CNCS Seminar
Tuesday, December 5, 2017, 12:00pm, 119 Physics
Abram Clark (Naval Postgraduate School)
Yielding in granular materials, from riverbeds to renormalization group
Abstract:- Granular materials are a part of a broad class of amorphous materials
that display yield stress behavior. When the applied shear stress is
below the yield stress, grains move temporarily, but only until
finding a mechanically stable (MS) configuration that is able to
resist the applied shear stress. Above the yield stress, the material
is no longer able to find MS configurations. However, the geometrical
reasons why MS states vanish at the yield stress is not well
understood. In this talk, I will show evidence from molecular dynamics
simulations that yielding in granular materials is akin to a
second-order critical point, where the mechanical behavior is
dominated by a correlation length that diverges at the yield
stress. MS states exist above the yield stress for finite systems, but
they vanish as the system size becomes large according to a critical
scaling function. The packing fraction and coordination number for MS
states are independent of the applied shear stress, implying that the
critical behavior we observe is distinct from the well known jamming
scenario. However, MS states at nonzero shear stress possess
anisotropic force and contact networks, suggesting that the yield
stress is set by the maximum anisotropy that can be realized in the
large-system limit. [video]
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