Benoit Devincre - Academia.edu (original) (raw)

Uploads

Papers by Benoit Devincre

Research paper thumbnail of On the Origins of Tension--Compression Asymmetry in Crystals and Implications for Cyclic Behavior

Most of crystalline materials exhibit a hysteresis on their deformation curve when mechanically l... more Most of crystalline materials exhibit a hysteresis on their deformation curve when mechanically loaded in alternating directions. This Bauschinger effect is the signature of mechanisms existing at the atomic scale and controlling the materials damage and ultimately their failure. Here, three-dimensional simulations of dislocation dynamics and statistical analyses of the microstructure evolution reveal two original elementary mechanisms. An asymmetry in the dislocation network junctions arising from the stress driven curvatures and the partial reversibility of plastic avalanches give an explanation to the traction-compression asymmetry observed in FCC single-crystals. These mechanisms are then connected in a physically justified way to larger-scale representations using a dislocation density based theory. Parameter-free predictions of the Bauschinger effect and strain hardening during cyclic deformation in different materials and over a range of loading directions and different plast...

Research paper thumbnail of Multiscale Phenomena in Materials{Experiments and Modeling Chairs

In-situ transmission electron microscopy of thin lms systems provides an ideal experimental labor... more In-situ transmission electron microscopy of thin lms systems provides an ideal experimental laboratory for the study of dislocation motion and dislocation-defect interactions in materials. Through careful consideration of the sample geometry and calibration of the experimental conditions it is possible to obtain accurate quantitative information about dislocation velocities, interaction stresses and

Research paper thumbnail of Misfit dislocation gettering in epitaxial films deposited on pit-patterned Si (001) substrates by Dislocation Dynamics simulations

Research paper thumbnail of From Dislocation Junctions to the Three Stages Curve

The strain hardening matrix of fcc crystals can be obtained from crystallographic continuum model... more The strain hardening matrix of fcc crystals can be obtained from crystallographic continuum models deriving from the Kocks-Mecking framework. DD simulations were used to compute the coefficients of the interaction matrix between slip systems and to extend an existing model for stages II and III in order to also include stage I. Other parameters of the model are the mean-free path of the dislocations and their critical annihilation distance by cross-slip, which can be estimated from various sources. The resulting constitutive formulation is inserted into a numerical crystalline model using a FE code, which is used here to test single crystal behavior. As a result, parameter-free deformation curves can be obtained for fcc crystals, which depend in a known manner on the nature of the material, the orientation of the crystal and temperature. This is illustrated by a comparison between aluminum and copper crystals initially oriented for easy glide at room temperature. In this type of mod...

Research paper thumbnail of Dislocation Dynamics simulations in epitaxial Si-Ge nanostructures

Research paper thumbnail of Discrete dislocation dynamics

Nickel Base Single Crystals Across Length Scales

Research paper thumbnail of On the Origin of the Hall-Petch Law: A 3D-Dislocation Dynamics Simulation Investigation

SSRN Electronic Journal

3D -DD simulations are performed with cubic grains ranging from 1 to 10 μm to investigate the phy... more 3D -DD simulations are performed with cubic grains ranging from 1 to 10 μm to investigate the physical mechanisms at the origin of the Hall- Petch law. In particular, the long-range stress (back stress) induced by the density of polarized dislocations ( GNDs ) accumulated at GBs is quantified separately from the short-range stress associated with the forest dislocation ( SSDs ) density. We show that the back stress and the associated strain hardening is independent of grain size at low strain. Hence, the grain size effect reproduced by 3D-DD simulations is controlled by an increase of the CRSS when decreasing grain size. Such evolution of the CRSS amplitude is controlled by two competing strengthening mechanisms justifying the generic <i>1/√d</i> dependent form of the Hall- Petch law observed in simulations and experiments.

Research paper thumbnail of A Molecular Dynamics-Informed Probabilistic Cross-Slip Model in Discrete Dislocation Dynamics

SSRN Electronic Journal

We present here a quantitative study of dislocation cross-slip, an essential thermally activated ... more We present here a quantitative study of dislocation cross-slip, an essential thermally activated process in deformation of metals, in discrete dislocation dynamics (DDD) simulations. We implemented a stress-dependent line-tension model in DDD simulations, with minimal information from molecular dynamics (MD) simulations. This model allows reproducing in DDD simulations the probabilistic cross-slip rate calculated in MD simulations for Cu in a large range of stresses and temperatures. This model opens new horizons in modelling cross-slip related mechanisms such as deformation softening, dislocation-precipitate interaction and dislocation patterning in realistic strain rates.

