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Bachir Bouiadjra B.,University Djilali Liabes | Bachir Bouiadjra B.,King Saud University | Achour T.,University Djilali Liabes | Berrahou M.,University Djilali Liabes | And 2 more authors.
Materials and Design | Year: 2010

In this study, the three-dimensional finite element method is used to analyse the advantages of the double symmetric composite repair compared to the single one in aircraft structures by analysing the mass again between the two techniques. This gain is defined as the ratio between the thickness of the double and single patches giving the same stress intensity factor (SIF) at the crack tip. The obtained results show that the mass gain resulting from the use of the double symmetric repair is important because of the double stress absorption. It also shown that, the adhesive properties must be optimised in order to improve the advantages of double symmetric composite repair. © 2010 Elsevier Ltd. All rights reserved.

Ho H.S.,CNRS Roberval Laboratory (Mechanical Research Unit) | Risbet M.,CNRS Roberval Laboratory (Mechanical Research Unit) | Feaugas X.,CNRS Study of Materials in Aggressive Environments Laboratory | Moulin G.,CNRS Roberval Laboratory (Mechanical Research Unit)
Scripta Materialia | Year: 2011

The strain localization of plastic deformation in slip bands may induce damage on the specimen surface, characterized by critical values of extrusion height and local irreversible plastic strain accumulated in the band. The functional dependency of the grain size on critical values of these parameters is investigated for nickel-based superalloys. It is confirmed that cracking occurs when certain conditions are fulfilled at the microscopic scale and that the critical value of local irreversible plastic strain accumulated in slip bands is independent of grain size. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Mechab B.,University Djilali Liabes | Serier B.,University Djilali Liabes | Bouiadjra B.B.,University Djilali Liabes | Bouiadjra B.B.,King Saud University | And 2 more authors.
International Journal of Pressure Vessels and Piping | Year: 2011

In this paper, the J integral was calculated for semi-elliptical surface cracks in pipes under bending using three-dimensional finite element analysis. The computations were performed for elastic and elastic-plastic behaviours. For the elastic case, the numerical results allowed the extrapolation of shape functions for analytical determination of the J integral. The results are in a good agreement with those in the literature if the ratio between the radius and the thickness of the pipe (R/t) is from 1 to 10. The analysis was extended to values of the ratio R/ t higher than 10. For the elastic-plastic, the numerical results are in good agreement with the analytical solution found in the literature for thick pipes (R/. t ≥ 10). The effect of the ratio R/t becomes sensible when the ratio of the applied moment to the moment of reference (M/Mo r) exceeds 0.9. © 2010 Elsevier Ltd.

Bourdoiseau J.-A.,CNRS Study of Materials in Aggressive Environments Laboratory | Bourdoiseau J.-A.,Andra Inc | Jeannin M.,CNRS Study of Materials in Aggressive Environments Laboratory | Remazeilles C.,CNRS Study of Materials in Aggressive Environments Laboratory | And 2 more authors.
Journal of Raman Spectroscopy | Year: 2011

In this study, Raman spectroscopy was used to precisely understand the mechanisms of oxidation of mackinawite (FeS). Two experimental conditions were considered: (1) oxidation in air at room temperature and (2) oxidation in acidic anoxic solutions at 80 °C. In both cases, the oxidation process began by the in situ oxidation of Fe(II) cations inside the crystal structure of mackinawite and led to Fe(III)-containing mackinawite, FeII 1-3xFeIII 2xS. The oxidation in air finally led to Fe(III) oxyhydroxides and elemental sulfur α-S8, but greigite (Fe3S4) was observed as an intermediate compound. In anoxic acidic solutions, the product of the oxidation was proved to depend on the Fe/S concentration ratio. For Fe/S = 3/4, greigite was the only product obtained, and this allowed us to determine unambiguously the Raman spectrum of this compound. © 2010 John Wiley & Sons, Ltd.

Azoulay I.,CNRS Study of Materials in Aggressive Environments Laboratory | Remazeilles C.,CNRS Study of Materials in Aggressive Environments Laboratory | Refait P.,CNRS Study of Materials in Aggressive Environments Laboratory
Corrosion Science | Year: 2012

Mixtures of Fe(OH) 2 and Fe 2(OH) 2CO 3 were obtained by precipitation from FeCl 2, NaOH and Na 2CO 3 solutions. These two-phase systems did not change with time and equilibrium conditions were supposed to be established after 6months. The standard Gibbs free energy of formation of chukanovite could then be estimated at -1171.5±3.0kJmol -1. In contrast, mixtures of FeCO 3 and Fe 2(OH) 2CO 3 could not been obtained by precipitation but siderite formed in some cases after 25months of ageing. Pourbaix diagrams of iron including chukanovite were drawn showing that the Fe(II) hydroxycarbonate was metastable, at 25°C, with respect to siderite. © 2012 Elsevier Ltd.

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