ASTM E749E749M-17 Standard Practice for Acoustic Emission Monitoring During Continuous Welding.pdf

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1、Designation: E749/E749M 17Standard Practice forAcoustic Emission Monitoring During Continuous Welding1This standard is issued under the fixed designation E749/E749M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last

2、revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice provides recommendations for acousticemission (AE) monitoring of weldments during and immedi-ately following

3、 their fabrication by continuous welding pro-cesses.1.2 The procedure described in this practice is applicable tothe detection and location of AE sources in weldments and intheir heat-affected zone during fabrication, particularly in thosecases where the time duration of welding is such that fusiona

4、nd solidification take place while welding is still in progress.1.3 The effectiveness of acoustic emission to detect discon-tinuities in the weldment and the heat-affected zone is depen-dent on the design of theAE system, theAE system verificationprocedure, the weld process, and the material type. M

5、aterialsthat have been monitored include low-carbon steels, low-alloysteels, stainless steels, and some aluminum alloys. The systemperformance must be verified for each application by demon-strating that the defects of concern can be detected with thedesired reliability.1.4 UnitsThe values stated in

6、 either SI units or inch-pound units are to be regarded separately as standard. Thevalues stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in non-conformance with the standard.1.5 This

7、standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.6 This international s

8、tandard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2

9、. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing NondestructiveTestingE569 Practice for Acoustic Emission Monitoring of Struc-tures During Controlled StimulationE650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE1316 Terminology for Nondestructive Exam

10、inations2.2 ASNT Standards:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certifi-cation of Nondestructive Testing Personnel2.3 AIA Standard:4NAS-410 Certification and Qualification of NondestructiveP

11、ersonnel (Quality Assurance Committee)2.4 ISO Standard:5ISO 9712 Non-Destructive Testing: Qualification and Certi-fication of NDT Personnel3. Terminology3.1 DefinitionsFor definitions of terms relating to acousticemission testing, see Section B of Terminology E1316.4. Significance and Use4.1 Detecti

12、on and location of AE sources in weldmentsduring fabrication may provide information related to theintegrity of the weld. Such information may be used to directrepair procedures on the weld or as a guide for application ofother nondestructive evaluation (NDE) methods. A majorattribute of applying AE

13、 for in-process monitoring of welds is1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.04 onAcoustic Emission Method.Current edition approved June 1, 2017. Published June 2017. Originallyapproved in 1980. L

14、ast previous edition approved in 2012 as E749 -12. DOI:10.1520/E0749-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe AS

15、TM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-ae

16、rospace.org.5Available from International Organization for Standardization (ISO), ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Ba

17、rr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom

18、mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1the ability of the method to provide immediate real-timeinformation on weld integrity. This feature makes the methoduseful to lower weld costs by repairing defects at the mostconvenient point in the produc

19、tion process. The AE activityfrom discontinuities in the weldment is stimulated by thethermal stresses from the welding process. The AE activityresulting from this stimulation is detected by AE sensors in thevicinity of the weldment, which convert the acoustic wavesinto electronic signals. The AE in

20、strumentation processessignals and provides means for immediate display or indicationof AE activity and for permanent recordings of the data.4.2 Items to be considered in preparation and planning formonitoring should include but not be limited to the following:4.2.1 Description of the system or obje

21、ct to be monitored orexamined,4.2.2 Extent of monitoring, that is, entire weld, cover passesonly, and so forth,4.2.3 Limitations or restrictions on the sensor mountingprocedures, if applicable,4.2.4 Performance parameters to be established and main-tained during the AE system verification procedure

22、(sensitivity,location accuracy, and so forth),4.2.5 Maximum time interval between AE system verifica-tion checks,4.2.6 Performance criteria for purchased equipment,4.2.7 Requirements for permanent records of the AEresponse, if applicable,4.2.8 Content and format of test report, if required, and4.2.9

23、 Operator qualification and certification, if required.5. Basis of Application5.1 The following items are subject to contractual agree-ment between the parties using or referencing this practice.5.2 Personnel Qualification:5.2.1 If specified in the contractual agreement, personnelperforming examinat

24、ions to this standard shall be qualified inaccordance with a nationally or internationally recognizedNDT personnel qualification practice or standard such asANSI/ASNT CP-189, SNT-TC-1A, NAS-410, ISO 9712, or asimilar document and certified by the employer or certifyingagency, as applicable. The prac

25、tice or standard used and itsapplicable revision shall be identified in the contractual agree-ment between the using parties.5.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E543. The applicabl

26、eedition of Practice E543 shall be specified in the contractualagreement.5.4 Procedures and TechniquesThe procedures and tech-niques to be utilized shall be as specified in the contractualagreement.6. Examination Preparation6.1 The following preparatory procedures should be com-pleted before initiat

27、ing AE monitoring:6.1.1 Select the location(s) where the sensor(s) will beacoustically coupled. The sensor(s) should be centrally locatednear the weldment to provide for optimal AE response from allportions of the weld. If the sensor(s) are piezoelectric, thislocation should be such that the maximum

28、 temperature staysbelow manufacturers specifications of the sensor(s). Take carein selecting the sensor mounting locations to avoid contact ordisturbance, or both, of the sensor by any of the welding orstructural positioning equipment. Typical distances from 150 to300 mm 6 to 12 in. from the heat-af

29、fected zone of the weldare usually satisfactory. Typical fixed sensor placement pat-terns that have been successfully used are shown in Figs. 1-3.6.1.1.1 If a fixed contact sensor(s) is used, clean the area(s)where attachment will be made to eliminate loose scale,welding flux, or other debris, and a

