Coupled Atomistics and Discrete Dislocations in 3d (CADD-3d)

Capturing plasticity at realistic dislocation densities with high configurational complexity requires a continuum-level discrete dislocation dynamics (DDD) description. However, many features controlling dislocation motion are inherently atomistic, such as the interaction of dislocations with solutes, precipitates, cracks, interfaces and such as the nucleation itself. In two dimensions, modeling these phenomena in a multi-scale manner was possible thanks to the method Coupled Atomistic and Discrete Dislocation dynamics (CADD2d). However many effects are de facto 3D which comes with new difficulties. A multiscale coupling in 3d will be presented during this seminar. The algorithm principle will be described in details, where dislocations can be described with atomistic resolution intimately coupled to a surrounding continuum domain in full 3d. If compared with the 2d case, dislocation lines may now span both domains simultaneously, therefore forming hybrid dislocations, partially represented with dislocated atoms and partially as discrete lines. It is common in such concurrent coupling strategies that continuum dislocation properties and atomistic dislocation properties need to match closely, so as to prevent bi-material interface effects to appear at the interface. An implementation prototype is presented based on the DDD code Paradis and on the MD code LAMMPS, altogether interfaced with the coupling code LibMultiScale. Simulations of the dynamics of a single hybrid dislocation and of a hybrid dislocation loop will illustrate the potential and robustness of the approach for near-seamless motion of dislocations into, across, and out of the atomistic domain. Finally we present the nucleation of dislocation loops emitted from a Frank-Read source and then transformed into DD dislocations, demonstrating the possibilities of our framework.

Presented at:
Séminaire, Centre des Matériaux, Evry, France, 2018-05-23
May 23 2018

 Record created 2019-02-22, last modified 2019-06-19

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