Ghaffari H O, Griffith W A, Pec M
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
School of Earth Sciences, Ohio State University, Columbus, Ohio, USA.
Sci Rep. 2019 Feb 13;9(1):1967. doi: 10.1038/s41598-018-38037-w.
Onset of permanent deformation in crystalline materials under a sharp indenter tip is accompanied by nucleation and propagation of defects. By measuring the spatio-temporal strain field near the indenter tip during indentation tests, we demonstrate that the dynamic strain history at the moment of a displacement burst carries characteristics of the formation and interaction of local excitations, or solitons. We show that dynamic propagation of multiple solitons is followed by a short time interval where the propagating fronts can accelerate suddenly. As a result of such abrupt local accelerations, duration of the fast-slip phase of a failure event is shortened. Our results show that formation and annihilation of solitons mediate the microscopic fast weakening phase, during which extreme acceleration and collision of solitons lead to non-Newtonian behavior and Lorentz contraction, i.e., shortening of solitons' characteristic length. The results open new horizons for understanding dynamic material response during failure and, more generally, complexity of earthquake sources.
在尖锐压头尖端作用下，晶体材料中永久变形的开始伴随着缺陷的形核与扩展。通过在压痕测试过程中测量压头尖端附近的时空应变场，我们证明了位移突发时刻的动态应变历史具有局部激发或孤子的形成与相互作用特征。我们表明，多个孤子的动态传播之后会有一个短时间间隔，在此期间传播前沿可能会突然加速。这种局部突然加速的结果是，失效事件快速滑动阶段的持续时间缩短。我们的结果表明，孤子的形成与湮灭介导了微观快速弱化阶段，在此阶段孤子的极端加速和碰撞导致非牛顿行为和洛伦兹收缩，即孤子特征长度的缩短。这些结果为理解材料失效过程中的动态响应以及更广泛地理解地震源的复杂性开辟了新的视野。
