Abstract
Stress-based ensembles incorporating temperaturelike variables have been proposed as a route to an equation of state for granular materials. To test the efficacy of this approach, we perform experiments on a two-dimensional photoelastic granular system under three loading conditions: uniaxial compression, biaxial compression, and simple shear. From the interparticle forces, we find that the distributions of the normal component of the coarse-grained force-moment tensor are exponential tailed, while the deviatoric component is Gaussian distributed. This implies that the correct stress-based statistical mechanics conserves both the force-moment tensor and the Maxwell-Cremona force-tiling area. As such, two variables of state arise: the tensorial angoricity () and a new temperaturelike quantity associated with the force-tile area which we name keramicity (). Each quantity is observed to be inversely proportional to the global confining pressure; however, only exhibits the protocol independence expected of a state variable, while behaves as a variable of process.
- Received 26 February 2018
- Revised 11 October 2018
DOI:https://doi.org/10.1103/PhysRevLett.122.038001
© 2019 American Physical Society
Physics Subject Headings (PhySH)
Synopsis
Hints of an Equation of State for Granular Materials
Published 23 January 2019
Experiments with a granular system have confirmed a temperature-like variable that could lead to an equation of state for this class of materials.
See more in Physics