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Cambridge Centre for Micromechanics
Compressive Failure of Composites
Designing with Composite Materials
Composite Sandwich Panels
Draping of Woven Materials
Anisotropic Elasticity
Adhesive Joints
Mechanical Properties of Metallic Foams and Lattice Material
Acoustic and Thermal Properties of Metal Foams
Sound Absorption in Metal Foams with Semi-open Cells
Heat Transfer in Lattice Materials
Micropolar Elasticity
Friction and Wear of Dry and Lubricated Contacts
Metal Working Tribology
Modelling Materials Processing
Powder Compaction of Composites
Strain Gradient Plasticity Theory
The Design and Performance of Ferroelectric Actuators
Road Materials
Thermal Shock Resistance of Solids
Thermal Management of Power Electronics with Phase Change Cooling
Cracking of Zirconia Refractories under Thermal Shock
Channelling and Tunnelling of Cracks under Thermal Shock
Mechanical, Thermal and Acoustic Properties of Steel Frames
Mechanics of Corrugated Packaging Boards
Failure Analysis
Interdisciplinary Research Centre in Superconductivity
Force Free Configurations
Vortex Dynamics
Superconducting Multilayers
Micro-Hall Probe Investigations
AC Losses in Superconducting Tapes
Superconducting Fault Current Limiters
Superconducting Magnetic Bearings
Ceramic Powder Processing by Evaporative Decomposition of Solution (EDS)
Melt Processed Bulk High Temperature Superconductors for Engineering Applications
Joining Techniques for High Temperature Superconductors
References
Director: Prof N.A. Fleck, Engineering Department
Co-Directors: Professor M.F. Ashby, Engineering Department
Dr T.W. Clyne, Materials Science and Metallurgy Department
Professor J.R. Willis, Department of Applied Mathematics and Theoretical Physics
An inter-Departmental Centre for research in Micromechanics was opened in March 1996. Micromechanics is "the application of the principles of mechanics, thermodynamics and kinetics to the modelling of material response at length scales ranging from the atomistic to the macroscopic". The Centre is housed in Engineering and hosts joint projects with the Departments of Applied Mathematics and Theoretical Physics, and Materials Science and Metallurgy. The current research thrusts of the Centre are (a) mechanics of composites, (b) processing (c) cellular solids and (d) tribology. The Centre has financial support from a number of EPSRC programmes and also from US and EC funding. A weekly workshop stimulates inter-disciplinary discussion on defined problems in micromechanics. A major aim of the Centre is to stimulate closer interaction with UK industry and with the best international researchers, and to co-ordinate research on fundamental and important problems.
Professor N.A. Fleck
Dr M.P.F. Sutcliffe
The practical design of composite components is often governed by their poor compressive strength. The Cambridge group has identified fibre waviness and matrix shear yield as the underlying reason for low compressive strength. Theoretical models are used to predict the effect of fibre waviness on strength. The effect of structural features such as holes and ply drops is being examined both theoretically and experimentally. The work is funded by EPSRC and is being done in collaboration with the Materials Science and Metallurgy Department in Cambridge, British Aerospace and Hexcel Composites. A novel method for measuring fibre waviness in composite specimens has been developed, using a simple image analysis program which identifies fibres in a photographic image of the specimen. Initiation of failure has been investigated using a model composite made of alternate layers of epoxy and steel. The effects of Z-pins and ply drops on compressive strength have been explored(E25,E49,E50).
Dr P.W.R. Beaumont
Successful designing with composite materials requires an understanding of the fundamental microscopic processes that limit the fracture stress, fatigue and design life-time of material and structure.
A predictive design methodology is being developed using analytical models of microscopic cracking phenomena. These models of damage growth are to be manipulated in a format suitable for the conceptual design of crack-insensitive, damage-tolerant composite material systems over a range of stress, temperature, and environment.
Research continues on the development of composite bonded repairs of ageing (fatigue cracked) metallic aircraft structures.
Professor N.A. Fleck
Dr M.P.F. Sutcliffe
A three year project on the mechanics of composite sandwich panels, in collaboration with Hexcel Composites, has just been completed. This work looks at the mechanics of failure of sandwich beams in three point bending, especially looking at indentation failure. A project has been initiated with Hexcel Limited on the behaviour of sandwich panels containing a polymeric foam core, subjected to bend loading and end loading. Design charts have been produced to optimise sandwich panel construction.
