Dynamics of Deep Water Moorings
Mechanics of Impact
Vehicle Dynamics and Road Damage
Probabilistic and Possibilistic Methods
Statistical Energy Analysis
Mechanics of Musical Instruments
Squeal of Vehicle Disk Breaks
Modelling of Vibration Damping
Transmission of Vibration from Railways into Buildings
Fault Identification using Neural Networks
Quality Control of Asymmetric Rotating Bladed Systems
Torsional Vibration of Non-Linear Engine Couplings
Wavelet and Time-Frequency Analysis
Vibration of Imperfect Periodic Systems
Professor R. S. Langley
Future oil production may occur in water depths in excess of 2000m. This project is investigating the statics and dynamics of deep water mooring lines made of fibrous materials. Both geometric and material non-linearities are of particular concern. This project is funded by BP-Amoco.
Dr W.J. Stronge
Fundamental research is continuing into deformation processes during impact with the aim of obtaining a physical basis for parameters representing low speed or "rigid body" impact where deformations are small. This research is relevant to limits on operation of mechanical linkages in high speed assembly operations, impact printers and sports mechanics. Effects of friction and tangential compliance on impact behaviour has been described in a review paper(F42). New developments in this field during the last 10 years are presented in a textbook, Impact Mechanics, published by Cambridge University Press(F43).
Applications of low speed impact theory to problems of granular flow have recently become more widespread. For systems of stiff granules with compliant contacts that are connected by unilateral constraints, new results show the spread of reaction impulse through the contacts as a dispersive wave. Interactions between neighbouring contacts depend on the local speed of wave propagation(F44,F45,F46).
Research continues on obtaining methods of assessing risk of perforation in metal structures subjected to impact by small sub-ordnance velocity fragments or missiles. Failure criteria representing kinematic constraints of deformation as well as material properties are being developed for oblique penetration and dishing of thin to moderately thick metal plates(F24).
Dr D. Cebon
Research continued on the use of advanced suspensions technologies to improve heavy vehicle safety and dynamic performance and reduce road damage. A number of papers have been published on the design, performance and control of computer-controlled 'semi-active' dampers for heavy vehicles(F15,F16,F17,F35) and the development and control of active anti-roll systems for lorries(F36,F37). The current phase of the project involves implementing these research results in an experimental tractor-semi-trailer vehicle. Considerable support for this work, in cash and kind, has been received from the industrial members of the Cambridge Vehicle Dynamics Consortium (Tinsley Bridge Limited, Arvin Meritor, Koni BV, Volvo Trucks, DERA, Shell, General Trailers, Fluid Power Design and Mektronika Systems). This work is co-funded by an EPSRC grant.
An EPSRC-funded project on the rolling resistance of lorry tyres was completed(F34). The research required development of a novel system for measuring the rolling resistance of large tyres, which is able to resolve longitudinal forces of 1-2 N in the presence of vertical forces of up to 50kN. New insights were developed into the mechanisms of rolling resistance and influence of tyre pressure, vehicle speed and vehicle vibration on energy losses.
An EC-funded project on the use of multiple-sensor 'weigh-in-motion' (WIM) systems for measuring the weights of heavy vehicles travelling at highway speeds was completed(F41). New methods for designing multiple-sensor arrays were developed. It was shown that these techniques can provide sufficient accuracy to enable the use of WIM systems for axle load enforcement.
Dr J.D. Smith
Measurement of transmission error for gear noise investigations has been extended so that smaller, more robust encoders can be used. A fully instrumented test rig for gear rattle problems has been devised and is in manufacture preparing to test non-linear modelling of typical automotive drive systems.
Railway line corrugation measurements(F5) have focussed on improving the electronics and tuning the mechanics of the trolleys to extend life and give reliable results even when debris is present.
Professor R.S. Langley
Uncertainty is normally modelled in statistical terms, although in many practical situations (for example the automobile and aerospace industries) the poor quality and quantity of the available input data does not justify a complex probabilistic analysis of the system. Recently a number of possibilistic methods have been developed, including interval analysis, convex set theory, and fuzzy set theory(F3,F0,F23,F38,F39). Current work is directed at providing a unified computational framework for probabilistic and possibilistic methods, so that the same code can be used to perform each of the methods. With this approach the method employed can readily be matched to the level of available knowledge regarding the input parameters. This work is in collaboration with DERA Farnborough and BAe Sowerby Research Centre.
