1,720,983 research outputs found
Design and manufacture of an oven for high temperature experiments of erosion-corrosion of SiCf/SiC into LiPb
No full textSiC composites are studied as structural and functional materials in the designs of DEMO liquid blankets and their applications are foreseen also for the test blanket modules of ITER. Among the chemical-physical characteristics to be studied, the assessment of the erosion and corrosion of the SiC composites in liquid blanket (lithium-lead) is of main importance in order to verify the stability of these materials under the operating conditions typical of fusion power reactors. In the framework of the Broader Approach research activities, an experiment with a relative velocity between the SiC composite specimen and the lithium-lead of 0.1-0.5 m s-1 at temperature of 1000 C has been planned. The experimental setup mainly consists of a high temperature oven wherein the SiC specimen is rotating into a lithium-lead bath. The experimental plan foresees the chemical analysis of the lithium-lead before and after exposure and the post exposure examination of the SiC composite samples in order to study the behavior of both fibers and interphase. The design of the experimental device has considered the compatibility of the materials used at high temperature: in this view, a preliminary test campaign has been carried out at ENEA laboratories on SiCf-SiC samples obtained via chemical vapor infiltration (CVI) of Tyranno SA fibers. In this paper, the results of the preliminary tests and the design of the experimental apparatus are described in details as well as the status of its construction. © 2013 Elsevier B.V
Comparison between FEM and high heat flux thermal fatigue testing results of ITER divertor plasma facing mock-ups
No full textThe divertor is one of the most challenging components of "DEMO" the next step ITER machine, so many tasks regarding modeling and experiments have been made in the past years to assess manufacturing processes, materials and thus the life-time of the components. In this context the finite element analysis (FEA) allows designers to explore multiple design options, to reduce physical prototypes and to optimize design performance. The comparison between the hydraulic thermal-mechanical analysis performed by ANSYS WORKBENCH 14.5 and the test results [1] on small-scale mock-ups manufactured with the Hot Radial Pressing (HRP) [2] technology is presented in this paper. During the thermal fatigue testing in the Efremov TSEFEY facility to assess the heat flux load-carrying capability of the mock-ups, only the surface temperature was measured, so the FEA was important because it allowed to know any other information (temperature inside the materials, local water temperature, local stress, etc.). FEA was performed coupling the thermal-hydraulic analysis, that calculated the temperature distributions on the components and the heat transfer coefficient (HTC) between water and heat sink tube, with the mechanical analysis. The comparison between analysis and testing results was based on the temperature maps of the loaded surface and on number of the cycles supported during the testing and those predicted by the mechanical analysis using the experimental fatigue curves for CuCrZr-IG, that is the structural material in the component. Also the behavior for Cu-OFHC interlayer material based on the experimental fatigue curves was considered and the ultimate tensile strength for W, because their failure affects the heat removal capability of the component. The good correlation found between FEA results and testing campaign validated again the use of FEA itself for future design improved concepts. © 2014 EURATOM-ENEA Association
Assessment of an ITER-like water-cooled divertor for DEMO
No full textThis paper presents main outcomes of activities, performed in the frame of the EFDA task WP12-DAS-02-T02 and whose main objective was to investigate the feasibility and the range of applicability of a water-cooled divertor (WCD) based on technology developed for ITER to DEMO1. That includes the analysis of the power handling limits, the impact of the end-of-life irradiation fluence, as well as the assessment of available material properties. The considered divertor configuration is a water-cooled monoblock divertor which should be suitable for DEMO operation. For this purpose also Copper alloys, with their high thermal conductivities and relative high strengths, have to be considered when high heat flux handling is required but the aspect of n-irradiation cannot be neglected. All these aspects are assessed for two heat sink materials possible candidates: CuCrZr-IG, EUROFER. For these materials the psychical and mechanical properties were investigated considering their behaviour under n-irradiation and focusing the attention on the conceivable DEMO operational window with respect to temperatures and n-irradiation material properties degradation. The work is then concluded with thermo-mechanical studies of appropriate FE models to predict the heat flux performance capability and lifetime of a W mono-block with cooling pipes made of different Cu-alloys and EUROFER. © 2013 IEEE
Hydrogen permeation through Pd-Ag membranes: Surface effects and Sieverts' law
No full textMetal membranes mainly made of Pd alloys can be applied in membrane reformers for ultrapure hydrogen production from hydrocarbons and alcohols. Knowledge of the hydrogen mass transfer mechanisms through metals is very important to the purpose of properly designing and operating the membrane reactors. With the aim of understanding the deviations from the ideal behavior of the transport mechanisms predicted by the Sieverts' law, a permeation model which takes into account the surface effects has been applied to the permeability measurements that have been carried out on dense Pd-Ag permeator tubes from 473 to 623 K. The model has been validated by the results of permeation tests in a wide range of pressure (200-800 kPa) and membrane thickness (84-200 μm). The new model modifies the Sieverts' law by introducing the mass transfer resistances due to surface effects. The values of the surface resistance and permeability calculated by the model have been compared with the literature. Finally, the new hydrogen permeation expression has been applied in order to analyze the cost of a separation system which would consist of tubular Pd-based membranes. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved
Optimisation and characterisation of tungsten thick coatings on copper based alloy substrates
No full textMapping tooth mechanical properties by FIMEC tests
No full textDentin has different morphology near the enamel and in the inner part, resulting in mechanical properties progressive changing in correspondence of structure variation. In order to obtain a local mechanical characterization of dentin, FIMEC (Flat-top cylinder Indenter for mechanical characterization),1 an instrumented indentation technique, has been employed. FIMEC uses a cylindrical punch and permits local measurements of Young’s modulus E, yield stress Y, stress-relaxation and creep. The punch diameter (Φ = 0.5 mm) is much larger than the tubule size thus data are not so largely scattered as in micro- and nano-indentation tests but, at the same time, is small enough to guarantee a good resolution in mapping the mechanical properties in different tooth positions. More details about the FIMEC test and its application for measurements on human teeth can be found in Cappelloni et al. (2010)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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