Diapositiva 1

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Smart Tunable Dynamic Vibration Absorbers
Gary H. Koopmann PSU, The Pennsylvania State
University University Park, PA
B. Tiseo, A. Concilio, A. Gianvito CIRA, The
Italian Aerospace Research Centre Capua, Italy

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Introduction

• Noise and Vibration are among the main factors
  that can affect aircraft passengers comfort
• Significant effort has been then focused to
  improve aircraft internal vibro-acoustic
  environment.

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Talk Objective
Design and Implementation of a SMA based Adaptive
Tunable Dynamic Vibration Absorber (ATDVA) to
Control the vibration field of a Planar
Structure.
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DVA as Attenuation Device

• When tonal disturbances are present, an effective
  way to control the system response may be
  represented by the use of Dynamic Vibration
  Absorber (DVA).
• DVA can be used to suppress a unwanted resonance
  or to attenuate the main system response at
  particularly forcing frequency.

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DVA Typical Applications
DVA to reduce floor vibrations due to human
movements. Uncomfortable vibrations were
encountered in the North Bank (Texas) at the
Arsenal Football Club, when the crowd jump a
particular rhythm such that to excite the
structure to resonance. The only alternative was
to use a vibration absorber.
DVA to control the transmitted vibration from the
engine of a DC9 aircraft to the fuselage. Douglas
corporation had to install Tuned Vibration
Absorbers on the engine yoke to reduce noise into
the cabin at the cruise frequency.
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Shape Memory Alloys (SMA)

• The mechanical properties of SMA change with
  temperature.

Shape Memory Effect (SME) The material is able
to recover the deformation due to the application
of a mechanical load, applied in the martensite
phase, when heated up above a certain temperature.
Superelastic Effect (SE) The material is able to
recover the deformation due to the application of
a mechanical load, applied in the austenite
phase, when unloaded.
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SMA Applications
SMA for SHAPE CONTROL The shape memory wire is
used to manipulate a flexible wing surface. The
wire on the bottom of the wing is shortened
through the shape memory effect, while the top
wire is stretched bending the edge downwards, the
opposite occurs when the wing must be bent
upwards. The shape memory effect is induced in
the wires simply by heating them with an electric
current, which is easily supplied through
electrical wiring.
SMA as ACTUATORS The shape memory wires are used
to transmit rotation to control aerodynamic
surface. The SMA torque tube is constituted by an
anisotropic laminate. SMA wires have been
embedded along the axial direction, among the
several laminae. Due to the anisotropy of the
shell, SMA contraction and corresponding axial
loads lead to torque action on the tube.
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SMA for Vibration Control
They have potential in the field of vibration
control because of the increase in the elastic
modulus from the cold to the hot state.
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SMA based Absorber The Concept
A SMA wire can be used as adaptive spring element
. Heating up the SMA wire through electrical
current, the internal tension changes and a
concomitant frequency shift is achieved, allowing
for tuning of DVA.
The device is able to adapt itself to vibration
frequency variation.
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A Tunable Device why ?

• A tunable device is able to control multi-tonal
  excitation
• A tunable device allows a less critical designing
  phase.

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Feasibility Study _at_ CAV (PSU)
The feasibility of the concept was proved by
preliminary experimental tests.
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Experimental Characterization of SMA Wires
NiTi wire Composition Nitinol 54.5 Titanium
balance Modulus of Elasticity 28 - 41103
MPa Length 180 mm Diameter 1.27 mm
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Experimental Characterization of SMA Wires
Mechanical test on SMA wire. First vibrating mode
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Experimental Characterization of SMA Wires
Thermal test on SMA wire. First vibrating mode
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ATDVA Architecture

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Preliminary Tests _at_ CAV (PSU)
Sandwich Panel Core Nomex Laminate
Carbon Dimensions 800 x 1200 x 9 mm
Vibration Test Hammer Test Acoustical Test TL
Measurements
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Preliminary Tests Results
Vibration Test
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Preliminary Tests Results
Acoustical Test TL Measurements
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ATDVA Experimental Characterization
Objective to evaluate the relationship between
Absorber Resonance Frequency and Current Intensity
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ATDVA Experimental Characterization Results
Mabs 1 Mp 60 Frequency shift
Mabs 1.5 Mp 25 Frequency shift
ATDVA Experimental CharacterizationEigenfrequency
(Hz) vs. Electrical Current (A)Mabs 1 Mp
(red) Mabs 1.5 Mp (blue)
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Investigated Application
The capability of the proposed ATDVA has been
tested on a typical aeronautic plate.
Aluminum Plate (480x760x1.5 mm)
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Plate Experimental Characterization

• Plate Resonance Frequencies
• Modal Shapes

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Plate Experimental Modal Shapes
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Vibration Test Plate Absorber
Modal Shape to be controlled (66 Hz Mode)
Objective to verify the effectiveness of the
absorber.
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Test Set - Up

• SHAKER Gaering Watson (1-3000 Hz)
• MEASUREMENT SYSTEM Polytec - Fiber Optic Laser
  Vibrometer Max freq. range 50 KHz
• POWER SUPPLY Delta ( I0-10 A V0-10 Volt)
• ACQUISITION SYSTEM LMS Scadas III (36 Input Ch.
  2 output Ch.)

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Results (Tuning on 66 Hz Mode)
Plate Absorber FRF varying the electrical
current. Single point acquisition
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Results (Tuning on 66 Hz Mode)
Plate Absorber FRF varying the electrical
current. One acquisition point
Plate Absorber FRF varying the electrical
current . Single point acquisition
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Results (Tuning on 66 Hz Mode)
System Vibration Energy I0 Ampere
System Vibration Energy I1.9 Ampere
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Results (Tuning on 66 Hz Mode)
COMPARISON System Vibration Energy I0 Ampere
System Vibration Energy I1.9 Ampere
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Overall system characteristics

• Aluminum Plate (480x760x1.5 mm)
• Atdva ( L100 mm Mabs14.5 gr )
• Mabs 1 Mp
• Sma material ( NiTi - 54.5 Ni L 100mm d1.2
  mm)
• Reduction attained 24 dB _at_ a single frequency
• Attenuation band 6 Hz

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Conclusions

• A new concept of an Adaptive Tuneable Dynamic
  Vibration Absorber (ATDVA), based on Shape Memory
  Alloy (SMA) elements instead of classical spring
  elements, was introduced.
• SMA may provide an adaptive mechanism through the
  control of its temperature.
• The device shows good potential in vibration
  control.