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DYNAMICS
Impact Damage in Carbon Fibre Composites
Mechanics of Impact
Vehicle Dynamics and Road Damage
Machine Elements
VIBRATIONS
Vibration Prediction in Complex Structures
Corrugation Prediction in Railway Lines
Mechanics of Musical Instruments
Pipeline Inspection
Railway Vibration
Track Settlement Adjacent to Bridge Abutments
Wavelet Analysis
References
Dr W.J. Stronge
Laminated carbon fibre composite (CFRP) shells suffer local damage due to impact; for some states of stress, small levels of damage can reduce the strength of composites although the fractures and delaminations are subsurface and difficult to detect. A numerical method of predicting the dynamic response of orthotropic cylindrical shells to non-penetrating impact has been developed(E8) and is being used to evaluate failure stresses in CFRP pressure vessels struck by low speed missiles.
Dr W.J. Stronge
Fundamental research is continuing into deformation processes during impact with the aim of obtaining a physical basis for parameters representing "rigid body" impact where deformations are small. This research is relevant to constraints on operation of mechanical linkages in high speed assembly operations, impact printers and sports mechanics. For collisions between hard bodies that are rough (i.e. where friction is not negligible) the energy absorbed during collision can be separated into part due to friction and part due to plastic deformation and elastic waves(E16).
Work is continuing on obtaining methods of assessing risk of perforation in metal structures subjected to impact by small sub-ordnance velocity fragments or missiles. Approximate failure criteria representing kinematic constraints on deformation as well as material properties are being developed(E20).
Dr D. Cebon
The Cambridge Vehicle Dynamics Consortium has continued to grow and attract funding from the heavy vehicle industry. Shell Oil and Crane Fruehauf joined the six existing industrial members (Tinsley Bridge, Meritor HVS, Koni Shock Absorbers, SP-Tyres, DERA and Volvo Trucks); and the University of Nottingham became the third University member (along with Cambridge and Cranfield). The research continues to concentrate on use of advanced suspension technologies to improve heavy vehicle safety and reduce road damage. Two new EPSRC research grants were awarded: one on active roll-control of heavy vehicle suspensions, and the other on energy losses in heavy vehicle tyres and suspensions. Both projects involve substantial contributions in cash and kind from the industrial members of the Consortium.
Papers have been published on modelling long-term performance of asphalt pavements(E3); road-damaging effects of heavy vehicles(E14,E15); assessing the `road-friendliness' of truck suspensions(E14,E15); and the dynamic interaction between heavy vehicles and highway bridges(E5).
Dr J.D. Smith
The work on Smith shocks for gear condition monitoring is progressing, with tests on a large gear set completed successfully. It appears that the approach will work very well for detecting scuffing and loss of lubrication but, as expected, is not likely to show pitting or tooth cracking. A book on gear noise is in preparation.
Methods of measuring railway line corrugations by seismic methods have progressed to allow the use of a manually propelled trolley for practical use on European railways. A course on gear noise has been given again for the British Gear Association.
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 popular approach to such problems is "Statistical Energy Analysis", in which a thermal analogy is used to model the flow of vibrational energy around a complex structure. It has recently been shown that there is an interaction between the strength of coupling and the system damping in such problems(E19), which must be taken into account to obtain reliable predictions.
Dr J. Woodhouse
Professor K.L. Johnson
Efforts have continued to formulate and validate convincing models for the growth of short-pitch corrugations on high-speed railway track (leading to socalled roaring rails). A detailed study has been made of the role of close conformity between the profiles of wheel and rail, since experimental evidence has suggested a link. The models show that conformity has an influence on the growth rate and pattern of corrugations, but it was not possible to find a mechanism by which conformity produces greatly accelerated growth(E1,E2).
Dr J. Woodhouse
The vibrational behaviour of musical instruments continues to provide challenging scientific problems. A short review of the mechanics of the bowed string has been written(E18). The way in which a violinist controls the contact force between bow and string involves subtle problems of force control through a flexible beam, similar to problems currently being faced in robotics and the control of large space structures. A significant contribution to this subject has arisen from the context of bowing, allowing controllers to be designed which provide robust force control on a system whose properties are time-varying(E17).
Dr H.E.M. Hunt
Professor D.E. Newland
Pipeline inspection for oil and gas pipelines is now being applied to problems which face the water industry. Pipelines which are prone to developing leaks may be identified with a vibrating pipeline inspection gadget (pig). The pig identifies areas of free-spanning and unsupported pipe.
Dr H.E.M. Hunt
Professor D.E. Newland
Modelling of vibration generated by railways continues with an emphasis on underground trains. Tunnels are modelled by means of repeating-element theory which, through the use of random-process theory, link in with existing structural models of infinite extent(E6). The models are being validated by track measurements. This work is carried out in conjunction with Tiflex Ltd, manufacturers of elastomeric products for vibration control.
Dr H.E.M. Hunt
Professor D.E. Newland
Computational modelling of the growth of track settlement adjacent to bridge abutments(E7) and a programme of experimental works to validate the model form the basis of an on-going collaboration with Netherlands Railways. The measurements are being made in Holland where track settlement is a serious problem. It has been found that sleeper impact due to voidage is the main cause of settlement.
