Anaël Lemaître

Rearrangements and dilatancy for sheared dense materials.

Constitutive equations are proposed for dense materials, based on the identification of two types of free-volume activated rearrangements associated with shear and compaction. Two situations are studied: the case of an amorphous solid in a stress-strain test, and the case of a lubricant in tribology test. Varying parameters, strain softening, shear thinning, and stick-slip motion can be observed.

Shear thickening and migration in granular suspensions.

We study the emergence of shear thickening in dense suspensions of non-Brownian particles. We combine local velocity and concentration measurements using magnetic resonance imaging with macroscopic rheometry experiments. In steady state, we observe that the material is heterogeneous, and we find that the local rheology presents a continuous transition at low shear rate from a viscous to a shear thickening, Bagnoldian, behavior with shear stresses proportional to the shear rate squared, as predicted by a scaling analysis. We show that the heterogeneity results from an unexpectedly fast migration of grains, which we attribute to the emergence of the Bagnoldian rheology. The migration process is observed to be accompanied by macroscopic transient discontinuous shear thickening, which is consequently not an intrinsic property of granular suspensions.

Phase Ordering and Onset of Collective Behavior in Chaotic Coupled Map Lattices

The phase-ordering properties of lattices of band-chaotic maps coupled diffusively with some coupling strength

Non-trivial collective behavior in extensively-chaotic dynamical systems: an update

g

Universal Additive Effect of Temperature on the Rheology of Amorphous Solids

are studied in order to determine the limit value

Tensorial analysis of Eshelby stresses in 3D supercooled liquids

{g}_{\mathrm{e}}

Ultrafast spherulitic crystal growth as a stress-induced phenomenon specific of fragile glass-formers

beyond which multistability disappears and nontrivial collective behavior is observed. The persistence of equivalent discrete spin variables and the characteristic length of the patterns observed scale algebraically with time during phase ordering. The associated exponents vary continuously with

Robustness of avalanche dynamics in sheared amorphous solids as probed by transverse diffusion.

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Inherent stress correlations in a quiescent two-dimensional liquid: Static analysis including finite-size effects

but remain proportional to each other, with a ratio close to that of the time-dependent Ginzburg-Landau equation. The corresponding individual values seem to be recovered in the space-continuous limit.

Analytical results for generalized persistence properties of smooth processes

Extensively-chaotic dynamical systems often exhibit non-trivial collective behavior: spatially-averaged quantities evolve in time, even in the infinite-size, infinite-time limit, in spite of local chaos in space and time. After a brief introduction, we give our current thoughts about the important problems related to this phenomenon. In particular, we discuss the nature of non-trivial collective behavior and the properties of the dynamical phase transitions observed at global bifurcation points between two types of collective motion.