Abstract
The flow of granular materials and metallic glasses is governed by strongly correlated, avalanche-like deformation. Recent comparisons focused on the scaling regimes of the small avalanches, where strong similarities were found in the two systems. Here, we investigate the regime of large avalanches by computing the temporal profile or “shape” of each one, i.e., the time derivative of the stress-time series during each avalanche. We then compare the experimental statistics and dynamics of these shapes in granular media and bulk metallic glasses. We complement the experiments with a mean-field model that predicts a critical size beyond which avalanches turn into large runaway events. We find that this transition is reflected in a characteristic change of the peak width of the avalanche profile from broad to narrow, and we introduce a new metric for characterizing this dynamic change. The comparison of the two systems points to the same deformation mechanism in both metallic glasses and granular materials.
Highlights
Many diverse materials systems show intermittent plasticity
Previous studies [1,2,3,4,5] indicate that both Bulk metallic glasses (BMGs) and granular materials show avalanche statistics that are consistent with the predictions of the mean-field model with threshold weakening; we see both similar statistics and similar dynamics for large and small avalanches in BMGs and granular materials [5]
In the large-avalanche regime, the durations decrease with avalanche size (BMGs), or they are roughly independent of size
Summary
Bulk metallic glasses (BMGs) [1,2,3], granular materials [3,4,5,6], high entropy alloys [7], and nanocrystals [3, 8, 9] all show characteristics of discrete flow. Both metallic glasses and granular materials show two types of avalanches that have been previously classified as “small” and “large.” Small avalanches slip progressively in small increments and cluster together in time. They are microscopic and power-law distributed in size and other metrics. Large avalanches recur quasi-periodically and span the entire system in the form of shear bands
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