STRUCTURAL VIBRATION AND ACOUSTICS GROUP

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• STRUCTURAL VIBRATION AND ACOUSTICS GROUP
• Kon-Well Wang
• Group Leader
• Liming Chang Gary Gray
• Steve Hambric Sabih Hayek
• Yun-Fan Hwang Bill Mark
• Eric Marsh Eric Mockensturm
• Tim McDevitt Marty Trethewey
• Andy Vavreck

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• STRUCTURAL VIBRATION AND ACOUSTICS GROUP
• RESEARCH ACTIVITY HIGHLIGHTS
• The Structural Dynamics and Controls Program
• (Dr. Kon-Well Wang)
• The Structural Acoustics Program
• (Dr. Steve Hambric)

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Structural Dynamics and Controls Research Program

• Recent Projects
• Fluidic Flexible Matrix Composite for Autonomous
  Structural Tailoring
• Piezoelectric Networking for Structural Damage
  Detection Enhancement
• Control of Large, Lightweight, High-Precision
  Space Reflectors
• Carbon Nanotube-based Damping Composites
• Vibration Delocalization and Control of Mistuned
  Periodic Structures
• Biologically Inspired Fibrillar Network Ion
  Transport Adaptive Structures
• Piezoelectric Circuitry for Adaptive Disturbance
  Rejection and Vibration Confinement
• Flexible Matrix Composite Driveshaft and Active
  Bearing Control
• Hybrid and Enhanced Active Constrained Layer
  Damping Treatments
• Piezo-Hydraulic Pump Actuation Systems for Band
  Brake Control in Automotive Transmissions

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Fluidic Flexible Matrix Composites for
Autonomous Structural Tailoring

• Kon-Well Wang
• Diefenderfer Chaired Professor in Mechanical
  Engineering
• Charles E. Bakis
• Professor of Engineering Science and Mechanics
• Christopher D. Rahn
• Professor of Mechanical Engineering
• Ying Shan
• PostDoc Fellow
• Amir Lotfi
• Suyi Li
• Graduate Students
• The Pennsylvania State University
• Shiv Joshi
• NextGen Aeronautics, Inc.

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Objective and Approach

• Objective To achieve novel adaptive structures
  with tunable mechanical (stiffness) properties
• Approach - Build upon a biologically-inspired
  adaptive structure concept and achieve the goal
  through circulatory system valve control on
  Fluidic-Flexible-Matrix-Composites (F2MC) -based
  structures

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Related Previous Work Penn State Fibrillar
Network Adaptive Structures

• Inspired by the fibrillar network configuration
  of plant cell walls

• High mechanical advantage flexible matrix
  composite (FMC) tube via fiber angles layups
  

• Can be integrated to form multi-cell structures

• Stiff fibers (carbon, glass)
• Soft matrix (elastomer)
• E1/E2 104
• Large transverse strain capability (gt100)

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New Observation -- Variable Stiffness
Fluid
Valve

• Observation -- Significant changes in stiffness
  by simply controlling valve to FMC cell
• Open Valve ? system can be flexible easy to
  pull
• Closed Valve ? system becomes very stiff (small
  deformation with large external load)

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New Idea -- Variable Stiffness Concept
Stiffness increase with closed valve is due to
fiber reinforcement configuration and the high
bulk modulus of the working fluid

• Idea - Based on this observation, we can develop
  structures with variable stiffness
• Can change stiffness significantly with simple
  valve control
• Semi-active or adaptive-passive structure with
  low power requirements

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Results and Discussions

• Preliminary experimental results
• Model development and experimental validation
• Analysis and design study

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F2MC Tube Fabrication

• F2MC tube is fabricated using wet-filament
  winding process
• Can tailor tube properties for different
  applications
• Fibers
• Matrices
• Ply angles
• Trial material systems carbon fiber/silicone
  matrix

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Preliminary Stiffness Variation Test

• Significant modulus variation via simple on-off
  valve control
• Modulus ratio 15.5

