Advanced Instrumentation for Acousto-Ultrasonic Based Structural Health Monitoring...

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  • 1

    Advanced Instrumentation for Acousto-Ultrasonic Based Structural

    Health Monitoring

    Joel Smithard, Steve Galea,

    Stephen van der Velden, Ian Powlesland,

    Cedric Rosalie, and Nik Rajic

    Aerospace Division

    UNCLASSIFIED – Approved For Public Release

  • 2

    Outline

    ▪ AUSAM+ overview

    ▪ Hardware

    ▪ Firmware and Software

    ▪ Operational Modes

    ▪ First-Of-Class Assessment

    ▪ System Demonstration

    ▪ MatLab Scripting

    ▪ Array of 16 sensing elements

    ▪ Acousto-Ultrasonic ‘fingerprint’

    ▪ Wrap-up

    UNCLASSIFIED – Approved For Public Release

  • 3

    AUSAM overview

    115 x 65 x 20 mm; size comparison to IPhone

    • Instrument Bandwidth 50 kHz – 5 MHz for actuation and response

    – High order Lamb waves provide a richer source of AU information

    • Interrogate using PZTs and FBGs

    UNCLASSIFIED – Approved For Public Release

  • 4

    AUSAM Hardware ▪ USB 2.0: power and communications

    ▪ High Voltage PZT Amplifier

    ▪ 50 KHz to 5 MHz frequency

    ▪ Drive on any channel(s)

    ▪ Receive on any channel(s)

    ▪ 1 to 1024 synchronous averages

    ▪ External isolated trigger in/out

    ▪ External Temperature and Strain measurements

    ▪ Connect up to 62 units

    Drive:

    • Maximum 200Vp-p drive pulse • Arbitrary function generator • Drive capacitive loads up to 10nF

    • Monitoring of drive load voltage and current

    Receiver:

    • 4 independent low noise receiver channels • 4 independent optical PIN diode channels • 4 Optical DC power measurements

    • Independent gain control from -4.5dB to 55dB

    UNCLASSIFIED – Approved For Public Release

  • 5

    AUSAM Firmware and Software Can replace

    with Raspberry Pi; connect over

    wireless

    Can replace with Python; wireless to

    Raspberry Pi

    UNCLASSIFIED – Approved For Public Release

  • 6

    AUSAM+ MatLab Object

    UNCLASSIFIED – Approved For Public Release

  • 7

    %%Setup

    ausam_master = AusamModel( 'bitfile', ‘..\aushmiv.bit', 'serial', '1606000DLL');

    ausam_slave1 = AusamModel(……

    ausam_slave2 = AusamModel(……

    …….

    ausam_slave1.Hardware.Unit(2).Leds='hhhhhhhh'; %LEDs driven by hardware function, eg LED1=trigger

    ausam_slave1.Hardware.Unit(2).TriggerControl = 11363; % one wire mode;

    …….

    % set channel gains (dB)

    gain = 43.5;

    ausam_master.Hardware.Unit(2).Channel(1).Gain = gain;

    ausam_master.Hardware.Unit(2).Channel(2).Gain = gain;

    …….

    skew = 11.51e-3;

    ausam_master.Hardware.Unit(2).Channel(1).Skew = skew;

    ausam_master.Hardware.Unit(2).Channel(2).Skew = skew;

    -----

    AUSAM+ Scripting (setup)

    UNCLASSIFIED – Approved For Public Release

  • 8

    %%Trigger done get/use the data

    ausam_master.Hardware.Unit(2).Channel(1).RequestADC;

    ausam_master.Hardware.Unit(2).Channel(2).RequestADC;

    …….

    % Data has now been moved from actual hardware to the MatLab object.

    PVDF_Array_element_16 = ausam_master.Hardware.Unit(2).Channel(4).Data;

    PVDF_Array_element_15 = ausam_master.Hardware.Unit(2).Channel(3).Data;

    ……..

    PVDF_Whole_Array = [PVDF_Array_element_1; PVDF_Array_element_2; ...

    figure(5),imagesc(fliplr(PVDF_Whole_Array'))

    % Plot all channels

    figure(1)

    subplot(2,2,1)

    plot(ausam_master.Hardware.Unit(2).Channel(1).Data)

    subplot(2,2,2)

    ……

    %Do some magic with it☺

    factor = ((2/2^12)/(10^(ausam_master.Hardware.Unit(2).Channel(4).Gain/20))); %gets ADC counts to volts

    [HT] = AUSAM_GenerateHilbertTransform(ausam_master.Hardware.Unit(2).Channel(4).DataCounts*factor);

    …….

    AUSAM+ Scripting (get the data)

    UNCLASSIFIED – Approved For Public Release

  • 9

    The AUSAM+ operates in three typical modes.

