Mechanics of Musical Instruments
Vibration Prediction in Complex Structures
Offshore Pipeline Inspection
Track Settlement Adjacent to Bridge Abutments
Dynamic In-situ Measurement of Materials Properties
Vehicle Dynamics and Road Damage
Dr C. Hogue
Work has continued on 3-D modelling of impacting bodies, with the detailed investigation of the roles of shape, friction, restitution and compliance. Experimental results obtained by video imaging have been used to validate and improve 3-D impact models.
Dr C. Hogue
A new project in household solid waste sorting techniques for recycling purposes was started, sponsored by COMDEC. Work done to date includes the design of a low-cost automatic sorting technique for glass and plastic for which a patent was filed. Current work investigates other methods and combinations of methods to sort a wider range of recyclables, as well as to colour sort glass and translucent materials.
Dr J.D. Smith
Extension of work on the use of Smith shocks for gear condition monitoring is progressing but is limited by the availability of high power gearboxes which can be damaged. Previous work on the effects of misalignment on high quality helical gears is being extended to predict the high forces generated when the gears lose contact. Prediction of the dynamic characteristics of long hydrostatic bearings with finite pocket volume is being investigated.
Problems associated with practical measurement techniques for low frequency and low amplitude vibrations have been encountered in industry and research is proceeding on finding solutions. A course on gear noise has been given again for the British Gear Association.
Dr J.A. Williams
Work on the mechanics of the interaction between both dry and lubricated surfaces has continued. Shakedown principles have been applied to the analysis of the changes in surface topography which take place during repeated sliding: subsequent progressive plastic flow of asperities leads to the formation of very thin, filmy wear debris by a process of plastic ratchetting brought about by the repeated pummelling of the softer surface by the asperities on the harder. A model for this mild wear regime, which is driven by normal loads rather than by friction, has been developed and is to be presented shortly. Shakedown principles have also been applied to surfaces whose strength properties vary with depth as a result of surface engineering by thermo-chemical hardening(E25) and, in collaboration with Sheffield University, are currently being extended to more complex case of coated surfaces where not only both the elastic and plastic material properties vary with depth but also the integrity of the bond between coating and substrate must be considered. Further work has also been completed on abrasive wear(E42,E45) and on the scratch hardness test(E41). Investigations into the role of adsorbed lubricant films in conditions of boundary lubrication and on the mechanisms of lubrication in metal cutting are continuing(E43).
The fourth Cambridge Tribology Course, run jointly with the Department of Materials Science and held under the auspices of the Cambridge Programme for Industry, took place in March 1996 and attracted some 25 delegates. The course will run again in Cambridge in September 1997.
Dr J. Woodhouse
The vibrational behaviour of musical instruments continues to provide challenging scientific problems. Two doctoral dissertations have been completed on the subject (by Pitteroff and Wood). The lecture notes from a Summer School on the subject have been published(E44). Collaboration with violin makers is leading to improved methods of ensuring quality control by using acoustical test methods for the fine adjustment of parts of the structure during the building process.
Dr J. Woodhouse
The vibration of complex structures cannot be successfully estimated by deterministic methods except at very low frequencies. At higher frequencies statistical methods must be used. A recent development, in collaboration with SAIC Ltd and DRA Winfrith, has been to apply statistical power flow modelling to the prediction of vibration levels in a ship or submarine hull structure, taking account of the coupling between different kinds of travelling wave brought about by structural features such as hatches and equipment mountings.
Prof. D.E. Newland
Theoretical work on the application of harmonic wavelets to time-frequency analysis has continued(E34). The emphasis has been on time-frequency and time-scale mapping, which are important for diagnostic vibration analysis, and the development of a variable Q transform is being explored. Trials are being carried out on a variety of artificial and measured data to compare the effectiveness of variable Q transforms with the short-time Fourier transform and Wigner-Ville methods. Signal deconstruction by harmonic wavelets appears to provide the basis for computationally-efficient algorithms for the construction of high-definition time-frequency maps. There is considerable current interest in the vibration analysis community and test data has been provided by a number of different sources including the NASA Kennedy Space Center. Professor Newland is again organising a symposium on Time-Frequency and Wavelet Analysis at the ASME's Biennial Vibration and Noise Conference which will be held in September 1997 in California.
Dr H.E.M. Hunt
Prof. D.E. Newland
Structural models of infinite extent continue to be employed for the study of the mechanisms of vibration generation by railways(E21,E22) and the propagation of vibration into buildings. The models include the influence of piled foundations and recent work is focussed on the effect of the tunnel structure itself on vibration propagation. This work is carried out in conjunction with Tiflex Ltd., manufacturers of elastomeric products for vibration control.
