(70i) Effects of Particle Friction on the Fatigue Failure of Granular Materials Under Cyclic Compression

The effects of particle friction on the dynamics and transport of granular systems is studied using LAMMPS simulation. First, the bidisperse systems are prepared below and close to the isotropic jamming point (φ_J). The systems consist of nearly 40000 particles, randomly positioned at x-y plane. The particles are spheres, and bidispersed (1:1 ratio) with diameters 1 and 1.4. The prepared initial samples are then subject to cyclic compression and decompression. This actuation quasi-statically moves the system below and above jamming point. The packing fraction of compressed states span between 0.84 (jamming point), and 0.89. The friction coefficient is also varied between 0 and 1. The dynamics of particles through consecutive compressed states are studied. By measuring mean square displacement and mixing parameter, I verify that several dynamical regimes exist for this system. At very low friction coefficients and close to jamming point, the particles show Brownian-like motion, the dynamics is caged, and the system resembles a glass. At intermediate friction coefficients, the system may exhibit large convective motion. This results show that non-zero particle friction strongly enhances the transport, and hence mixing in granular materials under isotropic drive. At higher friction coefficients, the system is stable and very resilient against motion. However, the results show that a fatigue failure transition occurs, if the system is actuated for sufficiently long times. This fatigue failure is demonstrated through a sudden and avalanche drop in material pressure.