ABSTRACT This study is interested in how to utilise the virtual time reversal (VTR) technique to locate the continuous AE source in cylindrical shell structure. Thus, a six-AE-sensor monitoring network was designed to divide cylindrical surface into two symmetric semi-cylindrical monitoring areas whose four vertexes and two geometrical centres were defined as the measuring points. The AE source can be located in certain semi-cylindrical monitoring area whose centre measuring point first captured the emitted AE signal. Besides, the response signals at other four measuring points were used to localise the AE source. To realise the VTR focusing of the AE signals, the proposed method solved two key problems. One is to search the shortest helical path between two arbitrary points on a cylindrical surface, which can provide the shortest distance from AE source to sensor. The other is to extract the specific frequency coefficients of wavelet transform for the continuous AE signal, which can meet with the requirement for the instantaneous abrupt characteristic of the signals to be processed using VTR focusing technique. Finally, a continuous leak experiment was carried out on a gas-filled steel pipe. The corresponding localisation method can accurately estimate the location of the continuous leak source.

中文翻译：

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基于六声发射传感器监测网络和VTR聚焦成像的圆柱壳结构声发射源定位与成像

摘要 本研究对如何利用虚拟时间反演（VTR）技术定位圆柱壳结构中的连续声发射源感兴趣。因此，设计了一个六声发射传感器监测网络，将圆柱表面划分为两个对称的半圆柱监测区域，其四个顶点和两个几何中心被定义为测量点。AE 源可以位于某个半圆柱形监测区域，其中心测量点首先捕获发射的 AE 信号。此外，其他四个测量点的响应信号用于定位AE源。为了实现AE信号的VTR聚焦，所提出的方法解决了两个关键问题。一种是搜索圆柱面上任意两点之间的最短螺旋路径，可以提供从 AE 源到传感器的最短距离。另一种是对连续AE信号提取小波变换的特定频率系数，满足VTR聚焦技术对待处理信号瞬时突变特性的要求。最后，对充气钢管进行了连续泄漏实验。相应的定位方法可以准确估计连续泄漏源的位置。