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Prediction of size effects and regularization of adiabatic shear band formation in single and poly-crystals : Gradient crystal plasticity approach

Abstract : Classical crystal plasticity models fail to capture experimentally observed size effects, namely, the smaller the size the greater thestrength. These models also show spurious mesh dependency in strain localization problems due to the lack of a characteristiclength scale in the constitutive framework. Strain gradient crystal plasticity models can overcome above mentioned limitations of the classical crystal plasticity models. However, implementing the strain gradient plasticity model in commercial finite element (FE) software is challenging due to the complex constitutive framework. In the present work, strain gradient crystal plasticity models, specifically reduced-order micromorphic crystal plasticity and Lagrange multiplier-based models, are used to predict the size effect insingle crystals microwire torsion tests. A comparison is performed between the predicted size effect using the Lagrange multiplier-based model and that made by the CurlFp model from the literature, which is based on the complete dislocation density tensor. Moreover, strain localization due to temperature rise is investigated. A thermodynamically consistent formulation of the constitutive equations is proposed for the classical and micromorphic crystal plasticity models. This thermodynamically consistent framework is applied to investigate the adiabatic shear band (ASB) formation process in single and polycrystalline Face-Centered Cubic (FCC) metallic materials. Five different crystal orientations of a single crystal hat-shaped specimen are considered to study the formation,intensity, and orientation of shear bands. The formation of ASB and the grain size effect are investigated in hat-shaped polycrystalline aggregates. Moreover, predicting the stored energy is essential to understand the plastic deformation and subsequent recovery and recrystallization mechanisms. Thermodynamically consistent classical and micromorphic crystal plasticity models are used to predictthe stored energy in single and poly-crystalline FCC metallic materials. To this end, we propose an easy way to implement themicromorphic plasticity model in commercial FE software using the analogy between classical thermo-mechanics and micromorphicplasticity theory.
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Submitted on : Friday, April 22, 2022 - 2:49:11 PM
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Vikram Phalke. Prediction of size effects and regularization of adiabatic shear band formation in single and poly-crystals : Gradient crystal plasticity approach. Material chemistry. Université Paris sciences et lettres, 2022. English. ⟨NNT : 2022UPSLM001⟩. ⟨tel-03649416⟩

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