1. Aeroelastic Behavior of a Typical Airfoil Section
with Shape Memory Alloy Springs
Vagner Candido de Sousa*
Department of Aeronautical Engineering
Engineering School of Sao Carlos
University of Sao Paulo, Brazil
* Visiting Scholar at the Dynamic and Smart Systems Lab
The University of Toledo (Summer/Fall, 2015)
2. Where we are
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SĂŁo Carlos
Campus
Research center
SĂŁo Paulo
(Capital)
State of SĂŁo Paulo
SĂŁo Carlos - SP
Brazil
3. University of SĂŁo Paulo
⢠A state university founded in 1934
⢠Campi: São Paulo (4), Bauru,
Piracicaba, Pirassununga, Lorena,
RibeirĂŁo Preto, SĂŁo Carlos (2)
⢠Undergrads: 58.204
⢠MSc: 14.149, PhD: 15.398
⢠Other: 5.041
⢠Professors: 6.008
⢠Articles: 16.013 (WoS/ISI)
3
* 2013
Campus 1
4. University of SĂŁo Paulo, Campus of SĂŁo Carlos
⢠Institute of Physics
⢠Institute of Mathematic and
Computer Sciences
⢠Institute of Architecture
⢠Institute of Chemistry
⢠Engineering School of São Carlos
â Dep. of Aeronautical Eng.
â Dep. Electrical Eng.
â Dep. Geotechnical Eng.
â Dep. Hydraulics
â Dep. Materials Eng.
â Dep. Mechanical Eng.
â Dep. Production Eng.
â Dep. Structural Eng.
â Dep. Transportation Eng.
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5. Department of Aeronautical Engineering
⢠Research
â Aerodynamics
â Aeroservoelasticity
â Flight Dynamics
â Aeronautical Structures
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6. Our lab â Laboratory of Aeroelasticity
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⢠Students (Summer, 2015)
â MSc: 1
â PhD: 6
â Post doc: 1
⢠Collaborations in
â USA
â Canada
â UK
⢠Facilities
â Blower wind tunnel
â Whirl Tower
â Smart table
â Sensors (accelerometers, laser
vibrometer)
â Acquisition system (dSPACE, LMS Scadas,
LDS Photon)
â Shakers (Modal Shop, APS Long-Stroke
Vibration Exciter)
7. Current topics of interest
⢠Fixed-wing and rotary-wing
aeroelasticity
⢠Smart materials for energy
harvesting and/or vibration control
⢠Wind energy harvesting (fixed and
rotary wing )
⢠Shape memory alloys
⢠Helicopters vibration damping
(piezoelectric based pitch link
device)
⢠Self-powered circuits for
piezoelectric active/semi-
active/semi-passive control
⢠Bio-inspired aircraft (morphing) and
aquatic robots
⢠In short,
Aeroelasticity
+
smart materials
7
8. Aeroelasticity
⢠Interaction between
aerodynamic forces and
structural motions
⢠Airfoil and non-airfoil structures
⢠Transmission lines
⢠Suspension bridges
⢠Tall chimneys and
buildings
⢠Static phenomena
â Divergence
â Control reversal
⢠Dynamic phenomena
â Buffeting
â Flutter (many kinds)
8
flowsol.co.uk
Wings
9. Very brief history (incidents related to aeroelasticity)
⢠1903 (Prof. Samuel P.) Langley
Monoplane
â Low torsional stiffness wings
⢠1916 Handley Page 0/400
Bomber
â Horizontal tail problems
9
10. Very brief history
⢠1918 Fokker D-VIII
â Wing failures in high-speed
dives
⢠1925 Albatros D.III
â Lower wing failures
10
11. Very brief history
⢠1930 Junker F-13
â Horizontal tail problems
⢠Region of strong rising gust in
England
⢠1938 Junkers 90-V1
â Crashed during a ânon-
conservativeâ flight test
11
13. Very brief history
⢠1960-1970 Rockets
â Problems observed during wind
tunnel tests and corrected
⢠1970-1980 Space shuttle
13
14. An important observation
⢠Most of those structures had
sufficient strength in static tests
⢠Problems appeared under
aerodynamic loads
â Related to aeroelastic
phenomena
14
15. Static aeroelasticity phenomena (elastic + aerodynamic forces)
⢠Divergence
â Static aerodynamic forces
become too large for the wing
