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Finite element modelling of grain-scale heterogeneities in polycrystalline aggregates

Abstract : Macroscopic properties of crystalline solids depend inherently on their underlying mi-croscopic structure. Studying the mechanisms operating at the microstructural scale during the various thermomechanical processes to which such materials may be subjected offers a valuable insight into their final in-use properties. The objective of this work is to investigate grain scale heterogeneities in polycrystalline aggregates subjected to large strains using the Crystal Plasticity Finite Element Method (CPFEM). For this purpose, highly resolved simulations, where each grain is represented explicitly, are needed. The first part of this work is devoted to a detailed account of the numerical framework implemented for such simulations. A classical elastic-viscoplastic crystal plasticity model is combined to a non-linear parallel finite element framework. The discretization of the digital microstructures is performed using non- conforming unstructured meshes. Most importantly, a level set approach is used to describe grain boundaries and to guide an adaptive anisotropic meshing strategy. Automatic remeshing, with appropriate transport of variables, is introduced in the proposed framework. In the second part of this work, the robustness and flexibility of our approach is demonstrated via different CPFEM applications. The deformation energy is used to assess heterogeneities in polycrystalline aggregates, highlighting the need to perform adaptive meshing so as to achieve a good compromise between accuracy and computation time. These grain-scale heterogeneities are to be accurately predicted during the deformation simulation if subsequent static recrystallization modelling is to be performed. An example of linking between the deformation and static recrystallization steps, using the proposed common approach, is illustrated. In terms of global texture predictions, the CPFEM framework is validated for a highly resolved model polycrystal subjected to more than 90 % thickness reduction in rolling. The importance of automatic remeshing in avoiding excessive mesh distortion, in such applications, is demonstrated. Most importantly, microtexture analysis is performed on digital microstructures that correspond, in a discrete sense, to an actual microstructure observed experimentally. Intragranular misorientation predictions and virtual 2D orientation maps are compared to the experimental ones, highlighting the difficulties pertaining to the validation of such grain-scale predictions.
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Submitted on : Thursday, March 17, 2011 - 3:56:16 PM
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  • HAL Id : pastel-00577855, version 1

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Héba Resk. Finite element modelling of grain-scale heterogeneities in polycrystalline aggregates. Materials. École Nationale Supérieure des Mines de Paris, 2010. English. ⟨NNT : 2010ENMP0047⟩. ⟨pastel-00577855⟩

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