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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.


Kemdehoundja M.,CNRS Study of Materials in Aggressive Environments Laboratory | Grosseau-Poussard J.L.,CNRS Study of Materials in Aggressive Environments Laboratory | Dinhut J.F.,CNRS Study of Materials in Aggressive Environments Laboratory
Applied Surface Science | Year: 2010

Raman spectroscopy has been used to characterise the buckling phenomenon of Cr2O3 films obtained by oxidation in air at 900 °C of Ni33 at%Cr. The observed circular blisters are described by measuring the radius from the optical top view, the profile via an autofocus device and the residual stress in each point of the chromia film: far away from the centre of the blister, in the vicinity and across the blister. The subsequent spalls are related to the morphology of the blisters and to the stress. © 2009 Elsevier B.V. All rights reserved.


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.


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.


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.


Bouhattate J.,CNRS Study of Materials in Aggressive Environments Laboratory | Legrand E.,CNRS Study of Materials in Aggressive Environments Laboratory | Feaugas X.,CNRS Study of Materials in Aggressive Environments Laboratory
International Journal of Hydrogen Energy | Year: 2011

Electrochemical permeation tests enable the experimental determination of the diffusion coefficient of a metal. To get a better understanding and a correction of experimental measures, we investigated the effects of hydrogen trapping on the diffusion of hydrogen through a metallic membrane by simulating a FEM model. The trap binding energy ΔET ranges from -0.1 to -0.32 eV, the density of traps ranges between 10-4 and 100 mol/m 3, and the thickness of the membrane fluctuates from 100 μm to 1 mm. It appears that the effective diffusion coefficient extracted from desorption flux data of a single membrane is not influenced by its geometry and depends on both the density of trapped hydrogen and the trap binding energy such as the apparent diffusion coefficient implemented in the code. Thus we do not detect any scale effect. In the other hand, the effective subsurface concentration evaluation using usually Fick's laws doesn't correspond directly to hydrogen concentration in the membrane. Analytical equations to solve the problem to extract erroneous data (diffusion coefficient and hydrogen concentration) to the experimental measurements of the flux vs time curves have been proposed. © 2011, Hydrogen Energy Publications, LLC. Published by 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.


Reffass M.,CNRS Study of Materials in Aggressive Environments Laboratory | Berziou C.,CNRS Study of Materials in Aggressive Environments Laboratory | Rebere C.,CNRS Study of Materials in Aggressive Environments Laboratory | Billard A.,University of Technology of Belfort - Montbéliard | Creus J.,CNRS Study of Materials in Aggressive Environments Laboratory
Corrosion Science | Year: 2010

Al-Mn coatings with different contents (0-41. at.%) were deposited on glass slides by magnetron co-sputtering. These coatings were characterised, before and after immersion tests, by X-ray diffraction, scanning electron microscopy (SEM) and electron probe microanalysis. The electrochemical measurements in a neutral saline solution showed that the pitting corrosion resistance of Al-Mn coatings increased with increasing Mn content as the pitting corrosion potentials are progressively shifted towards positive values. The immersion tests reveal that for all Mn contents, Al-Mn coatings keep a sacrificial character compared with steel. For Mn content above 26. at.%, XRD analysis showed the formation of an amorphous phase. This structure would be responsible for the high increase of the hardness of Al-Mn coatings and of the stabilisation of their open circuit potentials during the 48. h immersion tests. © 2010 Elsevier Ltd.


Jeannin M.,CNRS Study of Materials in Aggressive Environments Laboratory | Calonnec D.,CNRS Study of Materials in Aggressive Environments Laboratory | Sabot R.,CNRS Study of Materials in Aggressive Environments Laboratory | Refait Ph.,CNRS Study of Materials in Aggressive Environments Laboratory
Corrosion Science | Year: 2010

The role of different minerals (silica, kaolinite, chlorite and montmorillonite) in the corrosion processes of steel in 0.5 mol L-1 NaCl solutions was investigated. About 200-500 μm thick layers of minerals were deposited by sedimentation. Cyclic voltammetry indicated that the deposits favoured a general corrosion process, except montmorillonite that induced a pitting process, explained by the partial dissolution of the particles and their interaction with the steel surface. μ-Raman analyses of the corrosion products found at the steel/deposit interface after 2.5 and 20 h of polarization showed that interactions between minerals and dissolved Fe species could influence rust formation. © 2010 Elsevier Ltd. All rights reserved.


Jeannin M.,CNRS Study of Materials in Aggressive Environments Laboratory | Calonnec D.,CNRS Study of Materials in Aggressive Environments Laboratory | Sabot R.,CNRS Study of Materials in Aggressive Environments Laboratory | Refait P.,CNRS Study of Materials in Aggressive Environments Laboratory
Electrochimica Acta | Year: 2011

The role of clays in the corrosion processes of carbon steel was investigated. Four different minerals, silica, kaolinite, chlorite and montmorillonite, were considered. They were deposited by sedimentation on carbon steel electrodes. The electrochemical behaviour of steel electrodes covered with mineral deposits was studied in 0.1 mol L-1 NaHCO3 solutions by cyclic voltammetry (4 cycles between -0.8 V/SCE and -0.1 V/SCE) and compared to that of a bare electrode. Potentiostatic experiments were performed at -0.62 V/SCE, close to the corrosion potential, and the interfacial processes were investigated by electrochemical impedance spectroscopy. Analysis of the corrosion products accumulated at the inner side of the deposited mineral layer was performed by μ-Raman spectroscopy. As it could be expected, the deposits hindered the transport of dissolved oxygen and Fe(II) species, inducing changes in the interfacial solution and modification of the composition of the rust layer. Moreover, specific interactions between minerals and dissolved Fe species also influenced the corrosion processes. © 2010 Elsevier Ltd. All rights reserved.

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