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Papers by Monique Gaspérini

Research paper thumbnail of Comparison of 3D vs. 1D diffusion trapping modelling

Research paper thumbnail of Failure Mechanisms of an AISI 4135 Steel Submitted to the Disk Pressure Test under Helium and Hydrogen Gas

Key Engineering Materials, 2013

The present work focuses on the experimental multi-scale characterization of fracture of an AISI ... more The present work focuses on the experimental multi-scale characterization of fracture of an AISI 4135 steel by using the Disk Pressure Test (DPT). In order to precise the specific features of hydrogen embrittlement, comparison was made between disks burst under helium and hydrogen gas. SEM - EBSD analysis of disks samples before and after the test allowed to analyze and to compare the main microstructural mechanisms of the failure process. The location of the main crack initiation was consistent with Finite Element (FE) simulations of the DPT.

Research paper thumbnail of A Numerical and Experimental Study of the Disk Pressure Test

Volume 6B: Materials and Fabrication, 2013

ABSTRACT The Disk Pressure Test is used to select metallic materials for hydrogen storage and tra... more ABSTRACT The Disk Pressure Test is used to select metallic materials for hydrogen storage and transportation and consists of a thin metallic disk bulged out until fracture by applying a gas pressure on its lower face. The ratio of the fracture pressures obtained with a neutral gas and with hydrogen gas defines a phenomenological index for material hydrogen sensitivity. In order to use the Disk Pressure Test for the selection of materials exposed at high pressure (50–70 MPa), a thorough study of this method has been carried out. Experimental investigations of damage mechanisms at different scales and finite element computations of the test have been carried out to exhibit the main features of hydrogen embrittlement in low alloy Fe-Cr-Mo tempered steels during the disk rupture test. Finite Element computations of the test permitted to predict the global response and to understand the effect of boundary conditions and of material behavior on stress gradients and plastic strain distribution throughout the disk. Using hydrogen sensitive cohesive elements to model the global crack path, good agreement with experiment was obtained on the effect of disk thickness and of hydrogen pressure rate on the failure pressure. The relative influence of loading conditions and material behavior on the hydrogen embrittlement during the disk rupture test are discussed.

Research paper thumbnail of Modeling hydrogen dragging by mobile dislocations in finite element simulations

International Journal of Hydrogen Energy, 2022

Research paper thumbnail of List of Authors

Mechanics - Microstructure - Corrosion Coupling

Research paper thumbnail of Numerical simulation of the transient hydrogen trapping process using an analytical approximation of the McNabb and Foster equation. Part 2: Domain of validity

International Journal of Hydrogen Energy, 2021

In a previous study [1], a resolution scheme called Generalized Oriani's Approximation (GOA) ... more In a previous study [1], a resolution scheme called Generalized Oriani's Approximation (GOA) was proposed to solve a transient transport and trapping problem in the Abaqus Finite Element software. This proposition was motivated by the convergence of the Finite Element problem linked to the estimation of several functions during the computation (and especially the dudt one). In this study, the GOA is shown to be able to provide an accurate estimation of the trapped concentration in transient trapping processes as soon as the time increment is small enough for two configurations: hydrogen in metals and water in polymers. An estimation of the induced error is given. The GOA approach is illustrated on a simple configuration with various trapping parameters. Last, the ability of Abaqus to converge while modeling a transient trapping and transport problem is analyzed considering several dudt: it is shown especially that its estimation based on the GOA allows the solver to efficiently ...

Research paper thumbnail of Modélisation par éléments finis d'essais de caractérisation de la sensibilité des tôles métalliques à l'hydrogène

Coupled models for diffusion-plasticity-fracture have been implemented in Abaqus FE code, thanks ... more Coupled models for diffusion-plasticity-fracture have been implemented in Abaqus FE code, thanks to user subroutines. Computations were performed for the disk pressure test, including comparison with experimental data, for the U-bend test and for a virtual multicrystal.. Mots clefs : hydrogene, elements finis, zone cohesives, diffusion, plasticite cristalline, procedures utilisateurs

Research paper thumbnail of Simulation numérique par éléments finis d'agrégats polycristallins soumis à des chargements thermomécaniques issus du soudage