Professor R.S. Langley
Work has been directed at providing a hybrid dynamic analysis procedure that couples statistical energy analysis (SEA) and the finite element method. With this approach the long wavelength deformation of the structure is modelled deterministically using finite elements, while the short wavelength motion is modelled statistically using SEA. This addresses the complex dynamics that can occur in an automobile or marine structure at medium frequencies. This work is funded by Vibro-Acoustic Sciences via the RESOUND consortium.
Professor J. Woodhouse
The vibrational behaviour of musical instruments continues to provide challenging scientific problems. Detailed measurements and modelling have been undertaken to characterise the frictional behaviour of rosin, the material used to coat the hairs of a violin bow(F40,F50). It appears that the friction coefficient does not depend directly upon sliding speed, as has generally been assumed. Instead, it is governed by temperature in the contact regions, which depends only indirectly on sliding speed. With this new model, it is hoped to be able to demonstrate in the near future detailed agreement of bowed transients between measurements (using an automatic bowing machine) and simulations.
Among the necessary ingredients of these accurate simulations are the mechanical properties of instrument strings. Of these, the hardest to measure are the torsional properties. Recent results(F49), using an optical measurement technique, have given the best available information about the torsional wave speed and damping behaviour of real strings, in this case cello strings. It was shown that the behaviour is well described over a broad frequency range by constant-Q damping, and a method of incorporating this into time-marching simulation algorithms has been developed.
Professor J. Woodhouse
Brake squeal has long presented an intractable problem to manufacturers of vehicle braking systems. A project is now under way, with Bosch Braking Systems, to improve understanding of this phenomenon so that squeal-resistant designs can be developed on a rational basis. A new theoretical formulation of the phenomenon has been developed, and a laboratory rig built which will allow this model to be validated and developed.
Professor J. Woodhouse
Work has continued on the modelling of vibration damping in structures. The goal is to develop methods whereby measurements of (complex) modal properties can be used to determine the correct damping model for a structure, and to determine the spatial distribution of damping. Very promising results have been obtained using simulation studies, and preliminary measurements indicate that it should be possible to put the approach into practice on real structures.
Dr H.E.M. Hunt
Professor D.E. Newland
Computationally efficient procedures are being developed to evaluate measures for the control of vibration transmission from railways into buildings(F11,F13,F47,F48). The nature of the soil coupling between railway tunnels and piled foundations is being analysed in detail using boundary element methods. Using these models as benchmarks the objective is to establish the extent to which much simpler models are accurate and useful for design purposes. New performance indicators based on "Power Flow" are proving far more illuminating than the conventional "Insertion Loss".
Dr H.E.M. Hunt
A neural network approach to fault identification in structures using vibration data makes use of the maximum-likelihood method and Bayesian statistics. New assurance criteria, based on modal energies calculated from frequency-response functions, are used in conjunction with modal properties giving a better classification of faults than any of the individual methods(F25,F26,F27,F28).
Dr H.E.M. Hunt
Finding faults in bladed disc structures (turbines, compressors) can be carried out using vibration testing. In general, faults cause asymmetry which split normally-repeated modes. Research continues into reliable methods by which the blade most likely to fail in service can be identified.
Dr H.E.M. Hunt
Non-linear torsional vibration "dampers" are being used increasingly in marine-engine drive trains. Conventional linear analyses are inadequate and work has begun on methods to evaluate the effectiveness of non-linear components.
Professor D.E. Newland
Further applications of time-varying cross-spectral analysis have been studied by the harmonic wavelet method, including both amplitude and phase discrimination. The software is now being tested by a number of groups, including our own Geotechnical Research Group who are using it to analyse the dynamic response of centrifuge soil models. Current research is directed towards improving phase discrimination and its practical interpretation(F29,F30,F33).
Dr D. Cebon
Research into the 'localisation' of vibration in imperfect periodic structures was published(F51). A simple, efficient method was devised for measuring the characterising vibration localisation in such structures. The method has applications in periodic systems such as turbine blade assemblies and multi-bay trusses.
