Abstract. This paper presents a new mesoscopic full field approach for the modelling of microstructural evolutions and mechanical behavior of olivine aggregates. The mechanical framework is based on a reduced crystal plasticity (CP) formulation which is adapted to account for non-dislocation glide strain-accommodating mechanisms in olivine polycrystals. This mechanical description is coupled with a mixed velocity/pressure finite element (FE) formulation through a classical crystal plasticity finite element method (CPFEM) approach. The microstrutural evolutions, such as grain boundary migration and dynamic recrystallization, are also computed within a FE framework using an implicit description of the polycrystal through the level-set approach. This numerical framework is used to study the strain localization, at the polycrystal scale, on different types of pre-existing shear zones for thermomechanical conditions relevant to laboratory experiments. We show that both fine-grained and crystallographic textured pre-existing bands favor strain localization at the sample scale. The combination of both processes has a large effect on strain localization, which emphasizes the importance of these two microstructural characteristics (texture and grain size) on the mechanical behavior of the aggregate.

中文翻译：

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一种新的有限元方法来模拟橄榄石骨料中的微观应变局部化

摘要。本文提出了一种新的介观全场方法，用于对橄榄石聚集体的微观结构演变和力学行为进行建模。机械框架基于降低的晶体可塑性（CP）配方，该配方适用于解决橄榄石多晶中的非位错滑移应变适应机制。通过经典的晶体塑性有限元方法（CPFEM）方法，将这种机械描述与速度/压力混合有限元（FE）公式相结合。微观结构的演化，例如晶界迁移和动态再结晶，也通过水平集方法使用多晶晶体的隐式描述在有限元框架内进行计算。该数值框架用于研究多晶尺度下的应变局部化，在与实验室实验有关的热机械条件下，使用不同类型的预先存在的剪切带。我们表明，细粒度和晶体学纹理既存的条带都有利于样品规模的应变局部化。两种方法的结合对应变局部化有很大影响，这强调了这两个微观结构特征（质地和晶粒尺寸）对骨料力学性能的重要性。