Rotorcraft Acoustics and Dynamics Group · PDF file– Flutter testing . ES 5 ... o...

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Center for Acoustics and Vibration

Rotorcraft Acoustics and Dynamics

Group Activities

Edward C. Smith, Professor

Group Leader, Rotorcraft Acoustics and Dynamics Group Director, Penn State Vertical Lift Research Center

2013 CAV Workshop

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• Research Overview • Project Highlights

– Vibration energy harvesting with single crystal piezoelectric materials – Progress on ultrasonic deicing systems

Presentation Outline

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Interaction with Other PSU

Research Centers & Departments

Vertical Lift Research Center

of Excellence

National Center for Advanced

Drivetrain Technology

ARL

Condition Based Maintenance Dept.

Center for Acoustics

and Vibration

Institute for Computational

Science Composites Manufacturing

Technology Center

ARL

ARL iMAST

- Aerospace - Mechanical - Eng Sci & Mech - Acoustics - Mat Sci

PSU Depts

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Vertical Lift Center Tech Base

25

Faculty

40 +

Graduate

Students

100

Undergraduate

Students (Freshman Sem, AHS Chapter,

Senior Class, Design projects)

40 Continuing Education Students

(Short course)

4

Res Assoc

Penn State ARL

NRTC CRI

SBIR Programs

apply &

transition

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2012 Funding Pie Chart: $5.32M

VLRCOE VLC SMART NAVAIR MQ8

NAVAIR/FBS NAVAIR/TDS

Bell

Penn State

ONR

NASA DoD Fellows

ARO

Timken Timken/AATD

LORD

Boeing

Goodrich

Sikorsky Piasecki

GE NSF

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VLRCOE Facilities

• Rotating Test Stand > Ice Accretion Testing, CF Testing, etc

• Piloted Flight Simulation facility – XV-15, UH-60, & custom flight models – Force feedback – Terrain models – Ship airwake

9 ft dia 1200 RPM 125 HP Icing cloud Full scale CF Pneumatic slip ring Signal/power slip ring

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VLRCOE Facilities

• Subsonic Low Turbulence Wind Tunnel – 4.5 x 3.5 foot test section – 220 ft/s (150 mph) top speed – Very low turbulence <0.05% – Ideal for UAV airfoils: Low-Mod Re #

• 22 inch dia ducted fan testbed • Subsonic Wind Tunnel

– 3.5 x 2.5 foot test section – 140 ft/s top speed – Flutter testing

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Verification and Validation Test Beds: UH-60 Upper Cabin Structure

Transmission Support and Attachment Structure

Example - critical region of interest: FS360 / BL 16.5

Fwd

(~ 8 ft)

• Technology transition to airframe complex structure

• Detection performance V&V

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Verification and Validation Test Beds: Transmission Frame Mock-up

Transmission Support and Attachment Structure

Example - critical region

of interest: FS360 / BL

16.5

FS360 Electrodynamic shaker (out-of-plane excitation)

PZT actuator (in-plane excitation)

Straps – loose fastener progression and strap crack progression for damage detection measurements

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Scaled dynamic

model of tailboom (60 lbs, 6 ft)

Smart frame actuator

Airframe Active Control Testbed

Advanced damping

and isolation

devices

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VLRCOE Research areas

Aeromechanics: Higher speeds, better fuel efficiency, all weather • Unsteady airfoil design methods • Rotor hub flow physics for drag reduction • Icing physics, modeling, detection Flight Dynamics & control: autonomy, safety, new configs • Autonomous multi-lift systems

Structures: Lower weight, more reliability • Nano-tailored composites for improved toughness and

thermal conductivity

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Design Concepts: Speed, range, altitude • Aeroelastically tailored wing extensions and winglets for

Large Civil Tiltrotors • Control redundancy on compound rotorcraft for

performance, HQ, and survivability Vibration & Noise Control: Active rotors, variable W rotors • Physics of active rotors for performance and acoustics

VLRCOE Renewal tasks

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Propulsion and Drive Systems: weight, reliability, noise

reduction • Comprehensive analysis of gearbox loss of lubrication Affordability: condition-based maintenance, SHM • Health monitoring for joints in composite structures Maritime Operations: improving safety / reliability for manned

and autonomous operations in the dynamic interface • Advanced response types / cueing systems for naval ops • Autonomous shipboard take-off and landing

VLRCOE Renewal tasks

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Vertical Lift Consortium (Army, Navy + Industry TRANSITION PROGRAMS) • Durability Evaluation of Single Crystal Energy Harvesters – CBM TAJI

