1、Designation: E569 07 E569/E569M 13Standard Practice forAcoustic Emission Monitoring of Structures DuringControlled Stimulation1This standard is issued under the fixed designation E569;E569/E569M; the number immediately following the designation indicates theyear of original adoption or, in the case
2、of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This practice provides guidelines for acoustic emission (AE) examination or monitoring
3、 of structures, such as pressurevessels, piping systems, or other structures that can be stressed by mechanical or thermal means.1.2 The basic functions of an AE monitoring system are to detect, locate, and classify emission sources. Other methods ofnondestructive testing (NDT) may be used to furthe
4、r evaluate the significance of reported acoustic emission sources.1.3 UnitsThe values stated in either SI units or inch-pound units are to be regarded as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining
5、 values from thetwo systems may result in non-conformance with the standards.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determ
6、ine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructive TestingE650 Guide for Mounting Piezoelectric Acoustic Emission SensorsE750 Practice for Characterizing Acoustic Emission InstrumentationE13
7、16 Terminology for Nondestructive ExaminationsE2374 Guide for Acoustic Emission System Performance Verification2.2 Other Documents:3SNT-TC-1A Recommended Practice for Nondestructive Testing Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certification of Nond
8、estructive Testing Personnel2.3 AIA Standard:NAS-410 Certification and Qualification of Nondestructive Testing Personnel43. Terminology3.1 DefinitionsDefinitions of terms relating to acoustic emission may be found in Section B of Terminology E1316.3.2 Definitions of Terms Specific to This Standard:3
9、.2.1 AE activitythe presence of acoustic emission during an examination.3.2.2 active sourceone which exhibits increasing cumulative AE activity with increasing or constant stimulus.3.2.3 critically active sourceone which exhibits an increasing rate of change of cumulative AE activity with increasing
10、 orconstant stimulus.3.2.4 AE source intensityaverage energy, counts or amplitude per hit.1 This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic EmissionMethod.Current edition approved July 1, 2007
11、Jan. 1, 2013. Published July 2007January 2013. Originally approved in 1976. Last previous edition approved in 20022007 asE569 - 02.E569 - 07. DOI: 10.1520/E0569-07.10.1520/E0569_E0569M-13.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at servi
12、ceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4 Available from Aero
13、space Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http:/www.aia-aerospace.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous ve
14、rsion. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes se
15、ction appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.5 intense sourceone in which the AE source intensity of an active source consistently exceeds, by a specified amount, theaverage AE source in
16、tensity of active sources.3.2.6 critically intense sourceone in which the AE source intensity consistently increases with increasing stimulus or withtime under constant stimulus.4. Summary of Practice4.1 Acoustic emission examination of a structure usually requires application of a mechanical or the
17、rmal stimulus. Suchstimulation produces changes in the stresses in the structure. During stimulation of a structure, AE from discontinuities (such ascracks and inclusions) and from other areas of stress concentration, or from other acoustic sources (such as leaks, loose parts, andstructural motion)
18、can be detected by an instrumentation system, using sensors which, when stimulated by stress waves, generateelectrical signals.4.2 In addition to immediate evaluation of the emissions detected during the application of the stimulus, a permanent record ofthe number and location of emitting sources an
19、d the relative amount of AE detected from each source provides a basis forcomparison with sources detected during the examination and during subsequent stimulation.5. Significance and Use5.1 Controlled stimulation i.e. the application of mechanical or thermal load, can generate AE from flawed areas
20、of the structure.Sources may include flaw growth, oxide fracture, crack face stiction and release on load application, and crack face rubbing.5.2 The load range above normal service (peak) load is used to propagate fatigue cracks in the plastically strained region aheadof the crack tip. Crack propag
21、ation may not be a reliable source of AE, depending on the alloy and microstructure, the amount (rate)of crack extension, and possibility of brittle fracture in a segment of crack extension.5.3 Load increases resulting in significant ductile tearing may produce less emission than expected for the am
22、ount of crackgrowth. Processes that result in more brittle cleavage fractures are more detectable and produce more emission for smaller amountsof flaw growth. These include corrosion fatigue and stress corrosion cracking modes of flaw growth, and would also be more likelyin cast or welded structures
23、 than in fabricated (forged, rolled or extruded) structures. Distributed defect structures such as hydrogenembrittlement, or creep cavitation in high temperature steels may also produce significant emission without evidence of an existingcrack-like flaw.5.4 Application and relaxation of load can pro
24、duce secondary mechanically-induced emission that is not related to flawextension. This includes crack face stiction release on loadingusually evidenced by emission at the same rising load valueregardless of peak load; or crack face rubbing on load release as the fracture surfaces come back together
25、.5.5 The load rate can be a significant concern as instrumentation can become saturated with AE activity. The ability todifferentiate real data from background noise can be compromised.5.6 Background noise must be fully investigated and minimized before any AE monitoring can begin.6. Basis of Applic
26、ation6.1 The following items are subject to contractual agreement between the parties using or referencing this practice.6.2 Personnel Qualification6.2.1 If specified in the contractual agreement, personnel performing examinations to this standard shall be qualified inaccordance with a nationally an
27、d internationally recognized NDT personnel qualification practice or standard such asANSI/ASNT CP-189, SNT-TC-1A, NAS-410, or a similar document and certified by the employer or certifying agency, asapplicable. The practice or standard used and its applicable revision shall be identified in the cont
