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Xavier [email protected]
http://mivim.gel.ulaval.ca
Infrared Thermography for NDT: Potentials and Applications
Chaire de recherche du CanadaTitulaire : Xavier Maldague
Xavier MaldagueNovember 2013
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Outline
1. Infrared spectrum;2. Non‐Thermal infrared NDT;3. Thermal infrared NDT: Passive thermography;4. Thermal infrared NDT : Active thermography;5. Thermal infrared NDT : More Applications;6. Conclusions.
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1. Infrared spectrum1. Infrared spectrum
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Infrared spectrum
Thermal emissions
Non-thermal reflections
Reflectography/ transmittography
Thermography
THz Terahertz imagingElectromagnetic
spectrum
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Infrared spectrum
Thermal emissions
Non-thermal reflections
Reflectography/ transmittography
Thermography
THz Terahertz imagingElectromagnetic
spectrum
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2. Non‐thermal Infrared NDT2. Non‐thermal Infrared NDT
Non‐thermal IR vision NDT: sample illumination
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NIR/SWIR reflections or transmissions Reflectography
Transmittography
NIR reflectography/transmittography of GFRP
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900 – 1700 nm
NIR: reflection NIR: transmissionvisible images
GFRP: Glass Fiber Reinforced Plastic
front
back
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Infrared spectrum
Thermal emissions
Non-thermal reflections
Reflectography/ transmittography
Thermography
THz Terahertz imagingElectromagnetic
spectrum
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3. Thermal Infrared NDT: Passive Thermography3. Thermal Infrared NDT: Passive Thermography
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Passive thermography: introduction
The passive approach is used when the object of interest has enough thermal contrast with respect to the background in order to be detected with an infrared sensor. Typical applications include: surveillance, people tracking, humidity assessment in buildings, liquid levels in storage tanks, insulation problems, electrical components, etc.
Sources : http://www.x20.org/thermal/ http://www.temperatures.com/thermalimaging.html
Aeronautical application: (1/4)Water ingress detection in honeycomb
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AA BB CC DD
EE FF GG HH
frontbackVolume, V
[ml]F 1 0.2B 1 0.4G 1 0.6C 1 0.8E 10 2D 10 4H 10 6A 10 9
Cells filled with water
Defective area
Section of a military aircraft component
10 cells with 9 ml of water
not frozen frozen
Aeronautical application: (2/4)Water ingress detection in honeycomb
The impact of water volume
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(a) Early thermogram at t=295 s showing all defects (A to H); (b) Thermogram at t=518 s showing all defects except defect F; (c) Thermogram at t=1315 s showing only defects A, D and H.
Aeronautical application: (3/4)Water ingress detection in honeycomb
The impact of water volume
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The sound area (dotted black line) warms up following a logarithmicgrowth with respect to time
In the presence of water, temperature profiles diverge from logarithmic behavior (since it takes longer to warm up water).
The divergent time for all defects is approximately the same (roughly around 180 s), regardless of the water extend and volume
0 200 400 600 800 1000 1200 1400800
1000
1200
1400
1600
1800
2000
2200
2400
2600Temperature profiles, Telops HD
t [s]
T [
arbi
trary
uni
ts]
Sound area0.2 ml0.4 ml0.6 ml0.8 ml2 ml4 ml6 ml9 ml
Aeronautical application: (4/4)Water ingress detection in honeycomb
Data correlation
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0 200 400 600 800 1000 1200 1400-100
0
100
200
300
400
500
600
700
800Temperature profiles, Telops HD
t [s]
T [
arbi
trary
uni
ts]
9 ml6 ml4 ml2 ml0.8 ml0.6 ml0.4 ml0.2 ml
Time for maximum contrast = 336.2 s
V = f ( tmax )
Maximuncontrast = 146.8
V = 3.2E-08 t 2.685
R² = 0.9911
0
2
4
6
8
10
0 250 500 750 1000 1250 1500
Wat
er in
gres
s vol
ume
[ml]
Time for maximum contrast [s]
Thermograms at different distances
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268
269
270
271
272
273
274
275
276
277
278
270
275
280
285
290
295
275
280
285
290
295
275
280
285
290
295
300
305
1.5 m from target 4 m from target
10 m from target 20 m from target
0.4 ml defect
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4. Thermal Infrared NDT: Active Thermography4. Thermal Infrared NDT: Active Thermography
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Active thermography for NDT
Active thermography for NDT is based on the detection and recording by an infrared camera of thermal radiations emitted by object surface.
To detect defects, it is sometimes necessary to destabilize the object thermal state through heating or cooling (→ active thermography ).
The presence of an internal defect reveals itself on surface as atemperature perturbation above this defect.
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Thermal IR vision
Thermal emissions
Active thermography for NDT
Main advantages:
Possibility to perform one‐sided inspection (in reflection configuration); Carried out in real‐time; Appropriate on most composites materials and multi‐layer structures, including porous materials and industrial lines; Relatively unaffected by the object’s geometry, and well adapted for the inspection of large surfaces.
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Active thermography for NDT
Main problems:
Sensible to heating sources (type, duration, location);
Response time (very fast for metals => need for fast acquisition rates);
Affected by the object’s surface condition and thickness;
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Non‐uniform heating
+
=
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Advanced signal processing techniques
Thermal contrast‐based techniques (max. contrast, FWHM, etc.)
