Jamming of three-dimensional prolate granular materials

Area of Science:

• Physics
• Materials Science
• Soft Matter Physics

Background:

• Granular materials exhibit complex behaviors, including jamming and phase transitions.
• The jamming of elongated particles is less understood than that of spheres.
• Understanding jamming is crucial for applications ranging from powder flow to seismic activity.

Purpose of the Study:

• To investigate the jamming behavior of long thin rods in response to local perturbations.
• To determine the influence of particle aspect ratio and container size on jamming.
• To characterize the dynamic phase diagram and associated fluctuation spectra.

Main Methods:

• Experimental manipulation of rod aspect ratio and container size.
• Creation of a dynamic phase diagram to map different behaviors.
• Measurement of forces and fluctuation spectra during object pulling.

Main Results:

• Jamming into a solid-like state depends on particle aspect ratio and container size.
• A broad transition region exists between granular stick-slip and solid-like behavior.
• Fluctuation spectra exhibit power-law tails with exponents varying from -2 (stick-slip) to -1 (solid).
• Packing fraction depends on aspect ratio, with an aspect-ratio-independent contact number of approximately 5.25.

Conclusions:

• The jamming of long thin rods is a tunable phenomenon controlled by geometry.
• The observed transition region highlights the coexistence of different dynamic regimes.
• Fluctuation analysis provides insight into the underlying mechanisms of granular friction and rearrangement.