基于能量变化的微尺度金属应变突变准则研究

微尺度金属在塑性变形过程中呈现出显著的应变突变特性。本文以力加载条件下单晶Ni微米柱体和位移加载下Au纳米柱体为对象，探讨应变突变的判定准则与不同特征阶段的判别条件。首先从经典塑性理论Hill稳定性条件出发，分析微柱体变形过程中的动能变化，提出了应变突变发生与结束的判定准则。进一步分析柱体变形过程中的内能变化，结合动能变化的分析结果，给出了微尺度金属不同变形阶段的判别条件。通过与文献中实验与理论结果对比发现，基于动能变化的应变突变判定准则能够判断应变突变的发生与结束，基于能量变化的判别条件可以有效区分微柱体的不同变形阶段。最后对新理论准则的可靠性与适用性进行了讨论。

Strain Burst Criteria for Microscale Metal Based on Energy Change

Significant strain burst phenomenon is observed during the plastic deformation of microscale metal. This work aims to develop the strain burst criteria and judging conditions for different deformation stages of microscale metal, taking single-crystal Ni micro-pillar under force loading and Au nano-pillar under displacement loading as examples. Based on the classical Hill’s stability condition in continuum plasticity theory, the criteria for the occurrence and termination of the strain burst are proposed according to the variations of kinetic energy during the deformation process of small pillars. Furthermore, the internal energy evolution of pillars during the deformation process is analyzed. Based on the simultaneous changes of kinetic energy and internal energy, the judging conditions for different deformation stages of pillars are established. Then, these theoretical developments are verified by comparing their finite element outputs with the experimental and theoretical results in literature. It is found that the proposed strain burst criteria using kinetic energy increment can effectively identify the occurrence and termination of the strain burst events, and the judging conditions based on energy changes are capable of distinguishing different deformation stages of micro- and nano-pillars. The applicability and merits of the newly proposed criteria are discussed at the end of the paper.