Closed 121 MPa
Open 7.8 MPa
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Multi-Tube Sheet Test
Pressure Sensor
By changing structural materials and fiber
orientations ? can we do even better?
Closed 57 MPa
Multi-Tube Sheet
21X
Valves
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• Need to develop accurate model provide design
  guidelines
• Model derivation
• Model validation and analysis

Open 2.7 MPa

• Four ?35 deg. F2MC tubes embedded in silicone
  matrix
• Close/Open modulus ratio 21X

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3D Elasticity Model
Pressurized infinitely long cylinder with an
applied external axial force
Account for inner liner and FMC tube deformation
in the thickness direction
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Model Validation

• The 3-D model predictions agree very well with
  test results
• Can exercise the model for design and material
  selection

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Multi-Tube Sheet Analysis and Test

• Rules of Mixtures approach
• Assume perfect bonding between the tubes and the
  matrix material
• Assume the load (Pc) carried by the composite
  sheet is shared between the F2MC tubes (Pt) and
  the matrix (Pm)

Analytical predictions compared well with test
results
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High Performance Test Results

• Test structure with higher modulus change is
  developed based on analysis results
• ?35 deg. tube with stiffer inner liner --
  Closed/Open modulus ratio 56X

• Significant Improvement in Performance
• Old design 15.5x
• New design 56 x

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F2MC Design Space
Goal determine range of achievable modulus and
modulus ratio combinations using F2MC technology
c1t1/a2 c2t2/a2
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F2MC Design Space
F2MC can achieve a wide range of modulus and
modulus ratio combinations
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Piezoelectric Transducer Networking for
Structural Damage Detection Enhancement
K.W. Wang Diefenderfer Chaired Professor in
Mechanical EngineeringHeath HofmannAssociate
Professor of Electrical EngineeringLijun Jiang
Ph.D. studentMatthew Whitehead M.S. student
Sponsored byNational Science Foundation
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Structure Augmented with Distributed
Piezoelectric/Circuitry Networks
Distributed piezo-transducers and multiple-branch
circuitry networks with active source and passive
circuits
From Distributed Sensors

• Significantly increase DOF and design space
  dimension
• Can re-assign, confine and dissipate energy in
  circuitry without mechanical tailoring
• ? System much more adaptable to advanced
  monitoring and control
• Analogous to adding many more mechanical
  substructures, but no limitation in space,
  simpler in design, lighter in weight, and much
  easier to integrate with complex systems

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Some Research Highlights

• Structural Control Enhancement
• Active-Passive hybrid damping
• Narrowband disturbance rejection
• Vibration confinement/isolation
• Vibration delocalization of mistuned periodic
  structures
• Structural Health Monitoring Enhancement

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Background
Damage identification methods

• Localized identification methods Ultrasonic
  method, acoustic emission method, et al.

• Global damage identification methods (examine the
  changes in structural vibration characteristics)
• Frequency change based method
• Mode shape change based method
• Mode shape curvature change based method

Easiest to implement
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Problem Statement and Research Objective

• Problem Statement
• Limitations of the classical frequency change
  based methods
• The of measured natural frequencies usually is
  much smaller than the of D.O.F. required for
  accurate damage identification
• Difficulty in detecting small damage due to the
  usually low sensitivity of frequency shifts
  relative to damage effect

Research Objective To overcome the limitations
and develop a new method which can more
completely and accurately capture the damage
feature from structural frequency variations
while still maintain the simplicity of the method
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New Idea
Tunable Piezoelectric Transducer Circuitry

• Basic concept Directly integrate tunable
  inductance to the piezoelectric transducer to
  continuously and favorably alter the dynamics of
  the integrated system so that more information
  about the damage can be captured

Power Electronics for Concurrent Energy Harvesting
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Features of the New Method
How does the tunable inductance circuit help?
Pure mechanical structure
Integrated system
Additional resonant peaks introduced by the
circuitry dynamics

• Tuning the inductance systematically can result
  in a family of frequency responses

