Modélisation micromécanique de l'écrouissage des matériaux polycristallins contenant des hétérogénéités intragranulaires : Introduction à l'endommagement ductile

Abstract : A micromechanical modeling of the elastoplastic behavior of a polycrystalline material containing intra-granular heterogeneities is proposed. It is based on a two-level homogenization approach in order to take into account the influence of intra-crystalline heterogeneities, in the hardening and the ductile damage. Interactions indeed take place between these foreign particles and dislocations during the crystallographic slip, according to Orowan mechanism with formation of dislocations loops. A new formulation of intra-crstallyne hardening of heterogeneous grain is proposed. First, a micro-meso transition is employed to establish a constitutive relation for a single crystal containing particles. The behavior of the equivalent single crystal with particles is derived from the classical formulation of plasticity of the single crystal based on the Schmid's law and crystallographic gliding. Then, the transition to the macroscopic scale is performed with self-conscient scheme to determine the elastoplastic behavior of the macroscopic material.The equivalent bahavior of the model is characterized by a mixed anisotropic and kinematic hardening resulting from an evolution of inter- and intra-granular material microstructure. Results have been analyzed in light of second and third order internal stresses developed during the plastic flow. Especially, yield surfaces have been determined for various preloadings and particle volume fractions. The strong polarization of third order internal stresses localized in grain is at the origin of microvoids nucleation by crystal/particle interface decohesion. Cavities growth is related to the plastic straining of the surrounding crystal according to the principle of conservation of mass. The porosity variation has been analyzed according to the grain microstructure and also to the loading pattern to highlight the sensitivity of damaged material to the remote stress triaxiality
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Napo Bonfoh. Modélisation micromécanique de l'écrouissage des matériaux polycristallins contenant des hétérogénéités intragranulaires : Introduction à l'endommagement ductile. Autre. Université Paul Verlaine - Metz, 2001. Français. ⟨NNT : 2001METZ020S⟩. ⟨tel-01748959⟩

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