Date

2016-07-24

Author

Yalçınkaya, Tuncay

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Deformation of polycrystalline materials induce intra–granular, inter–granular and trans–granular deformation localization which results in spatially heterogeneous strain and stress distribution affecting the plasticity, damage and fracture of the material. Inter–granular localization is the most common mechanism considering the grain boundaries are natural locations triggering accumulation of the plastic slip and the geometrically necessary dislocations which accommodate the gradients of the inhomogeneous plastic strain. In this context the interactions between the dislocations and the grain boundaries play crucial role in the plastic deformation of metallic materials. However the representation of complex grain boundary-dislocation slip interaction mechanisms such as dislocation transmission, emission and dissociation of dislocations within the grain boundary is generally missing in plasticity models. It is obviously computationally not efficient to incorporate these dislocation mechanisms at nano–micro levels into the plasticity models, yet it is essential to include the coarse–grained representation due to their strong influence on the hardening of the materials. This issue has been a challenge and a complete understanding of this phenomenon and its macroscopic effects is still not at reach and the necessary input for computational models is still subject of ongoing discussions. This paper focuses on the continuum scale modeling of dislocation–grain boundary interactions and enriches a particular strain gradient crystal plasticity formulation (convex counter–part of [1] and [2] by incorporating explicitly the effect of grain boundaries on the plastic slip evolution. Within the framework of continuum thermodynamics, a consistent extension of the model is presented and a potential type non–dissipative grain boundary description in terms of grain boundary Burgers tensor (see e.g. [3]) is proposed. The 2D work in [4] has been extended to 3D through a fully coupled finite element solution algorithm which considers both the displacement and plastic slips as primary variables. For the treatment of grain boundaries an interface element is formulated. The proposed formulation is capable of capturing the effect of misorientation of neighboring grains and the orientation of the grain boundaries on slip evolution in a natural way, as demonstrated by bi–crystal specimen examples.

Subject Keywords

Grain boundaries, Crystal plasticity, Grain boundary–dislocation interaction, İnter–granular localizatio

URI

https://hdl.handle.net/11511/71538

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Department of Aerospace Engineering, Conference / Seminar