基于光纤耦合的钢轨缺陷超声波全光学激发与动态检测方法研究

Rail is one of the most important parts of the train operation. With the rapid development of high-speed railway and urban rail transit, the higher requirements are put forward for the in-service rail defect detection. Aiming at the limitation of existing rail flaw detection methods, a new fiber-coupled method based on all-optical ultrasound excitation and testing is proposed in this project. The main research contents and targets of this project are as follows. ⑴A nonlinear interferometric method based on the fiber-coupling with the advantages of high sensitivity, wide bandwidth and prompt measurement will be studied. The efficiency of the photocurrent conversion efficiency will be solved, and the extraction ability of weak ultrasonic signal will be enhanced. ⑵The method to improve the laser excitation mode, and to enhance the excitation efficiency will be studied in order to obtain the enhanced ultrasonic signal. ⑶The propagation characteristics of ultrasound in the rail and its interaction with defects will be studied, and the theoretical model for defect detecting system will be established. The research work of this project will provide a comprehensive, reliable, fast and effective detection method for in-service rail defect detection, and improve the technical means of rail flaw detection. Any progress in the research is of great scientific significance, practical demand and application value. Furthermore, this measuring method will provide the theoretical reference and technical support to the application of the method in other related fields.

钢轨是列车运行的基础，我国高速铁路以及城市轨道交通的快速发展对在役钢轨缺陷检测提出了更高要求。针对现有钢轨探伤方法的局限性，本项目拟探索一种基于光纤耦合的超声波全光学激发与检测的在役钢轨缺陷探测新方法，着重开展三方面的研究工作：⑴研究基于光纤耦合的高灵敏、大带宽、快速的激光非线性干涉测量方法，解决光电流转换效率问题，增强对微弱光声信号的提取能力；⑵研究改善激光激发方式、提高激发效率和探伤速度的方法，获得增强的超声信号；⑶研究激光在钢轨中所激发超声波的传播特性及其与缺陷的相互作用，建立缺陷检测系统的理论模型。本项目研究工作，将为在役钢轨缺陷检测提供一种全面可靠、快速有效的检测方法，提升钢轨探伤的技术手段，具有重要的科学意义、现实需求和应用价值。项目工作也将为该检测方法在其它相关领域的应用提供理论参考与技术支撑。

激光超声缺陷检测的显著特点是能够实现完全非接触测量，更加适合于高温高压有毒等恶劣环境下，以及各种复杂物体表面与几何形状的测量。实现完全非接触，必须构成激光激发、光学检测的全光学方法。常规光学线性干涉测振方法极易受到周围环境及被测表面的影响，对于钢轨表面状态，更难实现宽带微小的激光超声振动测量。针对钢轨缺陷检测的超声波全光学激发与检测，着重开展了三个方面的研究工作：⑴研究了非线性激光干涉与非干涉型离面/面内超声振动测量方法与系统，探寻了提高半导体器件光电流转换效率的途径，进而获得更高检测灵敏度和带宽；⑵改善激光激发方式，研究了激光在线源阵列、环光源的空间调制下，激发超声波以及超声波的传播特性，提高了超声波激发效率，获得了增强的超声信号；⑶研究了激光线源扫描激发超声检测缺陷的方法与装置，对钢轨踏面微小缺陷实现了有效检测。该方法的研究还能够解决无损检测中的一些共性问题，将在机械加工过程控制、集成电路无损检测、材料特性分析等多个领域发挥作用。