67 research outputs found
Source code related to "Periclase deforms slower than bridgmanite under mantle conditions"
No full textSource code of the 2.5 D Dislocation Dynamics used in "Periclase deforms slower than bridgmanite under mantle conditions"
This code implements glide and climb
It has been originally developped by:
Diego Gomez-Garcia
Benoit Devincre
Ladislas Kubin
Francesca Bioili
Riccardo Real
THREE DIMENSIONAL STRESS FIELD EXPRESSIONS FOR STRAIGHT DISLOCATION SEGMENTS
No full textInternational audienceNew expressions for the stress field of straight dislocation segments are derived from the de Wit's expressions for an infinite straight dislocation. Restricted to linear isotropic elasticity, these compact formulae are given in tensor and vector notation expressed in an arbitrary Cartesian reference frame. This solution, allows to compute the internal stress fields or the dislocation-dislocation interactions involved in three-dimensional simulations of plastic strain at spatial scales involving large numbers of dislocations
THREE DIMENSIONAL STRESS FIELD EXPRESSIONS FOR STRAIGHT DISLOCATION SEGMENTS
No full textInternational audienceNew expressions for the stress field of straight dislocation segments are derived from the de Wit's expressions for an infinite straight dislocation. Restricted to linear isotropic elasticity, these compact formulae are given in tensor and vector notation expressed in an arbitrary Cartesian reference frame. This solution, allows to compute the internal stress fields or the dislocation-dislocation interactions involved in three-dimensional simulations of plastic strain at spatial scales involving large numbers of dislocations
THREE DIMENSIONAL STRESS FIELD EXPRESSIONS FOR STRAIGHT DISLOCATION SEGMENTS
No full textInternational audienceNew expressions for the stress field of straight dislocation segments are derived from the de Wit's expressions for an infinite straight dislocation. Restricted to linear isotropic elasticity, these compact formulae are given in tensor and vector notation expressed in an arbitrary Cartesian reference frame. This solution, allows to compute the internal stress fields or the dislocation-dislocation interactions involved in three-dimensional simulations of plastic strain at spatial scales involving large numbers of dislocations
Computer Modelling of Dynamically-Induced Dislocation Patterning
No full textABSTRACTThe evolution of a random and initially homogeneous distribution of parallel and infinitely extended edge dislocations is studied by using elastic energy minimization without and in presence of a periodic external stress, τa. During the energy minimization without external stress (relaxation), randomly distributed dislocation dipoles are formed whereas, when the external stress is acting, the dislocations condense in walls. We investigated the spatial periodicity of this microstructure, λ, as a function of, τa, and of the total dislocation density. The elastic energy of the stress-induced microstructure is found to be comparable to the value obtained by relaxation. Thereby, emphasis is given to the dynamical character of patterning. A phenomenological model has been developed, explaining the correlation between λ and τa found in the simulations and comparing favorably with existing experimental data.</jats:p
A Multiscale Investigation of the Physical Origins of Tension–Compression Asymmetry in Crystals and their Implications for Cyclic Behavior
No full textMost of crystalline materials develop an hysteresis on their deformation curve when a mechanical loading is applied in alternating directions. This effect, also known as the Bauschinger effect, is intimately related to the reversibile part of the plastic deformation and controls the materials damage and ultimately their failure. In the present work, we associate mesoscale Dislocation Dynamics simulations and Finite Element simulations to identify two original dislocation mechanisms at the origin of the traction/compression asymmetry and quantify their impacts on the cyclic behaviour of FCC single-crystals. After demonstrating that no long-range internal stresses can be measured in the simulations, careful analysis of the dislocation network show that the Bauschinger effect is caused by an asymmetry in the stability of junctions formed from segments whose curvature is determined by the applied stress, and a significant portion of the stored dislocation segments is easily recovered during the backward motion of dislocations in previously explored regions of the crystal. These mechanisms are incorporated into a modified crystal plasticity framework with few parameters quantified from statistical analysis of Dislocation Dynamics simulations or from the literature. This strategy has a real predictive capability and the macroscale results are in good agreement with most of the experimental literature existing on the Bauschinger and cyclic deformation of FCC single-crystals. This work provides valuable mechanistic insight to assist in the interpretation of experiments and the design of structural components to consolidate their life under cyclic loading
Formation of geometrically necessary boundaries – Crystal plasticity & DD simulations
No full textOn the Origins of Tension–Compression Asymmetry in Crystals and Implications for Cyclic Behavior
No full textMost 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 plastic strain amplitudes are found to be in excellent agreement with experiments. This work brings invaluable mechanistic insights for the interpretation of experiments and for the design of structural components to consolidate their service life under cyclic load
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