F1. Aglietti, G.S., Langley, R.S., Rogers, E., Gabriel, S.B. Monte Carlo and form simulation of active control performance in the presence of structural uncertainty. Proceedings, International Colloquium on Numerical Modelling of Uncertainties, Euromech 405, Valenciennes, France (November 1999); Edited by P. Level, et al. (Presse Universitaires de Valenciennes, 2000).
F2. Aglietti, G.S., Langley, R.S., Rogers, E., Johnson, D.F. A study of robustness of active control systems for mass loaded satellite panels. 7th International Conference on Recent Advances in Structural Dynamics, Southampton (July 2000).
F3. Bremner, P.M., Langley, R.S. Computer program media, method and system for vibration and acoustic analysis of complex structural-acoustic systems. United States Patent 6090147 (July 2000).
F4. Fu, T.T., Cebon, D. Predicting fatigue lives for bi-modal stress spectral densities. International Journal of Fatigue, 22, (1), 11-21 (January 2000).
F5. Grassie, S.L., Saxon, M.J., Smith, J.D. Measurement of longitudinal rail irregularities and criteria for acceptable grinding. Journal of Sound and Vibration, 227, (5), 949-964 (November 1999).
F6. Greenwood, J.A. Non-Newtonian lubrication. Proceedings, 27th Leeds-Lyon Symposium on Tribology, Lyon, France (September 2000).
F7. Greenwood, J.A. Transverse roughness in elastohydrodynamic lubrication. Proceedings of the Institution of Mechanical Engineers Part J, Journal of Engineering Tribology, 213, (J5), 383-396 (1999).
F8. Greenwood, J.A. Two-dimensional flow of a non-Newtonian lubricant. Proceedings of the Institution of Mechanical Engineers Part J, Journal of Engineering Tribology, 214, (J1), 29-41 (2000).
F9. Greenwood, J.A. What is an asperity? Conference on Tribology of Information Storage Devices, Santa Clara, CA, USA (December 1999).
F10. Greenwood, J.A., Wu, J.J. Surface roughness and contact: an apology. 2000 AIMETA International Tribology Conference, L'Aquila, Italy (September 2000).
F11. Hunt, H.E.M. Base-isolation of buildings: a review. Acoustics 2000: Research into Practice, Institute of Acoustics Spring Conference, Liverpool, 22, (2), 205-211 (April 2000).
F12. Hunt, H.E.M. Noise from cars, noise from trains, noise from planes. International Journal of Acoustics and Vibration, 5, (1), 2 (March 2000).
F13. Hunt, H.E.M., Forrest. J. Floating slab track for vibration reduction: why simple models don't work. Proceedings, 7th International Congress on Sound and Vibration, Garmisch-Partenkirchen, Germany (July 2000); Edited by G. Guidati, H. Hunt, H. Heller, A. Heiss (Kramer Technology Publishing, Munich, Germany, 2000). CD Rom.
F14. Johnson, K.L. Contact mechanics and adhesion of viscoelastic spheres. Microstructure and Microtribology of Polymer Surfaces: Selected Papers, American Chemical Society International Symposium, Boston, MA, USA (August 1998); Edited by V.V.Tsukruk, K.J. Wahl, 24-41. ACS Symposium Series 741 (American Chemical Society, 2000). ISBN 0841236828.
F15. Kitching, K.J., Cebon, D., Cole, D.J. An experimental investigation of preview control. Vehicle System Dynamics, 32, (6), 459-478 (December 1999).
F16. Kitching, K.J., Cole, D.J., Cebon, D. Performance of a semi-active damper for heavy vehicles. Transactions of the ASME, Journal of Dynamic Systems Measurement and Control, 122, (3), 498-506 (September 2000).
F17. Kitching, K.J., Cole, D.J., Cebon, D. Theoretical investigations into the use of controllable suspensions to minimize road damage. Proceedings of the Institution of Mechanical Engineers Part D, Journal of Automobile Engineering, 214, (D1), 13-31 (2000).
F18. Langley, R.S. The dynamic analysis of uncertain structures. 7th International Conference on Recent Advances in Structural Dynamics, Southampton (July 2000).
F19. Langley, R.S. Models of uncertainty in structural dynamics. 138th Meeting of the Acoustical Society of America, Columbus, OH, USA (November 1999).