• Additional peaks can be positioned at any desired
  frequency band by tuning the inductance

Greatly enrich the frequency measurement data
and gain more information about the structural
damage
Higher sensitivity of frequency changes to
damage effects can be achieved by appropriately
positioning the additional peaks
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Synthesis and Analysis Results

• Developed new methodology to identify best
  inductance tuning range via frequency curve
  veering concept
• Modal update and iteration scheme to derive
  stiffness variation vector ? damaged element
  location and severity

Prediction error for damage located on different
elements
Prediction using new method with piezo-networking
is much more accurate than traditional
method On-going work apply feedback control to
increase sensitivity
Index of prediction error
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• STRUCTURAL VIBRATION AND ACOUSTICS GROUP
• RESEARCH ACTIVITY HIGHLIGHTS
• The Structural Dynamics and Controls Program
• (Dr. Kon-Well Wang)
• The Structural Acoustics Program
• (Dr. Steve Hambric)

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ARL/Penn State Structural-Acoustics Department
Research ProgramsPresented as part of the CAV
workshop Dr. Stephen HambricDr. Stephen
ConlonHarrison GyurkoAndrew Barnard8 May 2007
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Overview

• CRI
• Structural Condition Monitoring with Structural
  Intensity
• Student Research
• Measuring dynamic impedances of fluid films in
  journal bearings
• Measuring narrow-band sound directivity in
  reverberant water tanks
• Conference announcement NoiseCon 2007

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Structural Health Monitoring of Rotorcraft Blades
with Structural Intensity Investigators S.C.
Conlon, S.A. Hambric, K.M. Reichard Sponsor
Center for Rotorcraft Innovation
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Numerical assessments - Objective
Simplified rotor blade structure
Point force drive input for SI simulations
Support
Finite element (plate) model for study of energy
flow in low order blade modes ( 1st and 2nd
flapping, lag and torsion modes)
Leading Edge Damage
Leading edge damage modeled as local loss of
stiffness
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Numerical assessments - Objective

• Compute normal modes and forced frequency
  response with NASTRAN
• Compute structural intensity fields with McPOW
• NASTRAN post-processor
• Developed under Navy and Ford Motor Co. funding
• Validated against beam and plate bench tests
• Compare intensity fields in original, and damaged
  blades
• Do intensity fields change appreciably?

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Results 1st Torsional Mode

• Structural Intensity Plots of Damaged Blade
• 0.08 change in resonance frequency, no
  significant change in global mode shape
• Unit vectors indicate intensity direction, color
  bar indicates intensity magnitudes (dB)
• Significant energy recirculation at damage
  location

Mode Shape Undamaged blade 132.98 Hz, Damaged
blade 132.88 Hz
Structural Intensity of blade section around
leading edge damage location
Undamaged blade

Damaged blade
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Results 1st Lag mode

• Structural Intensity Plots of Damaged Blade
• Unit vectors indicating intensity direction,
  color bar indicating intensity magnitudes (dB)
• 0.28 change in resonance frequency, no
  significant change in global mode shape
• Significant energy recirculation at damage on
  leading edge and near damage location on spar

Mode Shape Undamaged blade 57.39 Hz, Damaged
blade 57.23 Hz
Structural Intensity of blade section around
leading edge damage location
Undamaged blade

Damaged blade
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Results 1st Lag Mode near root

• Structural Intensity Plots of Damaged Blade
• Unit vectors indicating intensity direction,
  color bar indicating intensity magnitudes (dB)
• 0.28 change in resonance frequency, no
  significant change in global mode shape
• Significant intensity magnitude changes at blade
  root remote to damage location

Mode Shape Undamaged blade 57.39 Hz, Damaged
blade 57.23 Hz
Structural Intensity of blade section at blade
root (remote to damage location)
Undamaged blade

Damaged blade
Max level -40.4 dB
Max level -24.4 dB
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Next steps

