飞机紧固件孔周裂纹检测远场涡流传感器设计及优化

Design and optimization of remote field eddy current sensor for crack detection around the hole of aircraft fasteners

飞机多层金属紧固结构作为飞机重要承力部件在连续受地-空-地循环载荷作用,使铆钉、高锁螺栓等紧固件孔周产生应力集中从而萌生疲劳裂纹。传统无损检测方法难以在在役情况下进行检测,而远场涡流检测技术在原理上突破集肤效应限制,对深层隐藏缺陷检测具有巨大优势。设计研发了与传统平面远场涡流传感器结构不同的新型平面远场涡流传感器,采取激励线圈与检测线圈同轴放置,大幅缩小了传感器尺寸,检测线圈位于激励线圈内部,且在检测线圈与激励线圈之间设计有磁场分流结构。通过有限元仿真对激励线圈尺寸、磁场分流结构材料及其组成方式进行系统的分析,得出最优的传感器设计方案。试验结果表明,设计研发的新型远场涡流传感器可以检测埋深4 mm、尺寸为(长×宽×深) 2×0. 2×4 mm的紧固件孔周裂纹,且随着缺陷长度的增大,信号幅值也随之增大。

As an important bearing component of the aircraft,the multi-layer metal fastener structure is subjected to continuous groundair-ground cyclic loading.The fatigue cracks occur around the hole of fastener,such as rivets and high-lock bolts due to the stress concentration.The traditional non-destructive testing method,however,is difficult to detect those cracks under in-situ conditions.The remote field eddy current testing technology breaks the skin effect limitation in principle,and has great advantages in detecting deep hidden defects.Therefore,this paper proposes a new design of remote field eddy current sensor with different structure from the traditional method.The excitation coil is placed coaxially with the detection coil,which is located inside the excitation coil with a magnetic field shunt between them.This kind of structure can greatly reduce the sensor size.The optimal design of the new sensor is obtained by utilizing the finite element simulation.This method analyzes the size of the excitation coil,structure material and composition of the magnetic field shunt.Experimental results show that the new sensor can detect perforation of the fasteners by the 2×0.2×4 mm(length×width×depth)at a depth of 4 mm.With the increasing of the defect length,the signal amplitude is increased greatly.