Parisi Giorgio, Procaccia Itamar, Rainone Corrado, Singh Murari
Dipartimento di Fisica, Sapienza Universitá di Roma, Istituto Nazionale di Fisica Nucleare, Sezione di Roma I, Istituto per i Processi Chimico-Fisici (IPCF)-Consiglio Nazionale delle Ricerche, I-00185 Rome, Italy;
Department of Chemical Physics, The Weizmann Institute of Science, Rehovot 76100, Israel
Proc Natl Acad Sci U S A. 2017 May 30;114(22):5577-5582. doi: 10.1073/pnas.1700075114. Epub 2017 May 16.
Amorphous solids increase their stress as a function of an applied strain until a mechanical yield point whereupon the stress cannot increase anymore, afterward exhibiting a steady state with a constant mean stress. In stress-controlled experiments, the system simply breaks when pushed beyond this mean stress. The ubiquity of this phenomenon over a huge variety of amorphous solids calls for a generic theory that is free of microscopic details. Here, we offer such a theory: The mechanical yield is a thermodynamic phase transition, where yield occurs as a spinodal phenomenon. At the spinodal point, there exists a divergent correlation length that is associated with the system-spanning instabilities (also known as shear bands), which are typical to the mechanical yield. The theory, the order parameter used, and the correlation functions that exhibit the divergent correlation length are universal in nature and can be applied to any amorphous solids that undergo mechanical yield.
非晶态固体的应力会随着施加的应变而增加，直到达到机械屈服点，此后应力不再增加，而是呈现出具有恒定平均应力的稳态。在应力控制实验中，当超过这个平均应力时，系统就会简单地破裂。这种现象在各种各样的非晶态固体中普遍存在，这就需要一种不受微观细节影响的通用理论。在此，我们提出这样一种理论：机械屈服是一种热力学相变，屈服是以旋节线现象的形式发生的。在旋节点处，存在一个发散的关联长度，它与贯穿整个系统的不稳定性（也称为剪切带）相关联，而这种不稳定性是机械屈服的典型特征。该理论、所使用的序参量以及呈现出发散关联长度的关联函数在本质上是通用的，可应用于任何经历机械屈服的非晶态固体。
