The Irreversibility Transition in Amorphous Solids Under Periodic Shear

A fundamental problem in the physics of amorphous materials is understanding the transition from reversible to irreversible plastic behavior and its connection to the concept of yield. Currently, continuum materials modeling relies on the use of phenomenological yield thresholds, however, in many cases the transition from elastic to plastic behavior is gradual, which makes it difficult to identify an exact yield criterion. Recent work has shown that under periodic shear, amorphous solids undergo a transition from deterministic, periodic behavior to chaotic, diffusive behavior as a function of the strain amplitude. Furthermore, this transition has been related to a depinning-like transition in which cooperative avalanche events become system-spanning at the same point. Here we provide an overview of recent work focused on an understanding of the nature of yield in amorphous systems from a cooperative and dynamical point of view.