Intelligent Automation, Inc.

15400 Calhoun Drive, Suite 400Rockville, MD 20855

DAMAGE DETECTION IN COMPOSITE CYLINDERS USING MODULATED GUIDED WAVE VIBRATION

June 21, 2011

Xiaoliang

(George) Zhao, Xue

(Kevin) Qi

Intelligent Automation, Inc.

Alexander Sutin

Steven Institute of Technology

Eric Abernethy

Naval Air Warfare Center Weapons Division

Introduction of IAI and Projects

Background and Motivation

Objectives

Method and Assumptions

Procedure

Preliminary Results and Discussion

Conclusion

Acknowledgment

Outline

2

Intelligent Automation Inc.

3

Company Overview

Woman‐owned small business 

Founded in 1987

Headquartered in Rockville, MD

125 Professional staff

$23M revenue for 2010

Won twice the Small Business 

“Tibbetts

Award”

(2000, 2007)

Organization

Sensors, Signals and Systems Division

•

Control and Signal Processing

•

Communications and  Sensors

•

Robotics & Electromechanical 

Systems

Distributed Intelligent Systems Division

•

Multi Agent Systems

•

Networks and Security

•

Air Traffic Management 

Education  & Training Technology 

Division

IAI Strengths

Sustained record of excellence in R&D

Strong qualifications in supporting large 

DOD and NASA programs through primes

IAI’s

Experience in NDE Sensors, Simulation, and Systems

Sensors–

Ultrasonic guided wave transducers–

EMAT(SH wave, Lamb wave, bulk wave)–

Wireless ultrasonic transducer node–

Piezoelectric sensor network for SHM –

Sol-gel piezoelectric transducer

patch–

Hybrid Tap Tester (AE, Microphone) –

Scanning acoustic microscope, eddy current system, 2D scanner, air coupled probes

Algorithm/Simulations–

Guided wave simulation toolbox –

Statistical ultrasonic guided wave tomography –

Physics of failure simulation

NDE/SHM Systems–

Impact echo–

Ultrasound–

Guided waves–

Nonlinear acoustics–

Acoustic emission–

Eddy current–

RF reflectometry–

Digital shearography–

Microwave/Terahertz–

Wireless sensor networks

4

microphone solenoid EMAT sensor

housing

connector

bumpermicrophone solenoid EMAT sensor

housing

connector

bumper

EMAT

High Temperature Piezo

Patch

Ultrasound array

Tap-echo probe

Guided Wave Simulation Tool

Wireless Ultrasonic Transducer Network

Statistical Tomography

Motivation of the R&D

Composite rocket motor cases are subject to damage due to fatigue, mechanical impact, and aging in a service environment. Early detection of these failures is desired for improving structure safety. Detection of tiny cracks are important!Current NDI methods for composites are limited to flat or nearly

flat composite plates.A real-time hand-held NDI system is desired to detect defects in both flat and curved composite structures.We propose a nonlinear guided wave imaging (NGWI) technique for detecting small incipient damages in complex composite structures. Higher sensitivity than its linear counterpart.

5

6

Introduction: Nonlinear Ultrasound

......322 lcσ

-

stress, ε

–

strain, β, γ

…. –

non-linear parameters (quadratic

nonlinearity, cubic nonlinearity, etc…) ρ0 -

density, cl – speed of longitudinal elastic wave

Nonlinearity may be ten times higher for media with cracks and flaws!

σ

εBilinear stress-strain relationship at the crack*

* D. Dutta, “A Nonlinear Acoustic Technique for Crack Detection in Metallic Structures,”

Structural Health Monitoring, (8) 3, 251-262, 2009.

7

-1.5

1.5

0 160

-1.5

1.5

0 160

f1

f2

-1.5

1.5

0 160

Nonlinear Elastic Wave Modulation Spectroscopy

The crack stiffness K()

K = K0 + Ko +

f2

-f1 f2

+f1

Frequency

Spectrum f2

f1

Simple, but effective and

sensitive !

8

Cross-modulation Test Setup Input Waves Output Waves

Object

Cracked Object

Power Spectrum

f1 f2Frequency

Pow

er

f1 f_ f2 f+

Frequency

Pow

er

f1 f2

f1 f- f2 f+

f1f2

Low frequency

High frequency

No crack = No modulation

Crack presence provides modulation ( f+ and f-

sidebands)

Processing block 

Tested part 

Signal 

generator

transducers

Computer

Power amplifier 

Signal 

generator

Vibrator 

f1

f2

Example setup

f1f2

Low frequency

High frequency

good

cracked

Example Samples Tested

9

Introduction: Ultrasonic Guided Waves

R

Z

R

Z

Example 8-layer (90/45/-45/0)s composite pipe.