Dr H.E.M. Hunt
Testing of the `vibrating pig'(E20) in conjunction with Vetco PipelineServices in Houston is complete. The pig generates vibration as it moves through off-shore oil pipelines and it is used to detect free spanning and loss of cover. Exposed pipelines are easily damaged by ocean currents and, in shallow water, by ships' keels and anchors.
Dr H.E.M. Hunt
Prof. D.E. Newland
Computational modelling of the growth of track settlement adjacent to bridge abutments is complete(E23,E24). The influence of track and vehicle dynamics is included and the effect of sleeper impact owing to voidage has been found to be very significant. A programme of experimental work is now being planned to validate the models against measurement of track settlement. This work has been carried out in conjunction with the Netherlands Railways and with Tiflex Ltd.
Dr H.E.M. Hunt
Measurement of elastic moduli by resonant and free vibration techniques is commonplace but recent work in the Department has concentrated on the measurement of more than one damping constant for lightly-damped materials. The difference, for example, between damping in shear and in bulk compression can give information about the material microstructure. This forms the basis of a novel NDT method based on the vibration of thin plates.
Dr D. Cebon
The Cambridge Vehicle Dynamics Consortium has continued to grow and attract funding from the heavy vehicle industry. Volvo Trucks joined the five existing industrial members this year. The research continues to concentrate on use of advanced suspension technologies to improve heavy vehicle safety(E28,E29) and reduce road damage(E2,E3,E4).
Research has progressed on the design and testing of a prototype semi-active truck damper(E26) and on developing suspension control strategies that minimise road damage due to dynamic tyre forces generated by heavy vehicles. Further progress has been made on developing control strategies to optimise the response of heavy vehicles with active suspensions, subjected to simultaneous inputs from road surface roughness, braking and steering(E14).
A long-term research project into methods for assessing the road damaging potential of heavy vehicles has essentially been completed. A vehicle assessment method based on simple laboratory tests of vehicle response and a suspension parameter estimation procedure has been developed. The method is thought to offer the best compromise between cost and accuracy and would be suitable for legislative purposes(E35,E36).
Papers have been published on the spatial repeatability of dynamic tyre forces(E6), the effects of spatial repeatability on road damage(E7), and the road-damaging potential of dynamic tyre forces of heavy vehicles measured in mixed traffic(E37). Each of these projects made extensive use of the `wheel load-measuring mat' developed previously by the research group. Further work has been published on modelling the structural deterioration of asphalt pavements during their service lives(E8,E9), and on the effects of truck tyre configuration on road damage(E5).
A two year grant for a study of `Multiple-Sensor Weigh-in-Motion' has begun. This work is part of a larger project, performed in collaboration with a number of other European Research Organisations.
Dr D. Cebon
Prof. M.F. Ashby
Dr N.A. Fleck
Theoretical and experimental research has continued on the behaviour of asphalts, particularly permanent deformation(E13) fatigue cracking(E11), and fracture(D29). This work is part of a multidisciplinary project on the failure mechanisms of asphalt pavements, funded by the EPSRC.
E1. BERNASCONI, D.J., FANDRICH, M.E., HOGUE, C. Experimental Studies of Rigid Body Collisions in 3-D. 19th International Congress of Theoretical and Applied Mechanics, Kyoto, Japan (August 1996).
E2. BESINGER, F.H., CEBON, D., COLE, D.J. Force control of a semi-active damper. Vehicle System Dynamics, 24, (9), 695-723 (1995).
E3. CEBON, D., BESINGER, F.H., COLE, D.J. Control strategies for semi-active lorry suspensions. Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automobile Engineering, 210, (D2), 161-178 (1996).
E4. COLE, D.J., CEBON, D. Truck suspension design to minimize road damage. Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automobile Engineering, 210, (D2), 95-107 (1996).
E5. COLE, D.J., CEBON, D. Truck tyres, suspension design, and road damage. International Rubber Conference, IRC '96, Manchester (June 1996).
E6. COLE, D.J., COLLOP, A.C., POTTER, T.E.C., CEBON, D. Spatial repeatability of measured dynamic tyre forces. Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automobile Engineering, 210, (D3), 185-197 (1996).
E7. COLLOP, A.C., CEBON, D. Dynamic tyre forces and long-term pavement performance, 26th FISITA Congress, Prague, Czech Republic (June 1996)
E8. COLLOP, A.C., CEBON, D. A model of whole-life flexible pavement performance. Proceedings of the Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Science, 209, (C6), 389-407 (1995).
