Experimentally Measuring Rolling and Sliding in Three-Dimensional Dense Granular Packings.

  title={Experimentally Measuring Rolling and Sliding in Three-Dimensional Dense Granular Packings.},
  author={Zackery A. Benson and Anton Peshkov and Nicole Yunger Halpern and Derek C. Richardson and Wolfgang Losert},
  journal={Physical review letters},
  volume={129 4},
We experimentally measure a three-dimensional (3D) granular system's reversibility under cyclic compression. We image the grains using a refractive-index-matched fluid, then analyze the images using the artificial intelligence of variational autoencoders. These techniques allow us to track all the grains' translations and 3D rotations with accuracy sufficient to infer sliding and rolling displacements. Our observations reveal unique roles played by 3D rotational motions in granular flows. We… 

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