B. Devincre
Centre national de la recherche scientifique
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Featured researches published by B. Devincre.
Science | 2008
B. Devincre; Thierry Hoc; L.P. Kubin
Predicting the strain hardening properties of crystals constitutes a long-standing challenge for dislocation theory. The main difficulty resides in the integration of dislocation processes through a wide range of time and length scales, up to macroscopic dimensions. In the present multiscale approach, dislocation dynamics simulations are used to establish a dislocation-based continuum model incorporating discrete and intermittent aspects of plastic flow. This is performed through the modeling of a key quantity, the mean free path of dislocations. The model is then integrated at the scale of bulk crystals, which allows for the detailed reproduction of the complex deformation curves of face-centered cubic crystals. Because of its predictive ability, the proposed framework has a large potential for further applications.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing | 2001
B. Devincre; L.P. Kubin; C. Lemarchand; Ronan Madec
Abstract This review is focused on recent progress achieved by mesoscopic simulations of plastic deformation. The methods presently available for discretizing the dislocation lines are critically discussed with emphasis on a new lattice-based model. Progress in large-scale simulations is represented by a study on the influence of long range elastic stresses on the formation of dislocation patterns in fcc crystals. A hybrid discrete-continuum method that provides an exact treatment of the boundary conditions is described and illustrated by an investigation of the critical conditions for dislocation motion in the channels of γ / γ ′ superalloys.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing | 1997
B. Devincre; L.P. Kubin
This paper reviews the three-dimensional simulations of dislocation dynamics and interactions at the mesoscopic scale. The simulation technique is briefly sketched and examples of applications are shown. A distinction is made between situations where uniform dislocation structures result from core properties (Ni3Al) and situations where dislocation interactions leads to pattern formation (f.c.c. crystals). Limitations and potentialities of the method are discussed.
Scripta Materialia | 2002
Ronan Madec; B. Devincre; L.P. Kubin
Dislocation dynamics simulations of multiple slip in f.c.c. crystals lead to the formation of patterned microstructures. The mechanisms participating to dislocation storage and dynamic recovery are investigated and discussed. Cross-slip and short-range interactions are found to govern the bifurcation from uniform to ordered microstructures.
Journal of The Mechanics and Physics of Solids | 2001
C. Lemarchand; B. Devincre; L.P. Kubin
Abstract The question of the description of the elastic fields of dislocations and of the plastic strains generated by their motion is central to the connection between dislocation-based and continuum approaches of plasticity. In the present work, the homogenization of the elementary shears produced by dislocations is discussed within the frame of a discrete-continuum numerical model. In the latter, a dislocation dynamics simulation is substituted for the constitutive form traditionally used in finite element calculations. As an illustrative example of the discrete-continuum model, the stress field of single dislocations is obtained as a solution of the boundary value problem. The hybrid code is also shown to account for size effects originating from line tension effects and from stress concentrations at the tip of dislocation pile-ups.
Philosophical Magazine | 1997
B. Devincre; Patrick Veyssière; L.P. Kubin; G. Saada
Abstract This work examines the flow stress anomaly of Ll2 alloys by means of a mesoscopic two-dimensional simulation of dislocation dynamics. The basic properties modelled are slip in the octahedral plane, the conditions at which screw dislocation segments are locked by formation of Kear-Wilsdorf locks and subsequently unlocked, and the mobility of jogs in the cube plane. The range of temperatures investigated varies between 200 and 600 K, scaling with the domain of anomaly of Ni3Al-based alloys. The simulations indicate that strain is mostly provided by the sliding of kinks. Two conditions are simultaneously required in order to reproduce the flow stress anomaly: firstly kink mobility should be hindered via the dragging of jogs and secondly, irrespective of the probability of locking, locks should not be destroyed easily. The simulations suggest, in addition, that two different flow stress regimes take place in the temperature domain of the stress anomaly. At the onset of the anomaly, the flow stress is...
Modelling and Simulation in Materials Science and Engineering | 1999
Meijie Tang; B. Devincre; L.P. Kubin
In body centred cubic (bcc) crystals at low temperatures, the thermally activated motion of screw dislocations by the kink-pair mechanism governs the yield properties and also affects the strain hardening properties. In this work, the average strength of dislocation junctions is derived and numerically estimated in the case of Nb and Ta crystals. This allows us to extend an existing simulation of dislocation dynamics in bcc crystals to the case of the motion of a screw dislocation line through a random distribution of forest obstacles. Numerical results are presented in the case of Ta crystals and at two temperatures, 160 K and 215 K. They are complemented by a simple model that applies quite generally to bcc metals at low temperatures. It is shown that forest hardening is made up of two contributions, a free-length effect that depends on the length of the mobile screw segments and whose dependence on forest obstacle density is logarithmic and a line tension effect linearly proportional to the obstacle density. As a result of the thermally activated character of screw dislocation mobility, the relative weight of the two contributions to forest hardening depends on the temperature and strain rate.
American Mineralogist | 2007
Julien Durinck; B. Devincre; L.P. Kubin; Patrick Cordier
Abstract This work addresses the modeling of dislocation interactions and dynamics in olivine. A 3D dislocation dynamics (DD) simulation developed for cubic and hexagonal metals is adapted to the orthorhombic symmetry of this mineral. Dislocation core effects and mobilities are introduced through available models or phenomenological laws and fitted based on available experimental results on single crystals. The stress dependencies of the mobilities of [100] and [001] dislocations are emphasized. Dislocations interactions are studied through a simple elastic analysis and further using a more realistic approach based on DD simulations. It is shown that no junction formation results from the interaction between [100] and [001] dislocations. The collinear interaction is thus the only potential mechanism for forest hardening although its efficiency is significantly reduced by lattice friction on screw dislocations, which decreases the probability for dislocation reactions. The Taylor relationship is often used to model the dependence of the flow stress with the dislocation density. In the presence of a strong lattice friction, Taylor strengthening is shown here to be only a minor contribution to the flow stress and should not be responsible for it
Computational Materials Science | 2002
Ronan Madec; B. Devincre; L.P. Kubin
Attractive non-coplanar dislocations that cannot react to form junctions can, nevertheless, form crossed states, i.e., junctions of null length. Such configurations have recently been described by Wickham and co-workers as an output of numerical simulations. The physical origin of the crossed states is cleared out and their conditions of occurrence are calculated within a simplified elastic frame. The results are further discussed by comparison with mesoscopic simulations of intersecting dislocations in fcc and bcc crystals.
Philosophical Magazine | 1999
B. Devincre; P. Veyssière; G. Saada
Abstract The origin of the anomalous temperature dependence of the giant work-hardening rate and of the modest strain-rate sensitivity observed in many L12 alloys is investigated by means of an ‘end-on’ simulation of dislocation dynamics in Ni3Al. The present model reproduces most of the atypical mechanical properties observed experimentally. The study of the evolution of the distribution of the Kear-Wilsdorf locks during plastic deformation indicates that the order of magnitude of the work-hardening rate stems from a preferred exhaustion of the weakest locks. In addition, the low strain-rate sensitivity measured is found to rely on the absence of a correlation between the dislocation properties which provide the plastic strain and those which determine the flow stress level.