E9. COLLOP, A.C., CEBON, D. Modelling whole-life pavement performance, Proceedings, 4th International Symposium on Heavy Vehicle Weights and Dimensions, Ann Arbor, MI (June 1995).
E10. COLLOP, A.C., CEBON, D. Parametric study of factors affecting flexible-pavement performance. Journal of Transportation Engineering, ASCE, 121, (6), 485-494 (1995).
E11. COLLOP, A.C., CEBON, D. Stiffness reductions of flexible pavements due to cumulative fatigue damage. Journal of Transportation Engineering, ASCE, 122, (2), 131-139 (1996).
E12. COLLOP, A.C., CEBON, D., COLE, D.J. Effects of spatial repeatability on long-term flexible pavement performance. Proceedings of the Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Science, 210, (C2), 97-109 (1996).
E13. DESHPANDE, V.S., CEBON, D. Plane strain deformation of a regular array of hexagonal particles with a bitumen binder. Cambridge University Engineering Department Report CUED/C-MATS/TR.231 (1996).
E14. DORLING, R.J., CEBON, D. Achievable roll response of automotive suspensions. Proceedings, AVEC'96, International Symposium on Advanced Vehicle Control, Aachen, Germany (June 1996).
E15. GREENWOOD, J.A. Contact of rough surfaces. Solid-Solid Interactions: Proceedings, 1st Royal Society-Unilever Indo-UK Forum in Materials Science and Engineering, London (September 1994); Edited by M.J. Adams, S.K. Biswas, B.J. Briscoe, A1.4, 41-53 (Imperial College Press, London, 1996).
E16. GREENWOOD, J.A. Contact pressure fluctuations, Proceedings of the Institution of Mechanical Engineers, Part I, Journal of Engineering Tribology, 210, (J4), 281-284 (1996).
E17. GREENWOOD, J.A. Flash temperatures for bodies moving at equal high speeds in opposite directions. Transactions of the ASME, Journal of Tribology, 118, 255-257 (January 1996).
E18. GREENWOOD, J.A., MORALES-ESPEJEL, G.E. The amplitude of the complementary function for wavy EHL contacts. Proceedings, 23rd Leeds-Lyon Symposium on Tribology, Leeds (September 1996).
E19. HOGUE, C., MALINGE, D., WOODHOUSE, J. Patent filed on an acoustic method for automatic waste sorting. British Patent Application 9602802.2 (February 1996).
E20. HUNT, H.E.M. Measurement of pipeline support using a vibrating pig. Proceedings, 4th International Congress on Sound and Vibration, St Petersburg, Russia, 1, 611-618 (June 1996) (International Science Publications, AL, USA, 1996)
E21. HUNT, H.E.M. Modelling of rail vehicles and track for calculation of ground-vibration transmission into buildings. Journal of Sound and Vibration, 193, (1), 185-194 (1996).
E22. HUNT, H.E.M. Modelling of structures of infinite extent for calculation of vibration transmission. Proceedings, International Congress MV2, New Advances in Modal Synthesis of Large Structures, Non-linear, Damped and Non-deterministic Cases, Lyon, France, 1, 187-199 (October 1995).
E23. HUNT, H.E.M. Track settlement adjacent to bridge abutments. Vehicle-Infrastructure Interaction IV, Engineering Foundation Conference, San Diego, CA (June 1996).
E24. HUNT, H.E.M., NEWLAND, D.E. The effect of variable foundation properties on railway-track vibration. Proceedings, 4th International Congress on Sound and Vibration, St Petersburg, Russia, 2, 1065-1072 (June 1996) (International Science Publications, AL, USA, 1996)
E25. KAPOOR, A., WILLIAMS, J.A. Shakedown limits in rolling-sliding point contacts on an anisotropic half-space. Wear, 191, 256-260 (1996).
E26. KITCHING, K.J., COLE, D.J., CEBON, D. The development of a heavy vehicle semi-active damper. Proceedings, AVEC'96 International Symposium on Advanced Vehicle Control, Aachen, Germany (June 1996).
E27. LIM, C.T., STRONGE, W.J. Energy losses in normal collision of rigid bodies. Proceedings, 2nd International Symposium on Impact Engineering, Beijing, China, 129-136 (September 1996).
E28. LIN, R.C., CEBON, D., COLE, D.J. Active roll-control of articulated vehicles. Vehicle System Dynamics, 26, (1), 17-43 (1996).
