Nonlinear Lamb Wave Micro-Crack Direction Identification in Plates with Mixed-Frequency Technique
Nonlinear Lamb Wave Micro-Crack Direction Identification in Plates with Mixed-Frequency Technique
复制标题
混频技术识别板材非线性兰姆波微裂纹方向
DOI：
10.3390/app10062135
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发表时间：
2020-03-01
影响因子：
2.7
通讯作者：
Li, Yifeng
中科院分区：
文献类型：
--
作者：
Guan, Liqiang;Zou, Mingxia;Li, Yifeng
本文利用混频技术研究了兰姆波产生的含非线性成分的微裂纹方向识别。进行了三维有限元模拟，以研究兰姆波信号与微裂纹之间的相互作用机制。在重新审视具有两种基频（\(f(1)\)和\(f(2)\)）的常规兰姆波激励信号时，发现如果板中存在非线性源，则有可能在边带产生新型频率（\(f(1)\pm f(2)\)）。采用脉冲反演法提取边带频率用于非线性超声检测。通过在微裂纹周围布置压电芯片阵列，校准了与不同微裂纹方向的基频和边带频率相关的声学非线性参数\(\beta\)。结果表明，\(\beta\)随裂纹方向不同而变化，这为非线性兰姆波与微裂纹相互作用的散射特征提供了有用信息，以表征其方向性。此外，通过改变微裂纹的尺寸，详细研究了不同方向微裂纹用相对非线性参数\(\beta'\)定义的散射程度。结果表明，与微裂纹其他方向的散射信号相比，裂纹的前向散射信号幅度较大，而后向散射信号幅度较小。此外，微裂纹前向的信号散射程度随微裂纹长度增加而增大，但随裂纹宽度增加而减小。再者，对于埋藏裂纹，兰姆波从微裂纹的前向散射程度随裂纹在板中埋藏深度增加而减小。总之，本研究结果有助于进一步推动利用混频技术的非线性兰姆波识别微裂纹方向。
This paper investigates the direction identification of micro-cracks with nonlinear components generated by Lamb wave with frequency-mixing technique. Three-dimensional finite element simulations were carried out to investigate the interaction mechanism between Lamb wave signals and micro-cracks. Upon re-visiting the conventional Lamb wave excitation signal with two kinds of fundamental frequencies (f1 and f2), it was found to be possible to generate new types of frequencies (f1 ± f2) at the sideband if nonlinear sources existed in the plate. A pulse inversion method was used to extract the sideband frequency for nonlinear ultrasonic detection. By arranging piezoelectric chip arrays around the micro-crack, the acoustic nonlinearity parameter β related to the fundamental frequency and the sideband frequency for different micro-crack directions was calibrated. It was shown that β varied for different crack directions, which provides useful information about the scattering features of the nonlinear Lamb wave interacting with the micro-crack to characterize its directivity. Moreover, the scattering degree defined with the relative nonlinear parameter β′ of the micro-crack in different directions was investigated in detail by changing the size of the micro-crack. The outcomes showed that the forward scattering signal of the crack had a greater amplitude, whereas the backscattering signal had a smaller amplitude compared with the scattering signals in other directions from micro-cracks. In addition, the signal scattering degree in the forward direction from micro-cracks increased with the increasing micro-crack length, but decreased with increasing crack width. Furthermore, for the buried crack, the forward scattering degree of Lamb wave from micro-crack decreased as crack was buried deeper in plate. In summary, the findings of this study can help to further advance the use of nonlinear Lamb wave with the frequency-mixing technique for identifying the direction of micro-cracks.