I. Aubert - Academia.edu (original) (raw)

Papers by I. Aubert

Research paper thumbnail of Effects of hydrogen charging on surface slip band morphology of a type 316L stainless steel

Environment-Induced Cracking of Materials, 2008

Research paper thumbnail of Characterization of intergranular stress corrosion cracking behavior of a FSW Al-Cu-Li 2050 nugget

Mechanics & Industry, 2015

Cetteétude est dédiée au comportement en corrosion sous contrainte d'un alliage Al-Cu-Li 2050 sou... more Cetteétude est dédiée au comportement en corrosion sous contrainte d'un alliage Al-Cu-Li 2050 soudé par FSW et s'inscrit dans le cadre de l'allègement des structures aéronautiques. En service, les structures soudées peuventêtre soumiseà la foisà des contraintes mécaniques età un environnement agressif. L'objectif de cetteétude est de caractériser le comportement en corrosion sous contrainte (CSC) du noyau de soudure FSW de l'alliage 2050. Dans un premier temps, un lien estétabli entre les hétérogénéités de microstructure induites par le procédé de soudage et les champs mécaniques locaux se développant lors d'un essai de traction, puis, entre ces hétérogénéités et le développement de fissures de CSC-IG du noyau de soudure.

Research paper thumbnail of Modification of Plastic Strain Localization Induced by Hydrogen Absorption

Advances in Materials Sciences, 2008

Research paper thumbnail of Oxidation and Mechanical Behaviour of Iron Based Alloys and Nickel Based Alloy for Spring Like Interconnects of the PRODHYGE High Temperature Electrolyser

Defect and Diffusion Forum, 2011

In the field of the ANR-PROD'HYGE project an original coaxial architecture for a High Temperature... more In the field of the ANR-PROD'HYGE project an original coaxial architecture for a High Temperature Electrolyser (French Atomic Energy Commission Patented) is studied which makes use of low-cost spring-like interconnects to cope with thermal dilatation. Components and materials used for this application must ensure high long-term chemical and mechanical stability which are investigated here. Oxidation resistance of EN1.4509 and CroFer22APUI iron based alloy as well as Haynes 230 nickel based alloy is investigated with thermogravimetric analysis (TGA) in humid conditions, with or without mixing with hydrogen. Experiments reveal that oxidation kinetics is increased by 30% volume of hydrogen in moisture. Oxide layer composition and morphology are then investigated using Energy Dispersive Spectroscopy (EDS), and Auger Electron Spectroscopy (AES). Preliminary tensile tests are performed at room temperature showing embrittlement due to rough oxide layer, and CroFer22APU softening due to grain growth at elevated temperature.

Research paper thumbnail of Study of Iron-Based Alloys in Solid Oxide Fuel Cell Temperature and Atmosphere Conditions, Effect of a Silver-Coating

Solid State Phenomena, 2011

The French Atomic Energy Commission has developed a High Temperature Electrolyzer having an origi... more The French Atomic Energy Commission has developed a High Temperature Electrolyzer having an original coaxial architecture. Important elements are spring-like interconnects which allow to cope with thermal dilatation. Specifications of these components are low-cost, long term electrical conductivity achieved by chemical and mechanical stability. Potential candidates are ironbased alloys on which thin silver-coating may be deposited. In this paper we study the interaction of such systems with a mixture of hot vapour and hydrogen that is representative of the electrolyzer environment. Oxidation kinetic is measured by thermogravimetry. The oxide layer composition and morphology of tested samples are then investigated using Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES). These analyses demonstrate that hydrogen content strongly impacts the oxidation mechanism.

Research paper thumbnail of Intergranular stress corrosion cracking of friction stir welded nugget on a 2050-T8 aluminum alloy

Advances in Materials Sciences, 2011

Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum allo... more Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum alloy 2050-T8. The weld nugget consists of fine equiaxed grains having average sizes from 4 to 20 μm, the grain size increases with decreasing of the distance from the weld surface. The ...

Research paper thumbnail of Constrained and unstable expansion of dislocation loops using an invariant formulation of the free energy

Mechanics of Materials, 1997

The expression of the free energy related with the Eshelby-Kröner's inelastic inclusion ... more The expression of the free energy related with the Eshelby-Kröner's inelastic inclusion problem is simplified using the theory of irreductible representations. This formulation simplifies significantly problems requiring energy derivatives and particularly moving boundary problems. As a first application, the stability of a dislocation loop under applied stress is studied and a new interpretation of the critical shear stress in single crystal is obtained. The second application deals with the problem of grain size effect in polycrystalline plasticity: The yield stress σy follows a relation like σy ≈ d−n where n = 12 holds for low grain size (equivalent to the classical Hall Petch relation) while for large grain size n is equal to unity.

