INVESTIGADORES
VIDALES Ana Maria
artículos
Título:
Static Response in Disk Packings
Autor/es:
MOUKARZEL, C.F.; PACHECO-MARTÍNEZ, H.; RUIZ, J.C.; VIDALES, A M
Revista:
Grannular Matter
Editorial:
Springer
Referencias:
Año: 2004 vol. 6 p. 61 - 66
ISSN:
1434-5021
Resumen:
We present experimental and numerical results
for displacement response functions in packings of rigid
frictional disks under gravity. The central disk on the bottom
layer is shifted upwards by a small amount, and the
motions of disks above it define the displacement response.
Disk motions are measured with the help of a still digital
camera. The responses so measured provide information
on the force-force response, that is, the excess force
at the bottom produced by a small overload in the bulk.
We find that, in experiments, the vertical-force response
shows a Gaussian-like shape, broadening roughly as the
square root of distance, as predicted by diffusive theories
for stress propagation in granulates. However, the diffusion
coefficient obtained from a fit of the response width
is ten times larger than predicted by such theories. Moreover
we notice that our data is compatible with a crossover
to linear broadening at large scales. In numerical simulations
on similar systems (but without friction), on the
other hand, a double-peaked response is found, indicating
wave-like propagation of stresses. We discuss the main
reasons for the different behaviors of experimental and
model systems, and compare our findings with previous
works.