Temporal force fluctuations measured by tracking individual particles in granular materials under shear

Area of Science:

• Physics
• Materials Science
• Complex Systems

Background:

• Granular materials exhibit unique mechanical properties governed by inter-particle forces.
• The jamming-unjamming transition is a critical phenomenon where a static granular material yields and flows.
• Understanding force networks is key to predicting granular material behavior under stress.

Purpose of the Study:

• To investigate temporal force fluctuations between particles and boundaries in dense, sheared granular systems.
• To characterize the power spectra of these force fluctuations and identify key behaviors.
• To explore the nature of heterogeneity in force transmission during shear.

Main Methods:

• Dense granular system under slow shear.
• Measurement of temporal force fluctuations between individual particles and the external boundary.
• Analysis of force fluctuation power spectra over extended time scales (60 hours).

Main Results:

• Force fluctuations span a broad range of time scales, exhibiting 1/f-type power spectra.
• A rollover to 1/f^2 behavior is observed above a characteristic turnover frequency (f*).
• Heterogeneous force fluctuation spectra between neighboring particles persist over long durations, resembling dynamic heterogeneities in supercooled liquids.

Conclusions:

• The jamming-unjamming transition in granular materials is associated with distinct temporal force dynamics.
• Broadband power-law behavior and significant heterogeneity characterize force fluctuations in sheared granular systems.
• These findings offer insights into the complex mechanics of granular matter and its analogies with other complex systems.