Numerical simulations of polycrystalline aggregates were made for an austenitic stainless steel s... more Numerical simulations of polycrystalline aggregates were made for an austenitic stainless steel submitted to cyclic thermomecanical loading resulting from a multipass welding operation. The constitutive behavior is based on crystalline plasticity mechanisms for f.c.c. single crystal, with temperature dependent elastoplasticity. Numerical procedures were developed for boundary conditions transfer at local scale and for normal and tangential stress computation at grain boundaries. Such simulations allow to study the variation of stress distribution for different crystallographic or morphologic textures. Mots clefs: simulation elements finis, plasticite cristalline, thermomecanique, anisotropie

Research paper thumbnail of Local-scale Modeling of Plasticity–Environment Interactions

Mechanics - Microstructure - Corrosion Coupling, 2019

Abstract: In the previous chapters we have presented the diversity and the complexity of the mult... more Abstract: In the previous chapters we have presented the diversity and the complexity of the multiscale degradation mechanisms for mechanics-microstructure-environment coupling problems. The aim of this chapter is to provide a quantitative evaluation of the durability of materials and structures subjected to mechanical and environmental solicitations.

Research paper thumbnail of Effet des chargements thermiques sur le transport et le piégeage de l'hydrogène dans les matériaux métalliques

Research paper thumbnail of Multidimensionnal simulations of the diffusion and trapping of hydrogen in divertor including thermal expansion

Research paper thumbnail of Scale Transition in Finite Element Simulations of Hydrogen–Plasticity Interactions

Research paper thumbnail of Effet du trajet de chargement sur l'amorçage de fissures de corrosion sous contrainte dans les aciers inoxydables écrouis

Research paper thumbnail of Contribution des champs mécaniques à l'échelle du polycristal à l'amorçage de fissures de corrosion sous contrainte

Research paper thumbnail of Identification methodology of a rate-sensitive constitutive law with mean field and full field modeling approaches for polycrystalline materials

Comptes Rendus Mecanique, 2020

The present paper deals with the consideration of the rate-sensitivity mechanical behavior of met... more The present paper deals with the consideration of the rate-sensitivity mechanical behavior of metallic materials, in the framework of mean field and full field homogenization approaches. We re-examine the possibility of describing properly this rate sensitivity with a simple and widely used power law expressed at the level of the slip system, and we propose a methodology to accelerate the identification of the global material constitutive law for Finite Element (FE) simulations. For such an aim, simulations of a tensile test are conducted, using a simple homogenization model (the Taylor one, used in a relaxed constraint form) and an FE code (Abaqus), both using the same single-crystal rate-dependent constitutive law. It is shown that, provided that the identification of this law is performed with care and well adapted to the examined case (rate-sensitive or insensitive materials, static and/or dynamic ranges), the simple power law can be used to simulate the macroscopic behavior of ...

Research paper thumbnail of Adaptation of hydrogen transport models at the polycrystal scale and application to the U-bend test

Procedia Structural Integrity

Abstract Hydrogen transport and trapping equations are implemented in a FE software, using User S... more Abstract Hydrogen transport and trapping equations are implemented in a FE software, using User Subroutines, and the obtained tool is applied to get the diffusion fields in a metallic sheet submitted to a U-Bend test. Based on a submodelling process, mechanical and diffusion fields have been computed at the polycrystal scale, from which statistical evaluation of the risk of failure of the sample has been estimated.

Research paper thumbnail of Mechanical bonding properties and interfacial morphologies of austenitic stainless steel clad plates

Materials Science and Engineering: A

Abstract The current paper focuses on the correlation between microstructure and mechanical prope... more Abstract The current paper focuses on the correlation between microstructure and mechanical properties in low-carbon steel/austenitic stainless steel clad composite fabricated by hot-roll bonding. For this reason, the morphology and interfacial characteristics, tensile properties shear strength and fracture toughness of the cladded material were evaluated. From the main results, it was found that carbon element diffusion caused the forming of a decarburized ferrite zone (DFZ) of the parent metal and a carburized austenite zone (CAZ) of the clad layer, and between these two area, a thin diffusion layer with rapid element component change are formed in the hot-roll cladding process. Stress-strain curves obtained from tensile testing of parent metal and clad layer can predict the bi-material tensile behavior. The shear test proved that the stainless steel clad plate presents an acceptable shear bond strength at the interface joint. Impact test toughness results confirm that fracture took place only in the parent metal side of cladded specimens; the clad layer was bent but without obvious fracture. Fractography was carried out using scanning electron microscope in the tensile, shear bond test specimens and Charpy impact ones. It reveals the presence of predominantly dimpled fracture. Charpy impact specimens of the interface failed in mixed mode while impact specimens of the base plate failed in ductile mode.

