中文摘要：

为对螺旋波纹管进行缺陷检测,研究纵向模态超声导波在螺旋波纹管中的传播特性。在Abaqus仿真软件平台中构建螺旋波纹管的计算模型,得到含有环向裂纹缺陷时的仿真结果。在此基础上,采用自主研制的电磁声换能器进行试验研究。试验所用的激励信号为经Hanning窗调制的20个振荡周期的正弦脉冲,中心频率为240 kHz,采用单一传感器在螺旋波纹管中激励和接收L（0,2）模态导波,实现对螺旋波纹管中人工裂纹缺陷的识别,分析并计算缺陷位置测量不确定度。有限元仿真和试验结果表明,超声导波技术可以实现对螺旋波纹管裂纹缺陷的检测。

英文摘要：

Propagation characteristics of longitudinal modes of ultrasonic guided waves are researched for the defect detection on helical bellows.The finite element models of helical bellows are created using commercial package Abaqus firstly and the results of numerical simulation with a circumferential crack have been calculated.Furthermore experimental research is developed using electromagnetic acoustic transducer.The sinusoidal tone burst modulated by a Hanning window with 20 cycles is used for exciting ultrasonic longitudinal guided wave mode L（0,2） at 240 kHz in helical bellows to detect artificial defects.Single transducer is applied for the excitation and reception of L（0,2） modes simultaneously.The crack in helical bellows can be identified and Uncertainty of measurement result has been calculated.The finite element analysis and experimental results show that it is feasible and effective to detect defects in helical bellows based on ultrasonic guided wave technology.