磁致伸缩扭转导波小管径弯管检测

摘要

针对扭转导波对小管径弯管的检测问题,分别采用数值模拟和实验方法进行研究.使用ANSYS软件模拟扭转导波在弯管中的传播;设计一种针对小管径管道的磁致伸缩扭转导波检测传感器,并对弯管进行检测,建立该传感器的导波激发和接收模型,利用理论模型对实验信号进行解读.研究结果表明:T(0,1)模态导波在小管径管道弯头处发生模态转换,部分T(0,1)模态转换成F(1,1)模态,F(1,1)模态具有方向性,垂直于弯头拱背-拱腹方向;模态转换会造成检测信号的双端面反射现象,第二个端面回波与第一个端面回波幅值比随频率的增大呈减小趋势;传感器激发出的纵向磁致伸缩力会导致实验信号中出现少量纵向模态导波.研究结论为磁致伸缩扭转导波对小管径弯管的检测提供理论指导.%Aiming to the problem of the inspection of small diameter bending pipes using torsional guided wave, finite element method and experiments were used to investigate the problem.ANSYS was used to simulate the propagation of torsional guided wave in bending pipe.A magnetostrictive torsional guided wave transducer was designed to inspect small diameter pipes.The exciting and receiving theoretical model of the transducer was built.The experimental signals were explained by using the theoretical model.Research results show that mode conversion happens at the elbow of the pipe and part of the T(0,1)mode converts to F(1,1)mode.The orientation of the F(1,1)mode perpendicular to the direction of extrados-intrados.The double end reflection phenomenon in inspection signal is caused by mode conversion.With the increase of frequency,the ratios between end echoes′trend towards alleviation.The longitudinal magnetostrictive forces excited by the transducer bring about small longitudinal guided wave in the signals.Conclusions will provide theoretical guide to the inspection of small diameter bend pipes using magnetostrictive torsional guided wave.