VICENTE MAURICIO PADRÓN [Material gráfico]

ÁLBUM FAMILIAR CASA DE COLÓNCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201

Technology developments of ELI-NP gamma beam system

The ELI-NP gamma beam system (GBS) is a linac based gamma-source in construction in Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy, from 0.2 to 19.5 MeV, and with intensity and brilliance beyond the state of the art, will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and an intense laser pulse at 100 Hz repetition rate. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation and laser recirculation at the interaction point. In this paper, the main technological developments carried out by the EuroGammaS consortium for the generation of the ELI-NP gamma beam will be described with a special emphasis on the electron linac technology, such as: RF-gun and C-band accelerating structures design fabrication and tests; low level RF (LLRF) and synchronization systems specifications and development. Finally, the laser recirculation apparatus design is briefly described and first results reported

Bubble assisted vacuum thermoforming: considerations to extend the use of in-situ stereo-DIC measurements to stretching of sagged thermoplastic sheets

International audienceIn bubble assisted vacuum thermoforming, measuring pressure-induced mechanical strains through the stereo-digital image correlation (stereo-DIC) technique while shaping thermoplastic sheet requires consideration of an appropriate reference state of surface deformations. However, when the stereoscopic measurements can be only performed after the heating step, the correlation problem should be well-posed otherwise the reliability of results is limited. This study focuses on stretching by bubble inflation processes following thermal warpage and sagging of initially flat sheets. For this purpose, an experimental rig is instrumented to heat high impact polystyrene (HIPS) sheets and to perform synchronized pressure and stereoscopic measurements during 1.5 s stretching. A two-step method is introduced to separate mechanical strains which are affected by the uncontrollable change of initial conditions from the global stereo-DIC strains. The first step relies on amplification of damped oscillations at the initiation of the inflation process due to sagging. Out-of-plane displacements confirm the existence of a temperature-dependent characteristic time that marks the transition from the sagged to the strained surface shapes. The second step uses these characteristic times to objectively shift the reference of image-correlation computations. To evaluate the effectiveness of the suggested method, inaccuracy levels of global strains are evaluated at a fixed pressure level under different thermal conditions. It is shown that inaccuracy levels are the highest when stereo-DIC measurements followed warpage and they decrease with amplification of sagging. The developed approach extends the use of in-situ stereo-DIC measurements when changes of initial conditions are uncontrollable and thermal strains cannot be measured

A comprehensive study of bubble inflation in vacuum-assisted thermoforming based on whole-field strain measurements

International audienceThis paper focuses on the potential use of stereo-DIC in thermoforming conditions to monitor large deformations of softened thermoplastic sheets posteriori to the sagging phenomenon. The study concerns HIPS sheets which are softened by the radiative heat-transfer mode then stretched by inflation of compressed-air for 1.5 s to form a large and quasi-spherical dome of 250 mm in diameter. While the bubble-inflation operation leads to large deformations of the softened sheet, it shows transitional geometrical instabilities due to the initial surface sagging. When the temperature-induced surface deformations are inaccessible by the stereoscopic system during the heating operation, the geometrical instabilities limit the identification of the reference of displacements which affects the accuracy of results based on image-correlation computations. To compare between the principal strains assessed from bubble-inflation tests conducted at different thermal conditions, a method for filtering these instabilities is developed in this study

Assessment of principal strain uncertainties in stereo-DIC due to uncontrollable change of initial boundary conditions during vacuum-assisted thermoforming

International audienceFull-field measurement of principal mechanical strains via the stereo-digital images correlation technique (stereo-DIC) during thermoforming of thin thermoplastic sheets was recently reported as a potential method to control the wall-thicknesses under the assumption of material’s incompressibility. The accuracy of mechanical strains during forming thermoplastic sheets are not only dependent of reconstruction and correlation errors of stereo-DIC, but also of the considered reference state of boundary conditions following the temperature-regulation of thermoplastic sheets. This paper introduces an experimental method based on high speed imaging techniques such as IR-thermography and stereo-DIC techniques to detect damped out-of-plane undulations which are associated with the initiation of dynamic inflation operations of thin sheets. The aim is to rely on the characteristic durations of these short-time events to objectively separate between mechanical strains which are affected by the uncontrollable change of boundary conditions from the global pressure-induced strains. An application case is presented to demonstrate that damped out-of-plane undulations are beneficial to avoid ill-posed stereo-DIC problems particularly when the boundary conditions are sensitive to regulation operations of temperature

Capteurs polymères : un potentiel en développement

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Capteurs polymères : un potentiel en développement

Le marché des capteurs, classiquement fondé sur l'usage de matériaux inorganiques, s'ouvre désormais de plus en plus largement à des systèmes utilisant des matériaux organiques comme éléments actifs. Cet essor est à mettre en relation avec la diversité chimique des matières plastiques et les nouvelles possibilités de détection associées à l'exploitation des propriétés spécifiques en résultant. Des recherches intensives sont ainsi menées afin de développer le potentiel important des matériaux polymères dans le secteur de la détection et de la mesure. Des exemples issus aussi bien de la recherche que des applications commerciales, et couvrant les principaux domaines d'utilisation sont présentés ici avec les différentes approches pouvant être mises à profit pour les mesures. Des applications très variées sont abordées telles que la détection de composés volatils (solvants, arômes, vapeur d'eau...), les électrodes ou encore les capteurs de force ou de température

Scalable production of multifunctional bio-based polyamide 11/graphene nanocomposites by melt extrusion processes via masterbatch approach

International audienceBio-based polyamide 11 (PA11)–graphene nanoplatelets (GNP) nanocomposites with different filler concentrations were prepared by melt extrusion using a masterbatch dilution process. Graphene platelets are uniformly distributed into the polymer matrix as revealed by scanning electron microscopy. The incorporation of graphene significantly improves the electrical conductivity and dielectric constant of PA11. GNPs favors the matrix crystallization; crystallization temperature and degree of crystallinity of the nanocomposites tend to increase with increase in graphene loading. Tensile properties (strength and modulus) are slightly improved by the incorporation of GNP into the PA11 matrix (up to +25% and +56%, respectively, for 5 wt% GNPs) at the expense of ductility (elongation at break divided by 5 for 5 wt% GNPs)

Weld-line sensitivity of injected amorphous polymers

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