Automated, Rapid Non-Destructive Inspection (NDI) of · PDF fileAutomated, Rapid...

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www.thermalwave.com Dr. Steven Shepard President Thermal Wave Imaging. Inc. Mr. Paul Kulowitch, NDI Engineer Team Leader Naval Air Warfare Center, Patuxent River Automated, Rapid Non-Destructive Inspection (NDI) of Large Scale Composite Structures

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Dr. Steven Shepard

President

Thermal Wave Imaging. Inc.

Mr. Paul Kulowitch,

NDI Engineer Team Leader

Naval Air Warfare Center,

Patuxent River

Automated, Rapid Non-Destructive Inspection

(NDI) of Large Scale Composite Structures

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Early diagnosis and repair of

structural problems based on

Nondestructive Inspection (NDI)

is essential for optimum platform

performance and readiness

NAVAIR NDI

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Current Problem

• Traditional methods used in metals ineffective (visual, coin tap)

• Point inspection methods time consuming for large structures

• Special coatings and structures may complicate inspection

• Disassembly for inspection undesirable

• Composite inspections

– Impact damage

– Water entrapment

– Delamination

– Disbonding of joined structures

– Heat damage

The increasing use of composites in Navy aircraft presents

numerous challenges to current NDI capability

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Fleet Requirements

• Decrease inspection time during scheduled maintenance

of large aircraft structures

• Aid inspector in discriminating between flaw indications

and normal variations

• Provide quantitative metric for operator decision

• Simplify operator training

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Current Approaches

Method Advantages Issues

Coin tap Low-cost Large, near surface features only

Ultrasound Excellent penetration

Well-established standards and

procedures

Point inspection or scanning required

Requires contact, couplant

Radiography Area inspection

Excellent crack detection

Insensitive to many voids or

delaminations

Thermography Area inspection

Provides information about flaw type

Operates in close proximity to aircraft

Limited depth range

Shearography Area inspection Limited depth range

Issues at edges and corners

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• Aggressive support of new and emerging NDI technologies through SBIR /

STTR programs

– Portable imaging ultrasound (Imperium)

– MWM Array Eddy Current (Jentek Sensors)

– Portable and quantitative thermography (Thermal Wave Imaging)

• High success rate of commercialization and transition to fleet

Advanced NDI Development

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• Long history of support and development of thermography for NDI

– Flash thermography

– Modeling

– Vibrothermography

– Thermographic Signal Reconstruction (TWI)

– Portable systems

NAVAIR and Thermography

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• Non-contact

• Single side access (no disassembly required)

• Flat or curved surfaces (no critical alignment required)

• Area inspection

• Image result

Thermography Advantages

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• High end cameras required

– expensive, large, delicate

• Limited operation in close proximity to aircraft

• Advanced signal processing required

• Training

• Time consuming for large area

Deployment Issues

An operator in close

proximity to the aircraft

inspects a small area with

flash thermography.

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NAVAIR Phase II SBIR

• Large area thermography at a large working distance from aircraft

• Apply advanced signal processing to non-standard signal

• Simplify / automate inspection and interpretation

Automated, Rapid Non-Destructive Inspection

(NDI) of Large Scale Composite Structures N092-097 Cherry Point

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Remote NDI: A New Paradigm

• NDI of large structures typically requires a fixed installation to scan a

point inspection device that is in close proximity to the surface over

a large area.

• We have developed a solution that is capable of inspecting a large

area quickly, and a distance from the target, while offering sensitivity

comparable to existing technologies.

Conventional

scanning TWI Large Standoff

< 50 ft

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LASLAT Projection NDI

• Rapid inspection of large structures

– Noncontact

– Results archived as single image

– Quantitative flaw analysis

• Fixed or portable implementation

– No fixed gantry or infrastructure required

– Mount on tripod, cart, truck, boat etc.

– Truck or boat mounted

• Performance comparable to close proximity methods

– Detection of subsurface voids, delamination, moisture, corrosion

• Inspection of inaccessible or hazardous components

Large Standoff / Large Area

Thermography (LASLAT)

< 50 ft

LASLAT uses TWI Thermographic Signal

Reconstruction to provide laboratory quality

results in a far-field system

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LASLAT

An operator in close

proximity to the aircraft

inspects a small area with

flash thermography.

IR camera

heat

projector

Baseline Approach

NDI system positioned far from

aircraft to inspect large area.

LASLAT Projection Thermography

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Thermographic Signal

Reconstruction (2000)

U.S. Patent 6,516,084

reconstructed

raw

0.000 5.781

1.182

6.208

2.363

6.635

3.545

7.063

4.726

7.490

5.908

7.918

ln (frame num)

ln (

T –

T0)

Fit raw log-log data with a

smooth function and use the

replica for analysis and

further processing.

• Excellent fitting

• Conversion < 5 sec

• Temporal noise reduction

• Store coefficients of fit

equation only

• Smaller file size

• Faster processing

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TSR Derivatives

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

0 1 2 3 4 5

ln (T

)

ln (t)

0.150 sec

TSR

2nd derivative

TSR

TSR

1st derivative

0.150 sec

-0.60

-0.50

-0.40

-0.30

-0.20

-0.10

0.00

0 1 2 3 4 5

d[ln

(T)]

/ d

[ln

(t)]

ln (t)

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0 1 2 3 4 5

d^2

[ln

(T)]

/ d

[ln

(t)]

^2

ln (t)

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Thermographic Signal

Reconstruction

Raw thermography data TSR processed

TTU

X-ray Conventional Flash Thermography

TSR

Disbond

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Extended Pulse Heating

heating period

t0

Early behavior of signals of interest

may be masked during heating period.

Heating and cooling occur simultaneously during extended heating

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Performance

Features Advantages Benefits

Large standoff distance Access to large structures

without fixed installation

Reduced cost and

adaptation to multiple

inspections

Operation in fuel vapor

areas

Large inspection area No fixed scanning apparatus

required

Reduced installation

cost

Reduced inspection time

TSR signal processing Improved detection

sensitivity

Meet/exceed existing

requirements

Verify/assist operator in

flaw detection

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TSR Processing

Proprietary Thermographic Signal Reconstruction processing extracts subsurface features that are undetectable in raw data.

TSR

Unprocessed

Time sequence of carbon fiber honeycomb panel acquired with LASLAT system at 50’.

Skin-to-core disbond

Inter-ply delamination

skin Al core

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System Performance

• Operating range 5-50 ft from inspection surface

• Instantaneous coverage area: ~2 ft2

• Total coverage area: ~ 400 ft2

Comparison of LASLAT at 45’ and close proximity commercial

thermography system on a composite panel with hidden flaws.

45’ projection Close proximity flash

Comparison of projection system at 45’ and close proximity commercial

flash thermography system on a composite panel with hidden flaws.

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Large Area Inspection

• Instantaneous coverage area: ~4 ft2

• Total coverage area: ~ 400 ft2

• 81 shots, 3-4 hr inspection time

• Software controlled: creates full area image and flaw detection

System area coverage at 50 ft. stand-off

23’

18’

2.5’

2’

System software automatically combines far-

field data into a single image.

6’

2’

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Current State of Development

• Current state: TRL 3-4

– Working prototype in lab environment

• Field demo scheduled Q1 2013

– Target state: TRL 5

Imaging

and

excitation

Signal

processing

Application

specific

hardware

Software

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Questions?