Research paper thumbnail of Mechanical behaviour of a solid with many stress corrosion growing cracks

Journal of Materials Science, 2005

ABSTRACT The theory of effective elastic properties of cracked solids is used to predict the degr... more ABSTRACT The theory of effective elastic properties of cracked solids is used to predict the degradation of mechanical properties of a stainless steel induced by stress corrosion growing cracks. The material is considered as an evolutionary composite with a cracked external volume (damaged elastic behaviour) and a safe internal volume (elastoplastic behaviour). From continuous surface observation of cracks by in situ videomicroscopy, the influence of interactions between multiple cracks is particularly studied. We show that coalescence of cracks can be neglected and that amplification and shielding effects counterbalance each other. This experimental study allows to choose the most suitable method to determine the effective elastic properties. Then, we propose a modelling to represent the overall mechanical behaviour of a solid with many surface cracks. Simulated and experimental slow strain rate curves are compared.

Research paper thumbnail of Simulation of hydrogen diffusion affected by stress-strain heterogeneity in polycrystalline stainless steel

International Journal of Hydrogen Energy, 2014

ABSTRACT The effect of microstructure-induced strain-stress heterogeneity on the evolution of hyd... more ABSTRACT The effect of microstructure-induced strain-stress heterogeneity on the evolution of hydrogen distribution was studied on 316 L stainless steel. A crystal plasticity-transient hydrogen diffusion finite element analysis was developed. To reach the stress-strain heterogeneity, synthetic microstructures were computed under uniaxial loading. The results show that hydrostatic stress gradients is the main cause of the hydrogen redistribution and the strain rate has a crucial effect on the redistribution degree. Statistical analysis of H-segregation reveals clustering of H-enriched zones at the mesoscopic scale.

Research paper thumbnail of Hydrogen effects on the plasticity of fcc nickel and austenitic alloys

Research paper thumbnail of Modelling of elastoplastic polycrystals and aspects of applications

Computational Materials Science, 1997

A micromechanical approach is developed to study the formation of induced dislocation cell struct... more A micromechanical approach is developed to study the formation of induced dislocation cell structure and the effects on the mechanical behavior of metals starting from the Helmholtz free energy and the dissipation of an elastoplastic solid containing moving surfaces of plastic strain discontinuity. The results are applied to an evolving two phase microstructure representing the dislocation cell structure induced by plastic straining. In this way, the internal variables are reduced to the plastic strain of each mechanical phase, the volume fraction and the morphology of the ellipsoidal inclusion describing the cell structure. We obtain the conjugate forces according to the formalism of irreversible thermodynamics.

Research paper thumbnail of Effects of hydrogen charging on surface slip band morphology of a type 316L stainless steel

Environment-Induced Cracking of Materials, 2008

Research paper thumbnail of Characterization of intergranular stress corrosion cracking behavior of a FSW Al-Cu-Li 2050 nugget

Mechanics & Industry, 2015

Cetteétude est dédiée au comportement en corrosion sous contrainte d'un alliage Al-Cu-Li 2050 sou... more Cetteétude est dédiée au comportement en corrosion sous contrainte d'un alliage Al-Cu-Li 2050 soudé par FSW et s'inscrit dans le cadre de l'allègement des structures aéronautiques. En service, les structures soudées peuventêtre soumiseà la foisà des contraintes mécaniques età un environnement agressif. L'objectif de cetteétude est de caractériser le comportement en corrosion sous contrainte (CSC) du noyau de soudure FSW de l'alliage 2050. Dans un premier temps, un lien estétabli entre les hétérogénéités de microstructure induites par le procédé de soudage et les champs mécaniques locaux se développant lors d'un essai de traction, puis, entre ces hétérogénéités et le développement de fissures de CSC-IG du noyau de soudure.

Research paper thumbnail of Modification of Plastic Strain Localization Induced by Hydrogen Absorption

Advances in Materials Sciences, 2008

Research paper thumbnail of Oxidation and Mechanical Behaviour of Iron Based Alloys and Nickel Based Alloy for Spring Like Interconnects of the PRODHYGE High Temperature Electrolyser

Defect and Diffusion Forum, 2011

In the field of the ANR-PROD'HYGE project an original coaxial architecture for a High Temperature... more In the field of the ANR-PROD'HYGE project an original coaxial architecture for a High Temperature Electrolyser (French Atomic Energy Commission Patented) is studied which makes use of low-cost spring-like interconnects to cope with thermal dilatation. Components and materials used for this application must ensure high long-term chemical and mechanical stability which are investigated here. Oxidation resistance of EN1.4509 and CroFer22APUI iron based alloy as well as Haynes 230 nickel based alloy is investigated with thermogravimetric analysis (TGA) in humid conditions, with or without mixing with hydrogen. Experiments reveal that oxidation kinetics is increased by 30% volume of hydrogen in moisture. Oxide layer composition and morphology are then investigated using Energy Dispersive Spectroscopy (EDS), and Auger Electron Spectroscopy (AES). Preliminary tensile tests are performed at room temperature showing embrittlement due to rough oxide layer, and CroFer22APU softening due to grain growth at elevated temperature.

