Potentials and Limitations of Nonlinear Ultrasonics for NDT

Experiences from the EU project AeronewsExperiences from the EU project Aeronews

Christophe Matteip

Potentials and Limitations of Nonlinear Ultrasonics for NDT

• Nonlinear ultrasonics for NDT

• Linear vs. Nonlinear UT• Nonlinearity and damage • Experimental techniques and potential procedures

• The project Aeronews: Application to aerospace structures

• Potentials: Experimental results obtained on couponsPotentials: Experimental results obtained on coupons• Challenges: Implementation on real structures

• Our conclusions: Monitoring vs Inspectiong p

Exova November 29, 2010

Linear UTLinear UT

time timeInput Output

time time

σ

f eq enc Frequency

τLinear relationship between strain and stress

frequency Frequency

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Nonlinear UT

timetimetime

InputOutput

σFrequency F

τ

Frequency Frequency

Nonlinear relationship between strain and stress

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Linear vs Nonlinear UTLinear vs Nonlinear UT

Modulus-Strain Stress-strain Modulus-time Strain-timeStrain amplitude

Frequency spectrum

Modulus

ε

σ Μ

Linear material

εε

εStrain

Modulus

εStrain

σ

time time

Μ

Non-linear t i l

ω

εε

From K Van Den Abeele et al., Res Nondestr Eval, 12. (2000)

εStrain

εStrain time

material(first order) time ω

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Nonlinearity and damageNonlinearity and damage

dσdσ dσ (1 ...)dε

K βε= − +dσdε

K=Traditional Non linear

σ σ

ε εε

if damage increasesif damage increases the modulus K decreases if damage increases β increases,

much more than K decreasesAttenuation increase

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Nonlinearity and damage

From P. Nagy, Ultrasonics 36 (1998)

Nonlinearity and damage

16

18

20

Nonlinear parameterABS

From P. Nagy, Ultrasonics 36 (1998)

10

12

14d

Para

met

ers

4

6

8

Nor

mal

ized

Linear parameters:

0

2

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2

Linear parameters:AttenuationVelocity

Number of Cycles [thousand]

Linear and ninlinear UT parameters as a function of fatigue cycles in ABS

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Nonlinearity and damage: Work at Exova on CFRP composite

nonlinear UTLinear UTsender

Laminate

Signal amplitude Harmonic amplitude

receiver

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Nonlinearity and damage: Work at Exova on CFRP composite

Nonlinear parameter (Second harmomic/First harmonic)

18 MHz 9MHz

Linear parameter(Signal amplitude 18 MHz) 0 cycles

18 MHz 9MHz

15 000 cycles

17 000 cycles

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Nonlinearity and damage: Work at Exova on CFRP composite

Exova

Nonlinearity and damage: Work at Exova on CFRP composite

Microdelamination: Matrix cracks:

+90 and +45 pliesUp to 20 mm long10 to 20 µm ”open”

90 and +45 pliesUp to 200 µm long10 to 20 µm ”open”

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Nonlinear ultrasonics for NDTNonlinear ultrasonics for NDT

Linear Ultrasonics: Detection of Flaws/Discontinuities• Detect geometric and material discontinuities (cracks, voids, inclusions, etc.)

• Linear UT Scattering, dispersion (guided waves), attenuationg, p (g ),• Characterize stiffness/density related properties• Used primarily at the later stage of component fatigue life

Nonlinear Ultrasonics: Characterization of Distributed Damage• Detect accumulated damage (dislocations, microcracks, microplasticity)• Characterize structure related properties• Can be used in the early stage of component fatigue life• Can be used in the early stage of component fatigue life

Exova November 29, 2010

Health monitoring of aircraft byHealth monitoring of aircraft by Nonlinear Elastic Wave SpectroscopyFP6 - Specific Targeted Research ProjectStructural Health MonitoringgAST-CT-2003-50292703/2004- 03/2008

Belgium: Catholic University Leuven Campus Kortrijk (KULeuven)Belgium: Catholic University Leuven, Campus Kortrijk (KULeuven)Free University Brussels (VUB)ASCO Industries (ASCO)

Czech Republic: DAKELAeronautical Research and Test Institute (VZLU)I tit t f Th h i (ITASCR)Institute of Thermomechanics (ITASCR)

France: GIP ULTRASONSNDT-Expert

Germany: Fraunhofer Institute for NDT, Saarbrücken (IZFP)Italy: Politecnico di Torino (POLITO)y ( )

University of Naples, Dept. of Aeron. Eng. (UNI-NA)Spain: Instituto de Acustica, CSIC

Boeing Research & Technology Europe – Madrid Sweden: Bodycote Celsius Saab Materialteknik (CSM) / ExovaUK: University of ExeterUK: University of Exeter

University of BristolUniversity of NottinghamCranfield University, College of Aeronautics, Cranfield

Exova November 29, 2010

Workpackage Workpackage titleLead

PartnerMan

monthsStart

MonthEnd Month Deliverable

WP1Optimisation study of NEWS techniques to

detect micro-scale damage in aircraft components and structures

UNIV BRIS and

IZFP171.5 0 48 D1-D5

Si l i f li b h i

WP2

Simulations support of nonlinear behaviour in micro-damaged structures and extension to early damage localization methods based

on NEWS

POLITO and CU 126.5 0 48 D6-D10

UNOTTWP3

Adaption of smart transducers and sensors for NEWS

UNOTT and

DAKEL145.8 0 48 D11-D13

WP4Integrated design of measurement and control system for NEWS techniques UNEXE 82.5 6 48 D14-D16control system for NEWS techniques

WP5Implementation and Validation of the complete system on a full scale model VZLU 48.5 12 48 D17-D21

WP6 Dissemination and Training ITASCR 40.15 0 48 D22-D23

WP7 Project ManagementKU-

Leuven 32.8 0 48 D24-D29

TOTAL 647.75

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WP1: Development of Experimental NEWS techniques: KU leuven

KU Leuven: Nonlinear analysis of the ring-down of a resonance mode

True resonance frequency frCW source

q y r

Amplitude AFrequency f(near resonance)

timetime

Stop CW

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WP1: Development of Experimental NEWS techniques: KU Leuven

0.3

on

Reference

250°C, 30 min

0.2

ncy

Red

uctio

)

300°C, 45 min

0.1ve F

requ

en(x

100

0

0

Rel

ativ

0

0 20 40 60Microstrain

Exova

WP1: Development of Experimental NEWS techniques: Exova

Pulse Inversion C-scanPulse Inversion C scan

sum=

h(t) linear h(t)

h(t) linear

h(t) nonlinear

sum=

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Aluminum

Aluminum

Pulse inversion signalsSummed signals

IF

I

I/F for 7 samplesDistribution of

Shear strength: 22.1 21.2 29.1 23.2 26.0 29.2 30.1

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WP1: Development of Experimental NEWS techniques: Exova

Exova

WP5: Full scale trials

Techniques tested:Techniques tested:

• NL guided wave• Harmonic detection using optical interferometry• NL time reversal mirror• NL time reversal mirror

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Challenges for Nonlinear NDT measurement on real structure

• High dependancy on damage but low amplitude effect.

N li ff t d d lit d• Nonlinear effect depends on amplitude• Calibration of the whole measurement chain• Energy repartion in sample• influence of coupling

• Several effects lead to different types of nonlinearity• Several effects lead to different types of nonlinearity• Plasticity, dislocations, microcracks, etc…

• How to define reference samples for distributed damage???

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Is SHM the right operation mode?Is SHM the right operation mode?

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Thank you for your attention !

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