Research paper thumbnail of FE simulation of the influence of plastic strain on hydrogen distribution during an U-bend test

International Journal of Mechanical Sciences

Abstract During an U-bend test, used for the macroscopic characterization of hydrogen embrittleme... more Abstract During an U-bend test, used for the macroscopic characterization of hydrogen embrittlement of thin sheets, a flat metallic strip is first given an U-shape and then submitted to hydrogen cathodic charging. Finite element simulations of this test have been performed for iron, based on the hydrogen transport equation accounting for diffusion and trapping. Focus is made on the influence of the geometric parameters of the forming process on the mechanical fields and hydrogen repartition in the sample. The results exhibit the variations of the total amount of hydrogen in the sample during the transient and steady-state stages. This parametric study is expected to be useful for the experimental choice of relevant test geometric parameters.

Research paper thumbnail of Effect of loading mode on blistering in iron submitted to plastic prestrain before hydrogen cathodic charging

International Journal of Hydrogen Energy

Tensile tests and simple shear tests have been performed on Armco iron sheets before hydrogen cat... more Tensile tests and simple shear tests have been performed on Armco iron sheets before hydrogen cathodic charging, in order to study the effect of loading mode on blistering of plastically prestrained samples. The experimental results from surfometry and image analysis show the decrease of the blisters size with prestrain increase, and quantitative differences between tensile or shear prestrain are exhibited. Phenomenological modeling of blister initiation is proposed, based on void expansion increase under internal pressure, and considering both plastic strain and pores as traps during hydrogen transport. Finite element simulations of material expansion due to hydrogen induced void growth lead to qualitative agreement with experimental tendencies.

Research paper thumbnail of Simulation numérique de la fissuration assistée par l'hydrogène de «l'essai de disque»

Matériaux & …, 2011

Page 1. Matériaux & Techniques 99, 141–144 (2011) c EDP Sciences, 2011 DOI: 10.1051/mattech/2... more Page 1. Matériaux & Techniques 99, 141–144 (2011) c EDP Sciences, 2011 DOI: 10.1051/mattech/2011041 www.mattech-journal.org Matériaux & Techniques Simulation numérique de la fissuration assistée par l'hydrogène de « l'essai de disque » ...

Research paper thumbnail of Comparison of 3D vs. 1D diffusion trapping modelling

Research paper thumbnail of Failure Mechanisms of an AISI 4135 Steel Submitted to the Disk Pressure Test under Helium and Hydrogen Gas

Key Engineering Materials, 2013

The present work focuses on the experimental multi-scale characterization of fracture of an AISI ... more The present work focuses on the experimental multi-scale characterization of fracture of an AISI 4135 steel by using the Disk Pressure Test (DPT). In order to precise the specific features of hydrogen embrittlement, comparison was made between disks burst under helium and hydrogen gas. SEM - EBSD analysis of disks samples before and after the test allowed to analyze and to compare the main microstructural mechanisms of the failure process. The location of the main crack initiation was consistent with Finite Element (FE) simulations of the DPT.

Research paper thumbnail of A Numerical and Experimental Study of the Disk Pressure Test

Volume 6B: Materials and Fabrication, 2013

ABSTRACT The Disk Pressure Test is used to select metallic materials for hydrogen storage and tra... more ABSTRACT The Disk Pressure Test is used to select metallic materials for hydrogen storage and transportation and consists of a thin metallic disk bulged out until fracture by applying a gas pressure on its lower face. The ratio of the fracture pressures obtained with a neutral gas and with hydrogen gas defines a phenomenological index for material hydrogen sensitivity. In order to use the Disk Pressure Test for the selection of materials exposed at high pressure (50–70 MPa), a thorough study of this method has been carried out. Experimental investigations of damage mechanisms at different scales and finite element computations of the test have been carried out to exhibit the main features of hydrogen embrittlement in low alloy Fe-Cr-Mo tempered steels during the disk rupture test. Finite Element computations of the test permitted to predict the global response and to understand the effect of boundary conditions and of material behavior on stress gradients and plastic strain distribution throughout the disk. Using hydrogen sensitive cohesive elements to model the global crack path, good agreement with experiment was obtained on the effect of disk thickness and of hydrogen pressure rate on the failure pressure. The relative influence of loading conditions and material behavior on the hydrogen embrittlement during the disk rupture test are discussed.