(Conlon, Reichard, Smith) • Guided Wave Sensors for Rotor Blade Damage Detection (Rose) –CBM TAJI • Evaluation of Pericyclic Transmission Concepts (Rao, Saribay, Bill, Smith) – Drive Systems TAJI

• Modeling of Rotor Blade Ultrasonic Deicing and Experimental Comparison with Electrothermal Ice Protection Systems (Palacios, Smith) • Time Frequency Transforms and Symbolic Dynamic Filtering for Rotor Stability Identification, (Horn, Ray) – Aeroelastic Stability TAJI • Cable Angle Feedback for Active External Load Control (Horn) – VMS TAJI • Aided/Automated Flare and Landing during Autorotation (Horn, Langelaan) • Rotor Hub CFD Computations (Kunz) • Mechanical Performance of Nanoreinforced Composites for Rotorcraft Applications - Advanced Materials TAJI, (Bakis and Koudela)

Other Current VLRCOE Projects

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Vertical Lift Consortium (Army, Navy + Industry TRANSITION PROGRAMS) • Static and Dynamic Characterization of Composite Materials for Future Driveshaft Systems (Bakis and Smith) • Analysis and Characterization of Textile-Based Crashworthy Payload Restraint Systems (Bakis, Yukish, Smith, Little)

• Centrifugally Driven Pneumatic Actuators for Active Rotors (Palacios, Smith)


Army Research Office (ARO)

• Novel Structural Health Monitoring Scheme for Glass-Fiber Composites using Nanofillers (Bakis, Wang- UM)

Office of Naval Research (ONR) • Innovative Energy Absorbers Based on Composite Tube (Bakis, Smith, Yukish)

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NASA

• Acoustically Tailored Panels for Low Cabin Noise (Hambric & Koudela) • High Fidelity CFD Analysis and Validation of Rotorcraft Gear Box Aerodynamics (Kunz) • Development of Nanoparticle-Enhanced Towpreg for Filament Wound Composites (Bakis)

NAVAIR • A Multi-Functional Ultrasonic Sensor System for Composite Rotor Blade Ice Protection, Ice Sensing, and Structural Health Monitoring (SBIR with FBS Inc, Smith and Palacios) • Innovative Methods for Real-Time Damage Alleviation (SBIR with Technical Data Associates, Horn, Ray) • MQ-8B VTUAV/Fire Scout Structural Dynamics Testing Support (Wyle Labs/NAVAIR, Conlon, Hambric)

NSF • Learning from Plants -- Biologically-Inspired Multi-Functional Active Composites (Bakis and Rahn)

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Bell Helicopter TEXTRON • Civil Certification Noise Prediction Tools (Brentner) • Analysis of Rotor Startup/Shutdown in Complex Winds (Smith, Kunz) • Alternate Control Laws for Fly-by-Wire Helicopters (Horn) • Tailboom Vibration Control (Smith, Rahn) • VLRCOE student fellowships

Boeing • Pericyclic Transmission Design Studies (Rao) • Gearbox Windage Loss SImulation (Kunz) • Titanium Hardening Study (Copley) Sikorsky • Dynamic Gear Testing - AATD FARDS program (Sonti) • Support for Hub Drag testing – VLRCOE program (Schmitz)

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GE Global Research

• Ice Accretion to Cascade Flow Configurations of Engine Compressors (Palacios)

LORD Corporation

• Conceptualization, Modeling, and Characterization of a CF Driven Multi- State Lead-Lag Bypass Damper (Lesieutre and Smith) • Vibration Control via Coupled Fluidic Pitch Links (Rahn and Smith)

Goodrich/UTC

• Deicing systems, etc

Timken

• Evaluating Carbo-Nitrided Pyrowear 675” (Isaacson) • Analysis of Gearbox Loss of Lubrication - VLRCOE task support (Kunz, Bill, Saribay)

Piasecki Aircraft Corporation

• Simulation Model Validation and Handling Qualities Analysis of the X-49A Compound Helicopter (Horn)

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Single Crystal Vibration Energy Harvester for Diagnostics

Michael Wozniak – Graduate Research Assistant

Advisors:

Dr. Stephen Conlon Dr. Edward Smith Dr. Karl Reichard

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1 8 5 5Background

• High demand for autonomous power solutions for use in structural health monitoring

Batteries have finite life and may be located in hard-to-reach areas Using existing power adds weight to the aircraft through use of wires

