1. Aeroelasticity (made simple)
Terry A. Weisshaar
Purdue University
Armstrong Hall 3329
Purdue Aeroelasticity

2. Purdue Aeroelasticity
Details
Class in ARMS 1021
Purdue Aeroelasticity

3. Grading - Tests and Homework
Homework is assigned on Fridays and is handed in at the beginning of each class the following Friday.
Homework counts 30% of final grade score
Two tests (two hours long) – each 35% of final grade score
One test the week before Spring Break – covers static aeroelasticity
Second exam during Finals Week – covers dynamic aeroelasticity
AAE556 – Spring 2008

4. Course materials Text distributed free
Reading assignments for each lecture
Help me edit
Notes, homework and supplemental material available on the AAE website
Look under AAE556 Restricted folder
Reading for Wednesday
Chapter 1
Chapter 2, sections
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5. Purdue Aeroelasticity
What’s it all about?
What is aeroelasticity?
Why is it important?
When is it important?
Key features of aeroelastic response
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6. Aeroelasticity definition & effects
Aeroelasticity is a design activity concerned with interactions between aerodynamic forces and structural deformation, both static and dynamic, and the influence of these interactions on aircraft performance.
Aerodynamic load and structural deflection interaction
Static stability
Control surface effectiveness
Flutter and dynamic response
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7. Classical aeroelastic problems
Static aeroelasticity
wing divergence , aero/structure stiffness
load redistribution - drag, stresses change
aileron reversal, lack of control
lift ineffectiveness, vertical tail yaw control
Flutter and dynamic response
self-excited wing vibration/destruction
self-excited panel vibration, LCO
Purdue Aeroelasticity

8. Venn diagram showing interactions
Aerodynamic forces
L=qSCL
Inertial
Forces
F=ma
Elastic
F=kx
Vibrations
Static
aeroelasticity
Dynamic
stability
Flutter
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9. Purdue Aeroelasticity
Flutter at a glance
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10. Early history- static aeroelasticity
Aerodynamic forces
L=qSCL
Elastic
Forces
F=kx
Static
aeroelasticity
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11. Aeroelasticity changes history and puts the hex on monoplanes
Langley
Wright
Bleriot
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12. Samuel Langley well financed, doomed to failure
Excessive wing twist caused by too much wing camber
Before
After
“almost everything unexpected during the development process is bad”
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13. The Wright Stuff innovation in action
Wing morphing (warping) in action
Wing warping
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14. Griffith Brewer weighs in on aeroelasticity – sort of …
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15. Bleriot XI - monoplane wing warping England here we come!
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16. Purdue Aeroelasticity
John B. Moissant
Moissant in Bleriot airplane airplane
Cross-Channel flight 1910
Moissant all-aluminum airplane 1910
The end of the trail-Dec. 31,
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17. Control effectiveness
Reduced ability, or loss of ability, to roll or turn quickly
aileron reversal
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18. Swept wing load redistribution
1.0
Total lift is the same
spanwise center of pressure moves inboard to reduce root bending moment
Aerodynamic forces
L=qSCL
Elastic
Forces
F=kx
Static
aeroelasticity
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19. Purdue Aeroelasticity
Forward swept wings
X-29 began as a Ph.D. dissertation topic in 1972
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20. Aeroelastic tailoring
Intentional use of directional stiffness and load interaction to create beneficial performance
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21. Flutter and dynamic response
Aerodynamic forces
L=qSCL
Inertial
Forces
F=ma
Elastic
F=kx
Vibrations
Static
aeroelasticity
Dynamic
stability
Flutter
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22. Purdue Aeroelasticity
Heinkel flutter
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23. Purdue Aeroelasticity
Flutter in practice
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24. Purdue Aeroelasticity
Classical Flutter
frequency
airspeed
wing bending and torsion
aileron frequency & motion
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25. Purdue Aeroelasticity
Glider flutter
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26. Engines and under-wing stores
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27. Supersonic and hypersonic flight
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28. Panel flutter – going into space
Frequency merging – amplitude limited by nonlinear effects - creates noise and fatigue
Supersonic flow
Dead air
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29. Purdue Aeroelasticity
Body-freedom flutter
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30. Aeroelasticity regulations
Civil aviation - FAR 23 and FAR 25
Military - Navy MIL-A-8870C
Air Force - AFGS-8722
Joint Services Guide Specification, Aircraft Structures
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31. Purdue Aeroelasticity
Military Specification Airplane strength and rigidity vibration, flutter and divergence
Prevent flutter, divergence and other dynamic and static instabilities
Control structural vibrations
Prevent fatigue failure
Prescribe structural dynamic analyses, laboratory and ground tests, flight tests required to demonstrate compliance with design requirements
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32. The future … new configurations, old and new problems
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