Research paper thumbnail of Stress fields of finite-size dislocation walls and prediction of back stress induced by geometrically necessary dislocations at grain boundaries

Journal of the Mechanics and Physics of Solids

At low strain, geometrically necessary dislocations (GND) confined in the close vicinity of grain... more At low strain, geometrically necessary dislocations (GND) confined in the close vicinity of grain boundaries can be approximated as a dislocation wall structure called a GND facet. Analytical solutions derived from Field Dislocations Mechanics (FDM) theory allow calculating the stress components associated with the GND facets but are unable to account for the stress field variation induced by finite size effect. Dislocation dynamics simulation is used to investigate the true stress field of GND facets. The geometry, dimension and dislocation density of three generic types of GND facets (twist, tilt and epitaxial facets) are systematically studied. In all cases, the stress field generated by GND facets is proportional to the surface GND density and its spatial distribution can be recovered using FDM solution combined with two scaling parameters identified from DD simulation results. This calculation procedure can be generalized to any crystal structure by relating the components of the surface Nye's tensor to the solutions of simple cubic slip systems. Finally, static and dynamic tests are made to validate the calculation of back stress within regular grains bounded by GND facets.

Research paper thumbnail of Dislocation Intersections and Reactions in FCC and BCC Crystals

MRS Proceedings

The various types of configurations formed in face-centered cubic (fcc) and body-centered cubic (... more The various types of configurations formed in face-centered cubic (fcc) and body-centered cubic (bcc) structures by two interacting, non-coplanar, dislocation segments of various orientations are examined and discussed. The focus is on junction formation and on a particular interaction, the collinear interaction, which deserves much more attention than paid up to now.

Research paper thumbnail of New Line Model for Optimized Dislocation Dynamics Simulations

MRS Proceedings

A new model for the discretisation of dislocation lines is presented, which is optimised for meso... more A new model for the discretisation of dislocation lines is presented, which is optimised for mesoscale simulations of dislocation dynamics. By comparison with the existing edge-screw model, the present one provides a better description of the stress field close to the dislocation lines. It simplifies the modelling of dislocation reactions and accelerates computations by allowing to make use of larger time steps. An application to attractive junctions and forest hardening is briefly sketched.

Research paper thumbnail of Dislocation driven nanosample plasticity: new insights from quantitative in-situ TEM tensile testing

Scientific reports, Jan 13, 2018

Intrinsic dislocation mechanisms in the vicinity of free surfaces of an almost FIB damage-free si... more Intrinsic dislocation mechanisms in the vicinity of free surfaces of an almost FIB damage-free single crystal Ni sample have been quantitatively investigated owing to a novel sample preparation method combining twin-jet electro-polishing, in-situ TEM heating and FIB. The results reveal that the small-scale plasticity is mainly controlled by the conversion of few tangled dislocations, still present after heating, into stable single arm sources (SASs) as well as by the successive operation of these sources. Strain hardening resulting from the operation of an individual SAS is reported and attributed to the decrease of the length of the source. Moreover, the impact of the shortening of the dislocation source on the intermittent plastic flow, characteristic of SASs, is discussed. These findings provide essential information for the understanding of the regime of 'dislocation source' controlled plasticity and the related mechanical size effect.

Research paper thumbnail of Connecting atomistic and mesoscale simulations of crystal plasticity

Nature

... Connecting atomistic and mesoscale simulations of crystal plasticity. Vasily Bulatov 1 ,Farid... more ... Connecting atomistic and mesoscale simulations of crystal plasticity. Vasily Bulatov 1 ,Farid F. Abraham 2 , Ladislas Kubin 3 , Benoit Devincre 3 &amp;amp; Sidney Yip 1. ... To read this story in full you will need to login or make a payment (see right). ...

Research paper thumbnail of Review Article: Case studies in future trends of computational and experimental nanomechanics

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

Density functional theory calculations of generalized stacking fault energy surfaces for eight fa... more Density functional theory calculations of generalized stacking fault energy surfaces for eight face-centered cubic transition metals

Research paper thumbnail of Modeling plasticity of MgO by 2.5D dislocation dynamics simulations

Materials Science and Engineering: A

In this study, we model the plasticity of MgO (periclase) using a 2.5-dimensional (2.5D) dislocat... more In this study, we model the plasticity of MgO (periclase) using a 2.5-dimensional (2.5D) dislocation dynamics (DD) simulation approach. This model allows us to incorporate climb in DD simulations to model the creep behavior at high-temperature. Since a 2D formulation of DD cannot capture some important features of dislocation activity (e.g. those involving line tension), local rules are introduced to take these features into account (this is the 2.5D approach). To ensure the validity of such approach, the model is applied over a wide temperature range with a view in the lower temperature regimes where the newly introduced mechanism (climb) is not active, to benchmark our model against previous 3D simulations and experimental data. Thus we consider successfully a low temperature (T ≤600 K) regime where plasticity is dominated by dislocation glide in the thermally activated regime; an intermediate regime (T =1000 K) where plasticity is dominated by dislocation-dislocation interactions; and a high-temperature regime (1500≤T ≤1800 K) which is the actual goal of the present study and where creep plasticity is governed by dislocation glide controlled by recovery (climb being considered here). We show that, taking into account the range of oxygen self-diffusion coefficients available in the literature, our simulations are able to describe properly the high-temperature creep behavior of MgO.

