NDT of Specimen of Complex Geometry Using Ultrasonic Adaptive Techniques - The F.A.U.S.T. System

Phased array techniques, providing an electronic control of the beam, are widely used in ultrasonic imaging. Such techniques, making use of array transducers with delayed transmission pulse on each element, allow to steer and focus the beam, enabling various testing configurations and imaging procedures : sector scanning and tomography, tracking echoes, depth focusing. In nuclear industry, various configurations of geometry and materials are encountered, which require many different testing configurations. The CEA (French Atomic Energy Commission) has developed an adaptive system based on phased array techniques dynamically controlled by a multi-channel acquisition system: theF.A.U.S.T. (Focusing Adaptive UltraSonic Tomography) system. This system aims at improving the performances of nondestructive testing, particularly for what concerns the adaptability to different control configurations and defect characterization. Previous works have described this system, its performances for beam forming and also its specific abilities for defect characterization using beam steering or spatial amplitude distribution at reception [1, 2]

Application of Dynamic Adaptive Focusing System to Ultrasonic Non Destructive Testing

To obtain the high performances requested by the safety authorities for ultrasonic inspections, in term of sizing, characterization and on-line monitoring, it is needed to vary the refracted angles, focusing depths and the size of the ultrasonic beams rapidly and over a wide range. This is not possible with conventional techniques which allow only fixed focusing. The F.A.U.S.T. (Focusing Adaptive UltraSonic Tomography) system, which is described in this paper, is an open and powerful tool designed to overcome the difficult problems in flaw assessment and monitoring

Integrated Models of Ultrasonic Examination for NDT Expertise

For several years, the French Atomic Energy Commission (CEA) has developed a system calledCIVA for multiple-technique NDE data acquisition and processing [1]. Modeling tools for ultrasonic non-destructive testing have been developed and implemented within this system allowing direct comparison between measured and predicted results. These models are not only devoted to laboratory uses but also must be usable by ultrasonic operators without special training in simulation techniques. Therefore, emphasis has been on finding the best compromise between as accurate as possible quantitative predictions and ease, simplicity and speed, crucial requirements in the industrial context

Application of Ultrasonic Beam Modeling to Phased Array Testing of Complex Geometry Components

For several years, the French Atomic Energy Commission (CEA) has developed phased array techniques to improve defect characterization and adaptability to various inspection configurations [1]. Such techniques allow to steer and focus the ultrasonic beam radiated by a transducer split into a set of individually addressed elements, using amplitude and delay laws. For most conventional systems, those delay laws are extracted from geometric ultrasonic paths between each element of the array and a geometric focusing applied to perform beam-forming abilities [2] for simple geometry components (e.g. beam- steering over a plane specimen), whereas experimental delays can be supplied to the array at transmission and reception to optimally adapt the ultrasonic beam to the detected defect, in a so-called self-focusing process [3,4]. This method, relevant for complex material or geometry leading to phase distortion or complex paths that cannot be predicted by simple geometrical calculations, obviously requires the existence of a reflector and the ultrasonic beam radiated by the experimental delay law cannot be known. Therefore this technique is used to improve defect detection (optimal sensibility) rather than defect characterization. To assess complex geometry components inspection with an adaptive system, the CEA has developed new modeling devoted to predict the ultrasonic field radiated by arbitrary transducers through complex geometry and material specimen [5]. A model allows to compute optimized delay laws to preserve the characteristics of the beam through the complex surface, as well as the actual radiated field using those delays. This paper presents two applications of this model : the inspection of a misaligned specimen, and the inspection of an irregular surface

Broadband Fields Radiated in a Solid by Water-Coupled Transducers: A Comparison of Approximate Models, Numerical Approaches and Experiments

