Modélisation de l'effet de taille dans le comportement élasto-viscoplastique des matériaux nanocristallins

Abstract : This study is dedicated to the modeling of the size effect in the elasticviscoplastic behavior of nanocrystalline materials. Among others. this work aims at identifying the mechanisms responsible for the breakdown of the hall Petch law as well as to propose a new map of deformation which could aver usefull for future improvement of experimental fabrication processes. A detailed state of the art is presente in the first chapter of this theses where the structure of NC materials is presented as well the fabrication process and existing models. The state of the art is followed by a first attempt model where the effect of Coble Creep as well as that of Lischik sliding are quantified. The macroscopic behavior of the material is retrieved via the use of a self consistent micromechanical scheme. The second par tof this work i dedicated to the modeling of the recently introduced grain boundary dislocation emission mechanism. A new constitutive law , based on the formalism of thennally activated mechanisms, is introduced to describe the combined effect of dislocation emission and dislocation penetration. The study is completed by both a method of evaluation of the parameters based on molecular dynamics simulations and by finite element analyses
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Laurent Capolungo. Modélisation de l'effet de taille dans le comportement élasto-viscoplastique des matériaux nanocristallins. Autre. Université Paul Verlaine - Metz, 2006. Français. ⟨NNT : 2006METZ037S⟩. ⟨tel-01749076⟩

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