Regensburg 2010 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 13: Granular Matter/ Contact Dynamics II
DY 13.11: Talk
Wednesday, March 24, 2010, 12:15–12:30, H47
Unjamming of granular packings due to local perturbations — •reza shaebani1, tamas unger2, dietrich wolf1, and janos kertesz2 — 1Computational and Statistical Physics Group, Department of Theoretical Physics, University of Duisburg-Essen, 47047 Duisburg, Germany — 2Department of Theoretical Physics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
One of the most exciting research challenges for granular media is to provide better understanding of the onset of yielding. When the external load on a static assembly of grains is changed at a certain point the load may become incompatible with the inner structure of the packing and the solid state loses its stability. How exactly this happens on the grain scale and what are the key features of the transition between statics and flow are intriguing and unresolved problems.
In this study, the unjamming response of dense disordered granular media is investigated based on CD and MD simulations. We break the static structure of the packings by small local deformations and induce motion of particles. We determine the critical force of the local perturbation that is needed to break the mechanical equilibrium and examine the generated displacement field. We find that displacements decay as a power law of the distance from the perturbation point. We show that the decay exponent and the critical force are nonmonotonic and have a sharp maximum at the friction coefficient 0.1. We find that the mechanical response properties are closely related to the problem of force-indeterminacy.