torsional stiffness to resist
â Aerodynamic loads increase the
incidence; increasing incidence
the aerodynamic loads increase
⢠Wing twists until it breaks
15
Langleyâs Aerodrome, 1903
First report of static divergence
16. Static aeroelasticity (elastic + aerodynamic forces)
⢠Control reversal
â Wings deform in such a way the
control surfaces do not respond
as expected to the pilotâs
commands
â MiG-25âs (formerly Ye-155R/P)
first flight revealed insufficient
wing rigidity
⢠The resulting control reversal
was dangerous, and
maneuverability limitations
were imposed
16
â On October 30, 1967
⢠Aileron reversal caused by
exceeding the instrument
speed limit crashed an Ye-
155P1
18. Dynamic aeroelasticity: buffeting
⢠Airfoil and non-airfoil structures
⢠Random vibration
⢠Usually just inconvenient
18
Laminar flow
Turbulent flow
(vortex shedding)
Flow separation
(transition region)
Surface subject
to turbulent flow
19. Dynamic aeroelasticity: âgallopingâ flutter
⢠Large amplitude, low frequency
oscillation
⢠Bluff bodies (usually non-airfoil)
â Transmission lines (mostly with
ice accretion)
â Cable affected by vortex
shedding of another cable
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20. Dynamic aeroelasticity: stall flutter
⢠Airfoil and non-airfoil
structures
⢠Periodic (partial or complete)
flow separation from the
airfoil during the oscillation
⢠Nonlinear aerodynamic
reaction to the motion of the
structure
â Suspension bridges
â Helicopter rotors (rotorcraft
blades)
â Turbomachinery blades
⢠Free vortices are generated in the
vicinity of the separation points
⢠The periodic vortex shedding
creates regions of reduced and
even reversed velocity in the
vicinity of the airfoil
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21. Dynamic aeroelasticity: âwhirl modeâ flutter
⢠Two Lockheed L-188 âElectraâ,
â Braniff Flight 542
⢠September 29, 1959
⢠near Buffalo, TX
⢠34 fatalities
â NW Orient Airlines Flight 710
⢠March 17, 1960
⢠near Cannelton, IN
⢠63 fatalities
⢠disintegrated during flight
â wing brake-up
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Actual aircraft before crash (stinsonflyer.com)
⢠In both cases,
â No survivors
â Inconclusive investigations
22. âWhirl modeâ flutter (a new investigation at NASA Langley)
⢠Wind tunnel tests of an Electra 1/8-
scale model showed:
â Overly stiff wing
â Outboard nacelles responding
differently than intended
â Flutter âpasses onâ from nacelle to
(even a âflutter-freeâ) wing
⢠Growing flutter magnitude
decreased the oscillation
frequency from 5 to 3 Hz
⢠Wing frequency was also 3 Hz
â Harmonic coupling
22
YouTube channel: NASA Langley CRGIS
Flutter Tests of the Full Span Lockheed Electra
24. Dynamic aeroelasticity: (aeroelastic) flutter
⢠Bending/torsion coupled motion
⢠Self-sustained unstable motion
⢠Antonov An-148
â March 5, 2011 (test flight)
â near Garbuzovo (350 mi south
of Moscow), Russia
⢠Airspeed indicator failed
(showing lower airspeed)
⢠Pilots accelerated 70 mi/h
above the design limit speed
⢠Low-frequency vibrations
created
⢠In-flight wing break-up
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25. Dynamic aeroelasticity: non-airfoil flutter
⢠Bending/torsion coupled motion
⢠Self-sustained unstable motion
⢠Tacoma Narrows Bridge
â Opened to traffic on July 1, 1940
â Collapsed on November 7, 1940
â Stationary wind design limit: 160 km/h
â Wind speed before failure: 60 km/h
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26. Aeroelastic flutter
⢠Under airflow excitation, structures
may exhibit aeroelastic oscillations
