The Dislocation Gallery
Elementary properties of dislocations are illustrated by downloadable video clips from the 3-D dislocation dynamics (DD) simulation microMegas, a GPL code developed at LEM (CNRS/ONERA).
This page, which is periodically updated, was created in January 1997 as a tutorial tool for illustrating dislocation properties and plastic flow in crystalline materials. Hence, please feel free to use the following clips. Comments and suggestions are welcome; please e-mail them to firstname.lastname@example.org.
Except if stated otherwise the simulations were performed in an FCC crystal (Cu) where the lattice resistance is extremely low.
--> Dislocation multiplication in crystals with high lattice resistance
--> Spiral (single-ended) source
--> Dynamics of two interacting Frank-Read sources
--> Dislocation dipole formation and destruction
--> Annihilation of screw dislocations by cross-slip
--> Pile-up relaxation with cross-slip
--> Dislocation reactions
--> Interactions of mobile non-coplanar dislocations
--> Primary dislocations interacting with a dislocation forest
--> All reactions of non-coplanar dislocations in FCC crystals
--> 3-D simulation of dislocation dynamics.
--> Strengthening by grain boundaries and non-shearable precipitates
--> Dislocation source in a columnar grain
--> Artificial self-annihilations with periodic boundary conditions
--> Frank-Read sources with periodic boundary conditions
--> Pattern formation in a 2.5D simulation
The ultimate objective of dislocation theory is the prediction of the mechanical response of crystalline materials. Because of the complexity of dislocation dynamics and interactions, and because plasticity is inherently a dissipative process far from equilibrium, this objective has not yet been fully reached. To provide an alternative approach to existing theoretical attempts, a mesoscopic simulation of dislocation dynamics and interactions was developed, which can be applied to materials with various crystal structures.
The method combines features deriving from molecular dynamics and cellular automata techniques. It is based on a discretization of space and time and incorporates all basic elastic and core properties of dislocations. Starting from an elementary length scale in the nanometer range and a time scale in the nanosecond range, this simulation yields outputs for simulated crystals of typical sizes between a few tens and a few hundreds of micrometers, with maximum strains in the one percent range.
This simulation provides potential means for checking existing models as well as elaborating new models for: - the plasticity of micro and nanomaterials, - the properties of self-organized dislocations microstructures and - the connection between discrete and continuous approaches of plasticity.