Department of Chemical Physics, the Weizmann Institute of Science, Rehovot 76100, Israel.
Phys Rev E. 2017 Sep;96(3-1):032907. doi: 10.1103/PhysRevE.96.032907. Epub 2017 Sep 14.
The mechanical failure of amorphous media is a ubiquitous phenomenon from material engineering to geology. It has been noticed for a long time that the phenomenon is "scale-free," indicating some type of criticality. In spite of attempts to invoke "Self-Organized Criticality," the physical origin of this criticality, and also its universal nature, being quite insensitive to the nature of microscopic interactions, remained elusive. Recently we proposed that the precise nature of this critical behavior is manifested by a spinodal point of a thermodynamic phase transition. Demonstrating this requires the introduction of an "order parameter" that is suitable for distinguishing between disordered amorphous systems. At the spinodal point there exists a divergent correlation length which is associated with the system-spanning instabilities (known also as shear bands) which are typical to the mechanical yield. The theory, the order parameter used and the correlation functions which exhibit the divergent correlation length are universal in nature and can be applied to any amorphous solid that undergoes mechanical yield. The phenomenon is seen at its sharpest in athermal systems, as is explained below; in this paper we extend the discussion also to thermal systems, showing that at sufficiently high temperatures the spinodal phenomenon is destroyed by thermal fluctuations.
非晶态介质的力学失效是从材料工程到地质学的普遍现象。长期以来，人们注意到这种现象是“无标度的”，表明存在某种临界性。尽管人们试图援引“自组织临界性”来解释这种临界性的物理起源及其对微观相互作用性质的普遍不敏感性，但这种临界性的物理起源仍难以捉摸。最近，我们提出这种临界行为的精确性质表现为热力学相变的旋节线。证明这一点需要引入一个“序参量”，该参量适合于区分无序的非晶态系统。在旋节线处存在发散的相关长度，它与跨越整个系统的不稳定性（也称为剪切带）有关，这些不稳定性是力学屈服的典型特征。该理论、所使用的序参量以及表现出发散相关长度的相关函数在本质上是普遍的，可以应用于任何经历力学屈服的非晶态固体。正如下面所解释的，这种现象在非热系统中最为明显；在本文中，我们将讨论扩展到热系统，表明在足够高的温度下，热波动会破坏旋节线现象。
