Linear Sampling Method applied to Non Destructive Testing of an elastic waveguide: theory, numerics and experiments

International audienceThis paper presents an application of the Linear Sampling Method to ultrasonic Non Destructive Testing of an elastic waveguide. In particular, the NDT context implies that both the solicitations and the measurements are located on the surface of the waveguide and are given in the time domain. Our strategy consists in using a modal formulation of the Linear Sampling Method at multiple frequencies, such modal formulation being justified theoretically in [1] for rigid obstacles and in [2] for cracks. Our strategy requires the inversion of some emission and reception matrices which deserve some special attention due to potential ill-conditioning. The feasibility of our method is proved with the help of artificial data as well as real data

Contrôle santé intégré par méthode ultrasonore des réparations composites collées sur des structures métalliques

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Tomographie passive par ondes guidées pour des applications de contrôle santé intégré

National audienc

Passive guided wave tomography for corrosion detection

Conference Code:124064International audienceStructural health monitoring (SHM) consists in embedding sensors in a structure in order to monitor its health status throughout its lifetime. The implementation of SHM systems is restricted in many situations by the necessity to store or to harvest the electric energy necessary to emit the waves which give information about the health of the structure. A promising way to tackle this constraint is to take advantage of the elastic noise naturally present in the structure in order to avoid the emission of the elastic waves by the SHM system. The complexity of the embedded SHM system is therefore reduced. We present here studies of a passive technique-the ambient elastic noise cross-correlation-applied to guided wave tomography. Experimental results which come from usual time-of-flight tomography as well as passive tomography will be described

Passive guided wave tomography for monitoring corrosion in pipes

International audienceThe use of guided waves enables to monitor wide areas of structures with a limited number of sensors and/or a limited acquisition time. In particular, guided wave tomography algorithms give a quantitative image of the residual thickness of the monitored structured, for example a corroded pipe. The idea is to use the dispersion curves to link a change in phase or group velocity to a change in thickness. The method developed at CEA-List includes an auto-calibration phase, eliminating the need of a baseline to work, therefore enabling its use in presence of varying environmental and operational conditions. One drawback of tomography techniques is that they need many sensors compared to more conventional algorithms such as RAPID or Delay and Sum. We propose here a passive version of tomography to limit its intrusiveness by using data obtained by post-processing the ambient elastic noise in the structure. This enables the use of Fiber Bragg Gratings (FBG) on optical fibers as ultrasonic sensors. The use of FBGs drastically reduces the burden of the system, as several gratings can be multiplexed on a single optical fiber. Furthermore, these sensors are suited for many applications because of their resistance to harsh conditions (extreme temperatures, explosive atmosphere, radiations…)

Tomographie Passive par Ondes Guidées pour le Monitoring de Corrosion dans les Tuyauteries

International audienceLa détection de défauts dans les tuyauteries par les techniques de contrôle non destructif joue un rôle crucial pour la prévention des risques de rupture ou de fuite dans plusieurs industries (pétrochimie et nucléaire notamment). Le contrôle santé des structures, plus connu sous l’acronyme anglais SHM – Structural Health Monitoring – est une approche qui consiste à munir une structure de capteurs pour suivre son état de santé. Les ondes élastiques guidées sont particulièrement adaptées pour les applications SHM de structures minces (type plaques, tubes ou cuves) grâce à leur capacité à se propager sur de longues distances. Nous présentons ici une approche originale de SHM pour la détection de corrosion dans les tuyauteries appelée « tomographie passive par ondes élastiques guidées ». Cette technologie est basée sur la combinaison d'algorithmes de tomographie par ondes élastiques guidées et d’une méthode passive appelée corrélation de champs élastiques diffus. Elle permet d'obtenir des cartographies absolues et précises de l'épaisseur d'une zone entourée par une distribution de capteurs, sans émettre d'ondes, simplement en analysant le bruit élastique qui existe naturellement dans la tuyauterie. Ce bruit peut être dû aux vibrations ambiantes ou encore aux turbulences du fluide en mouvement. Le type de corrosions imagées par cette technique sont des pertes d’épaisseur étendues, de taille souvent supérieur au centimètre. Ainsi, les corrosions type piqûres ou feuilletante ne sont pas traitées pour le moment. Nous présentons dans un premier temps les méthodes d’imagerie utilisées, en particulier sur la capacité de travailler en mode « absolu », à l’aide d’un procédé d’autocalibration, ce qui rend le diagnostic plus robuste aux fluctuations environnementales. Nous montrons ensuite des résultats de tomographie active et passive utilisant des signaux expérimentaux mesurés par des transducteurs piézoélectriques

