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飞机铆钉孔周裂纹的脉冲涡流检测【测控技术与仪器专业资料】,测控技术与仪器专业资料,飞机,铆钉,裂纹,脉冲,涡流,检测,测控,技术,仪器,专业,资料

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任务书I、毕业设计(论文)题目：飞机铆钉孔周裂纹的脉冲涡流检测II、毕 业设计(论文)使用的原始资料(数据)及设计技术要求：1、原始资料：参考文献；脉冲信号发生器说明书；计算机2、设计技术要求： (1)查找国内外飞机铆钉孔周裂纹的脉冲涡流检测研究方法资料； (2)制作试验用带孔周裂纹飞机多层铝合金铆接试块； (3)设计脉冲涡流检测传感器； (4)设计合理的实验方案，对传感器参数进行优化选择； (5)探头性能测试，对铆钉孔周裂纹进行检测并对采集的信号做消噪处理。III、毕 业设计(论文)工作内容及完成时间：1、查阅文献资料，英文资料翻译，撰写开题报告； 03.0904.102、购买实验材料，初步设计实验传感器； 04.1104.253、制作传感器及实验试块，并调试实验系统； 04.2605.074、设计合理的实验方案对传感器进行优化设计； 05.0805.19 5、整理实验数据，传感器设计定型； 05.2006.01 6、资料归档、进行课题总结； 06.0206.087、撰写毕业论文、答辩。 06.0906.26 、主 要参考资料：1 杨宾峰,罗飞路,张玉华，徐平. 脉冲涡流在飞机铆接结构无损检测中的应用研究J.计量技术,2005,(12):15-17.2 周德强,张斌强,田贵云,王海涛. 脉冲涡流检测中裂纹的深度定量及分类识别J.仪器仪表学报,2009,30(6):1191-1194.3 徐平等.飞机多层结构腐蚀缺陷监测系统的研究与实现J. 电子设计应用,2005,(10):96-98.4 周德强,闫向阳,尤丽华. 激励参数对脉冲涡流缺陷检测的仿真分析J. 无损检测,2012,34(10):8-11.5 Buzz Wincheski, Feng Yu, John Simpon. Development of SDT sensor based eddy current probe for detection of deep fatigue cracks in multilayer structure J.2010,43(8):718-725.6 G.Yang, Z.Zeng, Y.Deng, 3D EC-GMR sensor system for detection of subsurface defects at steel fastener sitesJ.2012,50:20-28.7 G.Yang, Z.Zeng, Y.Deng, Sensor-tilt invariance analysis for eddy current signalsJ.2012,52:1-8.8 Guang Yang, Antonello Tamburrino, Lalita Udpa. Pulsed Eddy-Current BasedGiant Magneto resistive System for the Inspection of Aircraft StructuresJ. 2010,46:910-917.for the Inspection of Aircraft Structures 测试与光电工程 学院 测控技术与仪器 专业类 班学生（签名）： 日期： 自 20xx 年3 月 9 日 至 20xx 年 6 月 26 日指导教师（签名）： 助理指导教师(并指出所负责的部分)：测控技术与仪器 系（室）主任（签名）：学士学位论文原创性声明本人声明，所呈交的论文是本人在导师的指导下独立完成的研究成果。除了文中特别加以标注引用的内容外，本论文不包含法律意义上已属于他人的任何形式的研究成果,也不包含本人已用于其他学位申请的论文或成果。对本文的研究作出重要贡献的个人和集体，均已在文中以明确方式表明。本人完全意识到本声明的法律后果由本人承担。作者签名： 日期：学位论文版权使用授权书本学位论文作者完全了解学校有关保留、使用学位论文的规定，同意学校保留并向国家有关部门或机构送交论文的复印件和电子版，允许论文被查阅和借阅。本人授权南昌航空大学科技学院可以将本论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存和汇编本学位论文作者签名： 日期：导师签名： 日期：Pulsed eddy current technique for defect detection in aircraftriveted structuresYunze Hen, Feilu Luo, Mengchun Pan, Feibing Weng, Xiangchao Hu, Junzhe Gao, Bo LiuCollege of Mechatronics and Automation, National University of Defense Technology; Changsha 410073, Chinaa r t i c l e i n f oArticle history:Received 1 July 2009Received in revised form29 October 2009Accepted 30 October 2009Available online 12 November 2009Keywords:Nondestructive testingPulsed eddy currentDifferential probeDefect detectionRiveted structurea b s t r a c tThe Pulsed Eddy Current (PEC) technique is an effective method of quantifying defects in multi-layerstructures. It is difficult to detect defects in riveted structures of aging aircraft. Based on theoreticalanalysis of PEC technique, three different probes, including a differential hall probe, a differential coilprobe, and a two-stage differential coil probe are designed to detect this kind of defects. The averagingmethod and wavelet analysis method are used to de-noise the hall response signals. By selecting peakamplitude and zero-crossing time of response signal in time domain as key features, defects in rivetedstructures can be detected effectively. The experimental results indicated that the differential coil probeacted as effectively as the differential hall probe. The defects between third layer and fourth layer inriveted structures can be detected by utilizing the two-stage differential coil probe. The PEC techniquehas a promising application foreground in the field of aeronautical nondestructive testing.Crown Copyright & 2009 Published by Elsevier Ltd. All rights reserved.1. IntroductionThe detection of second layer defects and hidden defects inriveted structures has been identified as major problems inaeronautical nondestructive testing. Traditional ultrasonic, eddycurrent and radiometric methods can detect first layer defects.However, it is difficult for these methods to detect second layerdefects. The pulsed eddy current (PEC) nondestructive testing is anew technology developed in recent years, which is an effectivemethod that has been demonstrated to be capable of quantifyingdefects in the multi-layer structures 13. In contrast to theconventional eddy current technique with a single frequencysinusoidal field excitation, PEC technique uses pulsed excitationthat is characterized by the richness of frequency contents 