• Rotorcraft have substantial vibration levels

(50 – 2000 Hz near/on drivetrain) ~800 Hz for gear mesh frequency Excellent platform for Piezoelectric Energy Harvesters

• Newer materials (single crystals) offer better piezoelectric properties than PZT

Higher piezoelectric charge coefficients (d31), larger electromechanical coupling factor (k31) and lower loss factors (tanδ)

Single crystal use in energy harvesters is limited with no commercial products available to date

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1 8 5 5Objectives

• Understand more clearly the application of single crystal piezoelectric materials to the rotorcraft operational environment

Conduct / report on comprehensive literature survey on mechanical & electrical reliability of piezoelectric based EH and single crystal components

Conduct vibration durability testing on representative single crystal components and EH

Explore durability single crystals & Energy Harvesters in extreme temperature environments

• Develop conceptual design and initial lab demonstration of new lightweight and compact energy harvesters

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1 8 5 5Endurance Testing • Objective:

Characterize sensitivity of EH natural frequency and open- circuit voltage under 120 hours of continuous operation at 1.0g base acceleration. (2x duration and 2x amplitude previous study)

• Start-up thermal transient present in first few hours (typical)

• Conclusions: o Tapered cantilever beam design shows stable resonance

and gives near-uniform strain Viable option for energy harvester geometry.

o Strain levels far below cited failure level ~55 με Margin to design higher strain systems (higher output) Static Strain Failure: ~1500 με

Usable beam length of 40mm

Usable beam mass of 15g 64g

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1 8 5 5Temperature Testing • Objective:

Characterize sensitivity of EH system natural frequency and open-circuit voltage for a temperature range of 0 to 70 °C (3x ∆Temp & 4x vibe amplitude previous study)

• Piezoelectric properties change with increasing temperature, leading to loss in voltage (same trend observed with traditional PZT)

• Conclusions: oResonance is stable over 0 - 70 °C oLoss of output voltage approaching phase transition (~75 °C) Can increase P-T temp by

decreasing %PT in PMN-PT sample, 28%PT = 95 °C

o28% PT may yield better performance at higher temperatures due to its higher phase transition temperature

6%

60%

PMN-0.32PT

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1 8 5 5Performance Testing

• Objectives: • Characterize sensitivity of EH

open-circuit voltage and power between 0.5g and 5.0g base acceleration (5x previous study)

• Validate the FEM model

• FEM prediction utilizes measured damping to accurately calculate output strain

• Conclusions: • No serious degradation of performance at

high acceleration levels o Some nonlinearity present at high

accelerations

• FE model correlates well with measurements o Accurate FEM model can be used for

device design, scaling, and optimization

~13%

Q = 57

Q = 43

Piezo: • 400

elements • 15

elements through thickness

(Beam length 40mm)

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1 8 5 5Compact Harvester Design

• Goal: 5mW of power at 800 Hz with 1.0g base acceleration

• Desired to create more representative energy harvester, and to validate the design process for scalability studies

• Monoblock structure design to minimize mechanical damping / maximize output power

• Predicted strain on the piezoelectric material from Finite Element software is 230με, corresponding to a predicted open circuit voltage of 48 Volts at 1.0g base acceleration at 800 Hz with Q = 175 o KCF = 25V at 0.5g @ 700 Hz o Techno-Sciences = 95V at 0.2g @ 60 Hz

• Scalability study in progress to characterize output power vs. mass vs. frequency

PMN-PT

Single

Crystal

Circuitry Measured Mass (weight): <40 grams (0.09 lbs)

40 mm

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1 8 5 5Performance Testing • Objectives:

• Characterize sensitivity of EH open-circuit voltage

and power between 0.5g and 5.0g base acceleration (5x previous study)

• Validate the FEM model

• FEM prediction utilizes measured damping to accurately calculate output strain

• Conclusions: o No serious degradation of performance at

high acceleration levels • Some nonlinearity present at high

accelerations

o FE model correlates well with measurements • Accurate FEM model can be used for

device design, scaling, and optimization

o Harvester produces enough power at 1.0g to power small sensor

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Progress Towards a Rotor Blade Ultrasonic Deicing System

Austin Overmeyer Research Assistant

Nic Diplacido

Research Assistant

Jose L. Palacios Research Associate

Edward Smith

Professor Aerospace Engineering

BACKGROUND

•Flight into Icing Conditions is Dangerous •Reduced vehicle performance

•Torque Rise •Stability & Control Issues •Excessive Vibration

•Operational Limitations

•Simply avoid ice •Few aircraft have limited icing clearances •Fewer have IPS

•Rotorcraft Compounding Factors •Mission Urgency •Mission Profile •Vehicle Sensitivity to Ice •Shedding

Electrothermal Background

• Only system qualified by the FAA and the DoD

• Heavy system (4 Blades 12,000 lbs Model: >160 lbs.)

