Clemmer Joel T, Salerno K Michael, Robbins Mark O
Sandia National Laboratories, Albuquerque, New Mexico 87123, USA.
Army Research Lab, Aberdeen, Maryland 21005, USA.
Phys Rev E. 2021 Apr;103(4-1):042606. doi: 10.1103/PhysRevE.103.042606.
Disordered solids respond to quasistatic shear with intermittent avalanches of plastic activity, an example of the crackling noise observed in many nonequilibrium critical systems. The temporal power spectrum of activity within disordered solids consists of three distinct domains: a novel power-law rise with frequency at low frequencies indicating anticorrelation, white-noise at intermediate frequencies, and a power-law decay at high frequencies. As the strain rate increases, the white-noise regime shrinks and ultimately disappears as the finite strain rate restricts the maximum size of an avalanche. A new strain-rate- and system-size-dependent theory is derived for power spectra in both the quasistatic and finite-strain-rate regimes. This theory is validated using data from overdamped two- and three-dimensional molecular dynamics simulations. We identify important exponents in the yielding transition including the dynamic exponent z which relates the size of an avalanche to its duration, the fractal dimension of avalanches, and the exponent characterizing the divergence in correlations with strain rate. Results are related to temporal correlations within a single avalanche and between multiple avalanches.
无序固体对准静态剪切的响应是伴随着塑性活动的间歇性雪崩，这是在许多非平衡临界系统中观察到的噼啪声的一个例子。无序固体内活动的时间功率谱由三个不同的区域组成：低频处随频率呈新型幂律上升，表明反相关；中频处为白噪声；高频处为幂律衰减。随着应变速率增加，白噪声区域缩小并最终消失，因为有限的应变速率限制了雪崩的最大尺寸。针对准静态和有限应变速率区域的功率谱，推导了一种新的依赖于应变速率和系统尺寸的理论。该理论通过过阻尼二维和三维分子动力学模拟的数据得到验证。我们确定了屈服转变中的重要指数，包括将雪崩大小与其持续时间相关联的动态指数z、雪崩的分形维数，以及表征与应变速率相关性发散的指数。结果与单个雪崩内以及多个雪崩之间的时间相关性有关。
