位移加载条件下微小尺寸单晶金属的应变突变模型及其间歇性塑性变形行为研究

微压缩实验发现，微小尺度单晶金属柱体在塑性变形过程中会发生显著的应变突变，呈现出特殊的间歇性塑性流动特征。本文以数百纳米直径的单晶Au柱体为研究对象，探讨其在位移加载条件下的间歇性流动行为。首先根据位移加载条件下的塑性变形特征，提出了分析其应变突变的三阶段模型。进一步结合经典晶体塑性理论框架的有限元方法，建立了以二阶功参量为基础的连续塑性力学模型。通过与实验结果相对比发现，新模型能够较好地描述位移加载条件下微小尺度面心立方单晶金属材料的应变突变现象，能够合理预测单晶柱体的特殊变形行为。此外，二阶功准则作为位移加载条件下应变突变现象的判据是有效的。进而使用该理论模型，探讨了微小金属柱体应变突变随机性、尺寸相关性以及率敏感性等问题。

Strain burst model and intermittent plastic flow of single crystal nanopillar under displacement loading mode

The micro-compression tests revealed significant strain bursts during plastic deformation of single crystal nanopillar, showing special intermittent plastic flow behaviors. In this paper, a three-stage formulation of the strain burst phenomenon is presented according to the experimental observations of single-crystal Au pillars with a diameter of several hundred nanometers under displacement loading mode. A continuum mechanics model with the second-order work parameter is then developed to describe the intermittent plastic flow within crystal plasticity framework, and their finite element implementation is realized. By comparing to the experimental results, the newly proposed theoretical model is verified to be able to describe the strain bursts and plastic flow of face-centered cubic single crystal under displacement loading mode, with a reasonable accuracy in predicting the plastic deformation behavior of nanopillars. In addition, the second-order work criterion is effective in judging the occurrence of strain bursts event under the condition of displacement loading. Using this model, the randomness, size dependency and rate sensitivity of strain bursts during the plastic deformation of nanopillars are further investigated in detail.