Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China.
Sensors (Basel). 2020 Jan 14;20(2):460. doi: 10.3390/s20020460.
The fundamental circumferential shear horizontal (CSH) wave is of practical importance in monitoring corrosion defects in large-diameter pipes due to its virtually non-dispersive characteristics. However, so far, there have been limited CSH wave transducers which can be used to constitute a structural health monitoring (SHM) system for pipes. Moreover, the CSH wave's capability of sizing the corrosion-like defect has not yet been confirmed by experiments. In this work, firstly, the mechanism of exciting CSH waves was analyzed. A method based on our previously developed bidirectional SH wave piezoelectric transducers was then proposed to excite the pure CSH mode and first order circumferential shear horizontal (CSH) mode. Both finite element simulations and experiments show that the bidirectional transducer is capable of exciting pure CSH mode traveling in both circumferential directions of a 1 - mm thick steel pipe from 100 to 300 kHz. Moreover, this transducer can also serve a sensor to detect CSH mode only by filtering circumferential Lamb waves over a wide frequency range from 100 to 450 kHz. After that, a method of sizing a rectangular notch defect by using CSH wave was proposed. Experiments on an 11 - mm thick steel pipe show that the depth and circumferential extent of a notch can be accurately determined by using the proposed method. Finally, experiments were performed to investigate the reflection and transmission characteristics of CSH and CSH waves from notches with different depths. It was found that transmission coefficients of CSH mode decrease with the increasing of notch depth, which indicates that it is possible to monitor the depth change of corrosion defects by using CSH wave.
由于具有近乎非色散的特性，基本周向剪切水平（CSH）波在监测大直径管道中的腐蚀缺陷方面具有实际意义。然而，到目前为止，能够用于构成管道结构健康监测（SHM）系统的 CSH 波换能器非常有限。此外，CSH 波对腐蚀类缺陷进行尺寸测量的能力尚未通过实验得到证实。在这项工作中，首先分析了激励 CSH 波的机制。然后提出了一种基于我们之前开发的双向 SH 波压电换能器的方法，以激励纯 CSH 模式和一阶周向剪切水平（CSH）模式。有限元模拟和实验均表明，双向换能器能够在 100 至 300 kHz 的范围内激励在 1 毫米厚的钢管中沿两个周向传播的纯 CSH 模式。此外，这种换能器还可以通过在 100 至 450 kHz 的宽频率范围内滤除周向兰姆波来充当传感器，仅检测 CSH 模式。然后，提出了一种利用 CSH 波对矩形缺口缺陷进行尺寸测量的方法。在 11 毫米厚的钢管上进行的实验表明，通过提出的方法可以精确确定缺口的深度和周向范围。最后，进行了实验以研究 CSH 和 CSH 波从具有不同深度的缺口的反射和传输特性。发现 CSH 模式的透射系数随缺口深度的增加而减小，这表明可以通过 CSH 波监测腐蚀缺陷的深度变化。
