Dynamic length scale and weakest link behavior in crystal plasticity

Irreversible deformation of crystals is often characterized by stochastic scale-free distributed intermittent local plastic bursts. Quenched obstacles with short-range interaction were found to limit the size of these events, which was termed as a transition from wild to mild fluctuations. Here, we show by analyzing the local yield thresholds in a discrete dislocation model that a dynamic length scale can be introduced based on weakest link principles, and this scale characterizes the extension of plastic events. The interplay between long-range dislocation interactions and short-range quenched disorder is found to destroy scale-free dynamical correlations, thus leading to event localization (that is, shortening of the length scale) which explains the crossover between the wild and mild regimes. Several methods are presented to determine the dynamic length scale which can be generalized to other types of heterogeneous materials.