4. Inaddition, PEC technique can minimize power consumption, whichis more promising in the development of portable instrument 5.Rose JH et al. described the corrosion characterization inaircraft lap splices for both air-core and ferrite-core PEC probeswith one plat coil 6. Giguere S et al. illustrated three featuresadopted in PEC testing to quantify defects and exemplify theirapplication 7. Sophian A et al. presented a new type of pulsededdy current sensor for defect detection in aircraft lap-jointstructures 8. Tian GY et al. presented a new feature called asrising point time to identify the different defect types and lift-off,which offers benefits such as independence of coil dimension andability to evaluate a defects depth regardless of its type or shape9. Zeng ZW et al. presented a three-dimensional finite-elementmodel of Maxwells equation for numerical simulation of theMagneto-optic/eddy current imaging (MOI) operation which wasuseful to detecting surface and subsurface cracks at rivet sites10. Li S et al. introduced development of differential probes inpulsed eddy current testing for noise suppression 11. In all thesestudies, the driving coil is excited by repeated pulses and theresponse signals are measured with different sensors, which maybe the driving coil, another coil, or a hall-effect sensor. However,differential coil probe and two-stage differential probe have notbeen proposed to detect the defects in airframe riveted structures.The main purpose of this paper is to detect the defects inairframe riveted structures. First and foremost, pulsed eddycurrent principle is introduced in Section 2. Next, three kind ofdifferential probes are proposed and designed in Section 3 and thePEC detection system is presented in detail in Section 4. Then,experiment results and discussion are shown in Section 5. Finally,conclusions and further work are outlined in Section 6.2. Pulsed eddy current principleThe PEC probe is excited with a repetitive broadband pulse.Since a broadband frequency spectrum is produced in one pulse,the response signals contain important information of defects12. Typical features such as peak amplitude and zero-crossingtime are used to detect and characterize defects 13,14. The keyfeatures (peak amplitude and zero-crossing time) of responseARTICLE IN PRESSContents lists available at ScienceDirectjournal homepage: /locate/ndteintNDT&E International0963-8695/$-see front matter Crown Copyright & 2009 Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.ndteint.2009.10.010nCorresponding author. Tel.: +86 13467698133.E-mail addresses: (Y. He), flluo (F. Luo).NDT&E International 43 (2010) 176181ARTICLE IN PRESSsignals in time domain are shown in Fig. 2(b). In experiments, it isfound that the peak amplitude of detecting signal is relative todefect volume and the zero-crossing time has a close relationshipwith defect depth. Specifically, the peak amplitude of responsesignal increases clearly with the increment of defect volume andthe deeper defect leads to the shorter zero-crossing time. Basedon that principle, the PEC response signals in time domain areanalyzed to detect the defects in riveted structures.3. Probe designThe basic principle of differential probe is to subtract thedefect signal from the reference signal which may be the responsewhen the probe is on the defect-free materials in most case, orresponse of probe in air 11. According to the difference in pick-up sensor, three kind of differential probes are presented anddesigned as follows.3.1. Differential hall probeIn PEC testing, the hall-effect sensor can be used to measurethe magnetic field signals, for example, in Tian GYs studies4,9,15. As shown in Fig. 1, the differential hall probe inauthors study consists of one exciting coil and two hall-effect sensors UGN3503. The exciting coil is a cylinder reeledby copper wire and the number of turns is 400. The innerdiameter, outer diameter, and height of exciting coil are 18, 22and 10 mm, respectively. The diameter of copper wire is 0.2 mm.Two hall-effect sensors are located axisymmetrically at thebottom of the exciting coil and differentially connected. Inexperiment,theexcitingcoilisexcitedbyarepetitivebroadband pulse to generate the eddy current in the specimen.When one of hall-effect sensors is on the defect area in specimen,it outputs changed voltage signal