• Does not allow for continuous application due to high power consumption (4 Blades 12,000 lbs Model: >20 KW, ~25 W/in2)

• Allows ice accretion up to 0.3 in (10% Torque Increase)

• Melted ice may flow aft and refreeze further

• Difficult to integrate with polymer erosion-resistant materials

ARMY HISS Icing Certification Testing Ice Protection System

Ultrasonic Deicing Background

CF

Drag Ice

Leading Edge Protection Cap

Piezoelectric actuators used to create ultrasonic waves which generate transverse shear stresses at the ice interface

a’

Leading Edge Mass (10 – 20% Weight of the Blade)

a’

1

Substitute with Active Piezoelectric Material

2

a’ a’

a’

a’ Ω

Objectives

1) Experimentally validate finite element tools used for modeling ultrasonic deicing systems 2) Utilize finite element tools to aid in the optimization of a bondline for the design of a robust ultrasonic deicing system 3) Implement an ultrasonic deicing controller which is capable of consistently tracking and actuating the ultrasonic modes required for deicing 4) Design and fabricate a robust ultrasonic deicing system

Shake Down Rotating Icing Tests: with and without ultrasound

80 Watts No Ultrasound

OUTLINE • Problem Statement

• FE Modeling Validation

•FE Mesh Convergence •Comparison of Electro-Mechanical Impedance •Comparison of Out-of-Plane Velocities

• Bondline Optimization, Validation and

Development

• Experimental Results of Ultrasonic Deicing System under Impact Icing Conditions

• Summary

FE Model Mesh Convergence • FEM mesh convergence study conducted to accurately predict the transverse shear stresses on the ice interface •Established model requirements

•Recommend Mesh Parameters: •Element Type: Quadratic •Approximate Mesh Size: 3mm •Elements Through the Thickness: 2 •Results within ± 6 % Deviation

Quadratic (20 node, 3D Element)

Mesh # Mesh Type Average

Size (mm) Thickness Elements

1 Linear 5 2

2 Quadratic 5 2

3 Quadratic 4 2

4 Quadratic 3 2

5 Quadratic 2 2

6 Quadratic 1 2

7 Quadratic 5 3

8 Quadratic 4 3

9 Quadratic 3 3

10 Quadratic 2 3

Converged Mesh

•13” Diameter x 0.032” Thick AL Plate

•3” Diameter x 0.015” Thick PZT-4 Disk

•0.015” Thick EP21 Bondline •Free-Free and clamped Boundary Conditions

•Actuated at the radial mode of the system ~28 kHz

•Out-of-Plane Velocity Magnitudes Measured in 2.5 mm spatial increments

•Velocities normalized to the input voltage potential across the actuator

Experimental Setup

Model Validation: Experimental Setup

Model Validation: Experimental Damping

Time-Response Method to calculate the damping ratio

ζ = 0.1883 %

•Used laser vibrometer to

experimentally quantify the material

damping in the host structure at

resonance (~28.5 kHz) using the

time-response method

•Implemented into FE models using

a Rayleigh Damping Model, where

the stiffness proportional term, was

assumed to dominate the response

•The measured damping ratio was

converted to a stiffness proportional

damping term for a given frequency

Model Validation: Impedance Comparison

• Comparison of the experimental and predicted electro-mechanical impedance of a host structure excited by an ultrasonic PZT-4 actuator

•Proper prediction of resonant frequency and impedance minimums

Robust Bondline Testing and FEM Validation

[Overmeyer, Palacios, Smith, AIAA 2012-1476]

Out-of-plane velocity for EP21 and

FM73/Mesh Bondlines

Bondline Development Issues

Layup Configurations

Bondline Development Specimen

•Initial single cure layups failed to properly insulate the top and bottom metal mesh layers

•3 Cure layup process developed to properly insulate the top and bottom metal mesh layers

Failed Electrical Insulation

Bondline Development

Layer Material Nominal Thickness (in) FM73 0.0100

Aluminum Mesh 0.0030

PZT

+

-

Host Structure

CURE CYCLE 1 CURE CYCLE 3 CURE CYCLE 2

FINAL BOND THICKNESS: 0.015”