E29. LIN, R.C., CEBON, D., COLE, D.J. Optimal roll control of a single-unit lorry. Proceedings of the Institution of Mechanical Engineers, Part D,, Journal of Automobile Engineering, 210, (D1), 45-55 (1996).
E30. LIU, D., STRONGE, W.J. Deformation of simply supported circular plate by central pressure pulse. International Journal of Solides and Structures, 33, (2), 283-299 (1996).
E31. LIU, D., STRONGE, W.J. Shear and bending deformation of rigid-plastic circular plates by central pressure pulse. International Journal of Impact Engineering, 18, (4), 383-402 (1996).
E32. MATEMILOLA, S.A., STRONGE, W.J. Impact damage and burst of filament-wound CFRP composite pressure vessel. ASME Conference on Pressure Vessels and Piping, Montreal, Canada (July 1996).
E33. MATEMILOLA, S.A., STRONGE, W.J. Impact induced dynamic deformations and stresses in CFRP composite laminates. Composites Engineering, 5, (2), 211-222 (1995).
E34. NEWLAND, D.E. Time-frequency analysis by harmonic wavelets and by the short-time Fourier transform, Proceedings, 4th International Congress on Sound and Vibration, St Petersburg, Russia, 3, 1975-1982 (June 1996) (International Science Publications, AL, USA, 1996)
E35. POTTER, T.E.C., CEBON, D., COLE, D.J. Assessing the relative road damaging potential of HGVs. Proceedings, 4th International Symposium on Heavy Vehicle Weights and Dimensions, Ann Arbor, MI (June 1995).
E36. POTTER, T.E.C., CEBON, D., COLE, D.J. Using parameter estimation to assess road damage. Proceedings, 14th IAVSD Symposium, The Dynamics of Vehicles on Roads and Tracks, Ann Arbor, MI (August 1995); Edited by L. Segal. Published as: Vehicle System Dynamics, supplement to vol. 25 (Swets and Zeitlinger, 1995).
E37. POTTER, T.E.C., CEBON, D., COLLOP, A.C., COLE, D.J. Road-damaging potential of measured dynamic tyre forces in mixed traffic. Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automobile Engineering, 210, (D3), 215-225 (1996).
E38. STRONGE, W.J. Energy transformation in collision of rough hard bodies. Proceedings, 19th International Congress of Theoretical and Applied Mechanics, Kyoto, Japan, FJ-6, 400. (August 1996).
E39. STRONGE, W.J., LIU, D. Analytical model for penetration and perforation of deformable plates. Proceedings, 2nd Intenational Symposium on Impact Engineering, Beijing, China, 14-17 (September 1996).
E40. VENNER, C.H., COUHIER, F., LUBRECHT, A.A., GREENWOOD, J.A. Amplitude reduction of waviness in transient EHL line contacts. Proceedings, 23rd Leeds-Lyon Symposium on Tribology, Leeds (September 1996).
E41. WILLIAMS, J.A. Analytical models of scratch hardness. Tribology International, 29, (8), 675-694 (1996).
E42. WILLIAMS, J.A. Wear by solid particles in lubricated contacts. Solid-Solid Interactions: Proceedings, 1st Royal Society-Unilever Indo-UK Forum in Materials Science and Engineering, London (September 1994); Edited by M.J. Adams, S.K. Biswas and B.J. Briscoe, 146-157 (Imperial College Press, London, 1996).
E43. WILLIAMS, J.A., XIE, Y. Friction between sliding surfaces carrying adsorbed lubricant layers. The Third Body Concept: Interpretation of Tribological Phenomena, Proceedings, 22nd Leeds-Lyon Symposium on Tribology, Lyon, France (September 1995); Edited by D. Dowson, et al, 651-664. Tribology Series 31 (Elsevier, 1996).
E44. WOODHOUSE, J. Self-sustained musical oscillators. In: Mechanics of Musical Instruments; Edited by A. Hirschberg, J. Kergomard, G. Weinreich, Chapter 5. International Centre for Mechanical Sciences Courses and Lectures 355 (Springer-Verlag, 1995).
E45. XIE, Y., WILLIAMS, J.A. The prediction of friction and wear when a soft surface slides against a harder rough surface. Wear, 196, 21-34 (1996).
E46. ZHANG, T.G., STRONGE, W.J. Rupture of thin ductile tubes by oblique impact of blunt missiles. Proceedings, 2nd International Symposium on Impact Engineering, Beijing, China, 129-136 (September 1996).