On the Accuracy of Elastic Strain Field Measurements by Laue Microdiffraction and High-Resolution EBSD: a Cross-Validation Experiment

Determining the accuracy of elastic strain measurements in plastically deformed alloys is an experimental challenge. To develop a novel cross-validation procedure, a controlled elasto-plastic strain gradient was created in a stainless steel single crystal by four point bending deformation. The corresponding elastic strain field was probed, with an intragranular spatial resolution, in-situ by Laue microdiffraction and ex-situ by High Resolution EBSD. Good agreement is found for the two independent measurements and the predictions of a mechanical model, at plastic strains below 0.5 %. The accuracy of the measurements is estimated at 3.2 × 10 − 4

Couplage fluage-recristallisation dans les alliages de zirconium

L'objectif de cette thèse est de comprendre et de modéliser le comportement du Zircaloy-4 au cours du transport du combustible usé. Nous avons développé un modèle couplant la recristallisation, la restauration et le comportement mécanique. L'utilisation de la microscopie électronique a validé les observations préexistantes sur la recristallisation statique et a montré que l'application d'une contrainte influence la germination et la croissance des nouveaux grains. Le premier effet est décrit physiquement en ajoutant un terme de friction au modèle de recristallisation et le second est implicitement inclus dans le modèle couplé. Le fluage est modélisé par un modèle polycristallin pour prendre en compte l'effet de l'anisotropie de comportement du zirconium et les hétérogénéités de la microstructure. Le comportement local est décrit par un modèle à bases physiques ajoutant un potentiel prédictif au modèle antérieur.The thesis aim is to understand and to model the behavior of Zircaloy-4 during the transport of spent fuel. We developed a model coupling the recrystallisation, the recovery and the mechanical behavior. Electron microscopy confirmed the pre-existent observations on static recrystallisation and showed that the application of a stress influences both the nucleation and the growing of new grain during recrystallisation. The former effect is physically described by adding a term of friction to the recrystallisation model and the latter implicitly included in the coupled modeI. The creep is modelled by a polycristallin mode] to take into account the etTect of the anisotropic behavior of zirconium and microstructure heterogeneity. The local behavior is described by a physically based model which adds a predictive potential to the previous model.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Gestion des risques associés aux soins : état des lieux et perspectives

International audienceMany actions have been committed in the area of Risk management during the last years in France. The objective of this article is two-fold: descriptive, presenting an overview of the state of the development, and analytic.It appears that if the knowledge of the causes of the undesirable events is more precise, and the official rules have been reinforced, the safety regulation has to be improved and consolidated. Between the imperative for improving safety at the local level and the needs for a better accountability, this article advocates some new ways for consolidating this safety regulation.La gestion des risques associés aux soins a fait l’objet de nombreuses actions ces dernières années en France. L’objectif de cet article est double, descriptif, en réalisant une synthèse de ces démarches, et critique. Il s’avère que si la connaissance sur les causes de survenue des évènements indésirables est plus précise, et que le cadre législatif s’est renforcé dans de nombreux domaines, la régulation de la sécurité reste encore à consolider. De nombreuses actions sont désormais mises en œuvre sur le plan de la déclaration des évènements indésirables et du développement des outils d’analyse (revue de morbi-mortalité, check-list, notamment). Par contre, une question persiste sur l’équilibre à trouver entre les interventions demandées par les pouvoirs publics et l’auto-évaluation conduite par les professionnels. Entre le souci de proximité dans l’accompagnement des professionnels à des fins d’amélioration et la quête de transparence sur le sujet, cet article expose des pistes de ce que pourraient être les perspectives de cette régulation

Effect of an applied stress on the recrystallization mechanisms of a zirconium alloy

International audienceThe effect of an applied stress on the mechanism and kinetics of recrystallization of the zirconium alloy Zircaloy-4 is investigated by electron backscattered diffraction. Applying stress during the recrystallization slows down the growth stage. According to the stress amplitude, the nucleation rate is either accelerated or slowed down. A simple model is proposed to take into account these phenomena. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

L'Affaire du Congo, 1905. Préface de Ch.-A. [Charles-André] Julien / Jules Saintoyant

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3D reconstruction of a multiscale microstructure by anisotropic tessellation models

International audienceIn the area of tessellation models, there is an intense activity to fully understand the classical models of Voronoi, Laguerre and Johnson-Mehl. Still, these models are all simulations of isotropic growth and are therefore limited to very simple and partly convex cell shapes. The here considered microstructure of martensitic steel has a much more complex and highly non convex cell shape, requiring new tessellation models. This paper presents a new approach for anisotropic tessellation models that resolve to the well-studied cases of Laguerre and Johnson-Mehl for spherical germs. Much better reconstructions can be achieved with these models and thus more realistic microstructure simulations can be produced for materials widely used in industry like martensitic and bainitic steels