Rotational diffusion and rotational correlations in frictional amorphous disk packings under shear

Area of Science:

• Physics
• Materials Science
• Mechanical Engineering

Background:

• Amorphous granular materials exhibit complex behaviors near their rigidification point.
• Understanding particle dynamics, including rotation, is crucial for predicting bulk material properties.
• Shear deformation is a common method to probe the mechanical response of granular systems.

Purpose of the Study:

• To investigate the microscopic features of particle rotations in amorphous disk packing under shear.
• To determine how volume fraction and inter-particle friction affect particle microrotation.
• To explore the relationship between rotational dynamics and system pressure.

Main Methods:

• Analysis of experimental measurements on disk packing subjected to simple shear deformation.
• Varying inter-particle friction coefficients and volume fractions.
• Quantifying particle microrotation and its spatial correlations.

Main Results:

• Shear deformation induces diffusive microrotation, which can be enhanced or suppressed by volume fraction and friction.
• Particle rotations exhibit persistent anticorrelated motion.
• Spatial correlations in microrotation are directly correlated with system pressure.

Conclusions:

• Collective dynamics in particle rotational degrees of freedom have significant mechanical relevance.
• Particle microrotation is a sensitive indicator of the mechanical state of amorphous packings.
• Friction and density play key roles in modulating rotational dynamics and system rigidity.