The Dislocations Gallery
Aim of this page:
The elementary properties of dislocations (the linear defects that carry plastic deformation in crystalline solids) are illustrated by snapshots realized with the 3-D dislocation dynamics (DD) simulation "microMegas" a GPL simulation code initially developed at the LEM (CNRS/ONERA).
This page was created in January 1997 as a tutorial tool for illustrating the theory of dislocations and plasticy in metals and alloys. New movies and illustrative results are episodically added to the dislocation Gallery. You are welcome to use it for teaching purposes. Remarks and/or comments are welcomed and can be e-mailed to devincre@zig.onera.fr
--> The Frank-Read source mechanism in materials with low lattice friction.
--> Dislocation multiplication in materials with high lattice friction.
--> Dislocation spiral (single-ended) source
--> Dynamics of two interacting Frank-Read sources.
--> Dislocation dipole.
--> Dislocation-dislocation annihilation by cross-slip.
--> The double cross-slip mechanism.
--> Contact dislocation reactions.
--> The "forest" hardening.
--> Interactions of primary dislocations with secondary slip systems .
--> More model simulations of slip-systems interactions.
--> 3-D simulation of dislocation dynamics.
--> Examples of kimatic strain hardening process.
--> Free surface effect and dislocation pile-up relaxation.
--> Self annihilation artifact with periodic boundary conditions in DD simulations
--> Frank-Read source in a small simulation volume with PBC.
--> Pattern formation in a 2.5 DD simulation
3D simulation of dislocation dynamics at the mesoscopic scale: the microMegas code
Dislocations are the elementary carriers of plastic flow. The ultimate aim of dislocation theory is the prediction of the mechanical properties 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 still not yet been fully reached. To provide an alternative approach to existing theoretical attempts, a mesoscopic simulation of dislocation dynamics and interactions has been developed, which can be applied to various crystalline structures.
The method used combines features deriving from molecular dynamics and cellular automata techniques. It is based on a discrimination of space and time and
incorporates all the basic properties of dislocations, viz. their core and elastic properties. 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 and for maximum strains in the range of one percent.
This simulation method provides potential means for checking the existing models as well as elaborating new models, for the investigation of the properties of self-organized dislocations configurations and for the connection between the discrete and continuous approaches of plasticity.
Some related scientific articles