Dr M.P.F. Sutcliffe
A project which investigates the way in which fabric composites drape over curved moulds has been completed. The software package LAMINATE MODELER, supplied by the collaborating company, Macneal Schwendler Corporation, was found to model well the behaviour of a standard pre-preg cloth. Further research in this area is planned.
Dr W.J. Stronge
Composites have anisotropic material properties that affect the stresses around discontinuities or points of stress concentration. In an anisotropic material the affect of a stress concentration is more widespread in the direction of large elastic modulus. Quantitative estimates of the rate of decay around stress concentrations have been obtained as a function of certain modulus ratios for generic patterns of stress distribution. The rate of decay depends on the complexity of the traction distribution rather than on the moment of the applied tractions.
Analytical methods have been developed for calculating contact stresses near a rigid indentor pressed into an elastic material that contains either voids or inclusions (e.g. stiff fibres). These methods that employ distributions of dislocations on interfaces, are useful when different sources of stress variation are sufficiently close so that they interact.
Dr M.P.F. Sutcliffe
Dr H.R. Shercliff
A collaborative project with TWI has been started, looking at mechanisms of failure in adhesive joints. By focussing initially on joints between transparent adherents, the damage evolution in the joint before failure has been identified. Work is now in progress to model this and so develop `R-curves' for crack initiation and growth.
A second collaborative PTP project with TWI has started, to study the design and performance of adhesive joints in composite materials. Finite element analysis is being used to test the validity of conventional criteria for the onset of damage, in the more complex stress states of adhesive joints.
Professor N.A. Fleck
Professor M.F. Ashby
Dr T.J. Lu
A co-ordinated activity continues on measuring and modelling the mechanical properties of metallic foams. These new engineering materials show great potential for use in energy absorption in automotive applications, as the foam cores for sandwich panels, and in heat transfer and acoustic attenuation applications. If they are to be used more widely, research is needed on their deformation and fracture properties, including fatigue and creep. A broad range of experiments are in progress, including multi-axial loading tests, high strain rate tests, fatigue and fracture studies, and sandwich panel testing. A comprehensive Design Guide for Metal foams has been compiled, and will be published by Butterworth-Heinemann in April 2000.
A new class of engineering materials has been designed and manufactured - lattice materials.
These are miniaturised truss structures with exceptionally high values of stiffness and strength when compared with cellular materials of comparable density(E9,E15,E19,E20,E37,E38,E41,E45,E53).
Dr T.J. Lu
Professor M.F. Ashby
Metal foams with open cells have application as heat-exchange elements. The heat-transfer characteristics
of metal foams are analysed. Predictive models, adapted to the optimisation of density, pore size, etc. are developed.
Metal foams offer a combination of attractive properties. Among these is the ability to absorb sound, suggesting their use for acoustic insulation as well as mechanical strength at low weight. Experiments to characterise sound absorption in metal foams are in progress.
Dr T.J. Lu
In this project, the feasibility of using aluminium foams with semi-open cells for sound absorption applications is studied. The foams are processed via negative-pressure infiltration, using a preform consisting of soluble spherical particles. An analytical model is developed to quantify the dependence of pore connectivity on processing parameters, including infiltration pressure, particle size, wetting angle, and surface tension of molten alloy. Normal sound absorption coefficient and static flow resistance are measured for samples having different porosity, pore size and pore opening. A theory is developed for idealised semi-open metallic foams, with a regular hexagonal hollow prism having one circular aperture on each of its eight surfaces as the unit cell. The theory is built upon the acoustic impedance of the circular apertures (orifices) and cavities due to viscous effects, and the principle of electro-acoustic analogy. The predicted sound absorption coefficients are compared with those measured. To help selecting processing parameters for producing semi-open metallic foams with desirable sound absorbing properties, emphasis is placed on revealing the correlation between sound absorption and morphological parameters such as pore size, pore opening, and porosity.
Dr T.J. Lu
Professor M.F. Ashby
Lattice-frame structured materials are a new development made possible by computer based design and control of numerically controlled processing. They consist of a 3-D network of struts or plates. The microstructural morphologies resemble those of cellular aluminium foam. Hence the overall heat transfer performance of both types of material is expected to be similar. Work has started to determine the relationships between thermal properties and microstructure by combining experimental measurement with analytical modelling and numerical simulation, and develop an implementation methodology that enables design engineers to select lattice-materials with microstructures optimised for best heat transfer performance at affordable costs.
