REAL-TIME ADATIVE IMAGING FOR ULTRASONIC NONDESTRUCTIVE TESTING OF STRUCTURES WITH IRREGULAR SHAES Sébastien Robert, Léonard Le Jeune, Vincent Saint-Martin CEA-LIST, 91191 Gif-sur-Yvette Cedex, France sebastien.robert@cea.fr Olivier Roy M2M, 1 rue de Terre-Neuve, 91940 Les Ulis, France o.roy@m2m-ndt.com 11th NDE May 19-21, 2015 Korea
Examples of complex specimens INTRODUCTION Butt weld Nuclear weld nozzle Resistance welding Corrosion Immersion testing configurations Immersion in a tank Wheel probes Flexible wedge Membrane filled with water Local immersion control devices 2
INTRODUCTION Development of adaptive focusing algorithms for immersion testing: Adaptive imaging under irregular and unknown surfaces Compensation of probe misalignements/inclinations during inspection Effects of irregular surfaces on ultrasonic imaging: 6 mm Measured surface 2 MHz 64 elements TFM image oor image quality Adaptive TFM TFM : Total Focusing Method 3
INTRODUCTION In M2M systems: Adaptive Total Focusing Method Step1: Surface imaging Step2: Material imaging Water Water Water Steel Adaptive focusing 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 4
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: lane Wave Imaging (WI) [2,3] lane Wave Imaging under complex surfaces Examples of post-processing results and comparison with TFM Conclusions and perspectives [1] L. Le Jeune et al., QNDE, AI Conf. roc. 1650, 1037 (2015) [2] S. Robert et al., French patent n FR1363246 (2013) [3] L. Le Jeune et al. International Congress on Ultrasonics (2015) 5
TOTAL FOCUSING METHOD Full Matrix Capture (FMC) and TFM N successive shots (N : nb of elements) One shot: 1 transmitting element All elements receiving Incident wave N-element array 1 transmitter Backscattered waves All receivers Steel NxN signals s ij (t) 6
TOTAL FOCUSING METHOD Full Matrix Capture (FMC) and TFM N successive shots (N : nb of elements) One shot: 1 transmitting element All elements receiving 1 transmitter i N-element array j T i T j All receivers Steel NxN signals s ij (t) 1. Calculation of times of flight t ij () for all the T-R pairs (i ; j) and points in the image t ij = T i +T j 2. Summation of NxN amplitudes s ij [t =t ij ()] N A( ) s t t N i 1 j 1 ij ij 7
ADATIVE TFM 1st step: TFM imaging in a semi-infinite water medium Elt n i Elt n j N A( ) s t t N i 1 j 1 ij ij t ij = T i +T j : time of flight in water T j Water T i Water Water Surface imaging Steel Geometry extraction 2nd step: dynamic time-of-flight calculation and TFM imaging in the material z E(x 1,0) x c 1 c 2 M(x,z) (x 2,z 2 ) Time of flight from element E to focusing point : 1 1 t ( E x, z ) x x z x x z c 2 2 2 2 1 2 1 c2 Impact point M(x 0, z 0 ) determined with the Fermat s principle: t ( x, z ) min t ( x, z) E 0 0 xz, E 8
Examples of post-processing results ADATIVE TFM Irregular surface Concave surface Convex surface 50 mm Array (64 els, 2 MHz) Surface image Surface image Surface image 9
Examples of post-processing results ADATIVE TFM Imaging with direct paths Imaging with half-skip modes (1) Surface imaging (2) Back-wall imaging Adaptive TFM for crack-type defects Complete 2d geometry 10
ADATIVE TFM Examples of real-time results Array: 64 elts - 5 MHz Experimental set-up Water-filled flexible wedge Aluminum specimen 30 mm 6 mm Notches (thickness: 10 mm ) Holes (diameter: 2 mm) 11
ADATIVE TFM Examples of real-time results robe displacement of 250 mm Adaptive TFM disabled Adaptive TFM enabled Measured surface robe 12
ADATIVE TFM Examples of real-time results Application: Thickness mesurement in welds (corrosion detection) Control hased-array: 64 elts - 10 MHz 0.25 mm pitch ~12 mm Side view Bottom view robe displacement Surface profile Defects? Back-wall echo 13
WI under complex interfaces LANE WAVE IMAGING TFM: One shot = one element WI: One shot = all elements + Delay law Cylindrical wave lane wave Wave with low acoustic power Wave with higher acoustic power Less sensitive to noise and attenuation 14
WI under complex interfaces LANE WAVE IMAGING TFM: One shot = one element WI: One shot = all elements i-th elt j-th elt q-th plane wave j-th elt T i T j T q T j ( ) N N TFM ij i j i 1 j 1 A s T T TFM and WI imaging algorithms are the same but: T i +T j ( ) Q N AWI sqj T q +T T j j q 1 j 1 T T i : time of flight of the i-th cylindrical wave q : time of flight of the q-th plane wave Q << N High frame rate with WI 15
WI under complex interfaces LANE WAVE IMAGING TFM WI Array: 64 elts - 5 MHz Incident plane waves +20 5 step -20 64 shots with 1 element 9 shots with 64 elements Better SNR 16
WI under complex interfaces LANE WAVE IMAGING TFM Displacement of 140 mm (5 mm step) 30 35 40 45 64 shots per position x 10 6 5 4 3 2 1 50 140 160 180 200 220 240 260 280 WI Displacement of 140 mm (5 mm step) 30 35 40 45 9 shots per position (-20 to 20 ) 50 140 160 180 200 220 240 260 280 x 10 6 3.5 3 2.5 2 1.5 1 0.5 17
ERSECTIVES AND CONCLUSIONS ADATIVE TOTAL FOCUSING METHOD: Adaptive TFM imaging in a M2M prototype UT system Frame rate up to 10 fps (A 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 ) ERSECTIVES: Adaptive TFM: commercial version in early 2016 (Gekko system) Adaptive lane Wave Imaging: use the SAUL method for fast surface measurement [4] 1 st shot 2 nd shot 3 rd shot Array + complex specimen Iterative SAUL processing Fast surface measurement [4] S. Robert et al. QNDE, AI Conf. roc. 1650, 1657 (2015) 18
Thank you for your attention. Questions? 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 Département Imagerie Simulation pour le Contrôle Etablissement public à caractère industriel et commercial RCS aris B 775 685 019