铁路钢轨裂纹的在线高速漏磁巡检-测试计量技术及仪器专业论文.docxVIP

摘要轮轨接触应力造成的高速铁路钢轨裂纹损伤，容易导致重大的交通安全事故。铁路部门迫 切需求高效、准确的钢轨裂纹巡检方法和设备。由于铁磁性材料的电磁特性与其组织结构密切 相关，电磁无损检测技术适用于钢轨材料结构性能的检测和评估。本文采用漏磁检测技术对钢 轨裂纹损伤进行非接触式的在线高速巡检，分析了巡检速度带来的影响，设计了适于裂纹高速 巡检的检测方法和装置，并做了试验验证。通过有限元仿真得出裂纹漏磁场为“磁泡”形状沿着空间三维发散分布，能反映裂纹的宽 度、深度、倾斜角度等特征信息。多个小间距连续裂纹的漏磁场会相互叠加。传感器提离和材 料饱和磁化对裂纹检测很重要。仿真中宽度 0.1mm、深度 1mm 裂纹的材料表面提离较小处有 较为明显的漏磁场，漏磁方法具有检测微小裂纹的可行性。裂纹高速漏磁巡检试验的结果表明， 在 200km/h 速度范围内能实现宽度最小 0.2mm、深度最小 2mm 裂纹损伤的快速巡检。提高巡 检速度带来的磁化迟滞效应使得缺陷漏磁场增强，涡电流效应使得缺陷漏磁场减弱和背景磁场 增强。钢轨纵向和横向磁化相结合，有利于多种倾角类型裂纹损伤的全面检测。巡检速度提高 时，霍尔和线圈检测到的裂纹漏磁信号幅值均单调增大，但不同巡检速度下的霍尔检测信号漂 移严重。将三维霍尔、线圈检测探头以及缠绕在磁轭臂上的检测线圈集成在一起进行检测，能 获得较多的裂纹缺陷信息，有利于不同速度下钢轨裂纹缺陷的量化分析和损伤评估。关键词：钢轨裂纹，漏磁检测，在线高速巡检，速度效应，有限元仿真iABSTRACTWheel-rail contact stress can cause various types of fatigue crack damage on the railway track. Rail crack defects, as the typical degradation, easily lead to fatal traffic accident. Efficient and accurate rail failure detection methods and equipments are urgently needed. Electromagnetic Non-Destructive Testing (ENDT) is suitable for the characterization of changes in the ferromagnetic materials’ structure, because the magnetization processes are closely related to their microstructure. In this paper, Magnetic flux leakage (MFL) technique is proposed for the non-contact, online high speed rail cracks detection. Velocity effect, produced in the rapid relative motion between the detection device and measured rail track, is analyzed. The detection methods and devices, suitable for high speed rail cracks detection, are proposed and verified with the experiments.On the analysis of the MFL detection in Finite Element Method (FEM) simulation, defect MFL field divergent distribute in 3-D space with the bubble shape, cracks with different width, depth and angle of inclination corresponding to different MFL field intensity and distribution. Multiple continuous cracks with small spacing will cause MFL field stack distribution. Sensor lift-off and saturation magnetization of the measured material are important for cracks detection. It