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管道弯头显著改变了导波传播特性,影响了对检测信号的解读,研究弯头对导波传播特性的影响是实现复杂管道系统导波检测的基础。采用半解析有限元法计算弯管导波频散曲线,分析了弯管导波频散曲线所呈现的不同特征,并基于弯管导波频散曲线,以低频L(0,1)模态导波为研究对象,实验研究了低频L(0,1)模态导波通过管道弯头时的模态变换特征。研究结果发现,当L(0,1)模态导波通过管道弯头时,不仅会发生L(0,1)到F(1,1)的模态变换,还会模态变换出反向L(0,1)模态导波,即弯头反射现象,且随着激励频率的降低和弯头弯曲半径的减小,弯头反射现象愈发明显。研究结果将深化对弯管导波传播特性的认识,推动导波检测技术在复杂管道系统检测中的应用。
Pipe bend significantly changed the characteristics of guided wave propagation, which affected the interpretation of the detection signal. Studying the influence of elbow on the propagation characteristics of the guided wave was the basis for the guided wave detection of complex pipe system. The semi-analytical finite element method is used to calculate the dispersion curve of the elbow waveguide. The different characteristics of the elbow waveguide dispersion curve are analyzed. Based on the curve of elbow waveguide dispersion, the low frequency L (0,1) mode The guided wave is the object of study. The modal transformation characteristics of low frequency L (0,1) mode guided wave through pipe elbow are experimentally studied. The results show that when the L (0,1) mode guided wave passes through the pipe elbow, not only the modal transformation of L (0,1) to F (1,1) but also the modal transformation of the reverse L (0,1) modal guided wave, that is, the phenomenon of elbow reflection, and with the decrease of excitation frequency and bend radius, elbow reflection phenomenon becomes more and more obvious. The results will deepen the understanding of the characteristics of elbow guided wave propagation and promote the application of guided wave detection technology in the detection of complex pipe systems.