SUPPRESSION OF BENDING{TORSION FLUTTER IN ACCELERATED FLIGHT WITH AERO-SERVO-VISCOELASTIC CONTROLS 1

The Theodorsen function [1] is generalized to non simple harmonic motion and for time dependent ight velocities encountered during maneuvers, changes in altitude, landings, takeo s, etc. A formulation and examination is undertaken of the dynamic responses of exible linear viscoelastic lifting surfaces in potential ow and under the in uences of unsteady aerodynamic forces, non-simple harmonic motion and time dependent ight velocities. Di erential, integral or proportional servo-controllers are added in order to stabilize the system and extend its lifetime. Parametric studies of servo-controllers led to no general conclusions because of the highly complicated phase relations. However, computational simulations indicate that a continual increase in servo control parameters does not necessarily culminate in utter velocity increases, but actually may decrease such thresholds after a maximum control condition has been achieved. The presence of ight maneuvers introduces time dependent velocities and coe cients in the governing integro-di erential relations. These are solved analytically by piecewise averaging of the coe cients over selected time intervals. Expanded necessary and sufcient utter conditions beyond the customary simple harmonic motion de nition are also formulated. 1Copyright©2011 by the authors. Published by the AIAA Inc., with permission. 2Natural Sciences and Engineering Research Council of Canada, Scholarship Award Holder. PhD Candidate in Aerospace Engineering. AIAA Student Member. Voice: 217-244-8273 Email: merrett2@illinois.edu Presenter. Now Assistant Professor of Mechanical and Aerospace Engineering, Carlton University. Email: Craig_Merrett@carleton.ca 3Professor Emeritus of Aerospace Engineering and Senior Academic Lead for Computational Structural/Solid Mechanics at NCSA. AIAA Fellow. Corresponding author. Voice: 217-333-2653 Cell: 217-840-1116 FAX: 217-244-0720 Email: h-hilton@illinois.edu 4BS in Aerospace Engineering May 2013 Candidate, AIAA Student Member, kalidin2@illinois.edu 5BS in Aerospace Engineering May 2013 Candidate, AIAA Student Member, schwar21@illinois.edu. AIAA Atmospheric Flight Mechanics Conference 08 11 August 2011, Portland, Oregon AIAA 2011-6208 Copyright © 2011 by Craig G. Merrett, Harry H. Hilton. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

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