Développement d'un modèle pour le contrôle non destructif par courants de Foucault de structures rivetées en aéronautique

Un des enjeux du Contrôle Non Destructif (CND) par Courants de Foucault (CF) dans le domaine aéronautique est l inspection de structures rivetées pour détecter d éventuels défauts qui peuvent se créer en pied de rivet. Pour apporter des éléments de réponse à cette problématique, EADS et le CEA LIST ont collaboré dans le cadre de ce travail de thèse avec le soutien de la Région Île-de-France afin de développer un modèle de simulation au sein de la plate-forme logicielle CIVA, adapté à ce type de configuration, pour la mise au point de méthodes de contrôle, leurs optimisations et leurs qualifications. L approche théorique choisie est le formalisme d équations intégrales de volume ; une des clés de voûte de cette méthode est l expression analytique des dyades de Green découlant des équations de Maxwell et leur mise en oeuvre numérique, ce qui permet une grande rapidité de résolution. L établissement d un modèle pour le contrôle par courants de Foucault de structures rivetées a nécessité tout d abord le développement d un modèle de contrôle d une structure stratifiée grâce à la mise en place des dyades de Green multi-couches. Ce modèle a été par la suite enrichi d un point de vue numérique, notamment par la mise en place d un algorithme itératif adapté à nos configurations de contrôle. Enfin, la prise en compte par le modèle d un défaut en pied de rivet met en jeu la présence de deux objets de tailles très différentes dans une même configuration. Le modèle a ensuite fait l objet de validations expérimentales et de comparaisons avec d autres modèles de simulation (éléments finis, semi-analytique et formulation potentielle) aux différentes étapes clefs de son élaboration.One of the Eddy Current Testing issues in aeronautics is the inspection of fastened structures to detect flaws nearby rivets which can grow because of mechanical stress. EADS and the CEA LIST have started a collaborative work with the support of the Île-de-France Region to develop a simulation tool of EC fastened structures testing, integrated to the CIVA platform, aimed at conceiving testing methods, optimizing and qualifying it. The volume integral method using the Green dyadic formalism has been chosen in order to get a fast resolution of Maxwell equations. A first milestone was to build a simulation model of multilayer structures testing, thanks to the use of the multilayer Green dyads. Because of the rivet volume, 60 times bigger than the one of a typical flaw, a large number of discretization cells are needed. Therefore an iterative method has been developed in order to numerically solve large calculation zones. Finally, the flaw response simulation mostly has to cope with a scale issue between the size of the rivet and the one of the flaw, the latter being much smaller in a direction than the former. The whole model has been experimentally validated and compared to other simulation models (finite elements method, semi-analytical model and potential formulation) at the important development steps: multilayer configuration, iteration resolution, and flaw signature.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

1.6 Some aspects of numerical modelling for additive manufacturing

International audienceThis chapter focusses on some aspects of numerical modelling of WAAM,WLAM, SLM and DED processes

A 3D Model for Eddy Current Inspection in Aeronautics: Application to Riveted Structures

International audienceEddy current technique is currently an operational tool used for fastener inspection which is an important issue for the maintenance of aircraft structures. The industry calls for faster, more sensitive and reliable NDT techniques for the detection and characterization of potential flaws nearby rivet. In order to reduce the development time and to optimize the design and the perfor-mances assessment of an inspection procedure, the CEA and EADS have started a collaborative work aiming at extending the modeling features of the CIVA non destructive simulation plat-form in order to handle the configuration of a layered planar structure with a rivet and an embedded flaw nearby. Therefore, an approach based on the Volume Integral Method using the Green dyadic formalism which greatly increases computation efficiency has been developed. The first step, mod-eling the rivet without flaw as a hole in a multi-stratified structure, has been reached and validated in several configurations with experimental data

Eddy Current Modelling for Inspection of Riveted Structures in Aeronautics

International audienceIn the framework of a collaborative project with EADS, a semi-analytical model based on a volume integral method has been developed to simulate eddy current (EC) inspection of riveted structures in aeronautics. The model handles a layered structure by considering a dyadic Green's approach where a fastener and a flaw are introduced as a variation of conductivity in a stack of slabs. Experimental data are used to validate the model

Modélisation d'un procédé de contrôle non destructif par courants de Foucault de structures rivetées en aéronautique

International audienceOne of the Eddy Current (EC) testing issues in aeronautics is the inspection of fastened structures to detect flaws nearby rivets which can grow because of mechanical stress. EADS and the CEA LIST have started a collaborative work with the support of the Île-de-France Region to develop a simulation tool of EC fastened structures testing, integrated to the CIVA platform, aimed at conceiving testing methods, optimizing and qualifying it. The volume integral method using a multilayer Green dyadic formalism has been chosen in order to get a fast resolution of Maxwell equations. The flaw response simulation mostly has to cope with a scale issue between the size of the rivet and the one of the flaw. The whole model has been experimentally validated and compared to other simulation models at the important development steps.Un des enjeux du CND par Courants de Foucault (CF) dans le domaine aéronautique est l'inspection de structures rivetées pour détecter d'éventuels défauts qui peuvent se créer en pied de rivet. Pour répondre à cette problématique, EADS et le CEA LIST ont collaboré avec le soutien de la Région Île-de-France afin de développer un modèle de simulation au sein de la plate-forme logicielle CIVA, adapté à ce type de configuration, pour la mise au point de méthodes de contrôle, leurs optimisations et leurs qualifications. L'approche théorique choisie est le formalisme d'équations intégrales de volume mettant en jeu des dyades de Green multi-couches et leur mise en oeuvre numérique, ce qui permet une grande rapidité de résolution. La prise en compte par le modèle d'un défaut en pied de rivet met en jeu la présence de deux objets de tailles très différentes dans une même configuration. Le modèle a ensuite fait l'objet de validations expérimentales et de comparaisons avec d'autres modèles de simulation aux différentes étapes clefs de son élaboration

Geographical variations in the prevalence of hypertension in France Cross-sectional analysis of the CONSTANCES cohort

International audienceAIMS:While international variations in the prevalence of hypertension are well described, less is known about intra-national disparities and their determinants. We wanted to describe the variations in hypertension prevalence within France and to determine how much lifestyle and socioeconomic factors contributed to explain these regional variations.METHODS:Participants (62,247 French adults aged 18 to 69 years) were recruited in the 16 centres of the CONSTANCES study between 2012 and 2015. Hypertension was defined as blood pressure higher than 140/90 mmHg and/or taking antihypertensive medications. The contribution of lifestyle and socioeconomic factors to hypertension prevalence variations among centres was examined using sequential hierarchical logistic models.RESULTS:Hypertension prevalence was 37.3% (95% confidence interval (CI) = 36.6-38.0) in men and 23.2% (95% CI = 22.7-23.8) in women. Hypertension prevalence rates varied by almost two-fold among centres (1.9 in men, 1.6 in women) with the highest prevalence in the north and the east of France. Body mass index was strongly associated with hypertension in women (odds ratio (OR)1-unit increase = 1.11 (95% CI = 1.11-1.12)) and was the highest contributor to between-centre variations (27% in women), followed by socioeconomic characteristics (e.g. ORhigh versus low education = 0.85 (95% CI = 0.83-0.87), contributing to 14% of variations in women). Together, family history of hypertension, body mass index, education, occupation and residential area socioeconomic level explained about 30% and 40% of between-centre variations in men and women, respectively.CONCLUSION:Hypertension prevalence greatly varies among French regions and this is partly explained by known lifestyle and socioeconomic factors. Nevertheless, these variations and all the hypertension determinants have not been fully deciphered yet