Differential Absolute Contrast, DAC
Thermographic Signal Reconstruction, TSR
Principal Component Thermography, PCT
Pulsed Phase Thermography, PPT
teQT ln
21lnln
A=USVT
)()()( tTtTtTaSd
nnN
k
Nnkjn tkTtF ImReexp
1
0
)2(
tTtttTT ddac
)(012
tTT
te
QTtT
0,0
3D diffusion equation
1D solution for a Dirac pulse
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Absolutecontrast
DAC
Example: DAC on CFRP
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Active thermography: approaches, techniques
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Pulsed thermography
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Pulsed thermography, PT
Metal corrosion, crack detection, disbonding, impact damage in composites, turbine blades, delaminations, porosity, defect characterization: depth, size, thermal properties, artworks.
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Active thermography: approaches, techniques
Lock‐in thermography, LT
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Phase
permanent regimesine wave heating
• same frequency• temporal shift
Thermal waves
input:
output:
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Lock‐in thermography, LT
Crack identification, disbonding, impact damage, cultural heritage inspection, artworks, cultural buildings.
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Active thermography: approaches, techniques
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Eddy current (or Inductive) thermography, ECT
Crack detection in electro‐conductive materials, detection of impact damage in composites, inspection of soldering joints.
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Inspection of honeycomb sandwich structures
Movie: Eddy current thermography
Crack inspection: simulation
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The approach for crack detection
SimulationGeometry of the specimen
Crack inspection: experimental
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Experimental setup Coil and specimen
Segmentaion result
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Active thermography: approaches, techniques
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Vibrothermography, VT
Coating wear, fatigue test, crack detection.
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Open microcracks in thermally‐sprayed‐coatings
The coating (~100‐200 m) is formed by a mixture of Tungsten‐Carbide and Cobalt powder accelerated and heated in aplasma jet and sprayed onto a 1 mm thick steel substrate.
12.8 mm
16 mm
~0.8 mm ~0.8 mm
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Optical PT Optical LT
Burst VT Line-scan ECT
Real crushed core produced during VT inspection
Paint detached from the surface
Comparative example: PT, LT, VT, ECT
Inspection of CF‐18 rudders (1/3)
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Inspection of CF‐18 rudders (2/3)
Impact of de‐noising with synthetic data
f=0.015 Hz f=0.04 Hz f=1.2 Hz
PPT from raw pulsed data
PPT from synthetic pulsed data
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Inspection of CF‐18 rudders (3/3)
Depth retrieval with phase profiles
0 0.2 0.4 0.58-0.05
0
0.05
0.1
0.15
f [Hz]
[rad
]
z1,raw z2,raw z1,synt z2,synt
z1=0.5 mm z2=2 mm
Sa
z1 z2
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5. Thermal Infrared NDT: More Applications5. Thermal Infrared NDT: More Applications
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Road and bridges inspection (1/3)
Notre‐Dame streetMontréal, CanadaNovember 4th, 2008
Interstate 35Minneapolis, August 3rd, 2007
Viaduc de la Concorde, Montréal, CanadaSeptember 30th, 2006
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Road and bridges inspection (2/3)
Reinforcement using composite layers
Traditional inspection with the "tap testing" techniqueToutry Bridge, France
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Road and bridges inspection (3/3)
Thermal stimulation
Images acquisition
Fiber distribution and orientation
Randomly‐Oriented Strands (ROS)
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Heat + Pressure
Fiber distribution and orientation
Complex‐shaped parts
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Fiber orientation measurement
Strength and stiffness
Fiber distribution and orientation: point scan
Laser point scan experimental setup
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Laboratory setup
Results show the ellipses major axes indicating the fiber direction for the same area at two different positions rotated 90o
6.37°
‐85.19°
Error of 1.5°
Artworks inspection (1/3)
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Artworks inspection (2/3)
OverlayHidden drawings
NIR camera (0.9‐1.7 m) incandescent lamp 90 V
Visible photograph
Artworks inspection (3/3)
OverlayDefects
Thermal camera (3‐5 m) PPT phase f=75 mHz
Visible photograph
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6. Conclusions6. Conclusions
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Conclusions
Infrared reflectography and transmittography employ the non‐thermal part of the infrared spectrum, where the opacity/transparency of materials, subjected to a specific infrared radiation, are exploited to detect internal anomalies in materials.
Infrared thermography works in the thermal part of the infrared spectrum under the principle that dissimilar materials provide different thermal signatures, useful for surface/subsurface defect detection.
Passive thermography is typically used in the field of security and surveillance, biological applications, the inspection of electrical and electronic components, and buildings among others.
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Conclusions (cont.)
Active thermography is widely used in aerospace and automobile industries and is finding new applications such as the inspection of bridges and roads and the assessment of artworks and cultural heritage.
Data processing techniques are required to enhance contrast, to improve the spatial resolution and to increase the signal‐to‐noise ratio of the infrared signal.
Continual technological progress in commercial infrared cameras and computers , as well as the constant development of new processing techniques, have promoted the appearance of new and innovative applications for infrared vision.
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Thank you for your attention !
