Propagation of a Finite‐Amplitude Elastic Pulse in a Bar of Berea Sandstone: A Detailed Look at the Mechanisms of Classical Nonlinearity, Hysteresis, and Nonequilibrium Dynamics
Propagation of a Finite‐Amplitude Elastic Pulse in a Bar of Berea Sandstone: A Detailed Look at the Mechanisms of Classical Nonlinearity, Hysteresis, and Nonequilibrium Dynamics
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有限振幅弹性脉冲在伯里亚砂岩中的传播：详细研究经典非线性、磁滞和非平衡动力学机制
DOI：
10.1002/2017jb014258
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
J. T. Cate
中科院分区：
文献类型：
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作者：
M. Remillieux;T. Ulrich;Harvey E. Goodman;J. T. Cate
我们研究了有限振幅弹性脉冲在伯里亚砂岩细长杆中的传播。在以前的工作中，已经进行了这种类型的实验，以量化经典的非线性，基于作为传播距离的函数的二次谐波的振幅增长。为了大大扩展早期的工作，使用非接触式扫描三维激光多普勒测振仪来跟踪粒子速度的轴向分量在整个杆表面上的演化，作为传播距离和源振幅的函数。有了这些新的测量，经典的非线性，滞后，和非平衡动力学的综合影响都被同时测量。我们证明了，具有经典非线性项和衰减项的一维波动方程的数值分辨率准确地捕获了波的光谱特征，直到二次谐波。然而，对于高次谐波的频谱内容被证明是强烈的滞后影响。这项工作还显示的数据，不仅量化经典的非线性，但也基于弹性脉冲的到达时间的相对变化的非平衡动力学的应变和距离的函数从源。最后，一个比较的谐振杆测量，用于量化非平衡动力学的参考实验，基于作为样本中的最大动态应变的函数的谐振频率的相对移位。
We study the propagation of a finite‐amplitude elastic pulse in a long thin bar of Berea sandstone. In previous work, this type of experiment has been conducted to quantify classical nonlinearity, based on the amplitude growth of the second harmonic as a function of propagation distance. To greatly expand on that early work, a noncontact scanning 3‐D laser Doppler vibrometer was used to track the evolution of the axial component of the particle velocity over the entire surface of the bar as functions of the propagation distance and source amplitude. With these new measurements, the combined effects of classical nonlinearity, hysteresis, and nonequilibrium dynamics have all been measured simultaneously. We show that the numerical resolution of the 1‐D wave equation with terms for classical nonlinearity and attenuation accurately captures the spectral features of the waves up to the second harmonic. However, for higher harmonics the spectral content is shown to be strongly influenced by hysteresis. This work also shows data which quantify not only classical nonlinearity but also the nonequilibrium dynamics based on the relative change in the arrival time of the elastic pulse as a function of strain and distance from the source. Finally, a comparison is made to a resonant bar measurement, a reference experiment used to quantify nonequilibrium dynamics, based on the relative shift of the resonance frequencies as a function of the maximum dynamic strain in the sample.