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5 results on '"Larreur, A"'

1. Three-dimensional numerical simulation of the nitriding process

Author

P. Duranton, Roland Fortunier, Jean-Michel Bergheau, J. Devaux, and M. Larreur

Subjects
Computer simulation, Precipitation (chemistry), Chemistry, Alloy steel, General Physics and Astronomy, Mineralogy, Mechanics, Nitride, engineering.material, Finite element method, chemistry.chemical_compound, Residual stress, engineering, Chromium nitride, Nitriding
Abstract

This paper presents a three-dimensional numerical simulation of a nitriding process applied to an industrial component. The aim of the simulation is to predict the residual stresses and distortions due to volume changes induced by chromium nitride (CrN) and carbides (M23C6 et M4C3) formation. The simulation is performed in two steps. The diffusion of nitrogen and the precipitation of chrome nitride and carbides are first simulated. Then stresses and strains are calculated, assuming an elastic behaviour of the component, and using a volume expansion due to the precipitate concentration. The proposed approach is applied on a gear tooth. Small holes and details were neglected. For symmetry reasons, only half a tooth is taken into account. As the main phenomena take place through the first millimetre from the outer surface, a special attention was paid on meshing. The mesh used for the diffusion and precipitation analysis is composed of 1 130 000 nodes and 1 110 000 elements. For the mechanical analysis, a coarser mesh including only 165 000 nodes and 290 000 elements was used.

Published
2004
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3. Physico-chemical interactions at the concrete-bitumen interface of nuclear waste repositories.

Author

Bertron, A., Ranaivomanana, H., Jacquemet, N., Erable, B., Sablayrolles, C., Escadeillas, G., and Albrecht, A.

Subjects
NITRATES, ORGANIC acids, INTERFACES (Physical sciences), BITUMEN, CONCRETE, STEEL, RADIOACTIVE waste repositories, LEACHING
Abstract

This study investigates the fate of nitrate and organic acids at the bitumen- concrete-steel interface within a repository storage cell for long-lived, intermediate- level, radioactive wastes. The interface was simulated by a multiphase system in which cementitious matrices (CEM V-paste specimens) were exposed to bitumen model leachates consisting of nitrates and acetic acid with and without oxalic acid, chemical compounds likely to be released by bitumen. Leaching experiments were conducted with daily renewal of the solutions in order to accelerate reactions. C-steel chips, simulating the presence of steel in the repository, were added in the systems for some experiments. The concentrations of anions (acetate, oxalate, nitrate, and nitrite) and cations (calcium, potassium, ammonium) and the pH were monitored over time. Mineralogical changes of the cementitious matrices were analysed by XRD. The results confirmed the stability of nitrates in the absence of steel, whereas, reduction of nitrates was observed in the presence of steel (production of NH4+). The action of acetic acid on the cementitious matrix was similar to that of ordinary leaching; no specific interaction was detected between acetate and cementitious cations. The reaction of oxalic acid with the cementitious phases led to the precipitation of calcium oxalate salts in the outer layer of the matrix. The concentration of oxalate was reduced by 65% inside the leaching medium. [ABSTRACT FROM AUTHOR]

Published
2013
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4. Biodeterioration of cementitious materials in biogas digester.

Author

Voegel, C., Bertron, A., and Erable, B.

Subjects
BIODEGRADATION, CEMENT composites, COMPOSITE materials research, BIOGAS, AUTOCLAVES
Abstract

Copyright of Matériaux et Techniques is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2015
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5. Catalyse biotique et abiotique de la réduction des nitrates en milieu alcalin dans le contexte du stockage profond des dechets radioactifs.

Author

Bertron, A., Erable, B., Alquier, M., Jacquemet, N., Kassim, C., Sablayrolles, C., Albasi, C., Basseguy, R., Strehaiano, P., Vignoles, M., Albrecht, A., and Escadeillas, G.

Subjects
CATALYSIS, DENITRIFICATION, ALKALINE solutions, RADIOACTIVE waste disposal, REACTIVITY (Chemistry), PHOTOVOLTAIC cells
Abstract

Copyright of Matériaux et Techniques is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2013
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