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飞机机身多层铆接结构厚度较大,结构复杂,传统无损检测方法难以用于对其进行外场检测。远场涡流检测技术不受集肤效应的限制,可穿透较大厚度的被测试件,对铆接结构中缺陷的检测具有潜在优势。为在铆接结构中实现远场涡流效应,从信号增强与磁场抑制两方面入手,设计一种新型平板远场涡流传感器。信号增强方面,给激励线圈加装磁路来聚集和引导磁场,从而增强间接耦合磁场;磁场抑制方面,在激励线圈与检测线圈之间加装磁场抑制单元来抑制直接耦合磁场。通过信号增强与磁场抑制的共同作用,从而在铆接结中实现远场涡流效应。围绕传感器设计这个核心,对信号增强单元以及磁场抑制单元的尺寸形状、材料组成进行仿真研究,综合得出最优的传感器设计方案。仿真与试验的结果验证了将远场涡流检测技术应用于铆接结构中缺陷检测的可行性。
The aircraft fuselage multi-layer riveting structure has a large thickness and complex structure, and the traditional nondestructive testing method is difficult to be used for field testing. Far-field eddy current testing technology is not limited by the skin effect, can penetrate a larger thickness of the test piece, the riveted structure defects detection has the potential advantage. In order to realize the far-field vortex effect in the riveted structure, a new type of flat-panel far-field vortex sensor is designed from two aspects of signal enhancement and magnetic field suppression. Signal enhancement, the excitation coil to install magnetic circuit to gather and guide the magnetic field, thereby enhancing the indirect coupling magnetic field; magnetic field suppression, the excitation coil and the detection coil between the magnetic field suppression unit to suppress direct coupling magnetic field. Through the combined effect of signal enhancement and magnetic field suppression, far-field vortex effects are achieved in riveted junctions. Around the sensor design of the core, the signal enhancement unit and the magnetic field suppression unit size and shape, material composition of the simulation study, synthesize the best sensor design. Simulation and experimental results verify the feasibility of applying far-field eddy current testing technique to the defect detection in riveted structures.