Dr W.J. Stronge
Micropolar elasticity theory has been used to analyse planar boundary value problems for stresses and deformations. This theory employs couple stresses to represent cell wall bending in cellular solids; these stresses are in addition to the direct and shear stresses acting on a representative element of a foam or honeycomb. Around any particular stress concentration, the rate of decay of couple stresses has been shown to be one order larger than that of direct and shear stresses(E57).
Dr J.A. Williams
Work on the shakedown of engineered surfaces has continued by extending analysis to the more general case of elliptical contacts(E16). In addition, a paper reviewing the relevance of residual stresses and shakedown to tribological contacts in general has been published(E61). The transitional behaviour of a single asperity contact from fully elastic conditions through the elastic-plastic range to complete plasticity has been explored numerically(E4); this work continues. A major review paper on wear modelling was presented as a keynote address at the 1999 biennial `Wear of Materials' meeting in Atlanta(E60) and presentations were made at the OECD International Wear Group meeting in Amsterdam. Further work on the tribological aspects of metal cutting has continued in collaboration with the Department of Materials Science. Industrial support has been forthcoming to continue work on both shakedown mechanics and the boundary lubrication of cam and follower contacts within internal combustion engines. The annual Cambridge Tribology Course was held at the end of September 1998 when more than thirty delegates from both industry and academia attended.
Dr M.P.F. Sutcliffe
Two EPSRC projects are investigating metal working tribology. The first, on friction in cold metal rolling, is in collaboration with Alcan International, Cegelec. This looks at the details of surface roughness and hydrodynamic effects. A collaboration with the Ecole des Mines de Paris includes this tribological model in a mechanical model of thin foil rolling. The second
project is on surface finish of stainless steel, with British Steel and Avesta Sheffield. Surface finish features have been characterised and the changes in these defects are being simulated on a strip drawing rig.
Dr H.R. Shercliff
A project on modelling friction stir welding(E44) in collaboration with TWI approaches completion, funded by the DTI post-graduate training partnership (PTP). A successful application to the EU 5th framework programme will continue this work, applied to welding of dissimilar light alloys. A second PTP project is using finite element analysis to study residual stresses in TIG-welded aerospace aluminium alloys(E43), in collaboration with British Aerospace, including microstructural models to allow for softening of the alloys during welding.
Modelling of processing of aluminium alloys continues with Alcan International. The advanced statistical method of Gaussian process modelling has been applied to recrystallisation of hot deformed alloys(E46), as part of a review of microstructural modelling presented at a Royal Society Discussion Meeting. Work continues with Alcan and the University of Manchester to integrate physically-based state variable approaches with statistical methods.
A UK Materials Modelling Group was initiated, with the intention of forming a network to promote collaboration and training in the UK in this field. An inaugural workshop on "Constitutive Modelling for Materials Processing" was held in Cambridge in September 1999 (http://www-materials.eng.cam.ac.uk/hrs/workshop.html).
Professor N.A. Fleck
Experiments and modelling have been performed to elucidate the mechanisms by which mixed powders, one ductile and the other rigid, consolidate under pressure at both low and high temperatures. The pressure-density characteristics are measured under purely hydrostatic and more complex triaxial loadings. Micromechanical models capture the constitutive response based on indentation theory. A study has begun on the compaction of particulate-reinforced powder composites, as part of an initiative to use SiC particle-reinforced aluminium alloy compacts in automotive applications. The multi-axial yield surface has been measured and the stage I compaction of composites has been modelled(E39,E40,E51).
Professor N.A. Fleck
A new theory of plasticity has been developed with the inclusion of a size effect, associated with strain gradients. The theory has been used to model a range of plasticity phenomena (such as indentation) where size effects are observed. Recently the theory has been extended to crystal plasticity and predictions have been compared with discrete dislocation calculations(E47,E48).
Professor N.A. Fleck
Ferroelectric materials have the ability to strain under an electric field and to produce an electrical charge under a mechanical stress. Recently, robust constitutive laws have been determined to describe the behaviour of these materials. Experiments on the cyclic behaviour reveal electrical and mechanical fatigue phenomena. A finite element program has been written in order to design practical devices (actuators and sensors) with these materials(E21,E22).
Dr D. Cebon
Professor M.F. Ashby
Professor N.A. Fleck
An EPSRC-funded project on damage mechanisms of asphalt paving materials has been completed, and several papers on asphalt deformation have been published(E10,E13,E14). This work has yielded a new understanding of the behaviour of asphalts, which may lead to improved methods of designing road materials, with enhanced durability.