caused by defect, while theother hall-effect sensor on crack-free materials outputs aninherent voltage signal. Therefore, the defect will lead to aFig. 2. The differential coil probe and the differential signal. (a) The differentialcoil probe. (b) The differential signal of probe.Fig. 1. The differential hall probe.Fig. 3. The structure of two-stage differential probe.Fig. 4. The schematic diagram of the experimental system.Fig. 5. The diagram of the exciting pulse.Y. He et al. / NDT&E International 43 (2010) 176181177ARTICLE IN PRESSremarkable change in the differentially output signal of thedifferential hall probe, which is the subtraction of two voltagesignals.3.2. Differential coil probeSimilar with the differential hall probe, the differential coilprobe consists of one exciting coil and two pick-up coils, which isshown in Fig. 2(a). The shape and parameters of the exciting coilare the same to these of the exciting coil in the differential hallprobe. The two pick-up coils are located axisymmetrically at thebottom of the exciting coil and are differentially connected. Theinner diameter, outer diameter and height of the pick-up coilsare1, 6 and 2 mm, respectively. The diameter of copper wire usedin pick-up coil is 0.06 mm and the number of turns is 800. Whenone of pick-up coils is on defect area in specimen, it outputs thechanged voltage signal caused by defect, while another pick-upcoilondefect-freematerialsoutputsaninherentvoltage.Therefore, the defect will lead to a change in the differentiallysignal. The differential coil output signal is shown in Fig. 2(b).3.3. Two-stage differential coil probeThe sensitivity and robustness of PEC testing can be seriouslyhampered by the lift-off effect, which deforms defect signals, thuscauses misinterpretation 11. Traditionally, the differential signalFig. 6. The schematic diagram of the riveted structure specimen.Fig. 7. The peak scanning waves of different defects on subsurface. (a) The originalpeak scanning waves. (b) The peak waves after processing.Fig. 8. The key features of different defects on surface. (a) The peak amplitude.(b) The zero-crossing time.Y. He et al. / NDT&E International 43 (2010) 176181178ARTICLE IN PRESSis worked out directly from the difference of a reference signalfrom a defect-free sample and a defect signal 15. To suppress thelift-off effect, optimization of probe is attempted. The structure oftwo-stage differential coils probe is shown in Fig. 3. Apparently,there are three reference coils used in the two-stage differentialprobe. The output signal is obtained after two-stage differentialamplification. The first stage is aimed to reduce the lift-off effect,whilethesecondtosubtractthereferencesignalthatiscorresponding with the defect-free material.4. Experimental SystemExperimental system is designed to produce the exciting pulseand to measure the response signal affected by defect inspecimen. As shown in Fig. 4, the PEC experimental system usedin this research consists of pulse generator, power amplifier,probe, specimen, signal process, data acquisition module, andsoftware.In generator module, Direct Digital Synthesizer (DDS) chipAD7008 is used to generate the exciting pulse. AD7008 directdigital synthesis chip is a numerically controlled oscillatoremploying a 32-bit phase accumulator, a 12-bit phase register,sine and cosine look-up tables and a 10-bit D/A converterintegrated on single CMOS chip. The power amplifier is employedto enhance the exciting magnetic field. The probes proposed inSection 3 are used to induce the response signals. The responsesignals are amplified by signal processing module, which iscomprised of PGA202 and PGA203. Then, the response signal issampled by data acquisition module with 100 kHz sampling rate.Software plays an important role in the PEC detection system,which is programmed by Microsoft Visual C+ 6.0, combined withMatlab 7. Modularized frame is adopted in order to upgradesoftware conveniently later 16.To verify performance of the differential hall/coil probesproposed in Section 3, some aluminum specimen whose sectionalviews shown in Fig. 5 are designed. Different sizes of slots aremachined by the side of rivet hole on the surface and subsurfaceof aluminum plate with the thickness of 3 mm. Two plates arefastened by snapped rivet and screws to simulate multi-layerriveted structure