基于时间反演的混凝土结构多维损伤成像监测方法研究

Due to the inhomogeneous, over-cluttering, high-scattering characteristics of concrete structures, the direction and the velocity of the Ultrasonic wave propagation always change, which results in target deviation when using the concrete image-based damage detection technique. TR (Time Reversal) technology has the advantage of adaptively focusing detection signal on the crack in the detection area. The auto-focusing characteristic of TR technology has the capacity of exactly locating the target. Therefore, the TR technology is very much suited for damage detection in inhomogeneous environment, such as concrete structures. This project will integrate the time reversal technology and embedded piezoceramic smart aggregate transducers to develop an innovative imaging based real-time health monitoring system for concrete structures. This innovative project includes the following major research components: 1) studies on arrangement of the piezoceramic transducer arrays, 2) the time reversal based the crack detection and imaging algorithms, 3) software development, 4）development of a new generation of smart aggergates with piezoceramic stack, and 5) comprehensive testng. This project provides a novel damage imaging based structural health monitoring approach that is highly efficient, intelligent, accutate, and real time, and will make significant contribution to improve safety level of civil structures.

混凝土结构内部复杂的环境对超声波易产生非均匀、多杂波、多散射的干扰，致使采用超声波损伤探测技术探测的目标位置发生偏失，严重影响了测量精度。时间反演（Time Reversal，TR）技术能够使信号自适应地在检测区域中聚焦成像，进而可以实现待探测目标的精确定位，在混凝土内部结构这种非均匀环境的损伤监测中具有广阔的应用前景。本项目拟将时间反演技术与智能骨料传感器系统相结合，开发一种基于混凝土结构损伤成像的智能实时监测系统，内容包括时间反演探测系统的探测单元在混凝土中的排布方式，基于时间反演技术的混凝土裂缝目标探测技术和成像技术，基于时间反演技术的混凝土成像监测软件，多压电陶瓷片叠加技术的第三代智能骨料，以及成像系统硬件系统的研究和开发。本项目的完成，可为大型混凝土结构提供一个高效、智能、精确、实时的新型监测系统及解决方案。

本课题依托时间反演技术，研究了混凝土裂缝目标探测。基于目标探测FDTD 仿真平台，同时通过智能骨料传感器阵列优化分析，消除混凝土内部的多径干扰，对若干优化后的智能骨料发送信号和接收信号进行处理，成功进行了混凝土超声成像，获得了初步成像结果。结果表明，这种依托时间反演方法的技术可以进行为目标探测提供了一种新思路。通过研究基于时间反演技术损伤目标探测技术，将时间反演应用于多种连接界面松动监测并取得了良好的效果。此外对新型智能骨料在混凝土的传波规律进行了理论分析与研究，用数值方程求解出了相应的压电性能。最后研究了多压电陶瓷片叠加式技术智能骨料在混凝土中的高频发射波传播距离问题，对新型智能骨料在混凝土中的高频超声波传播能力进行验证。