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Damage detection assessment by means of Acousto UltrasonicsAcousto Ultrasonics

Wissenschaftstag 2012 – DLR Braunschweigg g

Martin Bach

(with contribution of Airbus M&P EADS IW and DLR)(with contribution of Airbus M&P, EADS IW and DLR)18th of October 2012

Content

Damage detection assessment by means of acousto ultrasonics 2012/10/18

Content

• Introduction• Introduction

• Verification approach for damage assessment performance• Verification approach for damage assessment performance

• Conclusion and Outlook• Conclusion and Outlook

Property by Airbus and EADS IW SHM development team

Introduction (SHM)


Introduction (SHM)

SHM in order to…

• Reduce Maintenance Costs

• Increase Aircraft Availability Structural Health Monitoring

• Reduce Weight

Non-Destructive Testing

Interrogation Unit

AdhesiveSensor

Connection

Structural Item

SHM M it i f D St /St i C diti


• SHM: Monitoring of Damages, Stress/Strain, Conditions

Introduction (AU physical principle)


Introduction (AU – physical principle)

Acousto Ultrasonic (AU) is based on Guided Ultrasonic Waves (GUW, aka Lamb Waves), propagating reasonable distances in plate like structurespropagating reasonable distances in plate like structures

Damage detection is basically achieved byDamage detection is basically achieved by

• A network of permanently appliedpiezoelectric sensors to pitch-catch GUWs

• Comparison of these signal at reference state with an unknown state

• exploiting the physical dependency of GUW-propagation from the state of the structure, i.e. occurence of damages

Applicable for delamination and debonding in CFRP or to crack and corrosion in metal

The wave propagation especially in CFRP is “complex” (disperse, multiple wave modes,...)Robust technique is needed, esp. for analysis algorithmsq p y g


Introduction (AU Systems Components)


Introduction (AU Systems Components)• Software (on PC/laptop)

DAQ E i tUser interface & control

• DAQ-Equipment

• Sensors data evaluation

i l ti ADC

data storage

signal generation

amplification

ADC

pre-amplification

multiplexing

Single SMART layer

actuator sensorstructure

Demonstration system (2008)


Introduction (Way of Working)


Introduction (Way of Working)

PP A li ti iA li ti i ‘SHM P tf li ’‘SHM P tf li ’ProgrammeProgramme Application scenarioApplication scenario

= set of SHM technology solutions for generic application scenarios at TRL6 e g CFRP

‘SHM Portfolio’‘SHM Portfolio’

Ageing aircraftFuture aircraft

e.g. stringer debonding detection in A30X fuselage,

i d t ti i A320 scenarios at TRL6, e.g. CFRP stringer debonding detection from CFRP skin)

corrosion detection in A320 rear pressure bulk head

Technology solutionTechnology solutionTechnology adaptationTechnology adaptation

= selection of most appropriate SHM solution from ‘SHM toolbox’

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= the technology solution from the ‘SHM toolbox’ is adapted to the specific application scenario from the programme

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CRC ACSCRC ACS EADS MASEADS MAS

Airbus M&PAirbus M&PEADS IWEADS IW

DLRDLRFhGFhG

GoodrichGoodrich

SMSSMS

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MHI, KHI, FHI, UOTMHI, KHI, FHI, UOTAcellentAcellent

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Introduction (Technology Readiness)


Introduction (Technology Readiness)Stage TRL TRL Definition Requirements Criteria Status

1 System (sensor & interrogation unit) does not exist. It is TRL 1 1 TRL 1 2 TRL 1 1 TRL 1 2 /

Discover1 System (sensor & interrogation unit) does not exist. It is

only an idea on paper TRL 1.1, TRL 1.2, … TRL 1.1, TRL 1.2, … yes/no

2 System (sensor & interrogation unit) does not exist. In depth formulation of how should the equipment be TRL 2.1, TRL 1.2, … TRL 2.1, TRL 2.2, … yes/noRequirement SourcesRequirement Sources

• Testing TechnologyUnderstand 3 System (sensor & interrogation unit) does not exist. Only

part of it might be in a physical stage TRL 3.1, TRL 3.2, … TRL 3.1, TRL 3.2, … yes/no

4 System (sensor & interrogation unit) expected to be at a laboratory stage TRL 4.1, TRL 4.2, … TRL 4.1, TRL 4.2, … yes/no

Testing Technology

• Surface Technology

• Composite TechnologyAdapt

laboratory stage

5 System (sensor & interrogation unit) expected to be at a laboratory stage and compliant to aircraft environment TRL 5.1, TRL 5.2, … TRL 5.1, TRL 5.2, … yes/no

System (sensor & interrogation unit) expected to be at a

Co pos te ec o ogy

• Bonding Technology

• Metal TechnologyValidate 6 System (sensor & interrogation unit) expected to be at a

prototype stage and compliant to aircraft environment TRL 6.1, TRL 6.2, … TRL 6.1, TRL 6.2, … yes/no

f

7 System (sensor & interrogation unit) expected to be at a prototype stage tested in-flight TRL 7.1, TRL 7.2, … TRL 7.1, TRL 7.2, … yes/no

gy

• Assembling Technology

• Cabin / Fire and SafetyRefine

8System (sensor & interrogation unit) expected to be in its final form, qualified through further ground-tests and in-flight trials

