Skip to main content Accessibility help
×
Home

On flexure-torsion flutter criteria

  • A. Simpson (a1)

Abstract

The classical criteria of the 1920s for the avoidance of flexure-torsion flutter were based on parameters such as stiffness ratio and the position across the typical chord of the aerodynamic, elastic and mass centres.

In more recent times, and in the context of aeroelastic tailoring of lifting surfaces constructed with composite materials, a new terminology has emerged — as evident from technical papers produced in the USA over the past decade. The prevention of flexure-torsion flutter, or the raising of the critical speed, is now achieved by providing more wash-in or less wash-out , where these terms do not have their established aeronautical meanings — and for this reason (and other, non-semantic ones) are to be deprecated.

By recourse to a typical section model (with quasi-steady and unsteady compressible aerodynamics), the writer argues that, for conventionally constructed wings, the new criteria are ‘fuzzy’ and incomplete versions of the earlier criteria in respect of the positioning of the various ‘centres’ (i.e., elastic, mass and aerodynamic) across the typical chord, and therefore that the new terminology is redundant in this context.

For laminated composite wing structures, even when the construction is uniform and the fiexural axis straight, it is established that the inclination of this axis with respect to the CG and aerodynamic axes may be so large that the fiexural and shear centres at the tip could be several chords forward or aft of the mid-chord axis; the criteria of the 1920s are then irrelevant. The wash-in/wash-out criteria may then be said to ‘come into their own’, albeit that it is shown herein that they remain fuzzy and incomplete — even for quasisteady binary problems. A crude modal binary model of a rudimentary laminated composite wing is included to illustrate this and other features. By recourse to a higher-order flutter formulation, the writer demonstrates that the wash-in/wash-out criteria are, in certain respects, unreliable.

Copyright

References

Hide All
1. Frazer, R.A. and Duncan, W.J. The flutter of aeroplane wings, ARC R&M No 1155, HMSO, August 1928.
2. Frazer, R.A. and Duncan, W.J. Graphical treatment of flutter problems, NPL Report No T.2461, March 1927 (Unpublished).
3. Blenk, H. and Liebers, F. Gekoppelte Torsions- und Biegungs- scwingungenvonTragflugeln,ZeitschriftfurMotorluftschiffahrt, December 1925.
4. Collar, A.R. and Simpson, A. Matrices and Engineering Dynamics, Ellis Horwood, 1987.
5. Baldock, J.C.A. The identification of the flutter mechanism from a large-order flutter calculation, RAE TR78017, HMSO 1978.
6. Simpson, A. The solution of large flutter problems on small computers, Aeronaut J, 1984, 88, (874), pp 128140.
7. Duncan, W.J., Collar, A.R. and Lyon, H.M., Oscillation of elastic blades and wings in an airsteam, ARC R&M 1716, HMSO 1936.
8. Simpson, A. and Hitch, H.P.Y. Active control technology, Aeronaut J, June 1977, 81, pp 231-246. (Printed version of RAeS specialist lecture).
9. Collar, A.R. The Expanding Domain of Aeroelasticity, J RAeS, 1946, 50, (428), pp 613636.
10. Georohiades, G.A. and Banerjee, J.R. Role of modal interchange in the flutter of laminated composite wings, AIAA J Aircr, 1997, 25, (1), pp 157161.
11. Georghiades, G.A. and Banerjee, J.R., The significance of wash-out on the flutter behaviour of composite wings, Technical Note, Department of Mechanical Engineering & Aeronautics, City University, London, May 1997. (Accepted for publication in AIAA J Aircr).
12. Shirk, M.H., Hertz, T.J. and Weisshaar, T.A., Aeroelastic tailoring, AIAA J Aircr, 23, (1), January 1986, pp 618.
13. Hancock, G.J., Wright, J.R. and Simpson, A., On the teaching of the principles of flexure-torsion flutter, Aeronaut J, 1985, 89, (888), pp 285305.
14. Weisshaar, T.A. and Foist, B.L, Vibration tailoring of advanced composite lifting surfaces, AIAA J Aircr, February 1985, 22, (2), pp 141147.

Related content

Powered by UNSILO

On flexure-torsion flutter criteria

  • A. Simpson (a1)

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.