From critical behavior to catastrophic runaways: comparing sheared granular materials with bulk metallic glasses

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.

Similarity of internal and external friction: Soft matter frictional instabilities obey mean field dissipation through slip avalanches

“…3(a)] for most of the normal forces that were employed (except for the highest normal forces, where the scaling regime has shrunk too much to be visible in the figure). The large events seen especially for the highest forces are reflecting a weakening effect, such as static versus dynamic friction which is predicted to create large slips of similar size in addition to the smaller ones [5][6][7][17][18][19], consistent with the experiments shown here. Moreover, for the events in the scaling regime the maximum force drop rate v m and force drop duration T at size F , scale as v m |F ∼ (F ) σ ρ ∼ (F ) 1/2 and T |F ∼ F σ νz ∼ F 1/2 , respectively, which are in good agreement with the model predictions Here σ ρ and σ υz are critical exponents that are predicted by the model to be universal, i.e., determined by basic properties such as symmetries, dimensions, and range of interactions.…”

“…For a magnitude of applied normal force of F N = 1876 μN, the associated frictional forces go intermittently between zero and ∼800 µN, which presents unstable instantaneous friction coefficients ranging from a negligibly small number up to µ ∼ 0.43, a high number for a typically lubricious surface. The near periodicity of the large force drops in the data reflects a frictional weakening mechanism, related to static versus dynamic friction, that produces almost-periodic large slips in addition to smaller slips in between [6,[17][18][19].…”

“…x10 5 The near periodicity of the large force drops in the data reflects a frictional weakening mechanism, related to static versus dynamic friction, that produces almost-periodic large slips in addition to smaller slips in between [6,[17][18][19].…”

“…that weakening correspondingly changes the dynamics for the largest events [5][6][7][17][18][19]. Figure 4 shows the average temporal profiles of force drops of given size in the scaling regime of C(F ).…”

A Review of the Serrated-Flow Phenomenon and Its Role in the Deformation Behavior of High-Entropy Alloys

“…During deformation, several materials, such as BMGs, HEAs, densely packed granular materials, rocks, and other composite materials, can exhibit jerky flows that occur via slip avalanches [76,134,153,[249][250][251][252]. These slip avalanches typically exhibit a broad distribution of slip sizes, which can be described by relatively simple probability distribution function (pdf) models [253].…”