利用纵向导波进行管道裂纹参数识别的实验研究

EXPERIMENTAL RESEARCH OF CRACK PARAMETER IDENTIFICATION IN PIPES USING ULTRASONIC LONGITUDINAL GUIDED-WAVE

进行基于纵向应力导波的管道裂纹识别问题的实验研究。为了激发对称的L(0,2)模态,利用PZT-5制作与管道端面相同尺寸的压电环作为激发器,同时制作环向均布16个压电片并联作为接收传感器。首先在完好管道中分析导波信号,确定超声导波在管道中的有效检测长度约为50 m;通过对比频带宽度、衰减率等因素,发现导波中心频率为70 kHz时最适用于管道损伤检测;当频率不变时,周期数越多越有利于频率的控制,但当周期数太多时,波形容易发生叠加。在此基础上,进一步研究管道缺陷回波的特性,在含单、双裂纹的管道中分析回波特征,实现缺陷识别和定位;最后,分析裂纹参数对回波信号的影响特征,研究发现裂纹周向参数与反射系数之间近似满足线性关系。

An experimental research based on the longitudinal guided wave performed to identify pipeline crack. To excite and record symmetrical mode L（0,2） , a PZT （the solid solution of PbZrO3 and PbTiO3 ） ring made from PZT-5 with the same size of the cross section of pipe was used as the excitation sensor, and 16 piezoelectric slices distributing uniformly on the pipe end as the receiving sensor. The propagation of the guided wave studied in intact pipelines. It could be found that the transmission distance of the guided wave can be about 50 meters, and 70 kHz can be used as the most suitable center frequency for damage detection. Keep the frequency as constant, increasing the periods number of the excitated guided wave can induce to high power output. But too many periods will lead to waveform superpositions. On this basis, the flaw of the pipe with single and double fracture can be detected and located by the receiving waves. Finally, the parameter influence of the crack parameter on reflection coefficients was studied. It can be found that the relationship between the reflection coefficients and crack circumference parameters satisfies approximately linear relationship.