High performance thin-film optical filters with stress compensation

International audienceWe present a thorough description of high performance thin-film optical filters with high flatness. These components can combine several tens or hundreds of layers and are manufactured using plasma-assisted reactive magnetron sputtering. Stress compensation is achieved using dual side coatings with appropriate spectral function. Examples of highly reflecting mirrors at 515 nm with 15 nm flatness peak-to-valley over up to 75 mm diameter aperture, narrow bandpass filters and filters with broadband controlled transmission are described

Micromechanics Contribution to Coupled Transport and Mechanical Properties of Fractured Geomaterials

International audienceThis article is devoted to the modelling of interdependent mechanical and hydraulic behaviours of geomaterials in presence of a single through-wall fracture by means of micromechanics arguments. Experimental results of fractured concrete samples show non-linear evolutions for both mechanical and hydraulic behaviours with respect to confinement intensity. These non-linear responses are interpreted by the progressive closure of crack-like pores defining the pore volume of the fracture interfacial domain. Disregarding tortuosity effects, we adopt a 2D representation for these cracks. The key role of the fracture initial porosity is also emphasized. It allows to discuss the shape of the distribution of the local apertures distribution function classically used, intercepted here in terms of the distribution of initial crack–aspect ratio within the fracture domain. Application on fractured concrete samples shows the capability of the theoretical model to accurately reproduce the experimental results

Main Recent Contributions to SHS from France

International audienceBoth in situ TRXRD and IR thermography, on the one hand, and different levels of modeling, on the other, have generated a strong progress in the knowledge and control of numerous SHS reactions. The SHS of simple binary materials, such as intermetallics (FeAl, MoSi2, NbAl3, etc.), oxides (e.g. ZrO2), carbides (e.g. SiC) or nitrides, more complex materials, such as mullite, SiAlONs, MAX phases, composites (SiO2-Al2O3, NiAl-ZrO2 ), powders in their more complicated states, such as well controlled microstructures, fully densified intermetallics, smart composites, and hard coatings carried out by GFA researchers greatly contributed to the worldwide competition to harness the potential of SHS. On the occasion of the 40th anniversary of SHS, this paper is giving an overview of the main results obtained by GFA over the last ten years

La désinfection des trayons avant et après la traite : comment choisir les méthodes et les produits ?

National audienceLa désinfection des trayons constitue un élément essentiel de la prévention des mammites. Après la traite, elle a pour but de réduire la transmission des germes à réservoir mammaire, avant la traite, de limiter la contamination de la peau des trayons avant la pose des gobelets trayeurs. Les résultats obtenus sont meilleurs si la désinfection est effectuée avant et après la traite. Le mode de désinfection est à choisir en fonction de la situation sanitaire des vaches et des mamelles, de la saison et des infrastructures de l’élevage

Analyse micromécanique du couplage perméabilité-contrainte d'une argilite fracturée

International audienceA micromechanics-based analysis is developed throughout this paper in order to study stress loading/permeability couplings in cracked porous media. Fracture closure phenomena under macrocopic compressive stresses are addressed for a fracture modelled as an arrangement of parallel cracks. This first multiscale step emphasizes the key role of the cracks connectedness on the macroscopic permeability evolution with respect to the applied confining pressure.Cette étude présente une analyse micromécanique du couplage contrainte-perméabilité dans les milieux poreux fissurés. On aborde en particulier la question de la refermeture d'une fracture, modélisée par un réseau de fissures parallèles, sous l'effet d'un chargement macroscopique en compression. Cette première approche multi-échelle met l'accent sur le rôle déterminant de la connexion des fissures dans la loi d'évolution de la perméabilité macroscopique en fonction du chargement appliqué

Quasi-isotropic Biot’s Tensor for Anisotropic Porous Rocks: Experiments and Micromechanical Modelling

International audienceSeveral experimental studies, carried out on anisotropic rocks, have evidenced that even though strains, due to isotropic loading and/or internal fluid pressure, are strongly anisotropic, the resulting Biot’s tensor is almost isotropic. Those results were found on two different rocks: a clay rock (France—Bure argillite) and a sandstone from the Vosges region (France). Such (a priori) surprising results led us to develop micromechanical modelling in which anisotropy comes either from an anisotropic solid matrix (and isotropic pore space) or from an anisotropic pore space (and isotropic solid matrix). The obtained results have shown that for both cases the Biot’s tensor is virtually isotropic or presents a very weak anisotropy. This unambiguously supports the fact that a strongly anisotropic porous material is compatible with experimental measurements of isotropic (or quasi isotropic) Biot’s tenso

Tortuosity Effects in Coupled Advective Transport and Mechanical Properties of Fractured Geomaterials

International audienceThis article is concerned with tortuosity effects in coupled transport and mechanical properties of fractured geomaterials. Experimental results on confined fractured argillite samples are presented in terms of (1) progressive fracture reclosure and (2) fracture in plane permeability evolution, both depending upon confinement intensity. The observed non-linear mechanical response (fracture reclosure law) is physically interpreted as the progressive reclosure of local pores. The weak correlation between mechanical and hydraulic measurements is attributed to tortuosity effects which enhance the initial decrease of the permeability. The classical Self-Consistent scheme is herewith developed to qualitatively and quantitatively give theoretical basis likely to account for these tortuosity effects on permeability evolution

Influence of structural parameters on magnetoresistive properties of CuFeNi melt spun ribbons

International audienc

High performance thin-film optical filters with stress compensation

International audienceWe present a thorough description of high performance thin-film optical filters with high flatness. These components can combine several tens or hundreds of layers and are manufactured using plasma-assisted reactive magnetron sputtering. Stress compensation is achieved using dual side coatings with appropriate spectral function. Examples of highly reflecting mirrors at 515 nm with 15 nm flatness peak-to-valley over up to 75 mm diameter aperture, narrow bandpass filters and filters with broadband controlled transmission are described

Influence of magnetic interactions on magnetic and magnetoresistive properties of Cu 80 Fe 10 Ni 10 ribbons

International audienc