Experimental Test of the Edwards Volume Ensemble for Tapped Granular Packings

Area of Science:

• Physics
• Materials Science
• Statistical Mechanics

Background:

• Granular materials exhibit complex behaviors influenced by particle properties like friction.
• Understanding granular packings is crucial for various scientific and engineering applications.
• The Edwards volume ensemble provides a theoretical framework for statistical mechanics of granular systems.

Purpose of the Study:

• To experimentally investigate the effects of friction on granular packings under mechanical tapping.
• To validate the Edwards volume ensemble in three-dimensional granular systems.
• To establish a granular version of the thermodynamic zeroth law and determine entropy as a function of packing fraction and friction.

Main Methods:

• Utilizing X-ray tomography to analyze granular packings.
• Experimentally applying mechanical tapping to bead samples.
• Employing the Edwards framework to analyze statistical mechanics and density of states.

Main Results:

• Validation of the Edwards volume ensemble for granular systems.
• Establishment of a granular thermodynamic zeroth law.
• Quantification of entropy's dependence on packing fraction and friction.
• Determination of a granular jamming phase diagram based on coordination number and packing fraction.

Conclusions:

• Friction significantly influences granular statistical mechanics by altering the density of states.
• The study provides a framework for understanding granular entropy and jamming.
• Experimental validation supports the applicability of the Edwards ensemble to granular systems.