Shear-Jammed, Fragile, and Steady States in Homogeneously Strained Granular Materials.
Yiqiu Zhao1, Jonathan Barés1,2, Hu Zheng1,3,4
1Department of Physics & Center for Nonlinear and Complex Systems, Duke University, Durham, North Carolina 27708, USA.
Physical Review Letters
|November 9, 2019
Summary
Researchers explored the jamming phase diagram of sheared granular materials using a new Couette shear setup. They identified fragile states and transitions in quasistatic flow, revealing key insights into granular material behavior.
Area of Science:
- Physics
- Materials Science
- Engineering
Background:
- Granular materials exhibit complex behaviors under shear stress.
- Understanding the jamming transition is crucial for predicting material flow and stability.
Purpose of the Study:
- To investigate the jamming phase diagram of sheared granular materials.
- To characterize the transition between shear-jammed and fragile states.
- To explore the behavior of granular systems at different packing fractions and shear strains.
Main Methods:
- Utilized a novel multiring bottom Couette shear setup.
- Employed frictional photoelastic discs to study granular systems.
- Applied volume-conserving linear shear with minimal basal friction.
- Measured stress, strain, and contact network structure.
Main Results:
- Observed fragile states at packing fractions below the jamming point (ϕSJ ≈ 0.75).
- Identified a transition in quasistatic steady flow character around ϕSJ.
- Noted changes in contact number, fabric anisotropy, and nonrattler fraction near ϕSJ.
- Detected deviations from linear shear profiles and shear band localization at higher packing fractions.
Conclusions:
- The novel Couette setup allows access to previously difficult-to-study phase boundaries.
- The study provides a detailed map of the jamming phase diagram for sheared granular materials.
- Results offer insights into the fundamental mechanisms governing granular flow and jamming.
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