presentation sur les uav sma

7/26/2019 Presentation sur les UAV SMA

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An Investigation of Shape Memory

Alloys as Actuating Elements in

Aerospace Morphing Applications

Presented by Mr. Dimitri Karagiannis, INASCO



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An Investigation of Shape Memory Alloys as Actuating

Elements in Aerospace Morphing Applications

• Morphing aerospace structures

•

Shape memory effect and Shape MemoryAlloy (SMA) actuators

• Design tools for actuated structures

• Application in aerospace morphing

Presented by Dimitri Karagiannis, INASCO

• Contributing Organisations:

•

INASCO• AEROTRON Research

• University of Patras SAAM Group

The works have been carried out within the framework of Clean Sky SMyLE and SmyTE projects.



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Morphing aerospace structures

1. Weisshaar, T.A. (2006). Morphing Aircraft Technology-New Shapes for Aircraft Design, RTO-MP-AVT- 141, Neuilly-sur-Seine, France

http://www.cleansky.eu/content/page/clean-sky-

achievements

• Morphing is a technology or set of

technologies that allows air-vehicles toalter their characteristics to achieve

improved flight performance and control

authority or to complete tasks that are not

possible without this technology1.

• One of the key enabling technologies in

morphing aircraft structures is thelightweight driving actuators. Other

enabling technologies adaptive structures,

deformable smart skin, driving actuators,

flight dynamics and flight control.



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Shape Memory Effect• A shape-memory alloy (SMA) is

an alloy that "remembers" its

original shape and that when deformed

returns to its pre-deformed shape when

heated.

• The shape memory effect is the driving

mechanism for most SMA actuator

systems designed today and it is achievedthrough a change in the crystal structure

of the material between the martensite

and austenite phase.

• The first SMA to be discovered is NiTiNOL

by William J. Buehler in 1961. The name is

composed out of the two main elements,Ni and Ti, and the abbreviation of the

Naval Ordinance Laboratories (NOL)

where it was discovered.

• NiTi is the most widely used SMA .

Crystal Structure of NiTi

Lagoudas, Dimitris C, Shape Memory Alloys - Modeling and

Engineering Applications



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SMA actuators• Basic NiTi SMA shapes include commercially

available wire, tube, sheet and strip basic

products. These can be further processed to

suit the particular application.

• In our actuating elements and mechanisms we

have used manly SMA wires.

• The SMA are characterised using DSC and other

methods in order to assess the phase

transformation characteristics.



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SMA actuators• A stabilisation process of the thermomechanical

response of the actuator is always performed in

order to insure repeatable actuation cycles. This

process in called training.

• A dedicated training set up has been build and

is fully functional.

-100 -50 0 50 100 150

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0,00

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S

t r a i n

Temperature( C )

Training process Final cycle

First cycle



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SMA basic actuation concepts

• The SMA is actuated by increasing its

temperature above the phase

transformation threshold. In our case,

one way SMA with threshold of ~60oC

was utilized.

• The most common way to heat up SMA

wires is the Joule effect.• The duration of the actuation cycle

depends on how fast the SMA is heated

up and subsequently cooled down. The

actual alloy temperature depends on the

local heat transfer coefficient.

• Control of the SMA temperature is

required, as the development of high

temperatures will deteriorate the

actuation capability.



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SMA basic actuation concepts

Wire bundle SMA actuator Element with high force output

Flexy SMA patch ready for

integration

Composite plate with SMA wires (morphing

skin application)



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1D SMA actuators• SMA bundle-wire actuator is overwrapped by a heating

element in order to avoid using high power to heat up the

wires and avoid any current leaks that could lead to

dangerous situations. In this way the power to heat up the

wires is five times less when compared to the power

required by using the joule effect.

• The element is fully configurable in terms of length,

number of actuators (force) and heat exchange (duration

of actuation cycle).

• The period of a stroke of Δx=2.5mm and back can be

accelerated from 240sec to 70sec (aircooled).



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2D actuators

Basic 2D actuator dimensions:

LxD: (100 x 11)mm2, dSMA=0.1mm, Patch Thickness (tp)=0.7mm

Wire Spacing (H): Type A= 2mm – 4 wires, Type B: 1mm – 6 wires.

Repeated Loading for Type B specimens

• 2D actuators were fabricated using LTM217/Kevlar 29

prepregs. The thickness of each lamina was125microns. The specimens were prepared with six

prepreg layers, three on top and three on the bottom

of the SMA wires that were placed in the middle of

the thickness.

• A special frame – mould arrangement was used to

hold wires in place while manufacturing in the

autoclave.

• There have been various test carried out in the small scale

specimens in order to assess mechanical performance and

actuation behavior.

LTM217/kevlar



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2D smart skin• A smart skin that can deflect upwards to alter

aerodynamic properties was designed and tested.

• The skin was made of MTM resin with 3 layers +

SMA +3 layers. 74 wires of D=0.2mm have been

used. The plate is HxW =210x160 mm. The

thickness of the patch was 0,7mm. The wires are

wired in blocks of 5 (in parallel to make one

group). The 14 groups of 5 and one of 4 SMA

wires were connected in series. The totalresistance of actuators to be heated Rtot=29 Ohm.

• Power requirements ~30W.

