高速铁路钢轨轨底伤损超声导波检测技术基础研究

The subject is proposed to carry out the theory and experimental research on ultrasonic guided wave testing technique for rail foot damages of high-speed railway. At first, considering the binding constraint and contact effects from the spring fastener and pad on the sleepers, we try to build the acoustic waveguide physical mode for rail foot structure of rail tracks. Combined with the various research means such as theoretical analysis, numerical calculation, the dynamic photoelastic and testing signal processing, the excitation and propagation mechanism and scattering and attenuation characteristic of guided waves in the rail foot of track will be selective analyzed. Meanwhile, interrelation between the propagation guided waves mode with the fastener, interaction and reflective law between guided waves with typical damages in rail foot, interaction and reflective law between guided waves with aluminothermic welding joint will be selective studied also. Secondly, the detection mode guided wave excitation technique, guided waves information extraction method and signal processing technique for improving signal to noise ratio will be all investigated. At the same time, analysis of the actual noise disturbing effect and corresponding control methods will be presented. Thirdly, the research subjects will carry out the experimental testing to study interaction process between detection mode guided wave with damages in rail foot and fastener, and to investigate interrelation between guided wave signal with rail foot structure, typical damages and acoustic parameter. Based on the research work above, the guided wave testing prototype instrument for rail foot will be developed and be used in field experimental research. Based on the way such as mastering the control method for generating the detection mode guided waves, exploring this mode guided wave's propagation characteristic and the reflective properties from the typical damages or fastener in the rail foot, the guided wave testing instrument technique for rail foot damages detected in field will be obtained, and the theoretical and methodological basis of in service ultrasonic guided wave testing technology for rail foot of railroad will be established. This research work will lay a strong foundation to form and develop independent, innovative, intellectual property non-destructive testing technique for track structure of high-speed railway.

本项目提出开展高速铁路钢轨轨底伤损超声导波检测的理论方法和实验研究。首先，考虑轨枕上弹扣和垫板对轨底的紧固约束，建立轨道钢轨轨底结构的声波导物理模型。以理论分析、数值计算、动态光弹实验、测试信号处理等多种手段相结合，重点分析导波在钢轨轨底中的激发、传播、衰减、散射特性，研究各导波模式传播及与轨底紧固件的相互关系；研究导波与轨底典型伤损和铝热焊接头的相互作用及导波反射规律。其次，研究检测模式波的激发控制方法，研究如何获取导波信息以及提高导波信噪比的信号处理方法，分析实际噪声的影响和控制方法。再其次，开展实验检测工作，研究检测模式导波与轨底伤损和紧固件的相互作用过程，研究导波信号与结构、典型伤损和声学参数的关系。在此基础上，研制出轨底导波检测实验样机并开展现场实验，建立高速铁路钢轨轨底伤损的超声导波检测技术的理论和方法基础，为形成和开拓具有我国自主创新知识产权的高铁轨道结构的检测技术奠定基础。

随着我国高速和重载铁路技术的飞速发展，为保障运输安全对线路钢轨轨底伤损的超声无损检测技术提出了新要求。本课题以我国主要干线使用的CHN60型钢轨为研究对象，研究导波在钢轨轨底中的传播特性及在缺陷上的散射特性，并开展线路钢轨轨底超声导波检测方法研究。首先，采用有限元方法建立了包含弹扣和橡胶垫板紧固约束的钢轨轨底三维模型。通过模拟螺栓预紧过程，获得弹扣件的安装受力状态，掌握了导波与弹扣和垫板相互作用的机制及对轨底导波传播的影响。在此基础上建立将弹扣和垫板紧固约束简化为钢轨轨底和连续支撑层的三维声波导数值模型。运用半解析有限元方法快速计算并获得了钢轨轨底的导波模式。通过对纵向振动模态、横向振动模态和垂直振动模态频散曲线、衰减特性和波结构的计算，发现横向振动模态类似于伪瑞利波，垂直振动模态类似于兰姆波。对于横向振动模态导波，轨底介质质点的水平横向振动特性受弹扣和垫片影响最小，该模态是最适合于长距离检测轨底损伤的导波波型。其次，基于轨底横向振动模态瑞利波的特点，提出了设计了单晶片和阵列晶片的导波探头的方法，并研制了压电晶片中心振动频率为120kHz的导波探头。采用动态光弹方法观测了导波探头在钢轨轨底的激发的横向振动模式导波的声场并实验测量了导波的回波响应。然后，以线路钢轨轨底典型伤损的形貌特征为指导，建立了钢轨轨底典型缺陷的有限元模型。通过计算得到检测模式导波在钢轨轨底斜裂纹、轨底腐蚀等典型伤损上的反射和透射回波特性。实验研究了检测模式导波在不同截面、深度和倾斜角大小轨底裂纹上的散射回波特性。实验研究了检测模式导波在轨底铝热焊接头的反射和透射回波特性，谱分析可从焊缝余高反射回波中识别焊缝中缺陷反射回波信号。最后，通过实验给出了设计制作钢轨轨底伤损导波检测定标试块的方法和数据，开展了轨底导波检测的现场实验。本课题研究为增强我国自主知识产权的高铁轨道结构的检测技术提供了方法基础。