11th NDE | May 19-21, 2015 | Korea
REAL-TIME ADAPTIVE IMAGING FOR ULTRASONIC NONDESTRUCTIVE TESTING OF
STRUCTURES WITH IRREGULAR SHAPES
Sébastien Robert, Léonard Le Jeune, Vincent Saint-Martin
CEA-LIST, 91191 Gif-sur-Yvette Cedex, France
Olivier Roy
M2M, 1 rue de Terre-Neuve, 91940 Les Ulis, France
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Immersion in a tank Flexible wedge
Nuclear weld nozzle Butt weld Resistance welding
Membrane filled with water
Examples of complex specimens
Immersion testing configurations
INTRODUCTION
Wheel probes
Local immersion control devices
Corrosion
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INTRODUCTION
Development of adaptive focusing algorithms for immersion testing:
Adaptive imaging under irregular and unknown surfaces
Compensation of probe misalignements/inclinations during inspection
TFM image
Poor image quality Adaptive TFM
2 MHz
64 elements 6 mm
Measured surface
Effects of irregular surfaces on ultrasonic imaging:
TFM : Total Focusing Method
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In M2M systems: Adaptive Total Focusing Method
Step1: Surface imaging Step2: Material imaging
Water
Water
Water
Steel
TFM image of the flaws
Why using the TFM algorithm?
A same set of data (FMC) is processed to image both the surface and the material
Accuracy of the surface measurement (focusing on every point of the surface)
Generalization to multi-modal and 3D imaging
INTRODUCTION
Adaptive focusing
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OUTLINE
• Total Focusing Method (TFM)
Full Matrix Capture
Focusing algorithm
• Adaptive TFM [1]
Surface measurement and adaptive focusing
Examples of post-processing results (CIVA)
Examples of real-time results (M2M)
• Alternative approach: Plane Wave Imaging (PWI) [2,3]
Plane Wave Imaging under complex surfaces
Examples of post-processing results and comparison with TFM
• Conclusions and perspectives
[1] L. Le Jeune et al., QNDE, AIP Conf. Proc. 1650, 1037 (2015)
[2] S. Robert et al., French patent n°FR1363246 (2013)
[3] L. Le Jeune et al. International Congress on Ultrasonics (2015)
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• N successive shots (N : nb of elements)
• One shot: 1 transmitting element
All elements receiving
TOTAL FOCUSING METHOD
Full Matrix Capture (FMC) and TFM
1 transmitter
All receivers
…
NxN signals sij (t)
Steel
N-element array
Incident wave
Backscattered waves
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• N successive shots (N : nb of elements)
• One shot: 1 transmitting element
All elements receiving
TOTAL FOCUSING METHOD
Full Matrix Capture (FMC) and TFM
1 transmitter
All receivers
…
NxN signals sij (t)
Steel
N-element array
1. Calculation of times of flight tij(P) for all
the T-R pairs (i ; j) and points P in the image
tijP = Ti
P +Tj
P
2. Summation of NxN amplitudes sij[t =tij(P)]
1 1
( )N N
Pij ij
i j
A P s t t
TiP Tj
P
P
i j
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ADAPTIVE TFM
1st step: TFM imaging in a semi-infinite water medium
TiP
TjP
P Surface imaging Geometry extraction
Water
Steel
Elt n°i Elt n°j
: time of flight in water 1 1
( )N N
Pij ij
i j
A P s t t
tijP = TiP +TjP
Water
Water
2nd step: dynamic time-of-flight calculation and TFM imaging in the material
x z
P(x2,z2)
E(x1,0) Time of flight from element E to focusing point P:
M(x ,z)
2 2
2 21 2
1 2
1 1( , ) EPt x z x x z x x z
c c
Impact point M(x0 , z0) determined with the Fermat’s principle:
0 0,
( , ) min ( , )EP EPx z
t x z t x z
c1
c2
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ADAPTIVE TFM
Array (64 els, 2 MHz) 50 mm
Irregular surface Concave surface Convex surface
Examples of post-processing results
Surface image Surface image Surface image
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ADAPTIVE TFM
Examples of post-processing results
(1) Surface imaging
(2) Back-wall imaging
Adaptive TFM for crack-type defects
Imaging with half-skip modes Imaging with direct paths
Complete 2d geometry
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Experimental set-up
Array: 64 elts - 5 MHz
Water-filled flexible wedge
Aluminum specimen
Holes
(diameter: 2 mm)
Notches
(thickness: 10 mm )
30 mm 6 mm
Examples of real-time results
ADAPTIVE TFM
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Examples of real-time results
ADAPTIVE TFM
Probe displacement of 250 mm
Adaptive TFM disabled
Adaptive TFM enabled Measured surface
Probe
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Examples of real-time results
ADAPTIVE TFM
Application: Thickness mesurement in welds
(corrosion detection)
Control
Side view Bottom view
Phased-array:
64 elts - 10 MHz
0.25 mm pitch
Probe displacement
Surface profile
Back-wall echo
Defects?
