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Note on Biot's Dynamic Modulus

Published online by Cambridge University Press:  28 July 2016

W. J. Duncan*
Affiliation:
Aeronautics at University College, Hull

Extract

In reference 1 Biot has given a simple and valuable formula for what he calls the “ dynamic modulus “ of a flywheel system or airscrew in terms of resonance and anti-resonance frequencies. The resonance frequencies are the natural frequencies when the systems are free, and the anti-resonance frequencies are the natural frequencies when the end of the flywheel shaft (or the airscrew boss) is fixed. The dynamic modulus is defined to be the ratio of the amplitude of the applied periodic couple to the amplitude of the angular movement produced at the point of application, and is a function of the frequency of the periodic couple. A very useful application of the dynamic modulus can be made to engine-propeller systems, for the natural frequencies of the combination are such that the dynamic moduli of the two components are equal and opposite.

Type
Research Article
Copyright
Copyright © Royal Aeronautical Society 1941

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References

List of References

1. Biot, M. A.Coupled Oscillations of Aircraft Engine-Propeller Systems.” Journal of Aeronautical Sciences, Vol. 7, No. 9, July, 1940.CrossRefGoogle Scholar
2. Carter, B. C. “ The Vibration of Airscrew Blades with particular reference to their Response to Harmonic Torque Impulses in the Drive.” R.& M. 1758, July, 1936.Google Scholar