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.10

1

2

3

4

5

6

7

8

9

Frequency (MHz)

Cp

(km

/s)

0 0.5 1 1.5 2 2.5-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

Thickness (mm)

Am

plitu

de (m

m)

UrUUz

Calculated phase velocity dispersion curves for circumferential guided waves traveling in 0o

fiber direction.

Wave structures for wave mode #3 (the red line) at 238 kHz.

10

Guided waves are elastic waves propagating in solid media with boundaries. Since wave energy is trapped in between boundaries, it can travel a long distance, thus suitable for long range inspection. Multiple wave modes may exist in a structure, which can be represented as dispersion curves as shown here.

Combining ultrasonic guided waves for fast scanning capabilities with nonlinear acoustic technique for enhanced sensitivity

Potentially no need for baselines

Simple extension of current signal processing technologies for guided waves

Applicable to both metallic and composite materials

Nonlinear Guided Wave Modulation Spectroscopy

11

12

Nonlinear Guided Wave Modulation Simulation

AA

3m‐long 2mm‐thick Al Plate in good condition

Receiver

Input: 

30kHz+300kHz 

continuous wave.

0 50 100 150 200 250 300 350 400 4500

0.2

0.4

0.6

0.8

1

Frequency (Hz)

Am

plitu

de

out-of-plane displacement

Spectrum of received signal

0 1 2 3 4

x 10-4

-1.5

-1

-0.5

0

0.5

1

1.5x 10

-14

Time (sec)

Am

plitu

de

out-of-plane displacement

Received signal

ABAQUS FEM simulation was performed for nonlinear guided wave modulation

No side bands

13

Nonlinear Guided Wave Modulation Simulation (Cont’d)

AA3m‐long 4mm‐thick Al Plate

Input: 

30kHz+300kHz 

continuous wave. 3mm crack

Receiver

0 1 2 3 4

x 10-4

-2

-1.5

-1

-0.5

0

0.5

1

1.5x 10-13

Time (sec)

Am

plitu

de

out-of-plane displacement

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

x 105

0

0.2

0.4

0.6

0.8

1

Frequency (Hz)

Am

plitu

de

out-of-plane displacement

f2

-f1 f2

+f1

Strong modulations!

Spectrum of received signalReceived signal

14

Example Nonlinear Guided Wave Test Setup

Fatigue crack from a rivet hole (0.25”

in length)

15

Spectrum Results

The collected signal spectrum clearly shows the presence of crack in the plate!

The spectrum for the Aluminum sample with fatigue cracks measured with sensor pair 2-4.

The spectrum for the Aluminum sample with fatigue cracks measured with sensor pair 1-4.

16

Feasibility Study on Composite PlatesMagnetostrictive

emitter

Piezoelectric transducer

Piezoelectric sensor CC-scan of the composite plate showing damage area.

Signal generator

Power amplifier

Digital Oscilloscope Generator

Tested plate

Magnetostrictive emitter

Piezoceramic sensor

Digital Oscilloscope

85 90 95 100 105-80

-75

-70

-65

-60

-55

-50STB.015.txt

Frequency,kHz

Pow

er s

pect

rum

, dB

LF=3.4kHz

Experimental setup

Modulation side bands indicating damages

NGWI Experimental System Architecture

17

Nonlinear Guided Wave Imaging System for Damage Detection

Filament Wound Composite Cylinder Specimens

18

•

6’’

inner diameter quasi-

isotropic carbon/epoxy cylinders layup

[±30/90]3

,thickness 4.17 mm

•

Double layer rectangular 76.2-

micron-thick Teflon sheets embedded as flaws.

•

The carbon fiber used was Toray (Flower Mound, TX) T700S-24K. The matrix material was EPON 862 with EPIKURE W curative mixed together in a 100:26.4 ratio with 100% stoichiometry

respectively. The approximate fiber volume fraction was set at 0.63

Sample Description

19

11”

2.5”

5”

7.5”

+θ

Datum

R

I

G

H

T

L

E

F

T

Teflon a is located between Plies 1 and 2; Teflon b, d, and e are between Plies 3 and 4; c is between Plies 5 and 6a

b, d, e

c

Elastic Properties Dens.E1TGPa

E1CGPa

E2GPa

12 23 G12GPa

G23GPa

kg/m3

146 146 7.8 0.34 0.4 4.4 2.2 1560

Guided Wave Modeling for the Composite Cylinder

20

Estimated material properties of T700/862 unidirectional lamina for Vf = 0.63.

