Regensburg 2010 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 9: Granular Matter/ Contact Dynamics I
DY 9.5: Talk
Tuesday, March 23, 2010, 11:00–11:15, H47
Precursors of failure in granular systems — •Philipp Welker1 and Sean McNamara2 — 1Institut für Computerphysik, Universität Stuttgart, Germany — 2Institut de Physique de Rennes, Université de Rennes I, France
We study numerical simulations of large (N≈ 104) two-dimensional quasi-static granular assemblies subjected to a slowly increasing deviator stress (“biaxial test”). We report some peculiarities in the behavior of these packings that have not yet been adressed. The number of sliding contacts Ms is not necessarily related to stability: at approximatley half the peak stress, the increase of Ms slows down, a plateau develops, and a decrease follows.
The spatial organization of sliding contacts also changes: the formerly uniformly distributed sliding contacts become concentrated in certain regions in the second half of the simulation. This suggests that the loss of homogeneity occurs well before the appearance of shear bands. During the same period, events appear where Ms drops suddenly, and then rapidly recovers. We show that these events are in fact local re-arrangements in the packing, and that they are triggered by an instability. These events become more frequent as failure is approached. For these two reasons, these events are similar to the precursors recently observed in both numerical [1] and experimental [2], [3] studies of avalanches.
[1] L. Staron et al., Phys. Rev. Lett., 89, 204302 (2002).
[2] T. Scheller et al., Phys. Rev. E, 74, 031311 (2006).
[3] M.A. Aguirre et al., Phys. Rev. E, 73, 041307 (2006).