Rigorous System Design: The BIP Approach

Rigorous system design requires the use of a single powerful component framework allowing the representation of the designed system at different levels of detail, from application software to its implementation. This is essential for ensuring the overall coherency and correctness. The paper introduces a rigorous design flow based on the BIP (Behavior, Interaction, Priority) component framework. This design flow relies on several, tool-supported, source-to-source transformations allowing to progressively and correctly transform high level application software towards efficient implementations for specific platforms

Fracture toughness of Al replicated foam

Elastoplastic toughness testing of pure aluminium replicated foam is conducted following a J-procedure adapted from the ASTM E1820-08a standard using disc-shaped compact tension specimens. Tests cover a wide range of foam relative density V-m (10-24%). Resulting data show pronounced R-curve behaviour, computed J values increasing steadily beyond the crack blunting line before reaching a plateau, corresponding to a "steady-state" J value. Fractography reveals that the crack propagates via the rupture of struts normal to the crack plane, this being accompanied by limited plastic deformation of the struts near the crack plane, the extent of which, made visible by slip markings along the strut surface, increases in extent with V-m. Intact and fractured struts coexist over a significant portion of the crack plane, indicating that the strut rupture is stochastic. Measured crack initiation and steady-state propagation J values vary roughly as V-m(3); this is a stronger dependence than has been observed in commercial (closed-cell) metal foams. A simple model is proposed to describe the initiation toughness of these open-cell foams, which are characterized by a greater matrix ductility than other metal foams characterized in the literature. The model is based on an estimate of the crack tip opening displacement at the instant when a strut aligned in the loading direction fails by ductile rupture just ahead of the crack tip. The model accurately predicts the scaling law observed here between the toughness and the relative density of the foams, and provides a relatively good predictor of the absolute value of fracture toughness up to a relative density near 20%, while at higher densities measured toughness values exceed predictions. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

La géochimie organique des sédiments marins profonds, mission orgon 2, 1975 (Bassin de Cariaco et cône de l'Amazone)

Trois articles distincts traitent, le premier des généralités sur la mission ORLON, les deux autres des résultats obtenus à la mer dans les domaines de la microbiologie et de la biochimie des eaux. En microbiologie, une opposition existe entre le bassin de Cariaco d'une part, milieu anoxique riche en microflore et spécialement en bactéries sulfato-réductrices, et d'autre part la plaine du Demerara et le cône de l'Amazone, où les eaux ont des teneurs médiocres en microflore et les sédiments des teneurs si faibles qu'elles sont inférieures aux teneurs des eaux (phénomène qui n'existe jamais dans les milieux côtiers ou peu profonds). On met en évidence une relation directe entre teneurs en microflore et vitesse de sédimentation, qui permet d'avoir une vision cohérente des résultats obtenus tant à ORLON I qu'à ORLON 2. Dans le domaine de la biochimie des eaux, on a étudié outre l'eau sus-jacente au sédiment, les eaux interstitielles de 95 niveaux sédimentaires des carottes. L'utilisation d'un dispositif spécial de découpage des carottes prélevées à l'aide du carottier Reineck court a permis une étude fine des paramètres physiques (pH, Eh) et des constituants chimiques (O, dissous, S-- dissous, PO---, NH4 et alcalinité) des eaux interstitielles. L'influence des conditions régnant dans la Cariaco Trench sur la minéralisation de la matière organique a été étudiée au cours de l'enfouissement. Les mesures effectuées dans la mer du Demerara et sur le cône fossile de l'Amazone soulignent l'influence des conditions ambiantes et la pauvreté en matériel organique des régions océaniques profondes. Les dépôts côtiers de l'Amazone et du Para ont également été étudiés

Hole and notch sensitivity of aluminium replicated foam

The flow and failure behaviour of replicated pure aluminium foams in the presence of holes and notches is explored, varying the pore size and the notch depth or hole radius. Flat dog-bone tensile specimens containing a cylindrical hole, and cylindrical V-notched samples of 400 mu m and 75 mu m pore size microcellular aluminium were tested. Both pore size foams exhibit a notch strengthening effect, i.e. the peak failure stress increases as the depth of notches in cylindrical samples increases. In dog-bone samples, the presence of a hole ranging from 0 to 4 mm in diameter (in a sample 9 mm wide) does not affect the net section peak failure stress of the 75 mu m foam while the 400 mu m pore size foam exhibits a slight increase in net section failure stress as the hole diameter is increased to 2 mm. Plastic flow curves for notched and hole-containing samples are accurately predicted by a finite-element simulation based on the Deshpande-Fleck [Deshpande VS, Fleck NA. J Mech Phys Solids 2000;48:1253-83] flow law, showing that the observed trends in the data are predominantly mechanical in nature, and strongly linked to the presence of stress triaxiality at the centre of the notched samples. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved