基于超声导波的不可达特种设备管道腐蚀与裂纹损伤检测技术研究

The objection of the project is to proven a quantitative analysis method of defects using Ultrasonic Guided Waves for inaccessible regions of pipelines in special equipment. This project presents the studies of the propagation of the waves, simulation of wave interaction with defect and their sensitivity to defects which have been conducted in order to provide a sound scientific basis for the method. Issues of importance were the selection of the optimum guided wave modes and the establishment of relationships between the defect size and the strength of wave reflection.Currently, guided wave techniques are typically used as a screening tool to detect defects. Accurate quantitative analysis is still not available in field application. Although this is a complex subject, successful finish of this proposed project will lead to a series of discoveries in fundamental wave mechanics, a series of breakthroughs in field applications, and broader impact on the safety infrastructures.

本项目试图探索一种基于超声导波对不可管道缺陷定量化的新途径。主要内容包括由管道的频散方程求解各模式的相速度和群速度频散曲线，计算各模式下的振动位移分布并研究高温物性对导波频散影响；根据几种不可达结构的频散曲线特点，选择适合检测带托撑和高温管道的导波模式及频率；研究导波与缺陷的相互作用机理，基于正交分解和时频分析计算散射波的模式组分和量能配比，建立散射波组分与缺陷的初步关联；在此基础上，研究基于特征提取和特征选择的统计量设计和优化，提出基于支持向量集先缺陷分类（腐蚀 或裂纹）再进行尺寸计算的方法。为解决超声导波定量化表征缺陷的难题提供有价值的科学方法和技术实现途径。

通过建立管道频散方程，求解频散曲线、波结构、管道的内中外壁敏感性分析，结合三种常见不可达管道的结构、工况特点，确定了几种结构的模态选择原则。分析纵向导波和轴向导波的传播特点，利用圆交叉的原理确定缺陷的轴向和周向的位置；通过对含裂纹信息的回波信号进行统计分析，给出了统计特征与裂纹深度之间的关系；提出了一种缺陷图像重建技术，将接收到的信号分解成不同模态的分量，再利用FFT变换和反变换，重构任意位置任意时刻的波形，当确定了缺陷的位置和时间，就可以重构出缺陷的图像，进而确定缺陷的尺寸。