Research paper thumbnail of Study of Iron-Based Alloys in Solid Oxide Fuel Cell Temperature and Atmosphere Conditions, Effect of a Silver-Coating

Solid State Phenomena, 2011

The French Atomic Energy Commission has developed a High Temperature Electrolyzer having an origi... more The French Atomic Energy Commission has developed a High Temperature Electrolyzer having an original coaxial architecture. Important elements are spring-like interconnects which allow to cope with thermal dilatation. Specifications of these components are low-cost, long term electrical conductivity achieved by chemical and mechanical stability. Potential candidates are ironbased alloys on which thin silver-coating may be deposited. In this paper we study the interaction of such systems with a mixture of hot vapour and hydrogen that is representative of the electrolyzer environment. Oxidation kinetic is measured by thermogravimetry. The oxide layer composition and morphology of tested samples are then investigated using Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES). These analyses demonstrate that hydrogen content strongly impacts the oxidation mechanism.

Research paper thumbnail of Intergranular stress corrosion cracking of friction stir welded nugget on a 2050-T8 aluminum alloy

Advances in Materials Sciences, 2011

Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum allo... more Intergranular corrosion sensitivity is studied for the friction stir weld nugget of aluminum alloy 2050-T8. The weld nugget consists of fine equiaxed grains having average sizes from 4 to 20 μm, the grain size increases with decreasing of the distance from the weld surface. The ...

Research paper thumbnail of Constrained and unstable expansion of dislocation loops using an invariant formulation of the free energy

Mechanics of Materials, 1997

The expression of the free energy related with the Eshelby-Kröner's inelastic inclusion ... more The expression of the free energy related with the Eshelby-Kröner's inelastic inclusion problem is simplified using the theory of irreductible representations. This formulation simplifies significantly problems requiring energy derivatives and particularly moving boundary problems. As a first application, the stability of a dislocation loop under applied stress is studied and a new interpretation of the critical shear stress in single crystal is obtained. The second application deals with the problem of grain size effect in polycrystalline plasticity: The yield stress σy follows a relation like σy ≈ d−n where n = 12 holds for low grain size (equivalent to the classical Hall Petch relation) while for large grain size n is equal to unity.

Research paper thumbnail of Mechanical behaviour of a solid with many stress corrosion growing cracks

Journal of Materials Science, 2005

ABSTRACT The theory of effective elastic properties of cracked solids is used to predict the degr... more ABSTRACT The theory of effective elastic properties of cracked solids is used to predict the degradation of mechanical properties of a stainless steel induced by stress corrosion growing cracks. The material is considered as an evolutionary composite with a cracked external volume (damaged elastic behaviour) and a safe internal volume (elastoplastic behaviour). From continuous surface observation of cracks by in situ videomicroscopy, the influence of interactions between multiple cracks is particularly studied. We show that coalescence of cracks can be neglected and that amplification and shielding effects counterbalance each other. This experimental study allows to choose the most suitable method to determine the effective elastic properties. Then, we propose a modelling to represent the overall mechanical behaviour of a solid with many surface cracks. Simulated and experimental slow strain rate curves are compared.

Research paper thumbnail of Simulation of hydrogen diffusion affected by stress-strain heterogeneity in polycrystalline stainless steel

International Journal of Hydrogen Energy, 2014

ABSTRACT The effect of microstructure-induced strain-stress heterogeneity on the evolution of hyd... more ABSTRACT The effect of microstructure-induced strain-stress heterogeneity on the evolution of hydrogen distribution was studied on 316 L stainless steel. A crystal plasticity-transient hydrogen diffusion finite element analysis was developed. To reach the stress-strain heterogeneity, synthetic microstructures were computed under uniaxial loading. The results show that hydrostatic stress gradients is the main cause of the hydrogen redistribution and the strain rate has a crucial effect on the redistribution degree. Statistical analysis of H-segregation reveals clustering of H-enriched zones at the mesoscopic scale.

Research paper thumbnail of Hydrogen effects on the plasticity of fcc nickel and austenitic alloys

Research paper thumbnail of Modelling of elastoplastic polycrystals and aspects of applications

Computational Materials Science, 1997

A micromechanical approach is developed to study the formation of induced dislocation cell struct... more A micromechanical approach is developed to study the formation of induced dislocation cell structure and the effects on the mechanical behavior of metals starting from the Helmholtz free energy and the dissipation of an elastoplastic solid containing moving surfaces of plastic strain discontinuity. The results are applied to an evolving two phase microstructure representing the dislocation cell structure induced by plastic straining. In this way, the internal variables are reduced to the plastic strain of each mechanical phase, the volume fraction and the morphology of the ellipsoidal inclusion describing the cell structure. We obtain the conjugate forces according to the formalism of irreversible thermodynamics.