基于磁致伸缩导波动态聚焦原理的拱桥吊杆腐蚀断丝在线检测方法

In recent years, some serious accidents occurred in the main structure of arch bridge due to suspender breaking. The damage and wreck of suspenders has been the important factor to influence the security of arch bridge. Now there is no effective method for in-line inspection of arch bridge suspender. The project introduce a corrosion and broken wire in-line inspection method for arch bridge suspender based on magnetostrictive guided wave dynamical focusing theory.The steel strand in the suspender generate elastic guided wave under the exitation of magnetic field, and propogate along the suspender.The guided wave will reflect while encounting defects such as corrosion and broken wire, the reflect signal could be transformed to electric signal by the gudied wave sensor probe.With repect to the irregular defects in the suspender, the mechanism of guided wave field influenced by irregular scatterers will be studied;with repect to the suspender surrounded by PE coating, the propagation property of guided wave under multi-media complicated boundary conditions will also be studied.Based on time reversal mirror and by controlling the time delay of distributed magnetostrictive sensor array around the suspender,the guided wave will be focusing at the defects. The SNR of the guided wave signal will be enhanced by the time frequency signal processing techniques. By theory analysis,numerical simulate and experiment study,in-line inspection of arch bridge suspender will be realized, and provide the theoretical basis and technology platform for health monitoring of arch bridge.The project's achievements have important academic and engineering application value for inline inspection of the bridge cables, pipes and other ferromagnetic long range structure.

近年来我国发生多起因吊杆断裂引起拱桥整体结构破坏的重大事故，吊杆的损伤及破坏已成为危及拱桥安全的重要因素，而目前尚无有效的吊杆在线检测方法。本项目提出一种基于磁致伸缩导波动态聚焦原理的吊杆腐蚀断丝在线检测方法。吊杆钢绞线在外磁场作用下，产生弹性导波，导波沿吊杆传播遇到缺陷（腐蚀断丝）发生反射，通过导波传感器探头将反射信号转为电压信号。针对吊杆中缺陷散射体的非规则性，研究非规则散射体与导波声场作用机理；针对吊杆外包PE防腐层，研究多相介质边界条件下的导波传播特性；基于时间反转理论，通过在吊杆周向布置阵列式传感器探头，采用信号时延控制实现导波在缺陷处聚焦，结合时频信号处理技术提高导波信号的信噪比，通过理论分析、数值模拟和实验研究，最终实现吊杆腐蚀断丝的在线检测，为拱桥结构健康监测提供研究基础和技术平台。本项目研究成果在桥梁缆索、管道等铁磁性长距离结构的在线检测中具有重要的学术和工程应用价值。

近年来我国已发生多起因吊杆疲劳断裂引起拱桥整体结构破坏的重大事故，吊杆的损伤及破坏已成为钢管混凝土拱桥寿命的重要因素，而目前尚无有效的吊杆在线检测方法。本项目提出了一种磁致伸缩超声导波的吊杆腐蚀与断丝在线检测方法及仪器，主要研究内容包括：非规则多丝结构导波频散特性分析，复杂边界条件下导波传播特性，磁致伸缩导波传感器探头，信号相关分析与时频信号处理技术，吊杆腐蚀与断丝导波在线检测集成技术与实验。 .本项目的成功实施将为杆和缆索类结构的导波检测奠定重要的理论和实践基础，同时也为该领域提供一种具有自主知识产权和关键的共性技术手段。研究成果将满足我国大量在役拱桥吊杆在线检测的紧迫需求，在悬索桥的主缆、吊索，斜拉桥的斜拉索，工程锚杆及埋地管道等结构的健康监测具有广阔应用前景。

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