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arXiv 0911.4922cond-mat.softcond-mat.mtrl-sci
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剪切下二元混合物中晶体、多晶体和玻璃的塑性形变:集体屈服

Plastic deformations in crystal, polycrystal, and glass in binary mixtures under shear: Collective yielding

Hayato Shiba, Akira Onuki

摘要:

利用分子动力学模拟,我们研究了晶体,多晶和玻璃在一个由小颗粒和大颗粒组成的Lennard-Jones二元混合物中的二维动力学。当组分c以固定的尺寸比变化时,这些状态之间发生交叉。剪切作用于与由1800个颗粒组成的运动边界层接触的9000个颗粒的系统。用六重取向角α_j(t)和定义的无序变量D_j(t)来表示粒子的结构,其中无序变量D_j(t)表示粒子偏离六方有序的程度。塑性基本单元分为位错滑移和晶界滑移。在任何c,大规模的屈服事件发生在声学时间尺度上。此外,它们在狭窄的脆性区大量出现,形成剪切带。塑性流动的动力学是高度分层的,对于缓慢剪切具有广泛的时间尺度。我们还澄清了在体区域平均的剪切应力和壁应力施加在边界之间的关系。

英文摘要:

Using molecular dynamics simulation, we examine the dynamics of crystal, polycrystal, and glass in a Lennard-Jones binary mixture composed of small and large particles in two dimensions. The crossovers occur among these states as the composition c is varied at fixed size ratio. Shear is applied to a system of 9000 particles in contact with moving boundary layers composed of 1800 particles. The particle configurations are visualized with a sixfold orientation angle alpha_j(t) and a disorder variable D_j(t) defined for particle j, where the latter represents the deviation from hexagonal order. Fundamental plastic elements are classified into dislocation gliding and grain boundary sliding. At any c, large-scale yielding events occur on the acoustic time scale. Moreover, they multiply occur in narrow fragile areas, forming shear bands. The dynamics of plastic flow is highly hierarchical with a wide range of time scales for slow shearing. We also clarify the relationship between the shear stress averaged in the bulk region and the wall stress applied at the boundaries.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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