â due to interactions of
aerodynamic, elastic and inertial
forces
⢠At a critical airflow speed, lifting
surfaces undergo self-sustained
oscillations (linear flutter speed)
â Flutter: bending/torsion coupled
motion with growing amplitudes
⢠Potentially catastrophic
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27. Aeroelastic and vibration control
⢠Allows flight vehicles to operate
beyond the traditional flutter
boundaries
⢠Improves ride qualities
⢠Minimizes vibration fatigue
damage
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(Giurgiutiu 2000, JIMSS v. 11; Nitzsche et al 2015, JIMSS)
Controlled
Uncontrolled
Grows until the
structure fails
28. Conventional passive aeroelastic control / flutter prevention
⢠There is no universal solution
⢠Frequent strategies
â add mass or redistribute mass
(âmass balanceâ)
â increase torsional stiffness, i.e.,
increase ĎÎą
â increase (or decrease) Ďh/ĎÎą if it
is near one (for fixed ĎÎą)
â add damping to the structure
(hydraulic dampers)
â require the aircraft to be flown
below its critical Mach number
⢠Penalties
â Extra weight
â Non-optimized operation
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(Dowell et al. 2015, A Modern Course in Aeroelasticity, p. 118)
29. Conventional active aeroelastic control
⢠Aerodynamic control surfaces
operated by servo-hydraulic
actuators
⢠Penalties/limitations
â Multiple energy conversions
(mechanical, hydraulic, electrical)
â Large number of parts
⢠Potential failure sites
⢠Extra weight
â High vulnerability of the hydraulic
pipes network
â Limited frequency bandwidth
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(Giurgiutiu 2000, JIMSS v. 11)
30. Smart materials as an alternative (e.g., piezo actuators)
⢠Direct conversion of electrical
energy to high-frequency linear
motion (mechanical energy)
⢠Electrical energy is easier to
transmit throughout the aircraft
(electric lines are much less
vulnerable than hydraulic pipes)
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(Giurgiutiu 2000, JIMSS v. 11)
(reverse piezoelectric effect)
31. An example
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⢠Active control flap for noise and
vibration reduction
⢠Piezo-stack actuators
(Straub and King 1996)
32. Smart materials (piezos)
⢠Advantages
â Can be embedded in the
structure (e.g. on-blade
actuation)
â High energy/mass ratio
â Direct piezoelectric effect can
also be exploited
⢠Passive and active strategies
⢠Sensing and actuation
⢠Energy harvesting
⢠Disadvantages
â Piezos (reverse effect)
⢠Very small strokes (e.g. 0.1%)
⢠Requires displacement
amplification mechanisms
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33. Fixed wing aircraft studies
⢠Heeg 1993 (NASA Langley)
â Piezoelectric actuators
â Flutter suppression of a rigid
wing supported by springs
â +20% flutter speed
⢠McGowan et al. 1998
â 12% decrease flutter dynamic
pressure
â 75% decrease gust bending
moment
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34. A rotating-wing application of smart materials
⢠Feszty and Nitzsche 2011
â Carleton University, Canada
⢠Stiffness modulation using
piezoelectric actuators for vibration
control in helicopters
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(flight tested)
Nitzsche et al
2015, JIMSS
35. Flutter can be exploited for wind energy harvesting
⢠Vibrations in a general sense
can be exploited for energy
harvesting
â Direct piezoelectric effect
⢠Flutter oscillations can provide a
useful additional source of small
amounts of electrical power
â e.g., for embedded Structural
