Vol. 12, No. 2, 2017

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ISSN: 1559-3959
Interfacial microscopic boundary conditions associated with backstress-based higher-order gradient crystal plasticity theory

Mitsutoshi Kuroda

Vol. 12 (2017), No. 2, 193–218
Abstract

A strategy for modeling various interfacial boundary conditions associated with a higher-order gradient crystal plasticity theory is proposed. The gradient theory employed is based on the concept of the backstress that is produced in response to the spatial variation of the geometrically necessary dislocation densities. To set arbitrary interfacial boundary conditions for the crystallographic slip at the continuum level, a model with a single scalar quantity that aims to control the slipping rate at an interface is introduced. This scalar quantity is intended to represent the resultant effects of microscopic mechanisms such as absorption, emission, and transmission of the dislocations at an interface or a grain boundary (GB). As a realistic application of this basic idea, an orientation-dependent GB model is proposed, which incorporates effects of the degree of misorientation between the adjacent grains as well as the orientation of the GB plane relative to the grains. To illustrate capabilities of the proposed model, the bicrystalline micropillar compression problem is considered. Finite element simulations are performed for the bicrystalline micropillars including either a large-angle grain boundary (LAGB) or a coherent twin boundary (CTB) parallel to the compression axis. The numerical results are qualitatively compared with experimental observations reported in the literature. It is shown that the proposed GB model has a capability to represent the overall material responses associated with both LAGB and CTB using the same material parameter values.

Keywords
strain gradient plasticity, crystal plasticity, interfaces, grain boundaries, geometrically necessary dislocations
Milestones
Received: 20 May 2016
Revised: 13 August 2016
Accepted: 13 September 2016
Published: 14 December 2016
Authors
Mitsutoshi Kuroda
Graduate School of Science and Engineering
Mechanical Systems Engineering
Yamagata University
Jonan 4-3-16
Yonezawa
Yamagata 992-8510
Japan