Optimized Bondline Configuration and Curing Cycles

Bondline Development Issues

Voids Successfully filled

Geometry Mismatch Issues

•The voided area created by the geometry mismatch must be adequately filled by the bond line

•The process developed successfully filled the voids on a NACA0015, 16” Chord Airfoil

Rotational Test Setup •The goal of the initial testing is to prepare for testing on the KMAX Main Rotor Blade sections

•The initial test objectives are: •Achieve Full Span Deicing

•Determine Element on time •Zone Order •Frequency Sweep •Guide modeling efforts of airfoil test specimens

•Test Specimen: NACA0015, 16” Chord, 12” in span, SS Airfoil, 0.040” Thick

Rotational Test Setup

9 ft.

Icing Cloud

Control Room

ROTOR TIP VIEW WITH STROBE LIGHT

Initial Rotational Test Results

Test Conditions: 400 RPM 0° AOA Temperature: -10 °C MVD: 20 µm LWC: ~1.5 g/m3

Icing Time: 2 Minutes Measured Ice Thickness: ~4.5 mm

Conclusions

1) FE axisymmetric model validation: 5% discrepancy compared to the experimental measurements

2) Optimized bondline configurations increased the ice interfacial transverse shear stresses by as much as 15%

3) Prevented actuator fracture or debonding failures during rotor icing testing with novel configuration

4) Ultrasonic deicing (1.4 and 7.1 mm ice thickness ) of structures of rotor blade leading edges accomplished at representative CF forces (390 gs)

5) To promote ice shedding, frequency sweeping is required to redistribute transverse shear stress on the structure

6) The average load power: 0.63 W/cm2

7) Ultrasonic deicing protects within natural icing conditions (FAA Part 25/29 Appendix: C icing envelope)

M

k

b

F0sin(wt)

𝑚𝑥 + 𝑏𝑥 + 𝑘𝑥 = 𝐹0sin(𝜔𝑡)

Single Degree of Freedom System

• Lightly Damped • Homogeneous Initial

Conditions • Harmonically Driven

Maximum amplitude occurs during transient vibration when driven off resonance.

Axisymmetric Transient Vibration (68 KHz)

• Stress from same sample node along ice/Ti interface • Implicit Solution (100W) • Due to cracking and delamination of ice, resonant frequency changes by

up to 2kHz: driving a system at resonance continuously is not possible

Higher amplitude, relative to steady state, occurs during transient vibration when driven off resonance.

Bench Top Test: Freezer Ice • Axisymmetric geometry • Ice frozen in segmented

annulus • Plate supported on edges

by foam to simulate free-free BCs

• 19 mm radius PZT • Driving frequency near

68kHz • Four actuation methods

were compared

1. Multi-Frequency Bursts (0.55kHz Band, 20 bursts, 0.3s/burst) 2. Single Frequency Bursts (0kHz Band, 20 bursts, 0.3s/burst) 3. Single Frequency Tone (0kHz Band, 1 bursts, 6s/burst) 4. Frequency Sweeping Tone (0.55kHz Band, 1 bursts, 6s/burst)

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250

% D

eice

d

Max Power (W)

Multi-Frequency Bursts

Multi-Frequency BurstTrendSingle Frequency Bursts

Single Frequency BurstsTrendSingle Frequency Tone

Single Frequency ToneTrendFrequency Sweep

Frequency Sweep Trend

Bench Top Test: Freezer Ice

Burst actuation techniques improve de-icing area coverage by up to 390% when compared to continuous actuation tones, regardless of changes in frequency (0.55 kHz variation).

Rotor Ice Tests

• Rotation set at 400 RPM • Average ice thickness of 10.8 mm near tip • Frequency band of 0.55 kHz centered at resonance

Ice was cut with hot plate to encourage segmented delamination.

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250

% D

eice

d

Average Power (W)

Multi-Frequency Bursts

Multi-Frequency Burst Trend

Single Frequency Bursts

Single Frequency Burst Trend

Frequency Sweep

Testing was stopped due to voltages reaching experimental upper limit for system.

Conclusion • Low frequency SDF solutions and transient

ultrasonic FE analysis predict large amplitudes can be observed prior to reaching a steady state response

• Experimental results show that simply changing the frequency or driving continuously at resonance provide inferior deicing capabilities

The enhanced de-icing ability observed when employing multi-frequency bursts is due to the transient nature of the actuation method and not the changes in frequency.

Rotorcraft Acoustics and Dynamics Group · PDF file– Flutter testing . ES 5 ... o...

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