MTM44-1 epoxy

SMA wires

Deflection

Basic Patch dimensions:

LxD: (285 x 160)mm2, dSMA=0.3mm, Patch Thickness (tp)=1.5mm

Wire Spacing (H) = 2.5mm



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Design with SMA – Modeling tools• The constitutive SMA model has been

implemented in ABAQUS commercial FEAcode within the CleanSky project SMyLE.

• It is based on the model of D. Lagoudas2.

and is accurate and can be implemented

in FEA codes.

• This was implemented in ABAQUS by using

the User material subroutine (UMAT).

UMAT is a subroutine provided by

ABAQUS in order to define a material’s

mechanical behavior. The logical diagram

of the UMAT subroutine is presented on

top left.

• Good correlation between numerical

predictions (red curves) and experimental

data (blue curves).

• This design tool has proven valuable in

conceptual and detailed structural design.

2. Lagoudas, Dimitris C, Shape Memory Alloys - Modeling and Engineering Applications



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Design with SMA – Modeling tools• It has been verified that the dynamic thermo-

mechanical behaviour of SMA actuator is quitecomplex characterized by severe non-linear

phenomena, rendering the analytic modelling

of an SMA actuator quite difficult in many

practical applications.

• The objective of the proposed enhancement is

to present a complete methodology for

identifying the SMA actuator dynamics based,

exclusively, on experimental measurements,

without the need of analytic modelling.

• This is presently achieved through the Non

linear Auto Regressive with eXogenous

excitation (NARX) model class, which is able to

capture the dynamical behaviour of a fairlywide range of non linear phenomena.

Furthermore, the NARX model class may

properly be extended to the Functionally

Pooled NARX (FP-NARX) model class in order to

capture different and/or varying operating

conditions.

0 20 40 60 80 100 120 140-9

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1x 10

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Time index

D e f l e c t i o n ( m )

signal

simulation

Skin deflection



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Applications: Compliant Leading Edge

• The rib mechanism is called ‘Compliant Mechanism’ and it is designed to provide a targeted morphingairfoil shape utilizing NiTiNol SMA material. The desired airfoil leading edge displacement of themorphed shape with respect to the unmorphed is around 1.2 mm or 3° degrees in terms of rotationangle for a rib of 620mm chord-wise length.

• The structure has been modeled using the SMA thermo-mechanical element in ABAQUS FEA.

• Technical feasibility and predictions validation was performed by testing at relevant conditions.

• Good correlation between theoretical and experimental data.

Compliant Ribs CAD models FEA results



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Applications: Trailing edge morphing wing

• Geometric and aerodynamic specifications were

provided.

• Based on these inputs the DESA architecture was

designed and analyzed by in-house developed FEAmodules that allow for accurate simulation of the shape

memory effects. With the aid of these modules the static

and dynamic behavior of the DESA architecture was

modeled and critical design parameters evaluated.

• The output of this task will be 3D CAD models and design

drawings that will be used for DESA manufacturing.

DESA prototype concept

Flap clean and morphed shapes.

x/c

Flap pressure coefficient vs. norm. chord



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Applications: Trailing edge morphing wing• The solution incorporate two pivots per rib

which allow the airfoil to assure the correct

morphed and un-morphed shapes with theactuation of the proper SMA side.

• The temperature of the SMA wire is increased by

heating up an overbraided heating element

rather than passing current through the SMA. In

this way it is possible to use multiple wires and

increase the excreted force without increasingwith minimal power requirements. For the

actuation of the DESA prototype 60W were

enough.

• Four actuation sections were used. The overall

dimensions were 0.8m cord x 1m span length.

Pivot

SMA actuators

Overwrapped by heater

SMA actuatorsOverwrapped by heater



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Applications: Trailing edge morphing wing• The wing was tested in representative conditions

achieving TRL4.

• The wing was evaluated against aerodynamic loads by

performing morphing and un-morphing cycles under

full loading.

• The dynamic properties were also measured.

24 Kg

10 Kg

10 Kg

4 KgMoving Section 1

Moving Section 2

Constant Section 3

Constant Section 4

1. Distribution of loads

2. Prototype Deformation

3. Centerline prof ile

0 200 400 600 800

600

650

700

750

Initial Configuration Morphed Configuration

V e r t i c a l P o s i t i o n ( m m )

Chord (mm)

4. Measured response

20 40 60 80 100 120 140

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30

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60

70

T i p D i s p l a c e m e n t ( m m )

Temperature of Interior SMA wires (C)

MORPHING UNDER 8Kg LOAD

0 20 40 60 80 100

0

10

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30

40

50

60

70UN-MORPHING UNDER 8Kg LOAD

T i p D i s p l a c e m e n t ( m m )

Temperature of Exterior SMA wires (C)



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Applications: Trailing edge morphing wing

• All major objectives of project have been achieved.

•DESA prototype designed, manufactured and tested .

• Technical issues with the application of SMA actuators

have been successfully addressed.

• Low power consumption (~60W), Electrical safety.

• SMA characterisation and use of dedicated numerical

tools (dedicated FEA).

• Stabilization of SMA thermo-mechanical behavior.

• One publication produced (AIRTEC 2013).

• The works have been carried out within the framework of

Clean Sky SMyLE and SmyTE projects.



1919

Thank you for your attention

Contact details (to be added)For project information and details contact:

Mr. Dimitri Karagiannis, INASCo

[email protected],

+302109943427

mailto:[email protected]

mailto:[email protected]

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