Procédé et système de contrôle de santé intégré d'une structure mécanique par ondes élastiques diffuses

N° de publication : FR3060743 (A1) 2018-06-22Lien esp@cenet : https://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=0&ND=3&adjacent=true&locale=fr_EP&FT=D&date=20180622&CC=FR&NR=3060743A1&KC=A1 Également publié en tant que : WO2018109159 (A1) 2018-06-21/FR306060743 (B1) 2019-05-17/US2019317056 (A1) 2019-10-17/EP3555585 (A1) 2019-12-23A method for controlling the integrated health of a structure (S) supporting modes for guided propagation of elastic waves, comprising the following steps: a) acquiring an ambient noise propagating in the structure by means of at least one pair of non co-located elastic wave sensors (CA, CB); b) estimating a function representing a pulse response of the structure for the elastic propagation between the sensors forming said pair; c) extracting at least one dispersion curve of the elastic propagation in the structure by time-frequency analysis of this function representing a pulse response; and d) estimating at least one parameter indicating a mechanical property of a constituent material of the structure on the basis of the dispersion curve obtained during step c). A system for implementing such a method.Procédé de contrôle de la santé intégrée d'une structure (S) supportant des modes de propagation guidée d'ondes élastiques, comprenant les étapes suivantes : a) acquérir un bruit ambiant se propageant dans la structure au moyen d'au moins une paire d'élastiques non co-localisés capteurs d'ondes (CA, CB); b) estimer une fonction représentative d'une réponse impulsionnelle de la structure pour la propagation élastique entre les capteurs formant ladite paire ; c) extraire au moins une courbe de dispersion de la propagation élastique dans la structure par analyse temps-fréquence de cette fonction représentative d'une réponse impulsionnelle ; et d) estimer au moins un paramètre indicateur d'une propriété mécanique d'un matériau constitutif de la structure à partir de la courbe de dispersion obtenue lors de l'étape c). Un système pour la mise en oeuvre d'un tel procédé

Développement d'un noeud ultrason synchronisé par GPS sur base PEGASE 3 : application au monitoring de rail

International audienceRail breaks can be a source of dramatic accidents or service interruptions with huge economic andsocial impacts. Conventional inspection of rails is generally performed through manual inspectiondevices or inspection vehicles equipped with ultrasonic or electromagnetic sensors able to checksurface and internal defects along the rail in either contact or noncontact manner.Guided elastic waves are one of the most promising technology for Structural Health Monitoring ofelongated structures thanks to their capability to propagate over large distances and their sensitivityto critical defects such as cracks or corrosion. Piezoelectric transducers that are permanently andregularly spaced on the rail can be used to emit and receive such waves. Specific signal processing ofthe measured signals can detect, locate and characterize a rail damage before it reaches critical size.This type of system is able to send real time alert for safety issue and anticipate maintenanceoperations minimizing thus service interruptions.We present here the recent development, in a collaboration between CEA, UGE (formerly IFSTTAR)and Alstom, of guided waves based rail-monitoring system composed of permanent piezoelectrictransducers placed every kilometers on the rail and driven by electronic nodes. This system relies onthe generic PEGASE motherboard developed by UGE and its GPS-based time synchronization solutionthat ensures that distant electronic nodes share a common clock with an accuracy below tenths ofnanoseconds, sufficient to capture guided waves phenomena.A specific daughter board able to drive up to 8 ultrasonic transducers in the frequency range of 10 –200 kHz has been specifically designed for the node. It includes an FPGA that ensures low-level signalprocessing of measurements. The local diagnosis of each node are then transmitted to a remote server(using wireless protocols such as WiFi or 3G/4G depending on the application) that aggregates theinformation coming from the different nodes and send an alarm in case of rail damage detection.The presentation will describe the global SHM system (ultrasonic node and remote server operation)developed for rail monitoring and on-field applications of the solution

Linear Sampling Method applied to Non Destructive Testing of an elastic waveguide: theory, numerics and experiments

International audienceThis paper presents an application of the Linear Sampling Method to ultrasonic Non Destructive Testing of an elastic waveguide. In particular, the NDT context implies that both the solicitations and the measurements are located on the surface of the waveguide and are given in the time domain. Our strategy consists in using a modal formulation of the Linear Sampling Method at multiple frequencies, such modal formulation being justified theoretically in [1] for rigid obstacles and in [2] for cracks. Our strategy requires the inversion of some emission and reception matrices which deserve some special attention due to potential ill-conditioning. The feasibility of our method is proved with the help of artificial data as well as real data