高铁无砟轨道结构粘接界面缺陷的超声兰姆波检测方法研究

Interfacial gap or debonding between the mortar and track slab is the most common and serious injury form in the ballastless track structure of high-speed railway, which is related to the normal operation of high-speed trains and the safety of passengers. In view of their bonding structure belonging to a typical laminated sheet structure, this project will dig the potential of ultrasonic guided waves in nondestructive evaluation of bonding interface and explore the Lamb wave detection method for ballastless track structure with localized bonding interface. The model of Lamb wave propagating in multilayer structure with localized weak adhesion interface is theoretically established so as to select the inspecting Lamb mode that is sensitive to interfacial property. The relationship between Lamb wave propagating characteristics and the interfacial defect features is established for exploring the mechanism of interaction of Lamb wave with the interfacial defect. Effective signal processing method is developed to extract the real defect signal and separate the desired mode from the aliasing multiple modes. This project will research anomalous defective wave imaging algorithm based on the full wave field data, so as to improve the resolution and precision of quantitative defect map. The excitation, propagation and best reception of air-coupled ultrasonic Lamb wave signals are experimentally studied. The achievements of this project will provide a new academic way for Lamb wave propagation problem with localized weak adhesion defect and lay the theoretical groundwork in the application for Lamb wave nondestructive evaluation of the interfacial defects in the high speed railway ballastless track structure.

砂浆与轨道板离隙或脱空是高铁无砟轨道结构中最常见和最严重的损伤形式，关系到高速列车的正常运营和乘客的人身安全。鉴于二者粘接而成的复合结构属于典型的层状薄板结构，本项目将挖掘超声导波在粘接界面无损评价方面的潜力，研究存在局部粘接界面缺陷的无砟轨道结构兰姆波检测方法。从理论上建立包含局部弱粘接界面的多层介质兰姆波传播模型，寻求对界面性质敏感的兰姆波模式；考察兰姆波传播特性与界面缺陷特征之间的关系，探究兰姆波与界面缺陷相互作用机理；发展有效的信号处理方法，提取真正的缺陷信号并从混叠的多模式信号中分离出所需要的模式；探索基于全波场信息的异常（缺陷）波成像算法，提高定量化缺陷图像的分辨率和精度。从实验上研究空气耦合超声兰姆波信号的激发、传播和最佳接收。本项目研究成果在学术上提供解决含局部弱粘接界面缺陷兰姆波传播问题的新途径，在应用上为高铁无砟轨道结构粘接界面缺陷的兰姆波无损评价奠定理论基础。

本项目针对高速铁路无砟轨道板结构中的粘接缺陷，提出了空气耦合非接触超声导波检测方法，实现了缺陷的准确定位、定量评估和形象化图像表征，取得了一系列具有理论和实际价值的基础性研究成果。主要包括：①建立层状各向同性固体中的声传播模型，分析了无砟轨道板结构中超声兰姆波的传播特性。采用全局矩阵法计算大厚度轨道板中的波传播问题，避免了大频厚积时的数值不稳定；②研究CA砂浆不同粘接状态的超声导波表征方法。建立无砟轨道超声导波有限元模型，分析多种工况下CA砂浆脱粘的超声导波特征模态。针对脱粘引起的超声导波模态混叠问题，采用时间反转聚焦方法进行CA砂浆脱粘特征模态识别，并使用损伤指数定量评价脱粘的存在及严重程度；③基于能量泄漏原理，提出空气耦合超声导波实现无砟轨道结构脱粘缺陷快速检测的新方法。建立了空气耦合超声波斜入射条件下脱粘缺陷的检测模型。研究了兰姆波与缺陷相互作用规律，并探讨探头间距、探头尺寸等参数对检测结果的影响，进而优化实验系统参数，达到最佳的检测结果；④研究无砟轨道层间脱粘缺陷的超声阵列成像理论及方法。建立无砟轨道结构二维声传播模型，分析了声波在层间的反射、折射以及声传播路径特性。在此基础上，给出了无砟轨道层间脱粘缺陷的时域和频域表征方法；⑤建立无砟轨道结构多层声速理论模型，研究脱粘缺陷的高精度快速成像方法。将无砟轨道结构视为非均匀声速复合弹性板结构，研究超声波在无砟轨道结构中的传播规律，通过射线移动追踪正向SAFT(Synthetic Aperture Focusing Technique)方法实现高精度成像；采用不同编码方式并结合遗传算法优化了阵元位置，提高成像效率。本项目的研究成果为高铁无砟轨道结构粘接界面缺陷的兰姆波定量无损评价奠定理论基础。