Research paper thumbnail of Pure climb creep mechanism drives flow in Earth’s lower mantle

Science Advances

Climb creep provides an efficient deformation mechanism for bridgmanite under lower mantle condit... more Climb creep provides an efficient deformation mechanism for bridgmanite under lower mantle conditions.

Research paper thumbnail of Slip systems interactions in a-iron determined by dislocation dynamics simulations

Research paper thumbnail of Interaction of 〈100〉 dislocation loops with dislocations studied by dislocation dynamics in α-iron

Journal of Nuclear Materials, 2015

ABSTRACT Interstitial dislocation loops with Burgers vector of 〈1 0 0〉 type are formed in α-iron ... more ABSTRACT Interstitial dislocation loops with Burgers vector of 〈1 0 0〉 type are formed in α-iron under neutron or heavy ion irradiation. As the density and size of these loops increase with radiation dose and temperature, these defects are thought to play a key role in hardening and subsequent embrittlement of iron-based steels. The aim of the present work is to study the pinning strength of the loops on mobile dislocations. Prior to run massive Dislocation Dynamics (DD) simulations involving experimentally representative array of radiation defects and dislocations, the DD code and its parameterization are validated by comparing the individual loop–dislocation reactions with those obtained from direct atomistic Molecular Dynamics (MD) simulations. Several loop–dislocation reaction mechanisms are successfully reproduced as well as the values of the unpinning stress to detach mobile dislocations from the defects.

Research paper thumbnail of Dislocation Microstructures and Plastic Flow: A 3D Simulation

Solid State Phenomena, 1992

Research paper thumbnail of Modeling the creep properties of olivine by 2.5-dimensional dislocation dynamics simulations

Research paper thumbnail of On the Origins of Tension--Compression Asymmetry in Crystals and Implications for Cyclic Behavior

Most of crystalline materials exhibit a hysteresis on their deformation curve when mechanically l... more Most of crystalline materials exhibit a hysteresis on their deformation curve when mechanically loaded in alternating directions. This Bauschinger effect is the signature of mechanisms existing at the atomic scale and controlling the materials damage and ultimately their failure. Here, three-dimensional simulations of dislocation dynamics and statistical analyses of the microstructure evolution reveal two original elementary mechanisms. An asymmetry in the dislocation network junctions arising from the stress driven curvatures and the partial reversibility of plastic avalanches give an explanation to the traction-compression asymmetry observed in FCC single-crystals. These mechanisms are then connected in a physically justified way to larger-scale representations using a dislocation density based theory. Parameter-free predictions of the Bauschinger effect and strain hardening during cyclic deformation in different materials and over a range of loading directions and different plast...

Research paper thumbnail of Multiscale Phenomena in Materials{Experiments and Modeling Chairs

In-situ transmission electron microscopy of thin lms systems provides an ideal experimental labor... more In-situ transmission electron microscopy of thin lms systems provides an ideal experimental laboratory for the study of dislocation motion and dislocation-defect interactions in materials. Through careful consideration of the sample geometry and calibration of the experimental conditions it is possible to obtain accurate quantitative information about dislocation velocities, interaction stresses and

Research paper thumbnail of Misfit dislocation gettering in epitaxial films deposited on pit-patterned Si (001) substrates by Dislocation Dynamics simulations

Research paper thumbnail of From Dislocation Junctions to the Three Stages Curve

The strain hardening matrix of fcc crystals can be obtained from crystallographic continuum model... more The strain hardening matrix of fcc crystals can be obtained from crystallographic continuum models deriving from the Kocks-Mecking framework. DD simulations were used to compute the coefficients of the interaction matrix between slip systems and to extend an existing model for stages II and III in order to also include stage I. Other parameters of the model are the mean-free path of the dislocations and their critical annihilation distance by cross-slip, which can be estimated from various sources. The resulting constitutive formulation is inserted into a numerical crystalline model using a FE code, which is used here to test single crystal behavior. As a result, parameter-free deformation curves can be obtained for fcc crystals, which depend in a known manner on the nature of the material, the orientation of the crystal and temperature. This is illustrated by a comparison between aluminum and copper crystals initially oriented for easy glide at room temperature. In this type of mod...