Research paper thumbnail of Modeling hydrogen dragging by mobile dislocations in finite element simulations

International Journal of Hydrogen Energy, 2022

Research paper thumbnail of List of Authors

Mechanics - Microstructure - Corrosion Coupling

Research paper thumbnail of Numerical simulation of the transient hydrogen trapping process using an analytical approximation of the McNabb and Foster equation. Part 2: Domain of validity

International Journal of Hydrogen Energy, 2021

In a previous study [1], a resolution scheme called Generalized Oriani's Approximation (GOA) ... more In a previous study [1], a resolution scheme called Generalized Oriani's Approximation (GOA) was proposed to solve a transient transport and trapping problem in the Abaqus Finite Element software. This proposition was motivated by the convergence of the Finite Element problem linked to the estimation of several functions during the computation (and especially the dudt one). In this study, the GOA is shown to be able to provide an accurate estimation of the trapped concentration in transient trapping processes as soon as the time increment is small enough for two configurations: hydrogen in metals and water in polymers. An estimation of the induced error is given. The GOA approach is illustrated on a simple configuration with various trapping parameters. Last, the ability of Abaqus to converge while modeling a transient trapping and transport problem is analyzed considering several dudt: it is shown especially that its estimation based on the GOA allows the solver to efficiently ...

Research paper thumbnail of Modélisation par éléments finis d'essais de caractérisation de la sensibilité des tôles métalliques à l'hydrogène

Coupled models for diffusion-plasticity-fracture have been implemented in Abaqus FE code, thanks ... more Coupled models for diffusion-plasticity-fracture have been implemented in Abaqus FE code, thanks to user subroutines. Computations were performed for the disk pressure test, including comparison with experimental data, for the U-bend test and for a virtual multicrystal.. Mots clefs : hydrogene, elements finis, zone cohesives, diffusion, plasticite cristalline, procedures utilisateurs

Research paper thumbnail of Simulation numérique par éléments finis d'agrégats polycristallins soumis à des chargements thermomécaniques issus du soudage

Numerical simulations of polycrystalline aggregates were made for an austenitic stainless steel s... more Numerical simulations of polycrystalline aggregates were made for an austenitic stainless steel submitted to cyclic thermomecanical loading resulting from a multipass welding operation. The constitutive behavior is based on crystalline plasticity mechanisms for f.c.c. single crystal, with temperature dependent elastoplasticity. Numerical procedures were developed for boundary conditions transfer at local scale and for normal and tangential stress computation at grain boundaries. Such simulations allow to study the variation of stress distribution for different crystallographic or morphologic textures. Mots clefs: simulation elements finis, plasticite cristalline, thermomecanique, anisotropie

Research paper thumbnail of Local-scale Modeling of Plasticity–Environment Interactions

Mechanics - Microstructure - Corrosion Coupling, 2019

Abstract: In the previous chapters we have presented the diversity and the complexity of the mult... more Abstract: In the previous chapters we have presented the diversity and the complexity of the multiscale degradation mechanisms for mechanics-microstructure-environment coupling problems. The aim of this chapter is to provide a quantitative evaluation of the durability of materials and structures subjected to mechanical and environmental solicitations.

Research paper thumbnail of Effet des chargements thermiques sur le transport et le piégeage de l'hydrogène dans les matériaux métalliques

Research paper thumbnail of Multidimensionnal simulations of the diffusion and trapping of hydrogen in divertor including thermal expansion

Research paper thumbnail of Scale Transition in Finite Element Simulations of Hydrogen–Plasticity Interactions

Research paper thumbnail of Effet du trajet de chargement sur l'amorçage de fissures de corrosion sous contrainte dans les aciers inoxydables écrouis

Research paper thumbnail of Contribution des champs mécaniques à l'échelle du polycristal à l'amorçage de fissures de corrosion sous contrainte

Research paper thumbnail of Identification methodology of a rate-sensitive constitutive law with mean field and full field modeling approaches for polycrystalline materials

Comptes Rendus Mecanique, 2020

The present paper deals with the consideration of the rate-sensitivity mechanical behavior of met... more The present paper deals with the consideration of the rate-sensitivity mechanical behavior of metallic materials, in the framework of mean field and full field homogenization approaches. We re-examine the possibility of describing properly this rate sensitivity with a simple and widely used power law expressed at the level of the slip system, and we propose a methodology to accelerate the identification of the global material constitutive law for Finite Element (FE) simulations. For such an aim, simulations of a tensile test are conducted, using a simple homogenization model (the Taylor one, used in a relaxed constraint form) and an FE code (Abaqus), both using the same single-crystal rate-dependent constitutive law. It is shown that, provided that the identification of this law is performed with care and well adapted to the examined case (rate-sensitive or insensitive materials, static and/or dynamic ranges), the simple power law can be used to simulate the macroscopic behavior of ...

