A new finite element approach to model microscale strain localization within olivine aggregates

Abstract

Abstract. This paper presents a new mesoscopic full field approach for the modeling of microstructural evolutions and mechanical behavior of olivine\naggregates. The mechanical framework is based on a reduced crystal plasticity (CP) formulation which is adapted to account for non-dislocation glide\nstrain-accommodating mechanisms in olivine polycrystals. This mechanical description is coupled with a mixed velocity–pressure finite element (FE)\nformulation through a classical crystal plasticity finite element method (CPFEM) approach. The microstructural evolutions, such as grain boundary\nmigration and dynamic recrystallization, are also computed within a FE framework using an implicit description of the polycrystal through the\nlevel-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\nthermomechanical conditions relevant to laboratory experiments. We show that both fine-grained and crystallographic textured pre-existing bands\nfavor strain localization at the sample scale. The combination of both processes has a large effect on strain localization, which emphasizes the\nimportance of these two microstructural characteristics (texture and grain size) on the mechanical behavior of the aggregate. Table\xa01 summarizes the list of the acronyms used in the following.\n