Sun Xiaoqiang, Liu Hongjun, Zhao Youxuan, Qu Jianmin, Deng Mingxi, Hu Ning
College of Aerospace Engineering, Chongqing University, Chongqing 400044, PR China.
College of Aerospace Engineering, Chongqing University, Chongqing 400044, PR China; Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400044, PR China.
Ultrasonics. 2020 Sep;107:106172. doi: 10.1016/j.ultras.2020.106172. Epub 2020 May 16.
When a longitudinal wave (bulk wave) propagates in elastic solids with randomly distributed micro-cracks, the acoustic nonlinear behavior including the zero-frequency component and higher harmonics can be generated due to the clapping and slipping behavior of micro-cracks. In this paper, the analytical solution based on the bi-linear stiffness model of micro-cracks and the numerical simulation with random micro-crack modeling are implemented to investigate the behavior of the zero-frequency component. The theoretical and numerical results both show that the zero-frequency component of bulk waves can be generated by the micro-cracks, which is more sensitive than the conventional second harmonics. Meanwhile, we find that the acoustic nonlinearity parameter based on the zero-frequency component increases linearly with the crack density, the length of the micro-crack region and the fundamental frequency in the low-frequency region. Moreover, the zero-frequency component of the reflected waves is also investigated, indicating it can be used to locate the micro-crack region.
当纵波（体波）在含有随机分布微裂纹的弹性固体中传播时，由于微裂纹的拍打和滑动行为，会产生包括零频分量和高次谐波在内的声学非线性行为。本文基于微裂纹的双线性刚度模型实现了解析解，并通过随机微裂纹建模进行了数值模拟，以研究零频分量的行为。理论和数值结果均表明，体波的零频分量可由微裂纹产生，且其比传统二次谐波更敏感。同时，我们发现基于零频分量的声学非线性参数在低频区域随裂纹密度、微裂纹区域长度和基频呈线性增加。此外，还对反射波的零频分量进行了研究，表明其可用于定位微裂纹区域。
