混凝土耐久性损伤光纤光栅声发射传感机理与应用研究

Acoustic emission (AE) technique has been widely used in concrete and its durability because of its unique advantages. The currently available diagnostic approaches in AE detections and signal communication are restricted in abilities since detection methodology and sealing technology are unable to meet the critical environment. This results the detection which is solely implied in a small area instead of real-time remote inspection. Thanks to the fiber Bragg grating (FBG) based sensors, which is attributed with high withstanding of electromagnetic interference as well as corrosion, low losses in signal communication and network accessible, therefore, it is in several aspects advanced and suitable for AE detection in concrete structures. Our topic is about the investigation of the FBG based AE monitoring system in term of theory and methodology. The theoretical model for durability damage of concrete based on AE parameters can be constructed; the response model of FBG AE sensor is developed; the sensitivity improvement by suppressing the noise of the AE detecting system is aimed; the technologies for sealing and protection of sensor in high temperature, low temperature and corrosive environment are studied. The numerical simulation as well as practical simulation in laboratory environment can be established in order to guide the direction for applications such as concrete damage inspection. Note that at the front edge research, such proposed model for durability damage of concrete based on AE parameters, has never been reported in global scientific journal based on author's knowledge.

声发射技术因其独特的优势被越来越广泛地应用于混凝土结构及其耐久性的研究中。目前混凝土结构损伤监测所使用的声发射检测仪器由于检测原理、封装结构、应用环境的限制，通常只能铺设在近距离、较小范围的监测区域，不能实现远距离在线检测。光纤光栅具有抗电磁干扰、耐腐蚀、信号传输损耗小、易组网诸多优点，因而非常适合于混凝土结构声发射检测。本课题针对混凝土结构中声发射信号的检测，展开光纤光栅声发射传感机理和应用研究，研究基于声发射特征参数的混凝土耐久性损伤模型；光纤光栅声发射传感器的响应模型；声发射检测系统的噪声抑制和检测灵敏度提高的途径；混凝土结构高温、低温、腐蚀性环境中传感器的封装保护关键技术。建立光纤光栅声发射传感计算机仿真和实验室模拟平台，为实现光纤光栅进行混凝土结构的声发射检测打下基础。本课题提出的基于声发射特征参数建立混凝土结构耐久性损伤模型的方法，国内外尚未见报道。

本项目对基于光纤光栅声发射传感方法的混凝土结构损伤检测进行了系统的研究，并通过提出声发射源定位算法实现了结构损伤位置的定位识别。采用高斯-余弦函数对混凝土结构损伤产生的声发射信号进行仿真模拟，基于声发射波与光栅的相互作用原理建立了光纤光栅声发射传感模型，采用传输矩阵法系统研究了声发射波作用下光纤光栅反射光谱特性。通过仿真实验得出，光纤光栅反射光谱的中心波长、反射率、光谱形状等均对声发射波的幅值、波长等参数呈规律性响应特性，在此基础上建立基于声发射信号参数的混凝土结构损伤模型。针对传统的基于宽带光源的光纤光栅声发射传感解调方法的长时间稳定性差且易于受到外界环境干扰的问题，提出了基于宽带光源的低成本光纤光栅声发射传感解调方法；通过数值仿真及实验验证建立光纤光栅声发射传感系统的灵敏度模型，研究结果显示系统灵敏度受光纤光栅反射谱边沿斜率的影响最大。针对应用于高温环境中的混凝土结构损伤检测，研制了基于光纤光栅传感器的耐高温声发射传感系统；研究光纤光栅声发射传感器封装技术，设计了一种高信噪比的高温光纤光栅声发射传感器。提出的光纤光栅声发射传感系统在25℃~200℃的温度范围内，获得了良好的实验结果。对结构损伤进行定位识别研究，提出了一种新的光纤光栅声发射源定位系统和改进的到达时差定位方法，适用于不了解声发射信号速度的情况下进行结构损伤检测，定位绝对误差在0.06m以下；提出了基于重心坐标定位算法的光纤光栅声发射定位方法，定位结果为平均定位误差为5.4 mm，最大定位误差为9.2mm。本项目解决了光纤光栅声发射传感理论的诸多问题，研究成果在结构健康监测等领域具有广阔的应用前景。