30、ttach the sensor in accor-dance with Guide E650.6.1.1.2 If moving sensors are used, clean the coupling pathso that uniform sensitivity is maintained as the sensor moves.Fig. 4 shows side and top views of a typical configuration formoving sensors.6.1.2 Position and route the signal cables connecting

31、thesensor(s) to the AE instrumentation to avoid contacting the hotweld bead or entangling the welding and positioning equip-ment.6.1.3 Adjustment of Apparatus:6.1.3.1 After all sensors are mounted, connected, and op-erational (without objectionable background noise), the AEmonitoring system can then

32、 be adjusted using an AE simulator.6.1.3.2 Gain AdjustmentTo set or select the overall gainfor a channel (if necessary), locate the acoustic emissionsimulator at a selected distance adjacent to the sensor. Monitorthe response to the simulated emission, and adjust the overallchannel gain to a specifi

33、ed amplitude level. Repeat thisprocedure two times, placing the simulator at the same distancefrom the sensor but at different azimuthal positions relative tothe original simulator positions (see Fig. 5). Record the averagegain for the three simulator positions. Repeat the entireprocedure for each A

34、E sensor on the structure, and adjust thegains. The average gains for all channels should give responsesto the simulator that have peak voltages identical to within 63dB.6.1.4 Determination of Source-Location AccuracyCheckthe operation of the AE source-location function by analyzingsimulated AE sign

35、als from several random locations in theweld and on the structure, as well as from any specific criticallocations. For each placement of the simulator, determine andrecord the precision and accuracy of the AE location function.It should be noted that the accuracy of locating the simulatorsource will

36、 not necessarily be the same as for locating a realAEsource. During trial welding in multi-pass configurations, itshould be verified that location accuracy is maintained duringFIG. 1 Typical Sensor Placement for Single Channel AE Monitor-ing of a Linear WeldE749/E749M 172weld buildup. Experiments in

37、dicate that location accuracydepends on the percentage completion of multi-pass welds.6.2 Check the integrity of the welding ground return systemto eliminate the possibility of diverting the weld currents to theAE instrumentation ground.7. Apparatus7.1 The AE apparatus normally consists of sensors,p

38、reamplifiers, and electronic instrumentation with display andrecording capabilities. Acoustic emission monitoring duringwelding places many specialized requirements on AE appara-tus due to severe environmental factors and interfering noisesources. The following criteria provide guidelines to aid inm

39、inimizing these interfering factors, and maximizing theeffectiveness of the monitoring process:7.1.1 Sensors should be used that are capable of operating inthe temperature range to be encountered. Use of “high-temperature” sensors or waveguides to isolate conventionalsensors may be necessary for mul

40、ti-pass, high heat input welds,or welds maintained at elevated preheat temperatures. Thesensors should be electrically insulated from the structureunder test to ensure that the weld current or welder ground isnot coupled into the AE instrumentation. If the weld current ispulsed or has a significant

41、transient component, differentialsensors may aid in suppressing interference.7.1.2 Frequency Bandpass Filters are recommended tominimize background noise interference during AE monitoringof welding. A low-frequency limit to the passband in thevicinity of 100 kHz will aid in minimizing background noi

42、sedue to mechanical noise sources such as grinding, chipping,and manipulation of the structure under test. Radio frequencyinterference due to contactors and heavy electrical machinery,as well as the welding arc, may be minimized by use of ahigh-frequency limit to the passband ranging from 100 kHz to

43、1 MHz. The sensor operating frequency range should becompatible with the above considerations.7.2 The Welding Arc is a low-level continuous source ofAE.To minimize interference from the welding arc, the sensitivityof the AE monitoring apparatus should be adjusted so that arcnoise is below the trigge

44、r threshold. This sensitivity is themaximum usableAE sensitivity for weld monitoring and varieswith different welding methods. Table 1 indicates overall gainfor a particular system monitoring welding methods and usingtypical commercial piezoelectric transducers. This table is forgeneral guideline pu

45、rposes and not for direct reference.7.3 Single-Channel AE Instrumentation employing a singlesensor may provide information on the presence of disconti-nuities in a weld. For low-heat input welds, where the delaytime between fusion and AE activity is short, discontinuitiesmay also be located in the w

46、eld by noting the presence ofunusual AE activity and recording the position of the weldinghead when such activity occurs. As the weld heat inputincreases, the delay time between fusion and AE activityusually increases, thus making use of multichannel arrival timeinterval measurements necessary for A

47、E source location.7.4 TheAE apparatus should be capable of providing outputsignals that are proportional to overall acoustic activity (suchas RMS or Average Signal Level, ASL) and acoustic emissionenergy or count rate. In addition, AE counts, energy or peakamplitude for each AE event plotted versus

48、time is useful forAE monitoring of welds. The latter are particularly useful foracoustically active weld processes such as submerged-arcwelding where the presence of solid flux cracking contributesgreatly to the AE activity. Experience has shown that for thesetypes of welds, the AE activity from fla

49、ws and from normalslag bead cracking may have similar peak amplitudes andenergies. To prevent false alarms from acceptable slag beadactivity, gated rate monitors can sometimes be used to identifyflaw activity which generally consists of groups of AE eventsoccurring at much higher rates than the rate of slag beadevents.8. Examination Procedures8.1 Acoustic emission data may be accumulated during thewelding process. Due to the delay between weld fusion(solidification) and AE activity, monitoring must continue for atime period following welding to acquire all signif