Onset of Irreversibility in Cyclic Shear of Granular Packings
  We investigate the onset of irreversibility in a dense granular medium subjected to cyclic shear in a split-bottom geometry. To probe the micro and mesoscale we image bead trajectories in 3D throughout a series of shear strain oscillations. Though beads lose and regain contact with neighbors during a cycle, the topology of the contact network exhibits reversible properties for small oscillation amplitudes. With increasing reversal amplitude a transition to an irreversible diffusive regime occurs. 
Steven Slotterback and Mitch Mailman and Krisztian Ronaszegi and   Martin van Hecke and Michelle Girvan and Wolfgang Losert
cond-mat.soft