    1. Generating an excitation drive signal

    2. Performing an EM impedance sweep

    3. Active interrogation • pulse-echo

    • pitch-catch

    The first two modes focus on acquiring large excitation signals while the active interrogation modes focus on acquiring small AU responses.

    Operational Modes

    UNCLASSIFIED – Approved For Public Release

  • 10

    ▪ Acquisition system

    ▪ Drive amplifier

    ▪ Noise/Crosstalk

    ▪ ElectroMechanical (EM) Impedance

    ▪ Photodiodes

    ▪ Auxiliary functions

    ▪ User functionality

    UNCLASSIFIED – Approved For Public Release

    First-Of-Class Testing (FOCT)

  • 11

    Drive amplifier (FOCT)

    UNCLASSIFIED – Approved For Public Release

    Frequency sweep using a five cycle Hanning windowed

    sinusoidal signal, at maximum amplitude, applied to a 1 nF

    precision capacitor

    Improvement

    possible; not

    limited by

    hardware

  • 12

    UNCLASSIFIED – Approved For Public Release

    Drive amplifier (FOCT)

    The PSD of the AU response of a

    PZT element on an aluminium

    plate, in a pitch-catch

    configuration, when the actuator

    element is excited at 500 kHz

    1.2 MHz 100 Vp

    excitation signal

    applied to a 1 nF

    capacitor

    PSD of 500kHz response AUSAM and LeCroy

  • 13

    UNCLASSIFIED – Approved For Public Release

    Noise/Crosstalk (FOCT)

    Cha has 1 nF capacitor using

    100 mm long twisted pair wire,

    other channels open circuit

  • 14

    ElectroMechanical (EM) Impedance (FOCT)

    UNCLASSIFIED – Approved For Public Release

  • 15

    3 mm thick aluminium plate with 10 and 6.3 mm diameter PZT discs.

    All the data collected were from a single Hanning windowed sinusoidal drive pulse (ie. no averaging was applied)

    PZT System Demonstration

    UNCLASSIFIED – Approved For Public Release

  • 16

    Impedance magnitude

    10mm element

    UNCLASSIFIED – Approved For Public Release

    6.3mm element

    Reduction indicating good bond

    Reduction indicating good bond

  • 17

    UNCLASSIFIED – Approved For Public Release

    150 kHz pulse-echo and pitch-catch

    Drive Pulse Unfiltered Filtered

    pulse-echo

    10mm

    pitch-catch

    6.3mm

  • 18

    UNCLASSIFIED – Approved For Public Release

    1.5 MHz pulse-echo and pitch-catch

    Drive Pulse Unfiltered Filtered

    pitch-catch

    6.3mm

    pulse-echo

    10mm

  • 19

    4 AUSAM+ units: 16 Element Sensor

    UNCLASSIFIED – Approved For Public Release

  • 20

    AUSAM+ Sensitivity vs LeCroy DSO

    LeCroy

    AUSAM+

    UNCLASSIFIED – Approved For Public Release

  • 21

    16 Element Sensor Array: Wave Front

    UNCLASSIFIED – Approved For Public Release

  • 22

    UNCLASSIFIED – Approved For Public Release

    ‘Fingerprint’ Ball Impact 100mm From Array (2D FFT)

  • 23

    frequency-thickness (MHz-mm)

    w a v e n u m

    b e r

    (r a d /m

    )

    A 0

    SH 0

    S 0

    A 1

    S 1

    S 2

    0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0

    500

    1000

    1500

    2000

    ‘Fingerprint’ Active Acousto-Ultrasonic Drive

    UNCLASSIFIED – Approved For Public Release

    Acousto-Ultrasonic sweeps 0.1–2.5MHz, 100kHz steps

  • 24

    • A new small, robust, flexible instrument for Acousto-Ultrasonic interrogation.

    • Excite and monitor Lamb waves at frequencies up to 5 MHz.

    • Sinusoidal excitations of 200 Vp-p in the frequency range 200 kHz to 1.5 MHz while providing usable drive strength at frequencies 50-200kHz & 1.5-5 MHz.

    • The device was shown to have a relatively low noise floor and low electrical crosstalk between acquisition channels.

    • The performance of an in-built EM Impedance capability compared well to that of a commercial Impedance Analyser.

    • The module provides the ability to undertake strain and temperature measurements.

    • The compact AUSAM+ is small and light enough to find SHM application in a vast array of situations.

    • The Matlab hardware object provides enormous versatility allowing the user to easily interface with the hardware functionality thus permitting the development of customised in-house GUIs for a wide variety of activities and applications.

    UNCLASSIFIED – Approved For Public Release

    Wrap-up

  • 25

    UNCLASSIFIED – Approved For Public Release

    Questions

    stephen.vandervelden@dst.defence.gov.au