Health Monitoring systems
â Airfoil-based generators
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36. An example
⢠The RC glider was modified to
include:
â two piezoelectric patches
placed at the roots of the wings
⢠to harvest energy from wing
vibrations
â a cantilevered piezoelectric
beam installed in the fuselage
⢠to harvest energy from rigid
body motions of the aircraft
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(SR Anton and DJ Inman, 2008)
37. An airfoil model for flutter investigations
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(Mozaffari-Jovin et al 2015, JVC)
2D problem
38. How we investigate flutter in our lab
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⢠2-DOF (or 3-DOF)
â Plunge (h)
â Pitch (Îą)
â (Control surface position, β)
⢠Uâ is the airflow speed
40. Numerical results and experimental tests
⢠Linear case, U = 12 m/s ⢠Nonlinear case (freeplay in the
pitch DOF), U = 10 m/s
40
Continuous lines: experimental, dashed lines: simulation
Linear: Erturk et al. (2010), Appl. Phys. Lett. 96(18)
Nonlinear: Sousa et al. (2011), Smart Mater. Struct. 20(9)
41. Possibilities of study for an smart airfoil/flutter model
⢠Aeroelastic control
â Classical aeroelasticity
⢠Structural reinforcement
⢠Mass tuning
â âSmartâ materials
⢠Sensing and actuation
â Piezoelectric materials
â Shape memory materials
⢠Energy Harvesting
⢠Aeroelastic control + Energy
Harvesting
⢠Smart materials
⢠Piezoceramics
(electromechanical coupling)
â Active control (actuation)
â Passive (shunt damping)
â Hybrid
â Energy Harvesting
⢠SMAs
â Passive control (high loss factor,
hysteretic damping)
â Active control (stiffness and
frequency variation)
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42. SMA elements can be included in the airfoil model
(my current work)
42
kďĄ
⢠Motivation:
â Modify the aeroelastic
behavior of the airfoil by
exploiting the pseudoelastic
hysteresis of SMAs
SMA
behavior
44. An intermediate case is presented,
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ď¨ ďŠ1
0 3 N e 11.6 m¡sf U ď
ďĽď˝ ď˝
45. Thank you!
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Special thanks to:
The University of Toledo and MIME Department, Toledo â OH/USA
Dynamic and Smart Systems Lab (smartsys.eng.utoledo.edu)
Editor's Notes
Boa tarde, meu nome ĂŠ Vagner C..., sou aluno de mestrado no Dep. Eng. Aero, meu orientador ĂŠ o Prof. Dr. Carlos...;
Hoje vou apresentar uma âAnĂĄlise do comportamento...â;
Eu gostaria de agradecer aos membros da banca examinadora, Prof. Dr. (do ITA), Prof. Dr. FlĂĄvio Marques e Prof. Dr. Carlos De Marqui (EESC) e a todos os presentes;
no sistema experimental, o acoplamento piezelĂŠtrico ĂŠ introduzido no GDL de deslocamento linear;
as piezocerâmicas são coladas na região do engaste das vigas de aço-mola que atribuem rigidez ao GDL de deslocamento linear;
um fio-mola tambÊm atribui rigidez ao GDL de rotação;
Como o modelo ĂŠ desenvolvido em sua forma mais geral, todas as nĂŁo linearidades possĂveis neste trabalho sĂŁo introduzidas nas equaçþes de movimento;
no GDL de rotação do aerofólio (pitch), a não linearidade freeplay (modelada como uma mola bilinear) pode ocorrer de maneira isolada ou combinada com uma mola cúbica do tipo hardening;
no GDL de posição da superfĂcie de controle, somente a nĂŁo linearidade freeplay ĂŠ considerada;
no entanto, ĂŠ possĂvel combinar freeplay na superfĂcie de controle com mola cĂşbica em pitch;
nenhuma nĂŁo linearidade ĂŠ considerada no GDL de deslocamento linear (plunge) ou no domĂnio elĂŠtrico do problema;