Materials are often heterogeneous at various length scales, with variations in grain structure, defects, and composition which has a strong influence on the emergent macroscopic plastic behavior. In particular, heterogeneities lead to fluctuations in the plastic response in the form of jerky flow and ubiquitous strain bursts. One of the crucial aspects of plasticity modeling is scale bridging: In order to deliver physically correct crystal plasticity models, one needs to determine relevant microstructural length scales. In this paper we advance the idea that continuum descriptions of dislocation mediated plasticity cannot neglect dynamic correlations related to the avalanche behavior. We present an extensive weakest link analysis of crystal plasticity by means of three-dimensional discrete dislocation dynamics simulations with and without spherical precipitates. We investigate strain bursts and related length scales and conclude that while sufficiently strong obstacles to dislocation motion tend to confine the dislocation avalanches within well-defined sub-volumes, in pure dislocation systems the avalanches may span the system, implying that the dynamic length scale is, in fact, the size of the entire sample. Consequences of this finding on continuum modeling are thoroughly discussed.

中文翻译：

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关于识别晶体塑性中的动态长度标度


材料在不同的长度尺度上通常是异质的，晶粒结构、缺陷和成分的变化对新兴的宏观塑性行为有很大影响。特别是，异质性会导致塑性响应以抖动流和无处不在的应变爆发的形式出现波动。塑性建模的关键方面之一是尺度桥接：为了提供物理上正确的晶体塑性模型，需要确定相关的微观结构长度尺度。在本文中，我们提出了这样一个观点，即位错介导的可塑性的连续体描述不能忽视与雪崩行为相关的动态相关性。我们通过有和没有球形沉淀物的三维离散位错动力学模拟，对晶体塑性进行了广泛的最薄弱环节分析。我们研究了应变爆发和相关的长度尺度，并得出结论，虽然足够强的位错运动障碍往往将位错雪崩限制在明确定义的子体积内，但在纯位错系统中，雪崩可能会跨越整个系统，这意味着动态长度尺度实际上是整个样品的大小。彻底讨论了这一发现对连续体建模的影响。