Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · cond-mat/0506386

Deformation Modes of a Packing of Rigid Grains: Rotation, Counter-rotation, dislocation field

P. Evesque
View original source ↗Read source document ↗Export metadata ↓

Abstract

The properties of the processes of deformation of a packing of rigid grains are analysed when the exact distribution of the normal forces at contacts is known. Importance of grain rotation and of counter-rotation of adjacent grains is stressed. It is shown that all deformation modes form an incomplete vectorial space D. This allows the statistics of fluctuation to be determined. Parallel with anti-ferromagnetism is then drawn and frustration of rotation is shown to be the leading dissipating mechanism. However this does not allow making the parallel with spinglass due to the structure of the space of deformation modes which is vectorial, which ensures response linearity. In order to demonstrate experimentally the validity of the approach and the existence of the incomplete vectorial space of deformation, experimental examples are studied starting from regular arrays. They do demonstrate the mechanism of counter-rotation and the existence of the vectorial space of deformation. This theory is applied to compare different experiment and simulation results on the deformation of square and triangular lattices of rods, which can only be done through a statistical approach based on existence of different modes of deformation. Non linear behaviour of the modes is demonstrated experimentally; link with the continuous theory of dislocation is made. Pacs # : 5.40 ; 45.70 ; 62.20 ; 83.70.Fn

Explore related subjects

cond-mat.soft

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

P. Evesque. 2005-06-15. Deformation Modes of a Packing of Rigid Grains: Rotation, Counter-rotation, dislocation field. https://arxiv.org/abs/cond-mat/0506386

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Control of filament network rigidity by the condensation of crowding molecules

Understanding how liquid-liquid phase separation impacts the mechanics of filament networks is a fundamental physical problem at the heart of biological cellular processes and soft material design. While a few theoretical mechanisms have been proposed, a clear demonstration of the direct coupling of phase separation to the overall network stiffness is missing. We report experiments that reveal a universal mechanism by which the condensation of macromolecular crowders induces a rigidity transition in a model filament network. We reconstituted stiff sterically interacting helical filaments and polymeric crowders. Initially, the macromolecules were uniformly dissolved and the filaments formed bundles that assembled a rigid entangled network. Once the crowders condensed into droplets, the network structure lost its rigidity and its mechanical response weakened by an order-of-magnitude. The subsequent dissolution of the condensates was accompanied by the re-establishment of rigidity. Our results show that crowder phase separation modulates the mechanics of filament networks by tuning the osmotic pressure holding the network together. This principle may serve as a paradigm for devising dynamically tunable filamentous materials.

cond-mat.soft↗
arXiv2026

Speed up of passive tracers in mixtures with active chemical reactions

Diffusivity of passive tracers in complex mixtures is widely relevant for industrial applications and for probing biological systems. Interactions with the surrounding medium typically generate a drag force that suppresses tracer diffusion, although self-propulsion can accelerate tracers via active fluctuations. Similar effects are not understood in mixtures with particle conversion and exchange, although these are particularly relevant in biological contexts, where actively driven reactions prevail. By studying a thermodynamically consistent model of chemical reactions in mixtures, we show that reactions provide an additional relaxation pathway that suppresses interaction-induced memory, reducing the drag on tracers and restoring their diffusivity toward the value expected in the absence of solutes. Moreover, active reactions generate nonequilibrium fluctuations that can push tracer diffusivity beyond this limit, an effect we confirm with particle-based simulations. Our results identify chemical activity as a distinct route to controlling mass transport and offer a framework for interpreting microrheology experiments in chemically active mixtures.

cond-mat.soft↗
arXiv2026

Diffusion of charged rods across 3D varying section channels

We analyze the transport of rod-like particles by diffusion and drift in a three-dimensional channel with varying circular or elliptic cross section. Applying the Fick-Jacobs approximation to the transport equation of the particles' probability distribution, we derive an effective one-dimensional substitute model and the associated free energy profile. Our results show that the data for the mean first passage time of rods, once expressed as a function of the effective free energy barrier, collapse onto the same master curve as obtained for point or spherical particles. The observed universality provides a simple framework for predicting transport times of anisotropic particles in confined geometries without resolving the full multidimensional dynamics.

cond-mat.soft↗