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首页> 外文期刊>International Journal of Solids and Structures >A continuum model for intermittent deformation of single crystal micropillars
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A continuum model for intermittent deformation of single crystal micropillars

机译：单晶微柱间歇变形的连续模型

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摘要

Strain bursts are often observed during compression tests of single crystal micropillars. In this work,we formulate a new continuum model that accounts for the strain burstswithin the framework of crystal plasticity. The strain bursts are separated from the loading stage (nearly elastic loading) by introducing a dimensionless constant in the continuum model, and are detected by load serrations. The boundary conditions in the context of micropillar compression are studied and they are shown to be changing and unpredictable as plastic deformation proceeds. To evaluate the validity of our model, finite element simulations of the uniaxial compression tests on nickel micropillars are performed. Our simulations produce clearly visible strain bursts during the plastic flow and the produced intermittent flows are comparable with the experimental observations. For the bulk crystal, a series of strain bursts is identified in the course of plastic flow, despite an apparently smooth stress–strain response. We also show that the intermittent flow is intensified in the micrometer-scale due to both increasing numbers of the successive strain bursts and increasing amplitude of the strain burst, when the specimen size decreases. Finally, we show that the occurrences of the strain bursts are always associated with negative values of the second-order work.
机译：在单晶微柱的压缩试验中经常观察到应变破裂。在这项工作中，我们制定了一个新的连续模型，该模型考虑了晶体可塑性框架内的应变爆发。通过在连续体模型中引入无量纲常数，将应变爆发与载荷阶段（几乎是弹性载荷）分开，并通过载荷锯齿来检测。研究了在微柱压缩的情况下的边界条件，这些边界条件随着塑性变形的进行而变化并且不可预测。为了评估我们模型的有效性，对镍微柱进行了单轴压缩试验的有限元模拟。我们的模拟在塑性流动期间产生了清晰可见的应变破裂，并且所产生的间歇流动与实验观察结果相当。对于块状晶体，尽管表观应力-应变响应很平稳，但在塑性流动过程中仍会发现一系列应变破裂。我们还表明，当样本尺寸减小时，由于连续应变爆发的数量增加和应变爆发的幅度增加，间歇流在微米尺度上增强了。最后，我们证明了应变爆发的发生总是与二阶功的负值相关。

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