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Authors: Tamas Borzsonyi, Tamas Unger, Balazs Szabo, Frank Angenstein and Ralf Stannarius
When granular materials deform under external stress the deformation is often localized into narrow regions. These shear zones act as internal slip surfaces between solid-like blocks of the bulk. Here we study experimentally a recent theoretical prediction that shear zones behave in striking analogy with geometric optics [T. Unger, Phys.Rev. Lett. 98, 018301 (2007)] and compare our results with numerical simulations. We show that shear zones alter their orientations when crossing media boundaries similarly to light refraction but here the frictional properties of the materials take the role of the optical index of refraction. We find that the refraction phenomenon also exists in the presence of gravity, i.e. under natural pressure conditions. The internal deformation of the material was detected by two methods: excavation of the sample after shearing and MRI imaging. |
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