基于超声波能量扩散机理及新型智能骨料的混凝土轨道板\道床板早期损伤监测

The scattering effect of statistically varying aggregates in the concrete on the ultrasound wave is significant and complicated, which result in that the typical damage detection method based on ultrasound wave only can recognize the crack whose size is larger the aggregate but not detect an early damage with a small size. Therefore, in this project, the mechanism of ultrasonic energy diffusion of concrete is investigated to establish the relationship between the microstructure, including the damage, of the concrete and the ultrasonic energy diffusion, and based on this relationship a new damage detection method of the early damage of concrete structures is proposed. Moreover, a new generation of self-powered smart aggregate is developed to excite or receive the ultrasound waves wirelessly in all directions in concrete structures by using the tube-type PZTs, a new signal caching-transreceiving mechanism is designed to avoid packed dropouts during data transmission, and the wireless active sensing network for damage detection of concrete structures is also investigated and optimized. Combing this new early damage detection method of concrete structure and the new generation of smart aggregates, the size and location of the early damage of concrete structures can be detected, and a smart and green energy-saving health monitoring solution for concrete track plate or rail track of high-speed railways is also provided.

混凝土结构内部随机分布的非等尺寸颗粒对超声波极易产生多径散射，致使传统超声波损伤监测技术仅能识别尺寸大于随机颗粒的损伤，而对早期微损伤不敏感。本项目通过对超声波在多相异质混凝土中能量扩散机理的分析，建立包括结构损伤在内的混凝土内部微结构与超声波能量扩散之间的函数关系，提出混凝土结构早期损伤的定量识别方法。用于混凝土结构早期损伤识别的新型智能骨料及其主动传感网络的研究是基于圆管形压电陶瓷设计具有自供电及信号无线传输功能的新型智能骨料，来实现超声波信号的360度方向收发，建立新型智能骨料信号缓存-收发机制，解决新型骨料短时超声波信号不丢包传输的问题，并对基于新型智能骨料的主动传感网络进行优化。基于超声波能量扩散机理的混凝土结构早期损伤识别新方法与新型智能骨料的有机结合，可以实现混凝土结构早期损伤的定量定位识别，为高铁无砟道混凝土轨道板\道床板早期损伤在线监测提供一个智能、绿色节能的解决方案。

混凝土结构早期损伤识别及损伤扩展监测是混凝土结构安全、稳定运行的关键，本项目主要对基于超声波能量扩散机理及新型无线智能骨料的混凝土早期损伤识别方法进行了研究。.基于三维超声波能量扩散方程和介质弹性力学理论分析了结构损伤对超声波能量扩散系数的影响，推导得到了圆形结构损伤大小与超声波能量扩散系数之间的定量关系式，超声波能量扩散系数与结构损伤的直径的变化量近似成线性关系。基于一维超声波能量扩散方程提出了基于超声波能量扩散系数及超声波能量密度的混凝土结构早期损伤指数用于混凝土结构早期损伤的识别，设计了金属拉伸与混凝土试样三点弯曲实验，利用本项目所提出方法对金属材料和混凝土结构受载破坏过程中的结构早期损伤及其扩展过程进行了识别与监测，实验结果表明，基于超声能量扩散系数及超声波能量密度的结构损伤指数可以有效识别结构的损伤。.为了解决传统智能骨料布线及维护困难、激发传感输出小等问题，对新型无线及叠加式智能骨料特性进行了研究。考虑混凝土结构损伤积累与扩展特点及无线传感网络的能耗问题，本项目提出智能骨料激发器采用周期性激发正弦扫频信号、智能骨料传感器同步周期性接收的总体设计思路，分别基于AD9851和AD7705芯片组对无线智能骨料激发器及传感器的控制电路进行了设计，并对制作的无线智能骨料及其传感网络性能进行了测试。采用理论与实验相结合的方法分析了压电陶瓷厚度数量、电学连接方式、环氧树脂等对新型叠加骨料激发-传感特性、阻抗特性、混凝土结构中的传输特性进行了分析，结果表明，压电陶瓷数量及厚度对其阻抗特性影响较大，制作所需要的环氧树脂其影响较小，电学并联新型智能骨料适用于激发器，电学串联联接智能骨料适用于传感器。最后，本项目所设计的新型无线智能骨料结合基于超声波能量扩散理论结构损伤指数对混凝土试块受载破坏过程中的损伤进行了有效地识别。