Department of Physics, University of Illinois at Urbana Champaign, Urbana, Illinois 61801, USA.
Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW Calgary, Alberta T2N 1N4, Canada.
Phys Rev Lett. 2018 Jun 15;120(24):245501. doi: 10.1103/PhysRevLett.120.245501.
The total energy of acoustic emission (AE) events in externally stressed materials diverges when approaching macroscopic failure. Numerical and conceptual models explain this accelerated seismic release (ASR) as the approach to a critical point that coincides with ultimate failure. Here, we report ASR during soft uniaxial compression of three silica-based (SiO_{2}) nanoporous materials. Instead of a singular critical point, the distribution of AE energies is stationary, and variations in the activity rate are sufficient to explain the presence of multiple periods of ASR leading to distinct brittle failure events. We propose that critical failure is suppressed in the AE statistics by mechanisms of transient hardening. Some of the critical exponents estimated from the experiments are compatible with mean field models, while others are still open to interpretation in terms of the solution of frictional and fracture avalanche models.
声发射 (AE) 事件的总能量在接近宏观失效时会发散。数值和概念模型将这种加速的地震释放 (ASR) 解释为接近与最终失效重合的临界点。在这里，我们报告了在三种基于二氧化硅 (SiO_{2}) 的纳米多孔材料的软单轴压缩过程中的 ASR。AE 能量的分布不是固定的，而是处于稳定状态，而活动率的变化足以解释 ASR 的多个周期的存在，这些周期导致了不同的脆性失效事件。我们提出，在 AE 统计中，临界失效受到瞬态硬化机制的抑制。从实验中估计的一些临界指数与平均场模型兼容，而其他指数仍有待于根据摩擦和断裂雪崩模型的解来解释。
