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Infrared Testing of CFRP
Components: Comparisons of
Approaches using the Tanimoto
Criterion
by
Xavier Maldague
Saeed Sojasi, Fariba Khodayar,
Fernando Lopez, Clemente
Ibarra-Castando, Xavier
Maldague, Vladimir P. Vavilov,
Arseny O. Chulkov
http://mivim.gel.ulaval.ca
ND
T in C
anada 2015 Conference, June 15-17, 2015, E
dmonton, A
B (C
anada) - ww
w.ndt.net/app.N
DT
Canada2015
2
Outline
1. Review;
2. Case study;
3. Conclusions.
1. Review1. Review
3
4
Active and passive thermography scenarios
Pulsed thermography
5
Lock-in thermography
6
Vibro-thermography
7
LED
8
In this paper, high power LED arrays for pulse and lock-in
thermography are studied. Long pulse LED is compared to
conventional flash thermographic and square wave lock-in LED
excitation is compared to conventional lock-in approach. The
results with LEDs in fact are not good.
Burst vibro-thermography (left) and lock-in vibro-
thermography (right)
9
10
Transient regime
T
t
I
t
Pulsed thermography
defective
non-defective
Stationary regime
A
t
ωI
t
Lock-in thermography
φSa
φdef
PT vs. LT: Setup
milliseconds
11
PT vs. LT: Data acquisition
Pulsed thermography Lock-in thermography
tN
x
y
. . .t1 t2 t3t
∆t
S(t)
s
I
s1
s2s3
s4
ω t
t
tN
x
y
. . .t1 t2 t3t
∆t
TSa(t)
Td(t)
T
t. . .t1 t2 t3 tN
∆t
TSa(t)
tNtw ∆⋅=)(
Td(t)
( ) ( )242
231 SSSSA −+−=
−
−=
42
31arctanSS
SSφ
12
PT vs. LT: Basic processing
Pulsed thermography Lock-in thermography
tN
x
y
. . .t1 t2 t3t
∆t
defect
TSa(t)
Td(t)
T
t. . .t1 t2 t3 tN
∆T
0
∆Tmax
)()()( tTtTtTaSd −=∆
fN
x
y
. . .f1 f2 f3f
∆f
defect
φSa(t)
φd(t)
0
φi,j(f)
. . .
f
f1 f2
∆f
φSa(f)
φd(f)
f3
∆φi,j(f)
−
−=
42
31arctan1 SS
SSωφ
fN
Advanced processing
�Differential absolute contrast, DAC
� Thermographic signal reconstruction, TSR
�Pulsed phase thermography, PPT
13
( )tTt
ttTT ddac
′⋅′
−=∆ )(
( ) ( )te
QT πln
2
1lnln −
=∆
( ) nn
N
k
Nnkjn tkTtF ImReexp
1
0
)2( +=∆∆= ∑−
=
− π
Advanced processing
�Principal components thermography, PCT
�Partial least square, PLST
14
TUSVA =
FUQY
ETPX
T
T
+=
+=
PT characteristics LT characteristics VT characteristics
PT, LT and VT characteristics
� Several frequencies tested at a time (fast);
� Transient regime;
� Requires synchronization between the heat pulse and the acquisition;
� Affected by typical active thermography problems (non-uniform heating, emissivity variations, reflections, surface geometry..);
� Quantification requires advanced processing techniques;
� Typically, lots of energy are used in a single experiment
� One frequency tested at a time;
� Steady state regime;
� Requires monitoring the time dependence between the reference input signal and the output signal;
� Phase data is less affected than the raw temperature by typical active thermography problems;
� Quantification is straightforward through the diffusion length equation;
� Better control on the energy delivered to the specimen
� Under the effect of mechanical vibrations induced externally to the structure at a few fixed frequencies
� Heat is related by friction precisely at defect locations
� Makes use of mechanical waves to directly stimulate defects without heating the surface as in optical methods
� Mechanical elastic waves travel faster in solids and liquids than through the air
3. Case study:
CFRP006
3. Case study:
CFRP006
16
Setup
17
MWIR cooled
camera
MWIR cooled
camera
2 halogen lamps
Carbon fiber–
reinforced polymer
Carbon fiber–
reinforced polymer
Schematic representation and defect location for
specimen CFRP006
18
Summary of quantification results of PT
19
Raw image TSR(polynomial 4 and derivative 1) PCT
PPT PLST
Summary of quantification results of PT
20
0
10
20
30
40
50
60
70
80
90
100
t =1 .109 s polynomial 4 and
derivative 1 t = 0.03 6 s
polynomial 4 and
derivative 2 t = 0.05 4 s
EOF4 Phase image, f = 0.27
Hz
4th PLS loading
Pulsed Thermography
DAC
TSR
PCT
PPT
PLS
Summary of quantification results of LT(f=100mHZ)
21
Raw image
PCT
PPT
PLST
22
0
10
20
30
40
50
60
70
80
90
100
f = 100 mHz f = 200 mHz f = 300 mHz f = 400 mHz f = 700 mHz f = 1200 mHz
Lock-in Thermography
PCT
PPT
PLS
Summary of quantification results of LT
Summary of quantification results of VT(20kHz 0.125Hz 00-50 pct)
23
Raw image
PCT
PPT
PLST
VT(20kHz 0.125Hz 00-50 pct)
24
0
10
20
30
40
50
60
70
20kHz 0.125Hz 00-50 pct 20kHz 0.250Hz 00-50 pct 20kHz 0.250Hz 20-50 pct 20kHz 0.500Hz 20-50 pct 20kHz 0.500Hz 30-50 pct
Vibrothermography
PCT
PPT
PLS
Summary of quantification results of LED
25
0
5
10
15
20
25
30
35
40
45
50
t = 0.98 s polynomial 4 and
derivative 1
polynomial 4 and
derivative 2
EOF3 EOF2 f = 0.25 Hz f = 0.30 Hz 2nd PLS loading 2nd PLS loading
Tan
imo
to c
rite
rio
n
%
Achsentitel
LED
DAC (Pulsed thermography) TSR (Pulsed thermography) PCT (Pulsed thermography) PCT (Lock-in)
PPT (Pulsed thermography ) PPT (Lock-in) PLS (Pulsed thermography) PLS (Lock-in)
4. Conclusions4. Conclusions
26
Conclusion
27
It has been confirmed experimentally that infrared thermography is
a useful tool in non-destructive testing of CFRP composite. There
are different thermal NDT techniques of which efficiency depends
on material characteristics test conditions. In this paper, four types
of stimulating sources (pulse, lock-in, vibro and LED) have been
applied to a CFRP laminate. The qualitative defect detection based
on Tanimoto criterion was used to compare different signal
processing methods. In the raw images, the defects which are large
and near the surface are easily observed. To detect the defects
which are smaller and deeper, signal processing techniques such as
TSR, DAC, PPT, PCT and PLST need to be used. Surprisingly, the
results of using LED heating have not confirmed efficiency of this
stimulation approach, probably, because of slow and low power
input.
28