超声导波激励频率选取对其模式控制的影响

Influence of Ultrasonic Guided Wave Excitation Frequency on the Mode Control

超声导波在管道中传播模式有纵波、扭转波和弯曲波三种模式,由于扭转波在管道中传播具有非频散特性,在超声导波管道无损检测中得到广泛应用,但在管道中激发出扭转波的同时常常伴随着纵波的出现,导致超声导波检测信号难以识别和分析处理。针对这一问题,计算管道中超声导波传播频散曲线,通过控制扭转波激励频率在纵波的截止频率区范围内选取的方法,抑制纵波的产生。为了验证该方法的有效性和正确性,利用磁致伸缩导波无损检测装置对管道进行一系列不同激励频率的试验。研究结果表明:试验结果与理论结论相吻合,该方法为导波无损检测信号识别和工程应用提供了十分重要的理论依据和指导作用。

There are three modes for ultrasonic guided wave to propagate in the pipeline:longitudinal, torsional and flexural waves. The ultrasonic guided wave nondestructive detection is widely used in the pipeline, due to its non-dispersion characteristics. But it is often accompanied with the appearance of longitudinal wave when the torsional waves are stimulated in the pipeline, which leads to difficulties in identifying and analyzing the signal. To inhibit the generation of longitudinal wave, it's helpful to calculate the ultrasonic wave propagation dispersion curve of the pipeline, and control the torsional wave excitation frequency in longitudinal wave cutoff frequency range. In order to verify the effectiveness and correctness of the method, a series of experiments on different excitation frequency of pipeline were made, basing on magnetostrictive guided wave nondestructive testing device. The experimental results coincide with the theoretical conclusions, and this method provides a very important theoretical basis and guidance for the identification and engineering application of guided wave nondestructive testing signal.