Thermograph y

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Xxxxxx Titre xxxx NDT expert

NDT expert - The ultimate control

INFRARED

THERMOGRAPHYON AIRCRAFT


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Basic kit for the IRT control

Measurement chain

COMPAQ

V70

V70

(4)

(1)

(3)

(2)

Calibration

pieceheating 1- IR camera

2 control panel of the camera

3 Direct view on the screen

4 Signal processing of the acquisition

INSTRUMENTATION


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Instrumentation used in IRT

Choice of the camera :

Multiple use of the detector : IR night vision,

thermal control of active sources, military

application, .

Thermal sensitivity : (0,1till 0,01C)

Acquisition frequency (25 till 300

image/s)

Line acquisition mode or Focal Plane Array (FPA)


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Instrumentation used in IRT

Heating choices :

Different techniques : hot air blower, tubes, flash

lamps, hot water, pulsed heating, laser, sun for

space shuttle, heating blanckets

Surface heating or linear heating

Homogeneity, reproductibility, calibration,characterization


5/185Xxxxxx Titre xxxx NDT expert NDT expert - The ultimate control

IRT CONTROL ON COMPOSITE

transmission technique :

14mm

carbon

rubber

Applied

Heat

Transmitted

Heat

Without defect With defect

T



IRT CONTROL ON COMPOSITE

Reflexion technique :

Emitted

Heat

Reflected

Heat

Absorbed

Heat

T

With defectWithout defect

14mm

carbon

rubber

THERMOGRAM



Temperature variation in a point

Reflexion technique :

Transmission technique :

heating

T

time

heating

T

time

Without defect

With defect

(isolation)



Thermographic Inspection

Advantages of the method :

Global examination of partOnly ONE SIDE access is required for the examination

Real Time inspection

Apply for all composite structure and materials even porous

not very sensitive to part geometry, well suited for large surfaces

Disavantages :

Sensitive to heating mode (type,duration,position)

Response time must be studied

Exact composition of the pieces and the thicknesses must be known

Less definition than Ultrasonic C-Scan and Radiography

Inhomogeneous heating on complex part



DEFECTS ENCOUNTERED

Lack of adhesion of cohesion, bubbles

Delamination

Defects on surface coatings

Inclusions of foreign materials

Liquid ingress



Pulse heating method

Detection of defects inside a

honeycomb composite part

Reflexion method

Heating pulse : 0.1 sec



Pulse method reflexion inspection on part M88

7 defects visible

Contrast is

decreasing after

optimum image

Picture of part First image Heated part at T0

Optimum image 5 Sec after

10 sec after

1 2

3 4 5



7 defects are detected

Transmission face 1

Defects seen as darkspots

Reflexion face 1

Reflexion face 2

Transmission Vs Reflexion method



Modulated thermography

440 mm

370 mm

carbon

14 mm

Test sample, composite bonding Carbon/Elastomer

rubber



Phase Image Amplitude image

Method : reflexion heating, rubber side

Frequency : 0.006 Hz

Modulation : 1000 images




Method : transmission heating, rubber side



Phase imageAmplitude image



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16Xxxxxx Titre xxxx NDT expert NDT expert - The ultimate control

Disbonded area

A A

Cross section AA

rubber

aluminium

kevlar

bonding


Test sample, composite bonding Metal/Elastomer/Kevlar


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Phase imageAmplitude Image


Method : transmission heating, kevlar side




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Conclusions

Global method, quick, well suited for detection on composite

and complex shaped surface, and for large areas

Easy to set up on site (maintenance, expertise, production

control)

Quick evolution of the technology, lower price of detectors,

new powerfull software for analysis tools will increase :

maximum inspected thickness

spatial and thermal resolution

velocity of inspection

Documents

Thermograph y