title: Structural and mechanical features of the order-disorder transition in experimental hard-sphere packings.
abstract: Here we present an experimental and numerical investigation on the grain-scale geometrical and mechanical properties of partially crystallized structures made of macroscopic frictional grains. Crystallization is inevitable in arrangements of monosized hard spheres with packing densities exceeding Bernal's limiting density ϕ(Bernal)≈0.64. We study packings of monosized hard spheres whose density spans over a wide range (0.59<ϕ<0.72). These experiments harness x-ray computed tomography, three-dimensional image analysis, and numerical simulations to access precisely the geometry and the 3D structure of internal forces within the sphere packings. We show that clear geometrical transitions coincide with modifications of the mechanical backbone of the packing both at the grain and global scale. Notably, two transitions are identified at ϕ(Bernal)≈0.64 and ϕ(c)≈0.68. These results provide insights on how geometrical and mechanical features at the grain scale conspire to yield partially crystallized structures that are mechanically stable.
authors.affiliation: Department of Physics, University of Tehran, Tehran 14395-547, Iran.|School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Hanifpour
authors.affiliation: Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra, Australia.
authors.forename: N
authors.initials: N
authors.lastname: Francois
authors.affiliation: Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra, Australia.
authors.forename: V
authors.initials: V
authors.lastname: Robins
authors.affiliation: Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Kingston
authors.affiliation: Department of Physics, University of Tehran, Tehran 14395-547, Iran.|School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran.
authors.forename: S M Vaez
authors.initials: SM
authors.lastname: Allaei
authors.affiliation: Department of Applied Mathematics, Research School of Physics and Engineering, Australian National University, Canberra, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Saadatfar