Title: Fragility and hysteretic creep in frictional granular jamming

Author (Invited): Mahesh Bandi, Okinawa Institute of Science and Technology

Abstract:

We experimentally investigate the transition to a jammed state in a two-dimensional system of granular bi-dispersed disks subject to uniaxial compression. Several disk materials with different elastic moduli and friction coefficients $\mu$ are used. The first compression yields an exponential increase in pressure (as against the predicted power-law) over a small interval in packing fraction $\phi$. Corresponding changes in particle motion and stress chain domain area are also of an exponential form. The onset $\phi_c$ marking the initial increase in pressure varies with the material friction coefficient $\mu$. At larger $\phi$ above $\phi_c$, the pressure varies approximately linearly. Under repetitive cycling of the pressure, the onset $\phi_c$ increases slowly with repetition number. Hysteresis is also observed during repetitive loading. The experimental results are interpreted on the basis of recent numerical evidence for contact percolation transition elucidated by Shen et. al. as well as frictional jamming.