28、ractual agreement between theusing parties.6.3 Qualification of Nondestructive Testing AgenciesIf specified in the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E543. The applicable edition of Practice E543 shall be specified in the contractualagreement
29、.6.4 Timing of ExaminationThe timing of the examination shall be in accordance with a contractual agreement or with anestablished internal procedure.6.5 Extent of ExaminationMany applications will require an arrangement of sensors such that all areas of the structure aremonitored. In other applicati
30、ons, only a portion of the structure may require monitoring.6.6 Reporting Criteria/AcceptanceReporting criteria for the examination results shall be in accordance with Sections 1011,1112, and 1213.6.7 Reexamination of Repaired/Reworked ItemsReexamination of repaired/reworked items is not addressed i
31、n this standardand if required shall be specified in a contractual agreement.E569/E569M 1327. Examination Preparation7.1 Before the examination begins, make the following preparations for AE monitoring:7.1.1 Determine the type, number, and placement of sensors. This requires knowledge of both materi
32、al and physicalcharacteristics of the structure and the features of the instrumentation. This determination is also dependent upon the requiredprecision and accuracy of the examination.7.1.2 Establish communications between the control point for the application of the stimulus and the AE examination
33、 controlcenter.7.1.3 Provide a means for continuously recording a measure of the stimulus.7.1.4 Identify potential sources of extraneous acoustic noise, such as vibration, friction, and fluid flow. Such sources may requireacoustic isolation or control, in order not to mask valid acoustic emissions.7
34、.1.5 Attach the sensors; both the couplant and sensing device must be compatible with the surface conditions and thecomposition of the structural material being examined (see Guide E650).7.1.6 Verify the AE monitoring system in accordance with Section 89 and Guide E2374.8. Safety Precautions8.1 When
35、 examining vessels, ambient temperature should not be below the ductile-brittle transition temperature of the pressurevessel construction material.9. Calibration and StandardizationVerification9.1 Annual calibration and verification of pressure transducer, AE sensors, preamplifiers (if applicable),
36、signal processor(particularly the signal processor time reference), and AE electronic waveform generator should be performed. Equipment shouldbe adjusted so that it conforms to equipment manufacturers specifications. Instruments used for calibrations must have currentaccuracy certification that is t
37、raceable to the National Institute for Standards and Technology (NIST).9.2 Routine electronic evaluations (verification) must be performed any time there is concern about signal processorperformance. A waveform generator should be used in making evaluations. Each signal processor channel must respon
38、d with peakamplitude reading within 62 dBV of the electronic waveform generator output.9.3 A system performance verification (see Guide E2374) must be conducted immediately before, and immediately after, eachexamination. Performance verifications can also be conducted during the examination if there
39、 is any suspicion that the systemperformance may have changed. A performance verification uses a mechanical device to induce stress waves into the structure ata specified distance from each sensor. Induced stress waves stimulate a sensor in a manner similar to acoustic emission.Performance verificat
40、ions verify performance of the entire system (including couplant).9.3.1 The preferred technique for conducting a performance verification is a pencil lead break. Lead should be broken on thestructure at a distance of 4 in. (100 to 102 mm) 100 mm 4 in. from the sensor centerline. 2H lead, 0.3 mm diam
41、eter, 0.1 in. (2to 3 mm) 0.012 in. diameter, 2 - 3 mm 0.08 - 0.12 in. long should be used (see Fig. 45 of Guide E976). If circumstances requiredifferent values to be used, the values used shall be documented in the examination report.9.3.2 Location Sensitivity CheckA simulated AE source (such as a p
42、encil lead break) is created on the surface of the structurein order to check location sensitivity. Sensor source location sensitivity is determined as follows.9.3.2.1 Zone Location Sensitivity CheckEach channel shall have the same system examination threshold. The simulated AEsource generated anywh
43、ere on the vessel shall be detected by at least one sensor.9.3.2.2 Source Location Algorithm Sensitivity CheckEach channel shall have the same system examination threshold. Two ormore sensors define the structure mounted sensor array. The simulated AE source generated in each structure mounted senso
44、r arrayshall be detected by the minimum number of sensors required to locate the source within 65 % of sensor spacing.10. Examination Procedure10.1 Acoustic emission data may be accumulated during or after stimulation of the structure, or both, as specified in the writtenprocedure.10.1.1 During appl
45、ication of the stimulus, the locations of acoustic sources are usually determined through analysis of the timesof arrival of AE signals at multiple sensors. Such analysis may be performed through the use of an analysis computer. The computeraccumulates and analyzes data over a specified parametric r
46、ange. Examples of parameters are pressure, time, and stress. Eachchannel shall have the same system examination threshold. As the stimulus is applied, record the number and location of emittingsources and the amount of AE detected from each source. The AE rate at one or more sensors may be monitored
47、 and displayedin real time during stimulation. If the acoustic emission activity indicates a critically intense source, the AE operator shall stop theexamination and notify the owner of the structure or his designee immediately. The cause of the AE increase shall be investigatedbefore continuing the
48、 stimulation schedule.10.1.2 Continuous emission from any leak in a structure stimulated by pressure can mask acoustic emission from sources nearthe leak. Effects of leaks on acoustic emission measurements should be eliminated to adequately examine pressure boundaries.Knowledge of attenuation in the
49、 structure and the response of sensors affected by leak noise may help localize the leak.E569/E569M 13310.1.3 Following the examination, repeat the performance verification in accordance with 8.39.3.11. Examination Records11.1 All system performance verification data and instrument adjustments, including equipment description and performancedata, shall be included in the records of the examination with all pertinent qualification/certification records and be signed by theresponsible AE examiner. The information recorded should be sufficient to permit comp
