Climb-Enabled Discrete Dislocation Plasticity Analysis of the Deformation of a Particle Reinforced Composite
Climb-Enabled Discrete Dislocation Plasticity Analysis of the Deformation of a Particle Reinforced Composite
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DOI：
10.1115/1.4030319
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发表时间：
2015-07-01
影响因子：
2.6
通讯作者：
Deshpande, V. S.
中科院分区：
文献类型：
--
作者：
Ayas, C.;Dautzenberg, L. C. P.;Deshpande, V. S.
采用离散位错塑性（DDP）框架分析了单晶弹塑性基体中弹性颗粒组成的复合材料的剪切变形，其中位错运动通过爬升辅助滑动发生。强化的拓扑结构是这样的，位错不能连续地通过仅滑动的方式横过基体，而不会遇到位错无法穿透的粒子。当位错仅以滑移方式运动时，在一定体积分数下，剪切应力-应变响应表现为强烈的应变硬化，硬化速率随颗粒尺寸的减小而增大。这是由于在颗粒/基体界面处形成了位错堆积。与这些堆积相关的背应力导致了尺寸效应和强烈的鲍辛格效应。相反，当允许位错爬升时，位错堆积通过在颗粒/基体界面处形成低能量的位错壁结构而破裂。这显著降低了尺寸效应和应变硬化。事实上，随着爬升迁移率的增加，还预测了“逆粒径”效应，即强度随粒径的减小而降低。与位错仅通过滑动运动的情况相比，通过位错爬升沿基体/粒子界面进行的质量传递导致了响应的变化，也导致了晶格旋转和几何上必要的位错（GNDs）密度的减少。
The shear deformation of a composite comprising elastic particles in a single crystal elastic-plastic matrix is analyzed using a discrete dislocation plasticity (DDP) framework wherein dislocation motion occurs via climb-assisted glide. The topology of the reinforcement is such that dislocations cannot continuously transverse the matrix by glide-only without encountering the particles that are impenetrable to dislocations. When dislocation motion is via glide-only, the shear stress versus strain response is strongly strain hardening with the hardening rate increasing with decreasing particle size for a fixed volume fraction of particles. This is due to the formation of dislocation pile-ups at the particle/matrix interfaces. The back stresses associated with these pile-ups result in a size effect and a strong Bauschinger effect. By contrast, when dislocation climb is permitted, the dislocation pile-ups break up by forming lower energy dislocation wall structures at the particle/matrix interfaces. This results in a significantly reduced size effect and reduced strain hardening. In fact, with increasing climb mobility an "inverse size" effect is also predicted where the strength decreases with decreasing particle size. Mass transport along the matrix/particle interface by dislocation climb causes this change in the response and also results in a reduction in the lattice rotations and density of geometrically necessary dislocations (GNDs) compared to the case where dislocation motion is by glide-only.