• Refined blade model developed
• CRI team is identifying other damage types to
  consider
• Graduate student will continue work starting Fall
  2007

Cross section of solid model
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Experimental Determination of the
Distributed Dynamic Coefficients for a
Hydrodynamic Fluid Film Bearing Advisors S.A.
Hambric, K.M. Reichard Researcher Harrison
Gyurko (Ph.D. Acoustics pending) Sponsor ARL
EF Program
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Distributed Bearing Coefficients

• Current lumped parameter bearing coefficients are
  limited to modeling only 1st order vibratory
  motion
• A numerical method has been developed that
  distributes the stiffness and damping of the
  fluid film around the circumference of the
  bearing surface
• Objective validate distributed bearing
  coefficient method through laboratory testing

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Distributed Bearing Coefficients

• Fluid Film Bearing Test Rig
• Design
• Fixed shaft / floating bearing design
• Lubrication supplied by external oil pump loop
• Operation
• Vertical static loads applied by hanging mass
  pulley system
• Horz. and vert. dynamic excitation applied by
  shakers mounted to exterior of bearing housing
• Measurements
• Relative bearing/shaft displacements measured via
  non-contact capacitance probes
• Fluid film pressures measured via pressure
  sensors embedded around test bearing circumference

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Distributed Bearing Coefficients

• Experimentally obtained distributed stiffness and
  damping coefficients are derived from the
  measured displacement and pressure outputs
• Results will be compared to those calculated from
  the numerical model over various operating
  conditions
• excitation frequency
• shaft rotation frequency
• static bearing load
• oil inlet pressures
• Model validation and operating bounds will be
  determined through these comparisons

Numerically Obtained Distributed Coefficients
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Narrowband sound power and directivity
measurements in underwater reverberant
environments using NAH and supersonic
intensity Advisors S.A. Hambric, D.E. Capone,
S.C. Conlon Researchers Andrew R. Barnard
(Ph.D. Acoustics pending) Sponsor NAVSEA 073R
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Narrowband reverberant measurements Objective

• Objective
• Quantify free-field, narrowband acoustic
  radiation accurately in reverberant water tanks
• Background
• Current techniques limited to
• Third octave bandwidths,
• High frequency (based on tank size), or
• Anechoic termination
• Benefits
• Cost effective measurements
• High repeatability
• Lab controlled testing environment

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Narrowband reverberant measurements

• Experimental Setup

• Water filled thin walled (1/8) aluminum
  cylindrical shell
• Point driven via F3 shaker

5 degree of freedom scanning intensity
measurement system measures acoustic pressure and
particle acceleration
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Narrowband reverberant measurements

• Preliminary Results
• Non-propagating waves filtered from measurement
• Computed narrowband sound power
• Mapped radiated intensity field
• Compare well with traditional OTO measurements

Intensity Map _at_ 175 Hz (1,3) Cylindrical Mode
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Narrowband reverberant measurements

• The Road Ahead
• Improved cylinder scan
• Developed new intensity probes
• Add reverberant filtering
• Denser mesh definition
• Compare to traditional NAH formulations
• Repeat for air filled shell

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NoiseCon 2007 (www.inceusa.org/nc07)

• Steve Hambric General Chair
• Steve Conlon Technical Chair
• Oct 22-24, Reno, Nevada
• Abstracts due 21 May
• Papers due 16 July
• Students
• Paper competition multiple 1,000 awards
• Seminar on jobs in noise control engineering
• Reduced registration rate (100)

Hotel Grand Sierra Resort
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Structural Vibration and Acoustics Group

• Other Projects and Programs
• Experimental modal analysis (Marty Trethewey)
• Gear dynamics (Bill Mark)
• Machine lubrication (Liming Chang)
• Machine tools dynamics (Eric Marsh)
• Mechanics of flexible structures (Eric
  Mockensturm)
• Nonlinear dynamics (Gary Gray)
• Structural acoustics (Steve Hambric, Sabih Hayek,
  Yun-Fan Hwang, Tim McDevitt)