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Eddy Current Technique is a powerful method for detection of surface notches and of buried flaws during inspection of metallic parts. Recent EC array probes have demonstrated a fast and efficient control of large surfaces. Nevertheless, when the size of flaws decreases or the defect is rather deep, traditional winding coil probes turn out to be useless. Magnetoresistive sensors present the advantages of flat frequency response and micron size. . These sensors are hence very attractive for the detection of buried defects that require low frequencies because of skin depth effect. An optimization of the probe with magnetoresistive sensors as receivers has been made by simulations using CIVA software and finite elements methods with OPERA. EC probes for buried flaw detection have been designed. Experimental results have been compared with simulations. [ABSTRACT FROM AUTHOR]

The ECT inspection of a conductive component consists in detecting the perturbation of the induced currents due to a flaw. Among new detectors, Giant Magneto-Resistance (GMR) or Giant Magnetic Impedance sensors, which are sensitive to the magnetic field above the surface of the component, have shown growing interest due to their high performances with respect to classical bobbin coils. In this communication, we present a numerical model based on the volume integral approach which allows computing the components of the perturbed magnetic field due to a given notch embedded in a planar stratified media. Though the inducer may be chosen arbitrary in a list of potential exciting coils, rectangular coils or current foils are very useful for generating a uniform current flow orientated perpendicularly to the length of the flaw. This paper presents firstly some numerical results considering two kinds of distinct numerical models, and then some experimental results will be presented for different kinds of practical applications. This numerical model results in new computation facilities which have been translated into new functionalities in the last version of the CIVA software. [ABSTRACT FROM AUTHOR]

The inspection of materials used in aerospace, nuclear or transport industry is a critical issue for the safety of components exposed to stress or/and corrosion. The industry claims for faster, more sensitive, and more flexible techniques. Technologies based on Eddy Current (EC) flexible array probe and magnetic sensor with high sensitivity such as giant magneto-resistance (GMR) could be a good solution to detect surface-breaking flaws in complex shaped surfaces. The CEA has recently developed, with support from the French Institute for Radiological Protection and Nuclear Safety (IRSN), a flexible array probe based on micro-coils etched on Kapton. The probe’s performances have been assessed for the inspection of reactor residual heat removal pipes, and for aeronautical applications within the framework of the European project VERDICT. The experimental results confirm the very good detection of narrow cracks on plane and curve shaped surfaces. This paper also describes the recent progresses concerning the application of GMR sensors to EC testing, and the results obtained for the detection of small surface breaking flaws. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this paper, the images provided by a flying-spot camera dedicated to open-crack detection are considered. In this type of active thermography, thermal effect and the optical effects contribute to the elaboration of photothermal images. In this contribution a signal processing method, based on multiple principal component analysis is proposed in order to separately identify both thermal and optical effects from the raw images. The detection performance enhancement is characterized thanks to Receiver Operating Characteristic curves. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

The goal of this paper is to localize and reconstruct the shape of 3D flaws in conductive materials using a particular eddy current setup. To solve the non linear and ill-posed inverse problem, a bayesian estimation framework has been considered. In order to compensate the lack of information due to the band-pass behavior of the forward operator, a priori knowledge is introduced by using the beta prior law and the weak membrane model. To show the capabilities of the proposed approach, some 3D reconstructions from simulated data are presented. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]