TRL 8.1, TRL 8.2, … TRL 8.1, TRL 8.2, … yes/no

Use 9 System (sensor & interrogation unit) in its final form, TRL 9 1 TRL 9 2 TRL9 1 TRL 9 2 yes/no

• Manufacturing

• SystemsUse 9 y ( g ) ,

further proven through extensive in-service use TRL 9.1, TRL 9.2, … TRL9.1, TRL 9.2, … yes/no

• Authorities Property by Airbus and EADS IW SHM development team

Introduction (Damage Assessment Performance)


Introduction (Damage Assessment Performance)

Damage assessment is key function of the SHM system, however it depends on:

Test Parameter• Frequency / Wave modes• Actuation Signal shape / amplitude• Signal conditioning

Wave Propagation• Dispersion• Wave length• Attenuation• Mode conversion• Reflection• Scattering

Wave – Damage interaction• Type• Size• Position• Morphology Environmental Conditions

• Temperature • Load condition• Surface conditions

N i & Vib ti

Sensor network• Sensor placement• Sensor geometry• Sensor material properties• Bonding• Degradation

• Noise & Vibration• EMI

Detection Algorithms• Environmental compensation• Robustness• Complexity• Self-diagnosis

Material Properties• Damping• Ageing / degradation

• Degradation

DAQ-Equipment• Accuracy / precision• SNR

• Humidity• Surface protection / paint

• Shielding / EMI

Damage Assessment Performance

Structural Features• Stringers, frames, clips• Lay-up / thickness variations• Repairs

General Boundary Conditions• Cost-benefit trade-off• Weight penalty• Redundancy / Maintainability• Installation• Operational BCs• System Integration BC


Verification approach


Verification approachComparable to conventional NDT approach

• Fixed limiting factorsfor conv. NDT e.g.: Temperature, max./min. Thickness, Material

f SHM St t ( li ti i ) T t Sfor SHM e.g.: Structure (application scenario), Temperature, Sensor application method, Damage type, damage size, system, set-up etc.

• Damage detection/assessmentfor conv. NDT: POD (29/29, Hit-Miss, etc.)

for SHM: DAP (TBC by A/C OEM and authorities)


Verification approach (DAP)


Verification approach (DAP)Outcome of classification in reference to

real damage size areal damage size areal

detected damage size adetected

applicable damage limit alimit

Classification out-come actual classificationabove applicable limit below applicable limit

SHM Assessment areal > alimit areal ≤ alimit

above applicable limitadetected > alimit

True-positive(TP)

False-positive(FP)

below applicable limitadetected ≤ alimit

False-negative(FN)

True-negative(TN)

Working assumption: Probability to receive a certain damage size adetected in dependence of real damage areal size is known. Undetected damages are included as of size zero.


Verification approach (DAP con’t)


Verification approach (DAP, con’t)

The damage assessment performance (DAP) can be characterized byThe damage assessment performance (DAP) can be characterized by

Minimum detectable damage size for a defined probability of detection

Mean assessment accuracy as the difference between adetected|90 and arealy detected|90 real

Applicable limit value vs. applied threshold value for defined probability of classification

False-positive probability for adetected|50 and applicable limit value

Localization bound with a defined probability

for each position of the monitored area and the range of relevant damage sizes andfor each position of the monitored area and the range of relevant damage sizes and the relevant conditions.

Before making any plans for testing: Analyse the influence factors and conditions to be considered in the analysis.y


Verification approach (DAP con’t)


Verification approach (DAP, con’t)Verify Damage Assessment Performance

R li ti t t t t• Assessment of damage size

• Assessment of damage localization

Realistic test structure

Comparison of estimated

• Damage size from SHM system with

conventional NDT

• Location with actual location

Introduction of damage Dent after impact NDT SHM


Conclusion and Outlook


Conclusion and Outlook

• Scheme to rate classification capability

• Criteria for Damage Assessment Performance (DAP)

• Accuracy of damage assessment (size, location) affects potential benefit

R li bilit l i i k l d t h l d ifi• Reliability analysis requires knowledge on technology and specific environmental and operational conditions.

• Usage of model assisted PoD (MAPOD) -> Model assisted DAP analysis

Requires modelling capability of relevant influencing factors

R i d lli bilit f t t t d d d i t tiRequires modelling capability of structure, transducers and damage interaction

• Validation of requirements in order to generate test input parameters



Acknowledgment to:Acknowledgment to:

Benjamin Eckstein (EADS Deutschland GmbH)

Maria Moix Bonet (DLR)

Airbus Materials & Processes Bremen

Contact:

Martin Bach

EADS Innovation Works BremenEADS Innovation Works - Bremen

[email protected]

+49 421.538 7071


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