Dr T.J. Lu
Professor N.A. Fleck
The thermal shock resistance of a brittle solid has been analysed for an orthotropic plate suddenly exposed to a convective medium of different temperature. Lower bound solutions are obtained for the maximum thermal shock that the plate can sustain without catastrophic failure according to two distinct criteria. Merit indices of material properties are deduced, and optimal materials are selected on the basis of these criteria. The effect of porosity on thermal shock resistance is also explored, and merit indices for thermal fatigue are derived.
Dr T.J. Lu
This work studied the prospect of designing high power electronic packages with phase change cooling, with special emphasis on minimising the rising of junction temperature due to thermal transient effects. The model consists of a finite slab suddenly exposed to a uniform heat flux at the top surface and cooled by convective medium at the bottom. The phase change problem is divided into sub-problems and solved progressively. Before the slab starts to melt, both exact and approximate solutions are obtained for the temperature distribution. After the slab melts, quasi-steady state solutions are given both for the melt depth and surface temperature, and are compared with finite element predictions. These solutions are analysed to guide the design of advanced packages with optimised cooling strategies.
Dr T.J. Lu
Zirconia (ZrO2) is widely used in refractory applications (e.g., slag line sleeves for steel making) due to its high corrosion resistance. However, zirconia is unstable when subjected to thermal transients, which may cause cracking in the refractory. The evolution of stresses and strains in a zirconia-containing refractory tube subjected to a hot shock on the outer surface and convective cooling at the inner surface is analysed. To account for the temperature-induced phase transformation in the zirconia as well as the overall thermal expansion, a coefficient of total dilatation is introduced. The parameters that control the time-dependent stress and strain responses are identified by performing finite element calculations that span the range of variables relevant to steel making. The effects of tube thickness, hot shock duration, initial temperature, temperature dependence of elastic modulus, and transformation amplitude on stress and strain distributions are discussed, and heating and process strategies to eliminate surface cracking are suggested.
Dr T.J. Lu
Professor N.A. Fleck
Work continued on predicting the thermal shock resistance of solids. The propagation of a pre-existing edge crack across a finite plate subjected to cold shock has been studied. The plate, initially at uniform temperature, is exposed to a cold shock on one surface whilst three different types of heat transfer boundary condition are separately considered for the opposing face. For all three boundary conditions, the plate experiences tensile stressing near the cold-shocked surface and compressive stressing near the mid-plane. Consequently, a mode I edge crack extending into the compressive region may grow in one of three different modes: continued extension in plane strain, channelling and spalling. The thermal shock conditions governing each failure mode are quantified, with a focus on crack channelling and spalling. Failure maps for the various cracking patterns are constructed in terms of the critical temperature jump and Biot number, and merit indices are identified for materials selection against failure by thermal shock.
Dr T.J. Lu
Dr C.Y. Barlow
Cold formed sections can be found in many applications such as window reinforcements, metal track and stud for partitioning systems, metal framed buildings, mezzanine flooring etc. Because of its high strength but good forming properties, the material generally used is galvanised mild steel which is initially supplied in large coils and later slit to appropriate strip widths. One of the major growth areas for cold formed steel sections has been in the structural sector, particularly track and stud for plasterboard partitioning support. Steel track and stud is seen as an environmentally friendly, recyclable alternative to the timber that is traditionally used for studding and roofing trusses. This is a new program funded by EPSRC to improve the strength, rigidity, fire resistance and acoustic properties of cold-formed steel sections without compromising the process speed or increasing the material content. Basic methods of shape optimisation for stiffness and strength in sheet sections are also being developed.
Dr T.J. Lu
This work, supported by the Swedish packaging firm SCA, has in the past year focused on the compressive responses and failure mechanisms of corrugated sandwich panels subjected to uniform lateral compression. Particular focus is placed on illuminating the role of the initially sinusoidal fluting in dominating the overall deformation and local collapse of the board panel. Two types of specimens are considered, Flat Crush Test specimen and Concorra Medium Test specimen. Both specimens are modelled by curved beam elements and surface contact elements, and the elasto-plastic material is idealised by a bi-linear constitutive model satisfying the Mises flow theory. Extensive calculations are performed to obtain the compressive strength of each specimen as a function of a variety of geometrical and material parameters, and to study the global and local plastic collapse mechanisms during the deformation process. The effect of manufacturing-induced geometrical imperfections on the mechanical properties of the board panel is also quantified. Experimental measurements are conducted on two types of commercially available corrugated board panels to verify the accuracy of theoretical predictions.