F20. Langley, R.S. SEA: current and future research needs. Proceedings, 1st International AutoSEA Users Conference, San Diego, CA, USA (July 2000).
F21. Langley, R.S. Statistical energy analysis of structure-borne noise: progress and problems. Physical Acoustics 99, Institute of Physics, London (October 1999).
F22. Langley, R.S. Wave evolution, reflection and transmission along inhomogenous waveguides. Journal of Sound and Vibration, 227, (1), 131-158 (October 1999).
F23. Langley, R.S., Smith, J.R.D., Bremner, P.G. A hybrid FEA/SEA technique for the analysis of complex systems: application to plate and beam structures. 138th Meeting of the Acoustical Society of America, Columbus, OH, USA (November 1999).
F24. Liu, D., Stronge, W.J. Ballistic limit of metal plates struck by blunt deformable missiles: experiments. International Journal of Solids and Structures, 37, (10), 1403-1423 (March 2000).
F25. Marwala, T., Hunt, H.E.M. Damage detection using pseudo-modal energies. Cambridge University Engineering Department Technical Report CUED/C-MECH/TR.81 (February 2000).
F26. Marwala, T., Hunt, H.E.M. Feasibility of damage detection using vibration data in a population of cylinders. Proceedings, IMAC-XVIII, 18th IMAC Conference on Computational Challenges in Structural Dynamics, San Antonio, TX, USA (February 2000), 1577-1583. Proceedings of the SPIE - International Society of Optical Engineering 4062 (Society for Experimental Mechanics, Bethel, MD, USA, 2000). ISBN 0912053674.
F27. Marwala, T., Hunt, H.E.M. Maximum likelihood and Bayesian neural networks for fault detection using vibration data. Cambridge University Engineering Department Technical Report CUED/C-MECH/TR.80 (December 1999).
F28. Marwala, T., Hunt, H.E.M. Probabilistic fault identification using vibration data and neural networks. Proceedings, IMAC-XVIII, 18th IMAC Conference on Computational Challenges in Structural Dynamics, San Antonio, TX, USA (February 2000), 674-680. Proceedings of the SPIE - International Society of Optical Engineering 4062 (Society for Experimental Mechanics, Bethel, MD, USA, 2000). ISBN 0912053674.
F29. Newland, D.E. Computation of time-varying cross-spectra. Proceedings, 7th International Congress on Sound and Vibration, Garmisch-Partenkirchen, Germany (July 2000); Edited by G. Guidati, H. Hunt, H. Heller, A. Heiss, paper 060 (Kramer Technology Publishing, Munich, Germany, 2000). CD Rom.
F30. Newland, D.E. Harmonic wavelets in vibrations and acoustics. In: Wavelets: the Key to Intermittent Information? Edited by B.W. Silverman, J. C. Vassilicos, Chapter 13. (Oxford University Press, 2000). ISBN 019850716X.
F31. Newland, D.E. Priorities for engineering education. Massachusetts Institute of Technology New Millennium Colloquium on the Future of Civil and Environmental Education, Cambridge, MA, USA (March 2000). (Available on web at: http://www.eng.cam.ac.uk/~den/)
F32. Newland, D.E. Reflections on a Week's Visit to MIT, March 2000. Cambridge University Engineering Department (April 2000). (Available on web at: http://www.eng.cam.ac.uk/~den/)
F33. Newland, D.E., Butler, G.D. Application of time-frequency analysis to transient data from centrifuge earthquake testing. Shock and Vibration, 7, (4), 195-202 (2000).
F34. Popov, A.A., Cole, D.J., Cebon, D., Winkler, C.B. Energy loss in truck tyres and suspensions. The Dynamics of Vehicles on Roads and on Tracks: Proceedings,16th IAVSD Symposium, Pretoria, South Africa (August-September 1999); Edited by R. Fröhling. Published as: Vehicle System Dynamics, 33, Supplement, 516-527 (2000). ISBN 9026516290.
F35. Roebuck, R.L., Kitching, K.J., Cebon, D., DeRuiter, A. Developments in semi-active heavy vehicle suspensions. Proceedings, 6th International Symposium for Heavy Vehicle Weights and Dimensions, Saskatoon, Canada, 353-365 (June 2000).
