1、?1?2?6435?1?2?6435?9?0?-?0?-?0?-?0?5?0?-?0?-?0?-?0?I?0?0?-?0?0?0?6?0?-?0?0?-?-?u?0?0?0?Multifrequency eddy current inspection ofmultilayered structures in aircraftsAbstract:!With the rapid development of aviation industry in recent years,the aviationsafety is more and more important to us.In both mi
2、litary aviation and civil aviation field,how to make the preventive maintenance and prevent mechanical failure in operation ofaircrafts,is particularly important.Especially those overage aircrafts beyond the originaldesign life(20 to 25 years)are still in service,they are vulnerable to the influence
3、 ofcorrosion damage and fatigue crack.How to be efficiently and make accurate detection ofthese defects,which endanger the property and safety of life on board?One of the methodsis multi-frequency eddy current testing method.Its easy to produce fatigue crack near the rivets in riveting multi-layer s
4、tructures,proneto corrosion defects between the layers.Firstly,this paper introduces the principle of multi-frequency eddy current inspection technology.According to the questions mentioned above,we build the experimental platform to simulate multi-level structure in aircrafts.Secondly,Using double-
5、frequency eddy current detector to detect the simulated multilayer structure,discusses the differences and characteristics of single and multi-frequency eddy currenttesting,analyzes the advantages of multi-frequency eddy current testing in multilayerstructure detection.Equipment produce current in d
6、ifferent frequency and detect by one eddycurrent probe,various frequency signals can detect defects in different depth of multilayerstructure.The results show that multi-frequency eddy current testing realize the effectivedefects.Multi-frequency eddy current testing eliminates noisy signal caused by
7、 fasteners,interlayer and air gap,enhance the flaw signal.It has great advantages in detection of interiorof the aircraft skin.The testing practice and the conclusion of this article can be used formulti-frequency eddy current testing technology in the actual detection.Keyword:Multi-frequency eddy c
8、urrent Corrosion defectsRiveting multi-layer structures Crack defects.?q?r?q?r?9?2?9?2?9?2?9?2?2?Phasec2200?I?211?0?-21?0?-31?0?0?-41?-51?0?-?9?2?9?211?0?0?-20 xx.3.09320 xx.4.102.?0?-20 xx.4.1132015.4.2031?0?-20 xx.4.21320 xx.4.2541?-20 xx.4.26320 xx.5.1651?0?-20 xx.5.17320 xx.5.3161?0?-20 xx.6.013
9、20 xx.6.0671?9?0?-20 xx.6.07320 xx.6.26?2?21 J.A.Bieber,S.K.Shaligram,J.H.Rose,J.C.Moulder.Time-gating of Pulsed Eddy Current Signalsfor Defect Characterization and Discrimination in Aircraft Lap-JointsJ.Review of Progress inQNDE,1997,16B:1915-1921.2 SMITH R A,HUGO G R.Deep corrosion and crack detec
10、tion in aging aircraft using transient eddy-current NDEJ.Insight,2001,43(1)u14-24.3 J.A.Bieber,S.K.Shaligram,J.H.Rose,et al.Time-gating of pulsed eddy current signals for defectcharacterization and discrimination in aircraft lap-joints.Review of progress in QNDE,1997,16B:1915-1921.4 B.A.Lepine,B.P.W
11、allace,D.S.Forsyth,Pulsed eddy current method developments forbidden corrosiondetection in aircraft structures.NDT&E International,1999,4(1):1-10.5 S.Giguere,B.A.Lepine,J.M.S.Dubois,Pulsed eddy current technology:Characterizing material losswith gap and lift-off variations.Research in Nondestructive
12、 Evaluation,2001,(13):119-129.6 Ali Sohpian,Gui Yun Tian,et al.A feature extraction technique based on principal component analysisfor pulsed Eddy current NDTJ.NDT&E International,2002,(36):37-41.7 LIBBY H LtIntroduction to electromagnetic nondestructive test methodswMx t New York:JohnWileypSons Inc
13、,1971t8 Gui Yun Tian,Ali Sophian.Defect classification using a new feature for pulsed eddy currentSensorsJ.NDT&E International,2005(38):77-82.9 Ali Sophian.Characterization of Surface and Sub-surface Discontinuities in Metals UsingPulsed Eddy Current SensorsC.Thesis,the University of Huddersfield in
14、 partial fulfilment of therequirements for the degree of Doctor of Philosophy(The United Kingdom),2003.10 G.Y.Tian,Y.Li and C.Mandache.Study of Lift-Off Invariance for Pulsed Eddy-Current SignalsJ.IEEE Transaction on Magnetics,2009,45(1):184-191.?I?89?I?89?2?2?xx?)?xx?2?2?I?2?2?2?xx?)?xx?2?2?I?2?1?!
15、?!?(?“?!?)?)!?)!?)!2?(?!(?(?!(?)?,!(?-!(?.!3?)?/!)?(?!)?)?(!)?)!4?!?(?!?)?,!5?-!?(?/!?)?(?!6?,?(?!,?(?(?!,?(?(,!?(-?(.?1?1.1#?#?s?“?s?s?o?s?o?）?n?“?s?、?s?“?o?）?s?o?s?s?o?s?s?“?o?n?s?s?“?o?z?）?n?、?s?s?o?z?zo?s?o?、?z?、?s?。?o?s?o?1.2#?“?“?#1.2.1?1970?s；?Libby H L?。?s?sz?”?q?rI?Jo?、?s?2?o?、?s?s?n?n?：?I(
16、Jo?、?。?s?o 1983?s?IBG?、?qPreventive Multi-Frequency Eddy-current TechnologysPMFTr?、?8?s?1/1000?s?8?“o?s?s?n?n?s?8?s?s?、?I)?Jo 1993?s；?Thompson J G?、?s?I?Jo 2002?sEdward P?、?s?s。?s?s?I,Jo2003?sBos B V D?SAAB 2000?s?n?。?s?I-Jo2006?s?TMT?eddyMax 4U?Airbus A340-600?s?I.Jo 1.2.2?）?o 1992?s?；?ZETEC?MIZ-18A?I/Jo1995?ET-255A?I?Jo1998?I?Jo2000?s?EEC-39?4?8?s?I?(Jo2002?s?“?I?)?Jo 2009?s?、?/?s?n?I?Jo?s?s?z?hhMFE-1?s?3?s?s?。?s?I/?Jo?s?、?z?s?o 1.3?#?q?r?s?n?n?s?s?o?u?t?s?o(t?s?o?)t?Phasec2200?s?、?o?t?n?s?s?o
