We show here that rotations of round particles in amorphous disk packing reveal various nontrivial microscopic features when the packing is close to rigidification. We analyze experimental measurements on disk packing subjected to simple shear deformation with various inter-particle friction coefficients and across a range of volume fractions where the system is known to stiffen. The analysis of measurements indicates that shear induces diffusive microrotation, that can be both enhanced and suppressed depending upon the volume fraction as well as the inter-particle friction. Rotations also display persistent anticorrelated motion. Spatial correlations in microrotation are observed to be directly correlated with system pressure. These observations point towards the broader mechanical relevance of collective dynamics in the rotational degree of freedom of particles.
Bibliographical noteFunding Information:
We thank the organizers and participants of the Lorentz Center workshop ‘‘Granular Matter Across Scales’’ for fostering an environment where the seeds for this work were planted. We are grateful to the late Robert Behringer for inventing an experimental setup that suppresses shear localization. We thank Jie Ren for collecting some of the data used. AM and NN are supported in part by the United States National Science Foundation grant CMMI-1727433 and EEC-1840432 (which also involves SS). YL is supported by a University of Minnesota Doctoral Dissertation Fellowship.
© The Royal Society of Chemistry 2021.
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