外文原文-使用扫描霍尔显微镜观察由于应力或疲劳过程在奥氏体不锈钢的磁性图像的变化.pdf

1、Journal of Nondestructive Evaluation,Vol.20,No.3,September 2001(q 2001)Observation of Changes in Magnetic Images Due to a Strainor Fatigue Progress in Austenite Stainless Steels using aScanning Hall-Sensor MicroscopeA.Oota,1,*K.Miyake,1D.Sugiyama,2and H.Aoki2Received September 14,1999;Revised Septem

2、ber 15,2001Using a scanning Hall-sensor microscope with an active Hall element of area 50mm 3 50mm,wemeasured two-dimensional magnetic images of spontaneous magnetization on a surface of a numberof 304 stainless plates in a paramagnetic austenite phase.Stainless plates with a yield point of 31kg/mm2

3、were subjected to a strain or pulling-fatigue process at room temperature.In a strain state,most plates show the same progressive change in magnetic images resulting from a strain-inducedmartensite transformation,but others produce additional and/or different change although the originremains unsolv

4、ed.A pulling-fatigue process at a stress amplitude of 28 kg/mm2also produces somedifferences in the images from the strain process,at the early stage of fatigue progress.The studyshould provide a new horizon to elucidate the complex destructive-progress in strain or fatigueprocess of304 stainlessste

5、els that areused asstructural materials inelectric powerstations,chemicalplants and medical equipment.KEYWORDS:ScanningHall-sensormicroscope;magneticimages;spontaneousmagnetization;non-destructiveevaluation;stainless steel;austenite phase;strain-induced martensite transformation;fatigue process.tum

6、interference devices(SQUID)(2,3)and micro-HallI.INTRODUCTIONsensors(5,6)provides new and promising techniques forNDE of magnetic materials,because of many advantagesInvoking of social securities and environmentalover conventional techniques such as eddy current,ultra-problems demands higher levels o

7、f reliability and stabil-sound and x-ray imaging,etc.Magnetic imaging tech-ity for structural materials such as iron and stainlessnique using a SQUID has enabled a non-destructivesteels supporting infra-structuring in industries.Muchdetection of Lu ders bands in mild steels subjected toeffort has be

8、en made to develop non-destructive evalua-a strain process.(3)A scanning Hall-sensor microscopetion(NDE)techniquesto investigatethe destructivepro-(SHM)with an active Hall element of area 50mm 3gress under fatigue and/or strain processes in struc-50mm has also enabled a magnetic detection of smalltu

9、ral materials.(14)cracks(,10 mm long and,0.1 mm wide)in mild steelsRecent progress in magnetometers utilizing highly-caused by a fatigue process,(6)so that SHM can be usedsensitivemagneticsensorssuchassuperconductingquan-as a simple,economic and conventional tool for NDE ofmagnetic materials.We pres

10、ent here the magnetic imagesof spontaneous magnetization on a surface of 304 stain-*Corresponding author.E-mail:ootaeee.tut.ac.jpless steels subjected to strain or fatigue process at room1Toyohashi University of Technology,Tempaku-cho,Toyohashi,Aichitemperature observed using this microscope,and the

11、441-8580,Japan.influence of the destructive progress on the images of2Technical Research and Development Laboratories,Topy IndustriesLtd.,Akemi-cho,Toyohashi 441-8510,Japan.304 stainless steels.870195-9298/01/0900-0087/0 q 2001 Plenum Publishing Corporation88Oota,Miyake,Sugiyama,and Aoki2.EXPERIMENT

12、ALprogressive way.Measurements were repeated afterobserving the samples to higher levels and reducing theload to zero.In addition,a number of the plates A were2.1 Stainless Platessubjected to a pulling-fatigue test using a conventionalhydraulic-servo fatigue testing machine at a stress ampli-Commerc

13、ial 304 stainless steels with a yield pointof 31 kg/mm2and a tensile strength of 68 kg/mm2weretude of 28 kg/mm2and a frequency of 29.2 Hz,to eluci-date a destructive progress under a fatigue process.machinedintoa3.8mmthickplate.Theyhavethefollow-ing chemical composition except for iron:Cr,18.2 wt%;M

14、agnetic measurements were made as a parameter ofstress cycles in a progressive manner by stopping theNi,8.3 wt%;C,0.05 wt%;Si,0.43 wt%;Mn,0.89 wt%;P,0.03 wt%;S,0.05 wt%.As can be seen from Fig.machine and taking away the plate,until micro-cracksappeared in the sample.1,two types of stainless plates

15、A and B with differentgeometries were used for the study.There are notches onboth sides in the former,but not in the latter.2.2 MeasurementsToinduceaplasticdeformationatroomtemperature,Magnetic images of spontaneous magnetizationanumberofstainlessplatesoftypesAandBwereuniaxi-were measured on a surfa

16、ce of stainless plates under zeroally strained using a conventional Amsler-type testingexternal fields using SHM with an active area 50mm 3machine at a strain rate of approximately 0.001 s21along50 mm,of which the details have been published else-the length of the sample.Special attention was paid towhere.(6)The SHM was equipped with a micro-Hall sen-the environment around the machine so as not to magne-sor on a movable x-y stage using a stepping motor andtize the sample during the test.After re