Memory in 3D cyclically driven granular material

Abstract

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 such systems are capable of storing the history of previous compressions. While both mean translational and rotational displacements encode such memory, the response is fundamentally different for translations compared to rotations. For translational displacements, this memory of prior forcing depends on the coefficient of static inter-particle friction, but rotational memory is not altered by the level of friction.

Mechanical annealing and memories in a disordered solid

“…In this case, the envelope of annealing is revealed by the damage that occurs rapidly when that envelope is exceeded (Figs. 1D and 3D) (60,61), resembling the Mullins or Kaiser effect in other materials, whereby the largest applied deformation is remembered (32,44). Once annealed, our system allows memories of multiple strains to be written in single cycles, consistent with return point memory that was first studied in ferromagnets (30).…”

Effects of interparticle friction on the response of 3D cyclically compressed granular material

“…In fact, if one takes the sum of the normalized squared distance of each point from the black dashed line, values of 32.5, 24.2, 11.0, 16.8, 52.2 are obtained with increasing friction. At low friction, a lot of contacts are sliding [13], which lead to high frictional lost. The proportion of sliding contacts decrease with friction, however the dissipated energy per sliding contact increase.…”

“…The results presented in this paper are for a system which was subjected to 200 cycles of pure shear. We focus on small shear amplitudes, where the evolution of the system is small [12,13]. The linear displacements are calculated as the difference in position of the grains when the wall is at position 0 to an amplitude A. Rotations are defined by a rotation matrix between the orientation of each grain when the wall is at position 0 and compressed to A.…”

“…Moreover, in dense granular assemblies, energy loss is dominated by frictional dissipation that generates rotational motion. Although fundamental for frictional systems, only a few studies have an explicit focus on grain rotations [11][12][13][14][15][16].…”