F36. Sampson, D.J.M., Jeppesen, B.P., Cebon, D. Development of an active anti-roll control system for heavy vehicles. Proceedings, 6th International Symposium for Heavy Vehicle Weights and Dimensions, Saskatoon, Canada, 375-384 (June 2000).
F37. Sampson, D.J.M., McKevitt, G., Cebon, D. The development of an active roll control system for heavy vehicles. The Dynamics of Vehicles on Roads and on Tracks: Proceedings,16th IAVSD Symposium, Pretoria, South Africa (August-September 1999); Edited by R. Fröhling. Published as: Vehicle System Dynamics, 33, Supplement, 704-715 (2000). ISBN 9026516290.
F38. Shorter, P.J., Langley, R.S. The spatial correlation of vibrational wavefields and their application to mid-frequency structural-acoustics. Novem 2000, International Conference on Noise and Vibration Energy Methods, Lyon, France; Edited by G. Pavic (August/September 2000). CD Rom.
F39. Shorter, P.J., Langley, R.S. Wavefield suppression and its applications to mid-frequency structural-acoustics. Internoise 2000, 29th International Congress on Noise Control Engineering, Nice, France (August 2000).
F40. Smith, J.H., Woodhouse, J. The tribology of rosin. Journal of the Mechanics and Physics of Solids, 48, (8), 1633-1681 (August 2000).
F41. Stergioulas, L.K., Cebon, D., Macleod, M.D. Static weight estimation and system design for multiple-sensor weigh-in-motion. Proceedings of the Institution of Mechanical Engineers Part C, Journal of Mechanical Engineering Sciences, 214, (C8), 1019-1035 (2000).
F42. Stronge, W.J. Contact problems for elasto-plastic impact in multi-body systems. Keynote lecture. Impacts in Mechanical Systems - Analysis and Modelling, Euromech Colloquium 397, Grenoble, France (June/July 1999); Edited by B. Brogliato, 189-234. Lecture Notes in Physics 551 (Springer-Verlag, 2000). ISBN 354067523X
F43. Stronge, W.J. Impact Mechanics (Cambridge Universtiy Press, 2000). ISBN 0521632862.
F44. Stronge, W.J. Generalised impulse and generalised momentum applied to multibody impact with an energetic coefficient of restitution. ICTAM 2000: International Congress of Theoretical and Applied Mechanics, 20th IUTAM Congress, Chicago, IL, USA (August/September 2000).
F45. Stronge, W.J. Mechanics of impact for compliant mutli-body systems. IUTAM Symposium on Unilateral Multibody Contacts, Munich, Germany, (August 1998); Edited by F. Pfeiffer, Ch. Glocker, 137-144. Solid Mechanics and Its Applications 72 (Kluwer Academic Publishers, 2000). ISBN 0792360303.
F46. Stronge, W.J. Multi-body impact with friction. Multi-Body Dynamics: Monitoring and Simulation Techniques II: 2nd Triennial International Symposium on Multi-body Dynamics, Bradford (June 2000); Edited by H. Rahnekat, et al, 15-26 (Professional Engineering Publishing, 2000). ISBN 1860582583.
F47. Talbot, J.P., Hunt, H.E.M. An energy method for assessing the performance of base-isolated structures. NOVEM 2000, International Conference on Noise and Vibration Energy Methods, Lyon, France; Edited by G. Pavic (August/September 2000). CD Rom.
F48. Talbot, J.P., Hunt, H.E.M. On the performance of base-isolated buildings. Building Acoustics, 7, (3), 163-178 (2000).
F49. Woodhouse, J., Loach, A.R. The torsional behaviour of cello strings. Acustica/Acta Acustica, 85, (5), 735-740 (September/October 1999).
F50. Woodhouse, J., Schumacher, R.T., Garoff, S. Reconstruction of bowing point friction force in a bowed string. Journal of the Acoustical Society of America, 108, (1), 357-368 (July 2000).
F51. Yap, D.S.C., Cebon, D. Energy confinement in imperfect periodic systems. Journal of Sound and Vibration, 232, (4), 669-694 (May 2000).
[Table of Contents]
Last modified: September 2001