A Geometrical Interpretation of the Echo Formation of Short Pulses on Simple Shaped Targets

As a necessary step to turn into industrial a method to discriminate between crack-like and small volumic defects by means of ultrasonic NDE [1], we are studying the characterization of broad-band transducers by pulse-echo technique, particularly the influence of the shape and size of the target on the shape of the echo

French developments for improving In Service Inspection of SFRs

International audienceIn Service Inspection (ISI) is a major issue to be taken into account for future Sodium Fast Reactors safety, thus, a large R&D work is performed since 2010 in France for the future SFRs. ISI requirements have been taken into account since the early pre-conceptual design phase (specific rules for design have been merged into RCC-MRx design rules until 2012), then consolidated through the basic design phase with more detailed specifications leading to increase the ISI tools ability for immersed sodium structures of SFRs, at about 200°C (shut down conditions). Inspection within the main vessel are planned with transducers immersed in sodium and also with transducers located out of sodium medium. Finally, the qualification of ISI ultrasonic transducers (for Non Destructive Examination, Telemetry and Imaging) is being performed with experimental water and sodium testing, to be compared to simulation with CIVA software platform results. A pluri-annual R&D program mainly deals with the reactor block structures, the primary components and circuit, and the Power Conversion System. Specific developments have been performed for NDE of thick austenitic steel welds, NDE using guided Lamb waves, telemetry from the outside of reactor vessel, imaging of immersed structures and components within the large primary vessel (in a pool type reactor concept) and associated in sodium robotics (with in-sodium tightness). Some results of testing and simulation are given for some ASTRID project applications

A Theoretical Approach for the Discrimination of Crack Tip and Small Defect Echoes

Due to diffraction of US by crack tips, a misinterpretation of C-Scans can be made by mistaking detection of a large misoriented crack for a small flaw. As the latter is often tolerable, the former jeopardizes the life of the piece. Fig. 1. shows C-Scans at various amplification levels. The two spots due to diffraction by the near and far tips of a crack can be interpreted as arising from two small defects, even at high amplification level (+18 dB) for which S/N ratio becomes unacceptable

2008 ultrasonic benchmark studies of interface curvature—a summary

In the 2008 QNDE ultrasonic benchmark session researchers from five different institutions around the world examined the influence that the curvature of a cylindrical fluid‐solid interface has on the measured NDE immersion pulse‐echo response of a flat‐bottom hole (FBH) reflector. This was a repeat of a study conducted in the 2007 benchmark to try to determine the sources of differences seen in 2007 between model‐based predictions and experiments. Here, we will summarize the results obtained in 2008 and analyze the model‐based results and the experiments

Label-Free Optical Detection of Biomolecular Translocation through Nanopore Arrays

In recent years, nanopores have emerged as exceptionally promising single-molecule sensors due to their ability to detect biomolecules at subfemtomole levels in a label-free manner. Development of a high-throughput nanopore-based biosensor requires multiplexing of nanopore measurements. Electrical detection, however, poses a challenge, as each nanopore circuit must be electrically independent, which requires complex nanofluidics and embedded electrodes. Here, we present an optical method for simultaneous measurements of the ionic current across an array of solid-state nanopores, requiring no additional fabrication steps. Proof-of-principle experiments are conducted that show simultaneous optical detection and characterization of ssDNA and dsDNA using an array of pores. Through a comparison with electrical measurements, we show that optical measurements are capable of accessing equivalent transmembrane current information

Theoretical Predictions and Experimental Measurements of Echo-Responses from Angled Targets

A recently-developed model allows the prediction of echo-responses from targets of various geometry and acoustic impedance [1,2]. The model is briefly reviewed then used to predict echo-responses from angled planar targets, these results being compared with experimental measurements. This comparison allows the definition of its domain of applicability. Implications for QNDE are discussed. Particular attention is given to the physical interpretation of the results in term of scattering of the geometrical and edge wave components of the incident field.</p

A Geometrical Interpretation of the Echo Formation of Short Pulses on Simple Shaped Targets

As a necessary step to turn into industrial a method to discriminate between crack-like and small volumic defects by means of ultrasonic NDE [1], we are studying the characterization of broad-band transducers by pulse-echo technique, particularly the influence of the shape and size of the target on the shape of the echo.</p

Extension du modèle de Freedman de formation des échos au cas transitoire

This paper presents an extension of a model presented by the same authors in the previous CFA [1]. The model allows fast computations of the acoustical impulse-response of the problem of the radiation of ultrasonic pulses by realistic transducers, their scattering by immersed targets and their reception. In the previous version, the model was restricted to the case of small targets centered on the transducer axis. Here, it is shown that a more general formula can be derived allowing the computation of the echo-responses from targets not necessarely centered on axis which can be of arbitrary size. It is shown that the present model may be considered as an extension to the transient case of the well-known Freedman's model which derived from a CW theory. Basically, the idea is to restrict the computation to the contributions arising from the only parts of the target where interferences are constructive

Results of the 2013 UT modeling benchmark obtained with models implemented in CIVA

Conference of 40th Annual Review of Progress in Quantitative Nondestructive Evaluation, QNDE 2013, Incorporating the 10th International Conference on Barkhausen and Micro-Magnetics, ICBM 2013 ; Conference Date: 21 July 2013 Through 26 July 2013; Conference Code:105840International audienceThe 2013 Ultrasonic Testing (UT) modeling benchmark concerns direct echoes from side drilled holes (SDH), flat bottom holes (FBH) and corner echoes from backwall breaking artificial notches inspected with a matrix phased array probe. This communication presents the results obtained with the models implemented in the CIVA software: the pencilmodel is used to compute the field radiated by the probe, the Kirchhoff approximation is applied to predict the response of FBH and notches and the SOV (Separation Of Variables) model is used for the SDH responses. The comparison between simulated and experimental results are presented and discussed

DÉTERMINATION GÉOMTRIQUE DE RÉPONSES IMPULSIONNELLES ÉCHOGRAPHIQUES SUR DES CIBLES IMMERGÉES DE FORME SIMPLE

We propose a simple interpretation of the mechanism of echo formation for targets of simple shape (spheres, cones and small tilted disks) placed far from a plane broad band transducer on its axis. This interpretation is based on the description of the radiated field in terms of plane and edge waves component. This permits to find easily the approximate shape and amplitude of the impulse response. The echo is then obtained by convolution of the latter with the excitation signal.Nous proposons une interprétation simple du mécanisme de formation des échos pour des billes cônes et petits disques inclinés placés assez loin sur l'axe d'un traducteur plan large bande. Cette interprétation utilisant la description du champ émis en termes d'onde géométrique et de bord permet de retrouver facilement la forme schématique des réponses impulsionnelles pour les cibles considérées. L'écho est ensuite obtenu par convolution avec le signal d'excitation