~12 mm
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PWI under complex interfaces
PLANE WAVE IMAGING
PWI: One shot = all elements
+ Delay law
Plane wave
Cylindrical wave
Wave with low acoustic power Wave with higher acoustic power
TFM: One shot = one element
Less sensitive to noise and attenuation
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PWI under complex interfaces
PLANE WAVE IMAGING
TFM: One shot = one element PWI: One shot = all elements
TFM and PWI imaging algorithms are the same but:
P P
i-th elt j-th elt
TiP
TjP
q-th plane wave
TqP Tj
P
TqP : time of flight of the q-th plane wave Ti
P : time of flight of the i-th cylindrical wave
1 1
( )
N N
P PTFM ij i j
i j
A P s T TTiP +Tj
P 1 1
( )
Q N
P PPWI qj q j
q j
A P s T TTqP +Tj
P
Q << N High frame rate with PWI
j-th elt
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PWI under complex interfaces
PLANE WAVE IMAGING
64 shots with 1 element 9 shots with 64 elements
Better SNR
TFM PWI
+20°
-20°
Incident plane waves
5° step
Array: 64 elts - 5 MHz
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PWI under complex interfaces
PLANE WAVE IMAGING
140 160 180 200 220 240 260 280
30
35
40
45
50
0.5
1
1.5
2
2.5
3
3.5
x 106
140 160 180 200 220 240 260 280
30
35
40
45
50
1
2
3
4
5
x 106
TFM
PWI
Displacement of 140 mm (5 mm step)
Displacement of 140 mm (5 mm step)
9 shots per position
(-20 to 20°)
64 shots per position
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Adaptive TFM imaging in a M2M prototype UT system
Frame rate up to 10 fps (PA with 64 elements)
New local immersion control solution: flexible wedges + adaptive TFM
Various applications: thickness measurement (corrosion), defect detection under
complex surfaces (butt welds, nozzles, resistance welding…)
ADAPTIVE TOTAL FOCUSING METHOD:
PERSPECTIVES AND CONCLUSIONS
1st shot 2nd shot 3rd shot
Array + complex specimen Iterative SAUL processing Fast surface measurement
Adaptive TFM: commercial version in early 2016 (Gekko system)
Adaptive Plane Wave Imaging: use the SAUL method for fast surface measurement [4]
PERSPECTIVES:
[4] S. Robert et al. QNDE, AIP Conf. Proc. 1650, 1657 (2015)
Département Imagerie Simulation pour le Contrôle
Commissariat à l’énergie atomique et aux énergies alternatives
Institut Carnot CEA LIST
Centre de Saclay | 91191 Gif-sur-Yvette Cedex
T. +33 (0)1 69 08 75 97 | F. +33 (0)1 69 08 32 18
Etablissement public à caractère industriel et commercial | RCS Paris B 775 685 019
Thank you for your attention.
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