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Energy Fluctuations in Slowly Sheared Granular Materials.
Jie Zheng1, Aile Sun1, Yujie Wang1
1School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
Physical Review Letters
|January 5, 2019
Summary
This study experimentally measures particle-scale energy fluctuations in sheared granular materials. These fluctuations exhibit a temperature-like noise field, revealing an aging process in granular dynamics.
Area of Science:
- Granular physics
- Soft matter physics
- Statistical mechanics
Background:
- Granular materials exhibit complex behaviors under shear.
- Understanding particle-scale mechanics is crucial for macroscopic properties.
- Previous studies lacked direct measurement of energy fluctuations.
Purpose of the Study:
- To experimentally measure particle-scale energy fluctuations (ΔE) in sheared granular systems.
- To characterize the statistical distribution of these energy fluctuations.
- To link these fluctuations to the macroscopic stress-strain behavior and aging dynamics.
Main Methods:
- Utilized photoelastic disks to visualize and quantify particle-scale energy.
- Applied slow shear to an isotropically jammed granular layer.
- Analyzed the statistics and dynamics of energy fluctuations (ΔE).
Main Results:
- Demonstrated shear-induced stochastic strengthening and weakening of particle energies.
- Observed that ΔE behaves as a temperature-like noise field.
- Found a novel, Boltzmann-type, double-exponential distribution for ΔE at any shear strain γ.
- Extracted an effective temperature (χ) from energy fluctuations.
Conclusions:
- Interpreted slow startup shear as an aging process in granular materials.
- Showed that the effective temperature (χ) approaches one with increasing shear strain (γ).
- Drew parallels between granular aging and processes in spin glasses, thermal glasses, and metallic glasses.
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