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The Flow of Amorphous Solids: Elastoplastic Models and Mode-Coupling Approach

Abstract : Contrary to the case of simple fluids, a finite stress is required to initiate the flow of amorphous solids, a broad class of materials ranging from bulk metallic glasses to dense emulsions. The objective of this thesis is to model the flow of these materials in a general framework, with an emphasis on heterogeneities.In a first approach, using the liquid regime as a starting point, I have investigated to what extent inhomogeneities can be accommodated in the framework of the mode-coupling theory of rheology. A generic equation for the evolution of density inhomogeneities has been derived.At low temperatures, the flow is indeed quite heterogeneous: it consists of periods of elastic deformation interspersed with swift localised rearrangements of particles, that induce long-range elastic deformations and can thereby spark off new rearrangements. In a second approach, a model rooted in this scenario has been refined so as to reflect the interplay between the external drive and the localised rearrangements, which is at the origin of the flow curve of athermal solids. The latter has been reproduced satisfactorily.Turning to spatial correlations in the flow, we have shown that there exists no universal scaling for these correlations in elastoplastic models, although a broad class of correlation lengths scale with \dot{\gamma}^{\nicefrac{-1}{d}} in the shear-dominated regime in d dimensions.Besides, shear localisation has been observed in diverse variants of the model, whenever blocks are durably weakened following a plastic event.Finally, we have directly compared model predictions to experimental results on the flow of dense emulsions through microchannels and to athermal molecular dynamics simulations. Spurred on by the observation of some discrepancies, we have developed and implemented a more flexible code, based on a simplified Finite Element routine, which notably provides a better account of structural disorder and inertial effects.
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Contributor : Alexandre NICOLAS Connect in order to contact the contributor
Submitted on : Tuesday, November 25, 2014 - 1:33:48 PM
Last modification on : Friday, March 25, 2022 - 9:40:16 AM
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  • HAL Id : tel-01087018, version 1




Alexandre Nicolas. The Flow of Amorphous Solids: Elastoplastic Models and Mode-Coupling Approach. Soft Condensed Matter [cond-mat.soft]. Université de Grenoble, 2014. English. ⟨tel-01087018⟩



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