Work in Progress
Until this page is finished please refer to Media:LC_lock.pdf. Note: There are some errors associated with the junction length calculation in the code provided. These have been addressed and will be included in the forthcoming guide on this page.
Contents |
Introduction
This tutorial will:
- Study the formation and dissociation of Lomer-Cottrell (binary) junctions in fcc crystals using both DDLAB and ParaDiS
- Introduce running a batch of simulations, and calculating junction length and critical resolved shear stress to cause dissociation of the junction
- Determine the dependence of junction length and critical stress on the initial orientation of the intersecting dislocations
- Illustrate the mobility of nodes at the intersection of glide planes in DDLAB and ParaDiS
- Discuss any limitations. Physically the junction should be sessile. But in the simulation, the inner nodes of the junction segment are able to move. The end nodes of the junction are confined to the intersection line as they should.
This tutorial assumes that the reader is familiar with the basics of DDLAB. New users should read ______ before proceeding.
A copy of the input decks used in this tutorial can be downloaded from the link at the bottom of this page.
Background
Plastic deformation of metals is usually governed by the motion of dislocations and their reactions, such as nucleation, pinning, and multiplication. One particularly important interaction occurs when two dislocations on different glide planes approach each other. These dislocations could either repel or attract each other depending on their Burgers vectors and orientations. If they are pulled together, the dislocations will combine in a way that minimizes their energy. This often results in the "zipping" of the dislocations along the line of intersection of the glide planes to form a junction known as a Lomer-Cottrell lock. These junctions have been shown to be a governing cause of strain hardening in fcc crystals.