In number of configurations, ultrasonic tests in the French nuclear industry are made using water-coupled focused transducers. To study the influence of the various parameters involved in transducer/piece configurations, model-based predictions of the field radiated by transducers are very useful. A model (called Champ-Sons) has been developed at the French Atomic Energy Commission (CEA) to calculate the field radiated by focused or unfocused transducer through liquid/solid interface at normal or oblique incidence [1]. It can deal with radiating surface of complex (3-D) shape (spherical focusing, Fermat’s surfaces, multiple-elements [2] etc.). The calculation is done directly in the time domain for broadband sources and in the frequency domain for narrowband sources. In its present form Champ-Sons deals with either plane or cylindrical interfaces between a fluid and an isotropic solid. It is implemented in a user-friendly software developed at the CEA called CIVA [3] for NDT data processing (eddy-current, ultrasonics, neutrongraphy, radiography). Since non-canonical configurations are considered and pure numerical schemes are too computer intensive, the model treats the refraction at the fluid/solid interface in an approximate way. It has been validated experimentally [1]

A Characterization of Scale Invariant Responses in Enzymatic Networks

An ubiquitous property of biological sensory systems is adaptation: a step increase in stimulus triggers an initial change in a biochemical or physiological response, followed by a more gradual relaxation toward a basal, pre-stimulus level. Adaptation helps maintain essential variables within acceptable bounds and allows organisms to readjust themselves to an optimum and non-saturating sensitivity range when faced with a prolonged change in their environment. Recently, it was shown theoretically and experimentally that many adapting systems, both at the organism and single-cell level, enjoy a remarkable additional feature: scale invariance, meaning that the initial, transient behavior remains (approximately) the same even when the background signal level is scaled. In this work, we set out to investigate under what conditions a broadly used model of biochemical enzymatic networks will exhibit scale-invariant behavior. An exhaustive computational study led us to discover a new property of surprising simplicity and generality, uniform linearizations with fast output (ULFO), whose validity we show is both necessary and sufficient for scale invariance of enzymatic networks. Based on this study, we go on to develop a mathematical explanation of how ULFO results in scale invariance. Our work provides a surprisingly consistent, simple, and general framework for understanding this phenomenon, and results in concrete experimental predictions

The voltage-gated K+ channel Kv1.3 modulates platelet motility and α2β1 integrin-dependent adhesion to collagen

Kv1.3 is a voltage-gated K+-selective channel with roles in immunity, insulin-sensitivity, neuronal excitability and olfaction. Despite being one of the largest ionic conductances of the platelet surface membrane, its contribution to platelet function is poorly understood. Here we show that Kv1.3-deficient platelets display enhanced ADP-evoked platelet aggregation and secretion, and an increased surface expression of platelet integrin αIIb. In contrast, platelet adhesion and thrombus formation in vitro under arterial shear conditions on surfaces coated with collagen were reduced for samples from Kv1.3−/- compared to wild type mice. Use of collagen-mimetic peptides revealed a specific defect in the engagement with α2β1. Kv1.3−/- platelets developed significantly fewer, and shorter, filopodia than wild type platelets during adhesion to collagen fibrils. Kv1.3−/- mice displayed no significant difference in thrombus formation within cremaster muscle arterioles using a laser-induced injury model, thus other pro-thrombotic pathways compensate in vivo for the adhesion defect observed in vitro. This may include the increased platelet counts of Kv1.3−/- mice, due in part to a prolonged lifespan. The ability of Kv1.3 to modulate integrin-dependent platelet adhesion has important implications for understanding its contribution to normal physiological platelet function in addition to its reported roles in auto-immune diseases and thromboinflammatory models of stroke

Broadband Fields Radiated in a Solid by Water-Coupled Transducers: A Comparison of Approximate Models, Numerical Approaches and Experiments

In number of configurations, ultrasonic tests in the French nuclear industry are made using water-coupled focused transducers. To study the influence of the various parameters involved in transducer / piece configurations, model-based predictions of the field radiated by transducers are very useful. A model (called Champ-Sons) has been developed at th

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