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Plastic Cascades
People generally agree that the elementary objects responsible for plastic flow in crystalline material are the dislocations in the crystal.
For amorphous materials, on the other hand, despite decades of work, there is not such a strong consensus.
Argon first suggested that plasticity occurs in amorphous materials at low temperature via localized regions of intense shear strain.
With this picture in mind, Falk and Langer constructed a mean field theory of plasticity which naturally captured the gross phenomena of plasticity quite well.
After Argon's seminal work, Bulatov and Argon constructed a model which took into account the elastic interactions of these local shear zones.
In this model, cascades of shear transformations arose to form localized lines of slip, analogous to the nucleation and glide of a pair of dislocations, but without the need for any discussion of defects in an underlying crystalline structure.
In,[1], Anaël Lemaître and I were able to observe these local shears and their organization into lines of slip during cascades in atomistic computer simulations.
In,[5], we extended the study to include various central force interaction potentials, showing that the distribution of event sizes is independent of the interaction after a simple rescaling.
An important remaining question is how these localized zones of plasticity might be related to the larger scale localized features observed during compression tests of metallic glasses and other related materials.