Professor D.E. Newland
Signal decomposition by time-frequency and time-scale mapping is now used extensively in vibration analysis. Recent research has concentrated on comparing various different wavelet transforms with the short-time Fourier transform and the Wigner-Ville method. Harmonic wavelets have been found to be particularly suitable because of their simple structure in the frequency domain, but it is still difficult to produce high-definition time-frequency maps. Research has focused on improving harmonic wavelet transform algorithms and on utilising phase data which can be obtained from the complex harmonic wavelet formulation. Advice has been provided on a range of different applications, including biomedical signals, road vehicle test data, experimental earthquake simulations and NASA vibration monitoring test data.
E1. Bhaskar, A., Johnson, K.L., Wood, G.D., Woodhouse, J. Wheel-rail dynamics with closely conformal contact. Part I: dynamic modelling and stability analysis. Proceedings of the Institution of Mechanical Engineers, Part F, Journal of Rail and Rapid Transit, 211, (F1), 11-26 (1997).
E2. Bhaskar, A., Johnson, K.L., Wood, G.D., Woodhouse, J. Wheel-rail dynamics with closely conformal contact. Part II: forced response, results and conclusions. Proceedings of the Institution of Mechanical Engineers, Part F, Journal of Rail and Rapid Transit, 211, (F1), 27-40 (1997).
E3. Collop, A.C., Cebon, D. Effects of road-friendly suspensions on long term flexible pavement performance. Proceedings of the Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Sciences, 211, (C6), 411-424 (1997).
E4. Collop, A.C., Cebon, D. A theoretical model of long term flexible pavement performance. Proceeedings, 8th International Conference on Asphalt Pavements, Seattle, WA, USA, 1, 631-646 (August 1997).
E5. Green, M.F., Cebon, D. Dynamic interaction between heavy vehicles and highway bridges. Computers and Structures, 62, (2), 253-264 (1997).
E6. Hunt, H.E.M. Observations on the performance of vibration-isolated railway track. Proceedings, 1997 ASME Design Engineering Technology Conferences: 16th ASME Biennial Conference on Vibration and Noise, Sacramento, CA, USA, DETC97/VIB-4084 (September 1997). On CD-ROM.
E7. Hunt, H.E.M. Settlement of railway track near bridge abutments. Proceedings of the Institution of Civil Engineers, Transport, 123, (1), 68-73 (1997).
E8. Matemilola, S.A., Stronge, W.J. Impact response of composite cylinders. International Journal of Solids and Structures, 34, (21), 2669-2684 (1997).
E9. Newland, D.E. Practical signal analysis: do wavelets make any difference? Proceedings, 1997 ASME Design Engineering Technical Conferences: 16th ASME Bienniel Conference on Mechanical Vibration and Noise, Sacramento, CA, USA, DETC97/VIB-4135, 12 (September 1997). On CD-ROM.
E10. Newland, D. E. Random vibration. In: Encyclopedia of Acoustics; Edited by M.J. Crocker, 2, Part VI, chapter 66, 765-784 (Wiley, 1997).
E11. Newland, D.E. Time-frequency and time-scale signal analysis by harmonic wavelets. Signal Analysis and Prediction 1, Proceedings, 1st European Conference on Signal Analysis and Prediction, Prague, Czech Republic (June 1997); Edited by A. Prochazka, J. Uhlir, P. Sovka, 53-59 (ICT Press, 1997).
E12. Newland, D.E. Wavelet analysis of vibration signals. Part 2: wavelet applications. International Journal of Acoustics and Vibrations, 2, (1), 21-27 (1997).
E13. Potter, T.E.C., Cebon, D., Cole, D.J. Assessing `road-friendliness': a review. Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automotive Engineering, 211, (D6), 455-475 (1997).
E14. Potter,T.E.C., Cebon, D., Cole, D.J. Indirect methods for assessing road friendliness of lorry suspensions. Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automotive Engineering, 211, (D4), 243-256 (1997).
E15. Potter, T.E.C., Cebon, D., Cole, D.J., Collop, A.C. Road damage due to dynamic tyre forces measured on a public road. Heavy Vehicle Systems (International Journal of Vehicle Design), 3, (1-4), 346-362 (1996).
E16. Stronge, W.J. Energy losses in collision of rough `rigid' bodies. Structural Damage and Failure under Intense Loading, Manchester, Euromech Colloquium 362 (April 1997).
E17. Wood, G.D., Woodhouse, J. An investigation into robust force control through a constrained flexible beam. International Journal of Control, 68, (3), 539-578 (1997).
E18. Woodhouse, J. Stringed instruments: bowed. In: Encyclopedia of Acoustics; Edited by M.J. Crocker, 4, Part XIV, chapter 131, 1619-1626 (Wiley, 1997).
E19.Yap, F.F., Woodhouse, J. Investigation of damping effects on statistical energy analysis of coupled structures. Journal of Sound and Vibration, 197, (3), 351-371 (1996).
E20. Zhang, T.G., Stronge, W.J. Theory for ballistic limit of thin ductile tubes hit by blunt missiles. International Journal of Impact Engineering, 18, (7-8), 735-752 (1996).