of airframe. The diameter of rivet and screwis 3 mm.5. Results and discussion5.1. Differential hall probeThree defects with different depths on subsurface are detectedwith differential hall probe. The length?width?depth of threedefects, are respectively,10?1.5?1.2 mm3, 10?1.5?1.0 mm3,10?1.5?0.8 mm3. As shown in Fig. 6, the amplitude of theexciting pulse is 10 V, the repetition rate of the excitation is100 Hz and the duty ratio is 50%. In the course of probe rotatingon its axis around the rivet, the hall response signals of thedifferential probe are sampled in real time. At the same time, thepeak amplitude points of response signals are extracted andconnected to form peak waves.Fig. 9. The transient response signals of different defects on surface. (a) The original hall transient response signals. (b) The hall transient response signals after processing.(c) The coil transient response signals.Y. He et al. / NDT&E International 43 (2010) 176181179ARTICLE IN PRESSThe peak waves caused by defects are shown in Fig. 7. Thehorizontal coordinates represent the rotating angle; the verticalcoordinates represent the amplitude of peak waves. Fig. 7(a)shows the original results. It can be seen that the hall responsesignals are disturbed by unknown noise, which leads to theinaccuracy in detecting the defects. Therefore, the averagingmethod and wavelet de-noise method are used to process the hallresponses. Wavelet analysis is a relatively new technique in signalprocessing. The fundamental idea behind wavelet analysis is toanalyze according to scale, therefore both coarse and fine featuresof a data signal can be probed 17.The analysis is done in bothtime and frequency domains, while the similar and widely usedFourier analysis only provides a frequency aspect. This extraability makes wavelet analysis suitable to analyze transientphenomena in signal 18.Fig. 7(b) shows the results after data processing. As the probescans over thedefect, peak waves present a broad crest.Apparently, with the increase of the depth of defects whosewidth and length remain constant, peak values of crests increaseclearly, which provides an effective way to detect subsurface-breaking defects in riveted structure.5.2. Differential coil probeBased on principle that has been discussed in Section 2, thetime domain response signals are analyzed to get the informationof defects. In the experiment, the peak amplitude and the zero-crossing time are extracted and used as key features to detectdefects.Three defects with different depth and the same lengthand width on surface are detected with the differential coilprobe. The length?width?depth of three defects, are respec-tively, 8?0.8?1 mm3, 8?0.8?1.2 mm3, 8?0.8?1.4 mm3. Asshown in Fig. 6, the amplitude of the exciting pulse is 10 V,the repetition rate of the excitation is 100 Hz and the dutyratio is 50%. The experimental results are shown in Fig. 8.The horizontal coordinates represent the scanning time; thevertical coordinates represent the amplitude of transient res-ponse signal. As shown in Fig. 8(a), the peak amplitude valueis related with the depth of defects. Apparently, the peakamplitude value increases clearly with the increment of thedepth of defects whose width and length remain constant, whichprovides an effective means to evaluate the depth of surface-breaking defects. As shown in Fig. 8(b), the zero-crossing time isonly related with defect depth whose width and length remainconstant, which also provides an effective means to evaluatethe depth of surface-breaking defects. Therefore, we can evaluatethe depth of surface-breaking defects in riveted structures byextracting the peak amplitude and zero-crossing time of responsesignals.5.3. Results comparisonTo compare the performance of two differential probesproposed in Section 3, three defects on surface with differentwidth and the same length and depth are detected with twodifferential probes. The length?width?depth of three defectsare 8?0.6?1 mm3, 8?0.8?1 mm3, 8?1.0?1 mm3. As shownin Fig. 6, the amplitude of the exciting pulse is 10 V, the repetitionrate of the excitation is 100 Hz and the duty ratio is 50%. Fig. 9shows the detecting results of different differential probes.Fig. 9(a) shows the original response signals of differential hallprobe. The hall response signals are disturbed by noise, whichleads to the