Research paper thumbnail of Adaptation of hydrogen transport models at the polycrystal scale and application to the U-bend test

Procedia Structural Integrity

Abstract Hydrogen transport and trapping equations are implemented in a FE software, using User S... more Abstract Hydrogen transport and trapping equations are implemented in a FE software, using User Subroutines, and the obtained tool is applied to get the diffusion fields in a metallic sheet submitted to a U-Bend test. Based on a submodelling process, mechanical and diffusion fields have been computed at the polycrystal scale, from which statistical evaluation of the risk of failure of the sample has been estimated.

Research paper thumbnail of Mechanical bonding properties and interfacial morphologies of austenitic stainless steel clad plates

Materials Science and Engineering: A

Abstract The current paper focuses on the correlation between microstructure and mechanical prope... more Abstract The current paper focuses on the correlation between microstructure and mechanical properties in low-carbon steel/austenitic stainless steel clad composite fabricated by hot-roll bonding. For this reason, the morphology and interfacial characteristics, tensile properties shear strength and fracture toughness of the cladded material were evaluated. From the main results, it was found that carbon element diffusion caused the forming of a decarburized ferrite zone (DFZ) of the parent metal and a carburized austenite zone (CAZ) of the clad layer, and between these two area, a thin diffusion layer with rapid element component change are formed in the hot-roll cladding process. Stress-strain curves obtained from tensile testing of parent metal and clad layer can predict the bi-material tensile behavior. The shear test proved that the stainless steel clad plate presents an acceptable shear bond strength at the interface joint. Impact test toughness results confirm that fracture took place only in the parent metal side of cladded specimens; the clad layer was bent but without obvious fracture. Fractography was carried out using scanning electron microscope in the tensile, shear bond test specimens and Charpy impact ones. It reveals the presence of predominantly dimpled fracture. Charpy impact specimens of the interface failed in mixed mode while impact specimens of the base plate failed in ductile mode.

Research paper thumbnail of FE simulation of the influence of plastic strain on hydrogen distribution during an U-bend test

International Journal of Mechanical Sciences

Abstract During an U-bend test, used for the macroscopic characterization of hydrogen embrittleme... more Abstract During an U-bend test, used for the macroscopic characterization of hydrogen embrittlement of thin sheets, a flat metallic strip is first given an U-shape and then submitted to hydrogen cathodic charging. Finite element simulations of this test have been performed for iron, based on the hydrogen transport equation accounting for diffusion and trapping. Focus is made on the influence of the geometric parameters of the forming process on the mechanical fields and hydrogen repartition in the sample. The results exhibit the variations of the total amount of hydrogen in the sample during the transient and steady-state stages. This parametric study is expected to be useful for the experimental choice of relevant test geometric parameters.

Research paper thumbnail of Effect of loading mode on blistering in iron submitted to plastic prestrain before hydrogen cathodic charging

International Journal of Hydrogen Energy

Tensile tests and simple shear tests have been performed on Armco iron sheets before hydrogen cat... more Tensile tests and simple shear tests have been performed on Armco iron sheets before hydrogen cathodic charging, in order to study the effect of loading mode on blistering of plastically prestrained samples. The experimental results from surfometry and image analysis show the decrease of the blisters size with prestrain increase, and quantitative differences between tensile or shear prestrain are exhibited. Phenomenological modeling of blister initiation is proposed, based on void expansion increase under internal pressure, and considering both plastic strain and pores as traps during hydrogen transport. Finite element simulations of material expansion due to hydrogen induced void growth lead to qualitative agreement with experimental tendencies.

Research paper thumbnail of Simulation numérique de la fissuration assistée par l'hydrogène de «l'essai de disque»

Matériaux & …, 2011

Page 1. Matériaux & Techniques 99, 141–144 (2011) c EDP Sciences, 2011 DOI: 10.1051/mattech/2... more Page 1. Matériaux & Techniques 99, 141–144 (2011) c EDP Sciences, 2011 DOI: 10.1051/mattech/2011041 www.mattech-journal.org Matériaux & Techniques Simulation numérique de la fissuration assistée par l'hydrogène de « l'essai de disque » ...