AAE556 lecture 01 introduction Aeroelasticity(made simple)

i Homework counts 30% of final grade score i Two tests two hours long – each 35% of final grade score – One test the week before Spring Break – covers static aeroelasticity – Second exam

Terry A Weisshaar Purdue University

Aeroelasticity (made simple)

weisshaar@purdue.edu

Armstrong Hall 3329

765-494-5975

i Class in ARMS 1021

Grading - Tests and

Homework

i Homework is assigned on Fridays and is

handed in at the beginning of each class the following Friday

i Homework counts 30% of final grade score

i 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

Course materials

i Text distributed free

– Reading assignments for each lecture

– Help me edit

material available on the AAE website– Look under AAE556 Restricted folder

– Chapter 1

– Chapter 2, sections 2.1-2.5

What’s it all about?

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

Classical aeroelastic

problems

i Static aeroelasticity

– wing divergence , aero/structure stiffness

– load redistribution - drag, stresses change– aileron reversal, lack of control

– lift ineffectiveness, vertical tail yaw control

– self-excited wing vibration/destruction

– self-excited panel vibration, LCO

Venn diagram showing

interactions

Aerodynamic forces

L=qSCL

Inertial Forces F=ma

Dynamic stability

Flutter

Flutter at a glance

Aerodynamic forces

Aeroelasticity changes history and puts the hex on monoplanes

LangleyWrightBleriot

Samuel Langley well financed, doomed to failure

“almost everything unexpected during the

development process is bad”

Excessive wing twist

caused by too much wing

camber

The Wright Stuff innovation in action

Wing morphing

(warping) in action

Wing warping

Griffith Brewer weighs in on aeroelasticity – sort of …

Bleriot XI - monoplane wing warping

England here we come!

John B Moissant

1868-1910

Moissant all-aluminum airplane 1910

Moissant in Bleriot airplane airplane

Cross-Channel flight 1910

Control effectiveness

Reduced ability, or loss of ability, to roll or turn quickly

Swept wing load redistribution

Total lift is the

Forces F=kx aeroelasticityStatic

Forward swept wings

X-29 began as a Ph.D dissertation topic in 1972

Aeroelastic tailoring

Intentional use of directional stiffness and load interaction to create beneficial performance

Flutter and dynamic

response

Aerodynamic

forces L=qSCL

Inertial Forces F=ma

Flutter

Heinkel flutter

Flutter in practice

Classical Flutter

aileron frequency & motion wing bending and torsion

Glider flutter

Engines and under-wing

stores

Supersonic and

hypersonic flight

Panel flutter – going into space

Supersonic flow

Dead air

Frequency merging – amplitude limited by

nonlinear effects - creates noise and fatigue

Body-freedom flutter

Military Specification Airplane strength and rigidity vibration, flutter and divergence

i Prevent flutter, divergence

and other dynamic and

static instabilities

i Control structural vibrations

i Prevent fatigue failure

i Prescribe structural dynamic

analyses, laboratory and

ground tests, flight tests

required to demonstrate

compliance with design

requirements

The future … new configurations, old and

new problems

Loitering Configuration directs

radar energy away from side

threats

Penetrating Configuration direct radar energy away from frontal threats

Compromised Configuration

Tailored Survivability

Loitering Configuration directs

radar energy away from side

threats

Penetrating Configuration direct radar energy away from frontal threats

Compromised Configuration

Tailored Survivability