inaccuracy in extracting the feature. Therefore, thewavelet de-noise method are used to de-noise the hall responsesignals. Fig. 9(b) shows the hall response signals after processing.Fig. 9(c) shows the differential coil response signals. Apparently,the differential coil probe acted as effectively as the differentialhall probe in detecting defects in riveted structures. Furthermore,the response signals of coil do not need complicated dataprocessing and the cost of making coil is lower.5.4. Two-stage differential coils probeIn detection of deeper defects, to verify the performance of thetwo-stage differential probe proposed in Section 3, an aluminumspecimen whose schematic diagram shown in Fig. 10 is designed.A slot whose length, width and height, respectively, are 10, 1.5and 1 mm, is machined by the side of rivet hole on the bottom ofthe third aluminum plate with the thickness of 2 mm. Thethickness of first and second aluminum plate is 1 mm. Thethickness of fourth aluminum plate is 1.5 mm. These aluminumplates are fastened by snapped rivet and screws to simulateriveted structure of aircraft. In this experiment, the amplitude ofthe exciting pulse is 12.5 V, the repetition rate of the excitation is60 Hz and the duty ratio is 70%.To compare the performance of reducing lift-off effect betweenthe two-stage differential probe and regular probe, the samespecimen designed above is detected respectively utilizing two-stage differential coil probe and regular probe. Fig. 11 shows therotating results. The horizontal coordinates represent the rotatingangle; the vertical coordinates represent the amplitude of peakwaves. It can be seen that the result of two-stage differentialprobe is obviously better than that of regular probe. Therefore, weFig. 10. The defect between third and fourth layer.Fig. 11. The scanning peak waves of two-stage differential coil probe and regularprobe.Y. He et al. / NDT&E International 43 (2010) 176181180ARTICLE IN PRESSemphasize the analysis on the two-stage differential probe. Fig. 12shows the response signals of defect between third layer andfourthlayerdetectedbythetwo-stagedifferentialprobe.Fig. 12(a) shows the peak amplitude of response signals ofdefect and defect-free; Fig. 12(b) shows the zero-crossing time ofresponse signals of defect and defect-free. Apparently, the peakamplitude of defect will increase by 164 mV (from 3076 to3240 mV); the zero-crossing time will decrease approximately by45ms. Therefore, the two-stage differential probe is effective todetect the deeper defects in riveted structures.6. ConclusionsDefects often appear in airframe riveted structures andseriously threat the safety of aviation. In this paper, three kindof differential hall/coil probes are proposed to detect the defectsin riveted structures. The experiment results show that thedefects on surface and subsurface can be detected effectively andthe differential coil probe act as effectively as the differential hallprobe. In addition, defects between third layer and fourth layerof specimen can be detected easily by using the two-stagedifferential coil probe, which is more effective than the regularprobe.The PEC testing can also be used to identify and evaluate thedefects in multi-layer structures in ageing aircraft 16. Therefore,PEC testing will play an important role in the field of aeronauticalnondestructive testing. Future research of the authors will includedefect classification, the real-time defect identification, fielddefect evaluation, and in-service imaging detection.AcknowledgementsThe authors would like to extend their appreciation to BinFengYang in University of Air Force Engineering for his contributionsto the work.References1 Moulder JC, Bieber JA, Ward WW, et al.Scanned pulsed eddy currentinstrument for non-destructive inspection of aging aircraft. SPIE 1996;2945:213.2 Smith RA, Hugo GR. Transient eddy current NDE for aging aircraft-capabilitiesand limitations. Insight 2001;43(1):1425.3 Smith RA, Hugo GR. Deep corrosion and crack detection in aging aircraft usingtransient eddy current NDE. Review of Progress in Quantitative NDE1999:4011408.4 Tian GY, Sopian A. Defect classification using a new feature for pulsed eddycurrent sensors. NDT&E International 2005;38:7782.5 Li S, Huang SL, Zhao W, et al. Study of pulse eddy current probes detectingcracks extending in all directio