Research paper thumbnail of Dislocation Dynamics simulations in epitaxial Si-Ge nanostructures

Research paper thumbnail of Discrete dislocation dynamics

Nickel Base Single Crystals Across Length Scales

Research paper thumbnail of On the Origin of the Hall-Petch Law: A 3D-Dislocation Dynamics Simulation Investigation

SSRN Electronic Journal

3D -DD simulations are performed with cubic grains ranging from 1 to 10 μm to investigate the phy... more 3D -DD simulations are performed with cubic grains ranging from 1 to 10 μm to investigate the physical mechanisms at the origin of the Hall- Petch law. In particular, the long-range stress (back stress) induced by the density of polarized dislocations ( GNDs ) accumulated at GBs is quantified separately from the short-range stress associated with the forest dislocation ( SSDs ) density. We show that the back stress and the associated strain hardening is independent of grain size at low strain. Hence, the grain size effect reproduced by 3D-DD simulations is controlled by an increase of the CRSS when decreasing grain size. Such evolution of the CRSS amplitude is controlled by two competing strengthening mechanisms justifying the generic <i>1/√d</i> dependent form of the Hall- Petch law observed in simulations and experiments.

Research paper thumbnail of A Molecular Dynamics-Informed Probabilistic Cross-Slip Model in Discrete Dislocation Dynamics

SSRN Electronic Journal

We present here a quantitative study of dislocation cross-slip, an essential thermally activated ... more We present here a quantitative study of dislocation cross-slip, an essential thermally activated process in deformation of metals, in discrete dislocation dynamics (DDD) simulations. We implemented a stress-dependent line-tension model in DDD simulations, with minimal information from molecular dynamics (MD) simulations. This model allows reproducing in DDD simulations the probabilistic cross-slip rate calculated in MD simulations for Cu in a large range of stresses and temperatures. This model opens new horizons in modelling cross-slip related mechanisms such as deformation softening, dislocation-precipitate interaction and dislocation patterning in realistic strain rates.

Research paper thumbnail of Stress fields of finite-size dislocation walls and prediction of back stress induced by geometrically necessary dislocations at grain boundaries

Journal of the Mechanics and Physics of Solids

At low strain, geometrically necessary dislocations (GND) confined in the close vicinity of grain... more At low strain, geometrically necessary dislocations (GND) confined in the close vicinity of grain boundaries can be approximated as a dislocation wall structure called a GND facet. Analytical solutions derived from Field Dislocations Mechanics (FDM) theory allow calculating the stress components associated with the GND facets but are unable to account for the stress field variation induced by finite size effect. Dislocation dynamics simulation is used to investigate the true stress field of GND facets. The geometry, dimension and dislocation density of three generic types of GND facets (twist, tilt and epitaxial facets) are systematically studied. In all cases, the stress field generated by GND facets is proportional to the surface GND density and its spatial distribution can be recovered using FDM solution combined with two scaling parameters identified from DD simulation results. This calculation procedure can be generalized to any crystal structure by relating the components of the surface Nye's tensor to the solutions of simple cubic slip systems. Finally, static and dynamic tests are made to validate the calculation of back stress within regular grains bounded by GND facets.

Research paper thumbnail of Dislocation Intersections and Reactions in FCC and BCC Crystals

MRS Proceedings

The various types of configurations formed in face-centered cubic (fcc) and body-centered cubic (... more The various types of configurations formed in face-centered cubic (fcc) and body-centered cubic (bcc) structures by two interacting, non-coplanar, dislocation segments of various orientations are examined and discussed. The focus is on junction formation and on a particular interaction, the collinear interaction, which deserves much more attention than paid up to now.

Research paper thumbnail of New Line Model for Optimized Dislocation Dynamics Simulations

MRS Proceedings

A new model for the discretisation of dislocation lines is presented, which is optimised for meso... more A new model for the discretisation of dislocation lines is presented, which is optimised for mesoscale simulations of dislocation dynamics. By comparison with the existing edge-screw model, the present one provides a better description of the stress field close to the dislocation lines. It simplifies the modelling of dislocation reactions and accelerates computations by allowing to make use of larger time steps. An application to attractive junctions and forest hardening is briefly sketched.