Low frequency guided wave was chosen for stronger energy penetration and simple signal interpretation.

FEM Simulation for Delamination

Detection

21

delamination

between ply 1 and ply 2

Guided wave around 110 kHz is most sensitive to delaminations

!

Fabricated Transducer Array Based on Simulation

22

Hand-held, conformal, and easy to use!

Typical Guided Wave Inspection Result

23

Through transmission waveform

Damage inspection results

Array channels

No damage

Delamination

Damage blocks wave propagation which leads to lower transmission of energyCalibration was performed for channel difference compensation. No baseline is needed for each individual cylinder.Ultrasonic couplant

effect was considered, self-checking

to ensure good coupling to compositeRepeatability test: determine statistically the sensitivity levels of sensor array for damagesValidation. Impact with a hammer and find damage

Guided Wave Damage Detection Algorithm

24

Can detect and locate impact delaminations

in the composite cylinderBig Teflon film defect (1”

square, to simulate artificial

delamination) can be detectedSmall Teflon defect (0.5”

square) poses some

challenges, but with further signal processing, we should be able to detect itSample preparation is important for assessing the sensitivity

Guided Wave Inspection Results

25

26Proprietary Intelligent Automation, Inc.

Integration of Guided Wave with Nonlinear Acoustic Technique

LF vibrator

Guided wave array

Multiplexer box

PC software

Power amplifier

Signal generator

Test Results for Impact Delamination

27

Side bands

No LF excitation

With LF excitation

Side bands is clearly seen in for the damage!

Test result for damage localization

28

5 4 3 2 1

112

5 4 3 2 15 4 3 2 1

112112

file 27 Sensor #1

-90

-80

-70

-60

-50

-40

-30

-20

68000 70000 72000 74000 76000 78000 80000

Frequency, Hz

Spec

trum

, dB

file 29 Sensor #2

-90

-80

-70

-60

-50

-40

-30

-20

68000 70000 72000 74000 76000 78000 80000

Frequency, Hz

Spec

trum

, dB

file 23 Sensor #3

-90

-80

-70

-60

-50

-40

-30

-20

68000 70000 72000 74000 76000 78000 80000

Frequency, Hz

Spec

trum

, dB

file 33 Sensor #4

-90

-80

-70

-60

-50

-40

-30

-20

68000 70000 72000 74000 76000 78000 80000

Frequency, Hz

Spec

trum

, dB

file 35 Sensor #5

-90

-80

-70

-60

-50

-40

-30

-20

68000 70000 72000 74000 76000 78000 80000

Frequency, Hz

Spec

trum

, dB

Impact site

Guided wave Array

Result spectrums

Most notable modulations!

LF vibrator

Damage localization capability is good!

Nonlinear Guided Wave Modulation Result Discussion

Sensitive to “breathing”

surface touching cracksDid not detect embedded Teflon films, useful for differentiating damage typesNeed frequency tuning to “open up”

damages

Challenges for boundary touching parts Guided wave modes & nonlinearity ?

Guided wave and nonlinear acoustics technique can both detect and localize cracks/damages. Integration of the two techniques provides enhanced capabilities for field inspection composite SRM casesA prototype hand-held transducer array system has been fabricated with the assistance of our guided wave inspection simulation tool. Lab testing has demonstrated the effectiveness of the system for impact damage detectionSensitivity study of guided waves showed that delamination

of 0.5”

in diameter and cracks of 0.1”

can be detected reliably.Nonlinear acoustics showed good detection capability, and it can

enhance the guided wave inspection accuracy by providing the modulation spectrum and verifications.

Conclusions

30

Funding support from Navy SBIR contract #

N68936-10- C-0070

Penn State University Composites Manufacturing Technology Center (CMTC) and Prof. Charles Bakis

for

sample fabricationProgram manager Eric Abernethy

and engineers of

NAWCWD for guidance and comments on technology development.

Acknowledgment

31

Thank You and Questions?

32

15400 Calhoun Drive, Suite 400Rockville MD, 20855(301) 294-5200i-a-i.com

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