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On a Simplified Technique for the Determination of the Dynamic Properties of a Linear System with Damping

Published online by Cambridge University Press:  04 July 2016

E. Nissim*
Affiliation:
Aeronautical Department, Israel Institute of Technology

Extract

The experimental methods in current use for the determination of the dynamic properties of an arbitrary finite-freedom system are based on restrictive assumptions which may often be of questionable validity. The most common assumption is that the damping matrix can be reduced to a diagonal form by a congruent transformation using the modal matrix of the undamped system. Further, the damping is normally assumed to be hysteretic, or light if viscous.

Bishop and Gladwell give an excellent account of the theoretical background of the present experimental techniques. These can be divided into three groups:

  • 1. The method of Kennedy and Pancu which obtains experimentally the complex receptance of the system and extracts its dynamic properties from vectorial plots.

  • 2. The method of Trail-Nash and Asher which is based on the experimental determination of the in-phase response of the system and requires computation to be incorporated with the experimental procedure.

Type
Technical Notes
Copyright
Copyright © Royal Aeronautical Society 1967

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References

1.Bishop, R. E. D. and Gladwell, G. M. L.Philosophical Transactions. Royal Society of London, January 1963.Google Scholar
2.Kennedy, C. C. and Pancu, G. D. P.Use of Vectors in Vibration Measurement and Analysis. J of Aero Sciences, Vol 14, pp 603625, 1947.Google Scholar
3.Trail-Nash, R. W.On the Excitation of Pure Natural Modes in Aircraft Resonance Testing. J of the Aero Sp Sci, Vol 25, No 12, pp 775778, 1958.Google Scholar
4.Trail-Nash, R. W. Some Theoretical Aspects of Resonance Testing and Proposals for a Technique Combining Experiment and Computation. Report ARL/SM 280, Melbourne, April 1961.Google Scholar
5.Woodcock, D. L.The Aeronautical Quarterly, Feb 1963.Google Scholar
6.De Veubeke, B. M. FRAEIJS. AGARD Rep No 39.Google Scholar