Optimal calibration via virtual x-ray imaging for dual-energy techniques: application to glass wool

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Fusion entre les données ultrasonores et les images de radioscopie à haute résolution (application au contrôle de cordon de soudure)

Notre étude porte sur la fusion de données à haut niveau du contrôle ultrasonore (US) et du contrôle radioscopique (RX) en vue d'améliorer la fiabilité du contrôle automatique des défauts dans les joints soudés en acier. Le cadre mathématique que nous avons retenu est la théorie des croyances de Dempster-Shafer. L'étude des phénomènes physiques régissant la formation de l'image RX et du signal US nous a permis d'élaborer une méthode de traitement automatique spécifique pour détecter et recaler les défauts dans le même repère géométrique. Les techniques de traitements que nous avons retenues permettent de détecter des défauts de faible amplitude mais induisent par ailleurs de fausses détections. Nous avons alors mis au point une étape d'apprentissage afin de modéliser la confiance sur la présence du défaut : les paramètres d'un ensemble d'objets de référence (contraste-sur bruit, taille, élongation) sont comparés à l'analyse de l'expert humain. Ce travail fait apparaître des régions de l'espace des paramètres qui correspondent à des objets de même nature. Une méthode originale de calcul des parts de croyances permet de modéliser l'incertitude et l'imprécision du système automatique sur la nature de l'objet. Enfin, nous avons mis en place un protocole de fusion des données qui permet d'augmenter le degré de confiance sur la présence d'un défaut, de préciser sa nature, et d'améliorer la précision sur les dimensions du défaut.This thesis focuses on the development of radioscopic (XR) and ultrasonic (US) data fusion for the automatic inspection of steel welded joints in a way to enhance the reliability of defect detection. The mathematical model is the theory of evidence of Dempster-Shafer. The study of physical laws leading to the formation of XR image and US signal helped for the development of a specific processing for the detection and matching of defects. Unfortunately, the detection of low amplitude signal defects also yields false alarm detection. We therefore developed a training stage to attribute a confidence level to a detected object. During this stage, different features of reference defects were calculated (contrast-to-noise ratio, area, elongation ) and compared to the interpretation of human expert analysis. We distinguish different areas of the features space in which some types of objects are predominant. A novel method has been developed for attributing a degree of belief to an unknown object taking both uncertainty and imprecision into account. Eventually, the data fusion stage consists in combining confidence levels to increase the confidence in the presence of a defect, but also to precise its nature and dimensions.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceF

High-Resolution X-Ray Computed Tomography Using a Solid-State Linear Detector

International audienceIn this paper we present an original low cost acquisition system for computed tomographic imaging. On the first hand, the use of a linear detector consisting of sensitive elements 0.225 mm × 0.5 mm in size allows one to obtain a resolution of about 150 μm after magnification. Image quality has been assessed in terms of spatial resolution and contrast sensitivity by imaging test objects. The images ofin vitrovertebrae acquired by this experimental system show great improvement compared to the images acquired by a conventional medical scanner. On the other hand, an even better resolution (25 μm) has been obtained by using an x-ray sensitive Vidicon camera, and an industrial application is presented with advanced composite materials

2D and 3D Characterization of Metal Foams Using X-ray Tomography

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Development of a non destructive characterisation technique for the 3D investigation of micro-heterogeneous structural materials

International audienceno abstrac

Development of a non destructive characterisation technique for the 3D investigation of micro-heterogeneous structural materials

A non destructive characterisation technique, X ray tomography, has been developed in order to obtain 3D images of the interior of micro-heterogeneous materials with a high resolution. The X ray source is the ID 19 beamline at ESRF. Model and industrial materials have been successfully imaged with a resolution ranging from 1 to 6 µm3. Quantitative 3D data extracted from the reconstructed images give very valuable information on the microstructure of materials. An in situ tensile testing device has been developed in order to observe samples under load. Images of damage initiation and development under stress inside composite materials have been obtained

an investigation of segmentation methods and texture analysis applied to tomographic images of human cancellous bone

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<title>Hard x-ray phase tomographic investigation of materials using Fresnel diffraction of synchrotron radiation</title>

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3D display of high resolution vertebral structure images

International audienceA methodology for three-dimensional (3D) representation of vertebral trabecular structures was proposed. A set of X-ray CT images was obtained using a specific high resolution acquisition system. The images were then segmented in order to separate trabecular and cortical bone structures. Finally, the complex 3D surfaces were visualized using a volume rendering techniqu