Dr D.R.H. Jones
Numerous investigations of engineering and metallurgical failures have been carried out in collaboration with a wide range of industrial sponsors. Specific projects have ranged from the investigation and elimination of joint failures in electronic devices to the statistical analysis of structural failure in supertankers. As a result, an extensive knowledge base of information on the causes, mechanisms and implications of failures has been developed. The knowledge base has important applications to the design, manufacture, assessment and maintenance of safe and robust components and structures. Emphasis is placed on the generic nature of failure analysis and the transfer of technology and practice between different fields of application. A number of significant spin-offs have resulted from this work. Dr Jones is founder Editor-in-Chief of the Elsevier Science Journal Engineering Failure Analysis. This has developed into the prime international journal in the field and now acts as a major focus for international collaboration. A project with The Open University will lead to the production and use of distance learning materials in the field of forensic engineering. A project with the Instrumentation Group of the Institute for Manufacturing is investigating problems in the performance of automotive transmission components.
Dr A.M. Campbell
Dr D.A. Cardwell
Dr T.A. Coombs
This was the first IRC to be established and therefore the first to lose the dedicated funding. Dr A.M. Campbell took over as Director in April 1998 and it is pleasing to be able to report that funding remains at a high level. Although a looser organisation, there are now many more people who can apply for grants and successful applications for research contracts have been made from all five departments involved. Several younger members of the IRC have been appointed to university posts and are expected to expand the IRC in new directions in the years to come. The projects listed are all in collaboration with members of other departments.
Dr A.M. Campbell
This is a long standing problem in which longitudinal currents cause vortices to cut each other. The University supercomputer was used to solve the time dependent Ginzburg Landau equations in three dimensions to see how the vortex instabilities developed. A striking result was that a voltage could be developed without vortex cutting.
Dr A.M. Campbell
The project is investigating the role of surface currents in the critical current of BSCCO crystals. By measuring the voltages across a Corbino Disc it has been demonstrated that over a surprisingly wide range of temperature the critical current is dominated by surface effects. This has important implications for commercial BSCCO tapes.
Dr A.M. Campbell
One of the most striking aspects of high Tc superconductors is the collapse of the critical current density well below the upper critical field. Although the mechanism remains mysterious it is believed to be connected with the layer structure of these materials. We have been preparing thin multilayer films of low Tc superconductors, which are much simpler materials, and shown that many of the phenomena seen in high Tc materials can be seen in multilayers.
Dr A.M. Campbell
Probing the magnetic field on a micron scale in superconductors has exposed some surprising effects which were not apparent in macroscopic measurements. Tiny Hall probes are being used to see exactly where the currents are flowing and to distinguish between intergrain and intragrain critical currents.
Dr A.M. Campbell
The commercial application of superconducting cables is dependent on minimising the AC losses in the tapes. A programme at the IRC is measuring losses in a range of commercial tapes and developing the theory of multilayer helical conductors. In particular a technique of reducing losses by screening the tape with a ferromagnet is being explored.
Dr A.M. Campbell
The IRC has been a central partner in a LINK scheme with six companies to develop a commercial resistive fault current limiter. This is one of the applications of superconductors which is nearest market and the technology developed in Materials Science was successfully transferred to Advanced Ceramics who produced two hundred elements for testing in a 400 Amp 2kV limiter. The Engineering input to this was in matching the material to the system requirements and modelling the transition of the superconductor in these extreme overload conditions.
Dr A.M. Campbell
The levitation of magnets by superconductors is one of the most spectacular manifestations of the phenomenon, but it has important applications as a magnetic bearing. This is virtually lossless and there is no speed limitation, so it is ideal for magnetic energy storage with flywheels. A project with URENCO who make a complete system with a hydrodynamic bearing has led to the design and construction of a thrust bearing which levitates a 40 kg carbon fibre rotor. This is now being tested.
Dr D.A. Cardwell
Development of the evaporative decomposition of solution (EDS) technique for the processing of RE-Ba-Cu-O [(RE)BCO] powders has continued and has proved effective for doping precursor powders. Au-doped NdBCO prepared by this method, in particular, exhibits a reduced peritectic temperature compared with the undoped parent compound and hence has significant potential for self-seeded melt growth.
Dr D.A. Cardwell
The top seeded melt growth process has been applied to a range of (RE)BCO materials including NdBCO, Nd/Eu/GdBCO and doped YBCO. Experiments have been performed with a variety of seeds [MgO and (RE)BCO] under a variety of seeding conditions.
