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An Improved Displaced Frequency Method for Estimation of Dynamical Characteristics of Mechanical Systems

Published online by Cambridge University Press:  04 July 2016

A. Simpson
A. Simpson*
Affiliation:
University of Bristol
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Extract

The “displaced frequency” method is widely used in the aircraft industry for estimating the generalised masses and stiffnesses of aircraft, which are used in response and other aeroelastic calculations. The usual procedure is to measure the natural frequencies, ωi, and the associated normal modes, zi, by standard resonance testing techniques. (The number of frequencies and modes actually measured depends, of course, on the accuracy required in subsequent calculations.) A small mass, or group of masses, is then added to the structure at a convenient point or points and the resulting frequency changes, δωi noted. Now if αi and εi are generalised masses and stiffnesses respectively, then in normal co-ordinates

Type
Technical Notes
Information
The Aeronautical Journal , Volume 70 , Issue 666 , June 1966 , pp. 661 - 665
Copyright
Copyright © Royal Aeronautical Society 1966

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References

1. Gauzy, H. Vibration Testing by Harmonic Excitation. AGARD Manual on Aeroelasticity, Vol. I (1961).Google Scholar
2. Jennings, B. and Tomlinson, I. D. Vibration Study of a Model Wing. Undergraduate Thesis No. 88, University of Bristol, Department of Aeronautical Engineering.1965.Google Scholar
3. Collar, A. R. Some Notes on Jahn's Method for the Improvement of Approximate Latent Roots and Vectors of a Square Matrix. Q Journ Mech and Ann Math, Vol. 1, 1948.Google Scholar
4. Traill-Nash, R. Some Theoretical Aspects of Resonance Testing and Proposals for a Technique Combining Experimental and Computation. Dept of Supply; Australian Research Laboratories; Report ARL/SM 280, April 1961.Google Scholar