轮毂轴承广谱漏磁无损检测传感方法与应用研究

The automobile industry is one of the pillar industries of "Made in China 2025", and the hub bearing is a vital component in the automobile industry. Its surface is complex and scales of natural defects vary widely. It is very difficult to realize automated machine testing technology. The Magnetic Flux Leakage (MFL) testing method has advantages of high sensitivity and high degree of automation. However, the MFL method is difficult to detect micro-cracks, and several cracks will be missing detected for the magnetic head has high selectivity for tested cracks. In the project, the magnetic dipole theory and the Finite Element Method (FEM) are applied to reveal spatial spectrum features of the leakage magnetic field. The magnetic head based on loop measurement is used in this project. The spatial frequency response function of this probe is studied. Results show that each probe has its sensitive crack. Further, a leakage magnetic field sensing method of broad spatial spectrum is proposed based on measuring loops working in different spatial frequency composed of the permalloy. The coupling and decoupling principles are studied, and a novel probe within broad spatial spectrum is proposed. The quantitative assessment methods are proposed too. The imitation probe is established according to the tested surface. The automatic detection and the evaluation system are realized. This project clarifies the mechanism of the detection of cross-scale defect by the MFL method. A novel sensing method within wide-spectrum is proposed, and it makes up for the shortcomings of bearing NDT technology by the MFL method. It has important theoretical significance and practical value to detect cross-scale defects in hub bearings within automated NDT method.

汽车业是《中国制造2025》中的支柱产业之一，轮毂轴承是汽车产业中的关键零部件，其曲面复杂、自然缺陷尺度变化范围广，实现机器自动化检测的难度大。漏磁检测具有灵敏度高、易实现自动化等优点，但对微米尺度的裂纹检测困难、检测磁头对裂纹开口选择性高，易导致漏检。为此，首先以磁偶极子模型和有限元法为基础，对不同尺度裂纹产生漏磁场的空间频谱特性进行表征。然后，采用基于回路测量漏磁场的磁头结构，建立其空间频率响应函数，得到每种磁头的固有敏感裂纹尺度。进一步，提出广谱漏磁传感方法，采用坡莫合金材料构建不同空间频段的测量回路，揭示各测量回路耦合与解耦机制，获得广谱漏磁传感方法，实现缺陷的定量评估。最后，依据被检复杂曲面几何特征，设计阵列仿形漏磁传感器，实现轮毂轴承自动化无损检测。本项目阐明了跨尺度缺陷漏磁检测的机制，建立了广谱漏磁传感新方法，弥补了轴承漏磁检测技术的不足，具有重要的理论意义。

本项目围绕轮毂轴承裂纹的自动化无损检测需求，以磁记录技术为基础，采用漏磁检测法，研究了不同尺度缺陷漏磁场的空间频谱特性，研究了漏磁检测探头的空间频率响应模型。以漏磁场为输入，漏磁检测探头为相互作用系统，检测信号为输入，漏磁检测输出为漏磁场与探头系统的卷积。在频域内，漏磁检测输出为漏磁场与探头响应函数的乘积。以此为基础，本项目揭示了漏磁检测探头的空间敏感特性，研究结果表明特定尺寸的探头仅能检测有限尺度内的缺陷。针对自然缺陷尺度范围广这一难题，单一开口尺寸的探头难以覆盖所有的缺陷，为此需要设计多开口的广谱漏磁检测探头。本项目的结论主要有：（1）磁记录技术中的感应式磁头具有灵敏度高、响应速度快、磁饱和范围宽等一系列优点，可以在漏磁检测中取得良好的效果，尤其适用于轴承淬火微裂纹的漏磁检测；（2）在漏磁检测技术中，感应式磁头的敏感范围与开口宽度密切相关，探头开口越窄，探头敏感的裂纹也越窄；（3）特定开口尺寸的探头仅能检测一定尺度范围内的缺陷，缺陷尺度太小或太大均不能有效的检测；（4）针对自然缺陷尺度范围广这一难题，可以采用叠片型多开口探头，此时探头覆盖范围广，既能有效检测小尺度的微裂纹，同时可以有效检出大尺度缺陷。