High quality large grain YBCO has been grown in small batches under both thermal gradient and constant undercooling conditions. The growth rate of large grain NdBCO has been studied in detail as a function of ND4Ba2Cu2O10 content and undercooling and used to construct a melt process phase diagram. Large single grain samples of NdBCO have been fabricated using hot seeding under reduced oxygen for the first time. Seeded melt grown YBCO has been fabricated by a BaCuO liquid infiltration technique. Initial results show these samples to be largely pore-free, which has the potential to enhance their electrical and mechanical properties for a range of engineering applications. U-doped YBCO has been fabricated in large grain form using a NdBCO seed and controlled thermal gradients. The processing conditions for both a natural (0.718% U235) uranium dopant have been established. Trapped field measurements suggest that these samples exhibit increased flux pinning which may be enhanced further by irradiation with thermal neutrons.
Flux pinning and the irreversibility properties of large grain NdBCO have been investigated in detail over a wide temperature and magnetic field range. Flux pinning in this material appears to be dominated by normal and point pinning centres, in contrast to that reported elsewhere. The orientation of the crystallographic c-axis in bulk melt processed NdBCO is sensitive to the undercooling during melt growth and varies typically between 0 and 40º with respect to the sample surface. This has been correlated for the first time with grain morphology and used to account for the formation of a rhombohedral and rectangular grain geometry.
Dr D.A. Cardwell
A technique to join melt processed YBCO samples cut from large single grains has been applied to 0º and small angle (up to 15º) grain boundaries. In general the boundaries exhibit a slightly reduced superconducting transition temperature compared to that of the adjacent grains. Strong regions in the boundary of up to 1 mm in length, however, have been identified which exhibit high transport critical current densities at 77K. Surface preparation prior to join has been identified as a key process variable and should enable scale-up of the process to cm-sized samples for engineering applications.
E1. Andrews, E.W., Gibson, L.J., Ashby, M.F. The creep of cellular solids. Acta Materialia, 47, (10), 2853-2863 (1999).
E2. Baxter, G.J., Furu, T., Zhu, Q., Whiteman, J.A., Sellars, C.M. The influence of transient strain-rate deformation conditions on the deformed microstructure of aluminium alloy Al-1% Mg. Acta Materialia, 47, (8), 2367-2376 (1999).
E3. Bradley, A.D., Doyle, R.A., Charalambous, D., Lo, W., Cardwell, D.A., Campbell, A.M., Vanderbemden, P. Transport properties of bulk-bicrystal grain boundaries in artificially joined large-grain YBCO. IEEE Transactions on Applied Superconductivity, 9, (2), 2038-2041 (June 1999).
E4. Bressan, J.D., Genin, G.M., Williams, J.A. The influence of pressure, boundary film shear strength and elasticity on the friction between a hard asperity and a deforming softer surface. Lubrication at the Frontier: Proceedings, 24th Leeds-Lyon Symposium on Tribology, Lyon, France (September 1998); Edited by D. Dowson et al, 79-90 (Elsevier, 1999).
E5. Campbell, A.M. Field distributions in superconductors. In: Handbook of Applied Superconductivity; Edited by B. Seeber, 1 (IOP Publishing, 1998). ISBN 0750303778.
E6. Campbell, A.M. Fields and losses in high Tc conductors. IEEE Transactions on Applied Superconductivity, 9, (2), Part 2, 2137-2142 (1999).
E7. Campbell, A.M. Hysteresis losses. In: Handbook of Applied Superconductivity; Edited by B. Seeber, 1 (IOP Publishing, 1998). ISBN 0750303778.
E8. Campbell, A.M. Introduction to AC losses. In: Handbook of Applied Superconductivity; Edited by B. Seeber, 1, 173-185 (IOP Publishing, 1998). ISBN 0750303778.
E9. Chen, C., Lu, T.J., Fleck, N.A. Effect of imperfections on the yielding of two-dimensional foams. Journal of the Mechanics and Physics of Solids, 47, (11), 2235-2272 (1999).
E10. Cheung, C.Y., Cocks, A.C.F., Cebon, D. Isolated contact model of an idealized asphalt mix. International Journal of Mechanical Science, 41, (7), 767-792 (1999).
E11. Coombs, T., Campbell, A.M., Storey, R., Weller, R. Superconducting magnetic bearings for energy storage flywheels. IEEE Transactions on Applied Superconductivity, 9, (2), Part 1, 968-971 (1999).
E12. Court, R.S., Sutcliffe, M.P.F., Tavakoli, S.M. Fracture and failure analysis of adhesively bonded joints by video imaging techniques. Proceedings, Adhesion '99, 7th International Conference on Adhesion and Adhesives, Cambridge (September 1999).
