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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
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
• 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.
7/26/2019 Presentation sur les UAV SMA
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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.
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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.
7/26/2019 Presentation sur les UAV SMA
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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.
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t r a i n
Temperature( C )
Training process Final cycle
First cycle
7/26/2019 Presentation sur les UAV SMA
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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.
7/26/2019 Presentation sur les UAV SMA
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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)
7/26/2019 Presentation sur les UAV SMA
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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).
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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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Time index
D e f l e c t i o n ( m )
signal
simulation
Skin deflection
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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
7/26/2019 Presentation sur les UAV SMA
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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
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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
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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
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T i p D i s p l a c e m e n t ( m m )
Temperature of Exterior SMA wires (C)
7/26/2019 Presentation sur les UAV SMA
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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.
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Thank you for your attention
Contact details (to be added)For project information and details contact:
Mr. Dimitri Karagiannis, INASCo
+302109943427