Research paper thumbnail of Dislocation driven nanosample plasticity: new insights from quantitative in-situ TEM tensile testing

Scientific reports, Jan 13, 2018

Intrinsic dislocation mechanisms in the vicinity of free surfaces of an almost FIB damage-free si... more Intrinsic dislocation mechanisms in the vicinity of free surfaces of an almost FIB damage-free single crystal Ni sample have been quantitatively investigated owing to a novel sample preparation method combining twin-jet electro-polishing, in-situ TEM heating and FIB. The results reveal that the small-scale plasticity is mainly controlled by the conversion of few tangled dislocations, still present after heating, into stable single arm sources (SASs) as well as by the successive operation of these sources. Strain hardening resulting from the operation of an individual SAS is reported and attributed to the decrease of the length of the source. Moreover, the impact of the shortening of the dislocation source on the intermittent plastic flow, characteristic of SASs, is discussed. These findings provide essential information for the understanding of the regime of 'dislocation source' controlled plasticity and the related mechanical size effect.

Research paper thumbnail of Connecting atomistic and mesoscale simulations of crystal plasticity

Nature

... Connecting atomistic and mesoscale simulations of crystal plasticity. Vasily Bulatov 1 ,Farid... more ... Connecting atomistic and mesoscale simulations of crystal plasticity. Vasily Bulatov 1 ,Farid F. Abraham 2 , Ladislas Kubin 3 , Benoit Devincre 3 &amp;amp; Sidney Yip 1. ... To read this story in full you will need to login or make a payment (see right). ...

Research paper thumbnail of Review Article: Case studies in future trends of computational and experimental nanomechanics

Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films

Density functional theory calculations of generalized stacking fault energy surfaces for eight fa... more Density functional theory calculations of generalized stacking fault energy surfaces for eight face-centered cubic transition metals

Research paper thumbnail of Modeling plasticity of MgO by 2.5D dislocation dynamics simulations

Materials Science and Engineering: A

In this study, we model the plasticity of MgO (periclase) using a 2.5-dimensional (2.5D) dislocat... more In this study, we model the plasticity of MgO (periclase) using a 2.5-dimensional (2.5D) dislocation dynamics (DD) simulation approach. This model allows us to incorporate climb in DD simulations to model the creep behavior at high-temperature. Since a 2D formulation of DD cannot capture some important features of dislocation activity (e.g. those involving line tension), local rules are introduced to take these features into account (this is the 2.5D approach). To ensure the validity of such approach, the model is applied over a wide temperature range with a view in the lower temperature regimes where the newly introduced mechanism (climb) is not active, to benchmark our model against previous 3D simulations and experimental data. Thus we consider successfully a low temperature (T ≤600 K) regime where plasticity is dominated by dislocation glide in the thermally activated regime; an intermediate regime (T =1000 K) where plasticity is dominated by dislocation-dislocation interactions; and a high-temperature regime (1500≤T ≤1800 K) which is the actual goal of the present study and where creep plasticity is governed by dislocation glide controlled by recovery (climb being considered here). We show that, taking into account the range of oxygen self-diffusion coefficients available in the literature, our simulations are able to describe properly the high-temperature creep behavior of MgO.

Research paper thumbnail of Pure climb creep mechanism drives flow in Earth’s lower mantle

Science Advances

Climb creep provides an efficient deformation mechanism for bridgmanite under lower mantle condit... more Climb creep provides an efficient deformation mechanism for bridgmanite under lower mantle conditions.

Research paper thumbnail of Slip systems interactions in a-iron determined by dislocation dynamics simulations

Research paper thumbnail of Interaction of 〈100〉 dislocation loops with dislocations studied by dislocation dynamics in α-iron

Journal of Nuclear Materials, 2015

ABSTRACT Interstitial dislocation loops with Burgers vector of 〈1 0 0〉 type are formed in α-iron ... more ABSTRACT Interstitial dislocation loops with Burgers vector of 〈1 0 0〉 type are formed in α-iron under neutron or heavy ion irradiation. As the density and size of these loops increase with radiation dose and temperature, these defects are thought to play a key role in hardening and subsequent embrittlement of iron-based steels. The aim of the present work is to study the pinning strength of the loops on mobile dislocations. Prior to run massive Dislocation Dynamics (DD) simulations involving experimentally representative array of radiation defects and dislocations, the DD code and its parameterization are validated by comparing the individual loop–dislocation reactions with those obtained from direct atomistic Molecular Dynamics (MD) simulations. Several loop–dislocation reaction mechanisms are successfully reproduced as well as the values of the unpinning stress to detach mobile dislocations from the defects.

Research paper thumbnail of Dislocation Microstructures and Plastic Flow: A 3D Simulation

Solid State Phenomena, 1992

Research paper thumbnail of Modeling the creep properties of olivine by 2.5-dimensional dislocation dynamics simulations