E13. Deshpande, V.S., Cebon, D. Models of a particle reinforced nonlinear-viscous composite. Journal of Engineering Mechanics (ASCE), 125, (3), 255-262 (1999).
E14. Deshpande, V.S., Cebon, D. Steady-state constitutive relationship for idealised asphalt mixes. Mechanics of Materials, 31, (4), 271-287 (1999).
E15. Deshpande, V.S., Fleck, N.A. Multi-axial yield of aluminium alloy foams. Metal Foams and Porous Metal Structures: Metfoam '99, Bremen, Germany (June 1999); Edited by J. Banhart, M.F. Ashby, N.A. Fleck, 247-254 (Verlag Metall Innovation Technologie, Bremen, Germany, 1999). ISBN 3980574873.
E16. Dyson, I.N., Williams, J.A., Kapoor, A. The effect of surface hardening on the elastic shakedown of elliptical contacts. Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology, 213, (J4), 287-298 (1999).
E17. Furu, T., Shercliff, H.R., Baxter, G.J., Sellars, C.M. The influence of transient deformation conditions on recrystallization during thermomechanical processing of an Al-1% Mg alloy. Acta Materialia, 47, (8), 2377-2389 (1999).
E18. Greenwood, J.A., Johnson, K.L. An alternative to the Maugis model of adhesion between elastic spheres. Journal of Physics D: Applied Physics, 31, (22), 3279-3290 (November 1998).
E19. Harte, A.-M., Fleck, N.A., Ashby, M.F. Fatigue failure of an open cell and a closed cell aluminium alloy foam. Acta Materialia, 47, (8), 2511-2524 (1999).
E20. Harte, A.-M., Fleck, N.A., Ashby, M.F. Sandwich panel design using aluminium alloy foam. Metal Foams and Porous Metal Structures: Metfoam '99, Bremen, Germany (June 1999); Edited by J. Banhart, M.F. Ashby, N.A. Fleck, 307-312 (Verlag Metall Innovation Technologie, Bremen, Germany, 1999). ISBN 3980574873.
E21. Huber, J.E., Fleck, N.A., Landis, C.M., McMeeking, R.M. A constitutive model for ferroelectric polycrystals. Journal of the Mechanics and Physics of Solids, 47, (8), 1663-1697 (1999).
E22. Huber, J.E., Fleck, N.A., McMeeking, R.M. A crystal plasticity model for ferroelectrics. Ferroelectrics, 228, (1), 39-52 (1999).
E23. Johnson, K.L. The mechanics of adhesion. Tribology International, 31, (8), 418-423 (1998).
E24. Kovalev, L.K., Ilyushin, K.V., Larionoff, A.E., Kovalev, K.L., Penkin, V.T., Larionoff, S.A., Dew-Hughes, D., McCulloch, M.D., Cardwell, D.A., Lo, W., Akimov, I.I. Alternators which use HTSC wire coils and bulk YBCO materials. Proceedings, 17th International Cryogenic Engineering Conference, Bournemouth (July 1998); Edited by D. Dew-Hughes et al, 379-382 (IOP Publishing, 1998). ISBN 0750305975.
E25. Liu, D., Fleck, N.A. Scale effect in the initiation of cracking of a scarf joint. International Journal of Fracture, 95, (1-4), 67-88 (1999).
E26. Lo, W., Cardwell, D.A., Bradley, A.D., Doyle, R.A., Shi. Y.H., Lloyd, S. Development of non-weak link bulk YBCO grain boundaries for high magnetic field engineering applications. IEEE Transactions on Applied Superconductivity, 9, (2), Part 2, 2042-2045 (June 1999).
E27. Lo, W., Cardwell, D.A., Shi, Y.H. Spray dried Pt-doped Nd-Ba-Cu-O precursor powder for seeded peritectic processing of large superconducting grains. Materials Science and Engineering B: Solid State Materials for Advanced Technology, 65, (1), 1-10 (May 1999).
E28. Lo, W., Hari Babu, N., Cardwell, D.A., Shi, Y.H., Astill, D.M. Preparation and properties of large grain peritectically processed Nd-Ba-Cu-O. Advances in Superconductivity XI: Proceedings, 11th International Symposium on Superconductivity (ISS '98), Fukuoka, Japan (November 1998); Edited by N. Koshizuka, S. Tajima, 2, 721-724 (Springer, 1999).
