Memory in 3D Cyclically Driven Granular Matter

We perform experimental and numerical studies of a granular system under cyclic-compression to investigate reversibility and memory effects. We focus on the quasi-static forcing of dense systems, which is most relevant to a wide range of geophysical, industrial, and astrophysical problems. We find that soft-sphere simulations with proper stiffness and friction quantitatively reproduce both the translational and rotational displacements of the grains. We then utilize these simulations to demonstrate that this system is capable of storing the history of previous compressions. While both mean translational and rotational displacements encode memory of compression history, the response is fundamentally different for translations compared to rotations. Finally, for translational displacements, we observe that memory of prior forcing depends on the coefficient of static inter-particle friction, but rotational memory is not altered by the level of friction.