Cyclic Compression of Soft Granular Particles

We are experimentally investigating the response of soft granular materials to cyclic perturbations. From previous works we know that after several hundred cycles of cyclic compression, hard granular materials will converge to a steady state, where the particles will return to their original position at the end of a cycle of low amplitude compression. These steady states are linked to the memory formation in granular matter. However, this picture will change if a strong coupling between the reversible displacement of particles and irreversible rotations is introduced, leading to an overall irreversible and memory-less state. We study how the softness of particles will affect that picture using a cyclic compression apparatus with optical index matched particles which allow us to extract the motion of each individual particle in three dimensions. The deformation of the particles could lead to a coupling between the displacement and the rotations leading to a possibly irreversible state.