54 research outputs found
Rheology in dense assemblies of spherocylinders: frictional vs. frictionless
Using molecular dynamics simulations, we study the steady shear flow of dense
assemblies of anisotropic spherocylindrical particles of varying aspect ratios.
Comparing frictionless and frictional particles we discuss the specific role of
frictional inter-particle forces for the rheological properties of the system.
In the frictional system we evidence a shear-thickening regime, similar to that
for spherical particles. Furthermore, friction suppresses alignment of the
spherocylinders along the flow direction. Finally, the jamming density in
frictional systems is rather insensitive to variations in aspect-ratio, quite
contrary to what is known from frictionless systems
The Role of Architecture in the Elastic Response of Semiflexible Polymer and Fiber Networks
We study the elasticity of cross-linked networks of thermally fluctuating
stiff polymers. As compared to their purely mechanical counterparts, it is
shown that these thermal networks have a qualitatively different elastic
response. By accounting for the entropic origin of the single-polymer
elasticity, the networks acquire a strong susceptibility to polydispersity and
structural randomness that is completely absent in athermal models. In
extensive numerical studies we systematically vary the architecture of the
networks and identify a wealth of phenomena that clearly show the strong
dependence of the emergent macroscopic moduli on the underlying mesoscopic
network structure. In particular, we highlight the importance of the full
polymer length that to a large extent controls the elastic response of the
network, surprisingly, even in parameter regions where it does not enter the
macroscopic moduli explicitly. We provide theoretical scaling arguments to
relate the observed macroscopic elasticity to the physical mechanisms on the
microscopic and the mesoscopic scale.Comment: 12 pages, 8 figures, (v3) final versio
The jamming transition as probed by quasistatic shear flow
We study the rheology of amorphous packings of soft, frictionless particles
close to jamming. Implementing a quasistatic simulation method we generate a
well defined ensemble of states that directly samples the system at its
yield-stress. A continuous jamming transition from a freely-flowing state to a
yield stress situation takes place at a well defined packing fraction, where
the scaling laws characteristic of isostatic solids are observed. We propose
that long-range correlations observed below the transition are dominated by
this isostatic point, while those that are observed above the transition are
characteristic of dense, disordered elastic media.Comment: 4 pages, 6 figures, revised versio
- …