worden, K.
It is often hard to optimise constrained layer damping (CLD) for structures more complicated than simple beams and plates as its performance depends on its location, the shape of the applied patch, the mode shapes of the structure and the material properties. This paper considers the use of cellular automata (CA) in conjunction with finite element analysis to obtain an efficient coverage of CLD on structures. The effectiveness of several different sets of local rules governing the CA are compared against each other for a structure with known optimum coverage-namely a plate. The algorithm which attempts to replicate most closely known optimal configurations is considered the most successful. This algorithm is then used to generate an efficient CLD treatment that targets several modes of a curved composite panel. To validate the modelling approaches used, results are also presented of a comparison between theoretical and experimentally obtained modal properties of the damped curved panel.
Elsevier Science B.V., Amsterdam
2009-01-09
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9209/1/Rongong_4_Strategies.pdf
Chia, C M., Rongong, J.A. and Worden, K. (2009) Strategies for using cellular automata to locate constrained layer damping on vibrating structures. Journal of Sound and Vibration, 319 (1-2). pp. 119-139. ISSN 0022-460X
http://dx.doi.org/10.1016/j.jsv.2008.06.023
doi:10.1016/j.jsv.2008.06.023
oai:eprints.whiterose.ac.uk:9210
2014-09-15T01:35:23Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9210/
Evolution of constrained layer damping using a cellular automaton algorithm
Chia, C.M.
Rongong, J.A.
Worden, K.
Constrained layer damping (CLD) is a highly effective passive vibration control strategy if optimized adequately. Factors controlling CLD performance are well documented for the flexural modes of beams but not for more complicated mode shapes or structures. The current paper introduces an approach that is suitable for locating CLD on any type of structure. It follows the cellular automaton (CA) principle and relies on the use of finite element models to describe the vibration properties of the structure. The ability of the algorithm to reach the best solution is demonstrated by applying it to the bending and torsion modes of a plate. Configurations that give the most weight-efficient coverage for each type of mode are first obtained by adapting the existing 'optimum length' principle used for treated beams. Next, a CA algorithm is developed, which grows CLD patches one at a time on the surface of the plate according to a simple set of rules. The effectiveness of the algorithm is then assessed by comparing the generated configurations with the known optimum ones.
Professional Engineering Publishing
2008
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9210/2/rongongja5.pdf
Chia, C.M., Rongong, J.A. and Worden, K. (2008) Evolution of constrained layer damping using a cellular automaton algorithm. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 222 (4). pp. 585-597. ISSN 0954-4062
http://dx.doi.org/10.1243/09544062jmes638
doi:10.1243/09544062jmes638
oai:eprints.whiterose.ac.uk:9211
2013-02-08T16:58:59Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9211/
The dynamic characterisation of disk geometry particle dampers
Liu, W.
Tomlinson, G.R.
Rongong, J.A.
Particle dampers (PDs) have the advantages of being simple in geometry, small in volume and applicable in extreme temperature environments. Experimental studies have shown that PDs can offer considerable potential for suppressing structural resonant conditions over a wide frequency range. In this paper, the nonlinear characteristics of PDs are studied experimentally in a series of response-level-controlled tests. The effect of the geometry is studied and a method is developed to model the nonlinear damping of PDs as equivalent viscous dampers that can be applied directly to engineering structures at the design stage.
Elsevier Science B.V.
2005-02-23
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9211/1/Rongong_8_The.pdf
Liu, W., Tomlinson, G.R. and Rongong, J.A. (2005) The dynamic characterisation of disk geometry particle dampers. Journal of Sound and Vibration, 280 (3-5). pp. 849-861. ISSN 0022-460X
http://dx.doi.org/10.1016/j.jsv.2003.12.047
doi:10.1016/j.jsv.2003.12.047
oai:eprints.whiterose.ac.uk:9212
2014-09-15T01:35:26Z
7374617475733D707562
74797065733D61727469636C65
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4543
756E69743D536865666669656C64:536865666669656C642E464345:536865666669656C642E4D4154
696E737469747574696F6E3D536865666669656C64
7072696D6F3D6861735F7075626C6963
https://eprints.whiterose.ac.uk/9212/
Plasma deposition of constrained layer damping coatings
Rongong, J.A.
Goruppa, A.A.
Buravalla, V.R.
Tomlinson, G.R.
Jones, F.R.
Plasma techniques are used to generate constrained layer damping (CLD) coatings on metallic substrates. The process involves the deposition of relatively thick, hard ceramic layers on to soft polymeric damping materials while maintaining the integrity of both layers. Reactive plasma sputter-deposition from an aluminium alloy target is used to deposit alumina layers, with Young's modulus in the range 77-220GPa and thickness up to 335 μ, on top of a silicone film. This methodology is also used to deposit a 40 μ alumina layer on a conventional viscoelastic damping film to produce an integral damping coating. Plasma CLD systems are shown to give at least 50 per cent more damping than equivalent metal-foil-based treatments. Numerical methods for rapid prediction of the performance of such coatings are discussed and validated by comparison with experimental results.
Professional Engineering Publishing
2004
Article
PeerReviewed
text
en
https://eprints.whiterose.ac.uk/9212/2/rongongja9.pdf
Rongong, J.A., Goruppa, A.A., Buravalla, V.R. et al. (2 more authors) (2004) Plasma deposition of constrained layer damping coatings. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 218 (7). pp. 669-680. ISSN 0954-4062
http://dx.doi.org/10.1243/0954406041319581
doi:10.1243/0954406041319581
oai:eprints.whiterose.ac.uk:9213
2015-10-21T15:22:33Z
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