E29. Lu, T.J. Heat transfer efficiency of metal honeycombs. International Journal of Heat and Mass Transfer, 42, (11), 2031-2040 (June 1999).
E30. Lu, T.J., Chen, C. Thermal transport and fire retardance properties of cellular aluminium alloys. Acta Materialia, 47, (5), 1469-1485 (1999).
E31. Lu, T.J., Hess, A., Ashby, M.F. Sound absorption in metallic foams. Journal of Applied Physics, 85, (11), 7528-7539 (1999).
E32. Lubrecht, A.A., Graille, D., Venner, C.H., Greenwood, J.A. Waviness amplitude reduction in EHL line contacts under rolling-sliding. Transactions of the ASME, Journal of Tribology, 120, (4), 705-709
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E33. Majoros, M., Glowacki, B.A., Campbell, A.M., Han, Z., Vase, P. AC losses in BiPbSCaCuO/Ag multifilamentary tapes in conditions similar to transmission lines. Physica C: Superconductivity and Its Applications, 310, (1-4), 95-100 (1998).
E34. Majoros, M., Glowacki, B.A., Campbell, A.M., Han, Z., Vase, P. Apparent AC losses in helical BiPbSrCaCuO-2223/Ag multifilamentary tape measured by different potential taps at power frequencies. Physica C: Superconductivity and Its Applications, 314, (1-2), 1-11 (1999).
E35. Majoros, M., Jansak, L., Zannella, S., Curcio, F., LaCascia, P., Ottoboni, V., Friend, C.M., Lelay, L., Glowacki, B.A., Campbell, A.M. Temperature dependence of transport AC losses in Bi-2223/Ag multifilamentary tapes. Physica C: Superconductivity and Its Applications, 310, (1-4), 6-11 (1998).
E36. Manninen, S., Hämäläinen, K., Dixon, M.A.G., Cooper, M.J., Cardwell, D.A., Buslaps, T. Electronic properties of YBa2Cu3O7-d and Bi2Sr2CaCu2O8 superconductors studied by Compton scattering technique. Physica C: Superconductivity and Its Applications, 314, (1-2), 19-26 (1999).
E37. McCullough, K.Y.G., Fleck, N.A., Ashby, M.F. Toughness of aluminium alloy foams. Acta Materialia, 47, (8), 2331-2343 (1999).
E38. McCullough, K.Y.G., Fleck, N.A., Ashby, M.F. Uniaxial stress-strain behaviour of aluminium alloy foams. Acta Materialia, 47, (8), 2323-2330 (1999).
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E51. Storåkers, B., Fleck, N.A., McMeeking, R.M. The viscoplastic compaction of composite powders. Journal of the Mechanics and Physics of Solids, 47, (4), 785-815 (1999).
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E54. Sumiyoshi, F., Kinoshita, R., Miyazono, Y., Campbell, A.M., Ohmatsu, K. Proposal of new type Ag-BSCCO tapes and wires with low losses. IEEE Transactions on Applied Superconductivity, 9, (2), Part 2, 2549-2552 (June 1999).
E55. Sutcliffe, M.P.F. Flattening of random rough surfaces in metal-forming processes. Transactions of the ASME, Journal of Tribology, 121, (3), 433-440 (July 1999).
E56. Vanderbemden, P., Cloots, R., Ausloos, M., Doyle, R.A., Bradley, A.D., Lo, W., Cardwell, D.A., Campbell, A.M. Intragranular and intergranular superconducting properties of bulk melt-textured YBCO. IEEE Transactions of Applied Superconductivity, 9, (2), Part 2, 2308-2311 (June 1999).
E57. Wang, X., Lu, T.J. Optimized acoustic properties of cellular solids. Journal of the Acoustical Society of America, 106, (2), 756-765 (1999).
E58. Wang, X., Stronge, W.J. Micropolar theory for two-dimensional stresses in elastic honeycomb. Proceedings of the Royal Society of London, Series A: Mathematical, Physical and Engineering Sciences, A455, (1986), 2091-2116 (June 1999).
E59. Weller, R.A., Campbell, A.M., Coombs, T.A., Cardwell, D.A., Storey, R.J., HanCox, J. Computer modelling of superconducting film type fault current limiters. IEEE Transactions on Applied Superconductivitiy, 9, (2), Part 1, 1377-1380 (June 1999).
E60. Williams, J.A. Wear modelling: analytical, computational and mapping: a continuum mechanics approach. Wear, 225-229, 1-17 (1999).
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Last modified: June 2000