近日，美国宾夕法尼亚大学的Andrea J.Liu及其研究小组取得一项新进展。经过不懈努力，他们发现影响无序固体延展性的微观因素
该团队研究了三种无序固体模型：模拟原子玻璃、实验颗粒填料和模拟聚合物玻璃。他们使用不同的策略来调整每个系统，以展示两种不同程度的应变局部化。同时，他们构建了结构弹塑性（StEP）模型，该模型使用基于机器学习的描述符“柔软度”来表示无序局部结构的稳定性，并将系统描述简化为控制应变局部化的几个微观特征。这些模型是基于计算出的柔软度和重排的相关性。
在没有附加参数的情况下，模型与所研究的所有系统观察到的应力-应变曲线和柔软度统计数据表现出半定量的一致性。StEP模型还表明，初始结构、重排对局部结构的近场效应和重排尺寸分别是导致三种体系延展性变化的主要原因。因此，StEP模型提供了应变局部化如何依赖于结构、塑性和弹性相互作用的微观理解。
据悉，有一些经验策略可以调整无序固体中应变局部化的程度，但这些策略是针对特定系统的，缺乏解释其有效性或局限性的理论框架。
附：英文原文
Title: Identifying microscopic factors that influence ductility in disordered solids
Author: Xiao, Hongyi, Zhang, Ge, Yang, Entao, Ivancic, Robert, Ridout, Sean, Riggleman, Robert, Durian, Douglas J., Liu, Andrea J.
Issue&Volume: 2023-10-9
Abstract: There are empirical strategies for tuning the degree of strain localization in disordered solids, but they are system-specific and no theoretical framework explains their effectiveness or limitations. Here, we study three model disordered solids: a simulated atomic glass, an experimental granular packing, and a simulated polymer glass. We tune each system using a different strategy to exhibit two different degrees of strain localization. In tandem, we construct structuro-elastoplastic (StEP) models, which reduce descriptions of the systems to a few microscopic features that control strain localization, using a machine learning-based descriptor, softness, to represent the stability of the disordered local structure. The models are based on calculated correlations of softness and rearrangements. Without additional parameters, the models exhibit semiquantitative agreement with observed stress–strain curves and softness statistics for all systems studied. Moreover, the StEP models reveal that initial structure, the near-field effect of rearrangements on local structure, and rearrangement size, respectively, are responsible for the changes in ductility observed in the three systems. Thus, StEP models provide microscopic understanding of how strain localization depends on the interplay of structure, plasticity, and elasticity.
DOI: 10.1073/pnas.2307552120
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2307552120