Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anisotropic nonlinear elasticity in a spherical bead pack: influence of
  the fabric anisotropy   Stress-strain measurements and ultrasound propagation experiments in glass
bead packs have been simultaneously conducted to characterize the
stress-induced anisotropy under uniaxial loading. These measurements, realized
respectively with finite and incremental deformations of the granular assembly,
are analyzed within the framework of the effective medium theory based on the
Hertz-Mindlin contact theory. Our work shows that both compressional and shear
wave velocities and consequently the incremental elastic moduli agree fairly
well with the effective medium model by Johnson et al. [J. Appl. Mech. 65, 380
(1998)], but the anisotropic stress ratio resulting from finite deformation
does not at all. As indicated by numerical simulations, the discrepancy may
arise from the fact that the model doesn't properly allow the grains to relax
from the affine motion approximation. Here we find that the interaction nature
at the grain contact could also play a crucial role for the relevant prediction
by the model; indeed, such discrepancy can be significantly reduced if the
frictional resistance between grains is removed. Another main experimental
finding is the influence of the inherent anisotropy of granular packs, realized
by different protocols of the sample preparation. Our results reveal that
compressional waves are more sensitive to the stress-induced anisotropy,
whereas the shear waves are more sensitive to the fabric anisotropy, not being
accounted in analytical effective medium models.

2
The categories of this paper are: math
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas