1、Designation: E 569 07Standard Practice forAcoustic Emission Monitoring of Structures DuringControlled Stimulation1This standard is issued under the fixed designation E 569; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides guidelines for acoustic emission(AE) examination or monitoring of structures, such as pressu
3、revessels, piping systems, or other structures that can be stressedby mechanical or thermal means.1.2 The basic functions of an AE monitoring system are todetect, locate, and classify emission sources. Other methods ofnondestructive testing (NDT) may be used to further evaluatethe significance of ac
4、oustic emission sources.1.3 This 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 prio
5、r to use.2. Referenced Documents2.1 ASTM Standards:2E 543 Specification for Agencies Performing Nondestruc-tive TestingE 650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE 750 Practice for CharacterizingAcoustic Emission Instru-mentationE 1316 Terminology for Nondestructive ExaminationsE
6、 2374 Guide for Acoustic Emission System PerformanceVerification2.2 Other Documents:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certi-fication of Nondestructive Testing Personnel2.3 AIA Standard:NA
7、S-410 Certification and Qualification of NondestructiveTesting Personnel43. Terminology3.1 DefinitionsDefinitions of terms relating to acousticemission may be found in Section B of Terminology E 1316.3.2 Definitions of Terms Specific to this Standard:3.2.1 AE activitythe presence of acoustic emissio
8、n duringan examination.3.2.2 active sourceone which exhibits increasing cumu-lative AE activity with increasing or constant stimulus.3.2.3 critically active sourceone which exhibits an in-creasing rate of change of cumulativeAE activity with increas-ing or constant stimulus.3.2.4 AE source intensity
9、average energy, counts or am-plitude per hit.3.2.5 intense sourceone in which the AE source intensityof an active source consistently exceeds, by a specified amount,the average AE source intensity of active sources.3.2.6 critically intense sourceone in which the AE sourceintensity consistently incre
10、ases with increasing stimulus orwith time under constant stimulus.4. Summary of Practice4.1 Acoustic emission examination of a structure usuallyrequires application of a mechanical or thermal stimulus. Suchstimulation produces changes in the stresses in the structure.During stimulation of a structur
11、e, AE from discontinuities(such as cracks and inclusions) and from other areas of stressconcentration, or from other acoustic sources (such as leaks,loose parts, and structural motion) can be detected by aninstrumentation system, using sensors which, when stimulatedby stress waves, generate electric
12、al signals.4.2 In addition to immediate evaluation of the emissionsdetected during the application of the stimulus, a permanentrecord of the number and location of emitting sources and therelative amount of AE detected from each source provides a1This practice is under the jurisdiction of ASTM Commi
13、ttee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.04 onAcoustic Emission Method.Current edition approved July 1, 2007. Published July 2007. Originally approvedin 1976. Last previous edition approved in 2002 as E 569 - 02.2For referenced ASTM standards, visit th
14、e 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 ASTM website.3Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln.,
15、 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-aerospace.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
16、 United States.basis for comparison with sources detected during the exami-nation and during subsequent stimulation.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 Qualification5.2.1 If specifie
17、d in the contractual agreement, personnelperforming examinations to this standard shall be qualified inaccordance with a nationally and internationally recognizedNDT personnel qualification practice or standard such asANSI/ASNT CP-189, SNT-TC-1A, NAS-410, or a similardocument and certified by the em
18、ployer or certifying agency,as applicable. The practice or standard used and its applicablerevision shall be identified in the contractual agreement be-tween the using parties.5.3 Qualification of Nondestructive Testing AgenciesIfspecified in the contractual agreement, NDT agencies shall bequalified
19、 and evaluated as described in Practice E 543. Theapplicable edition of Practice E 543 shall be specified in thecontractual agreement.5.4 Timing of ExaminationThe timing of the examinationshall be in accordance with a contractual agreement or with anestablished internal procedure.5.5 Extent of Exami
20、nationMany applications will requirean arrangement of sensors such that all areas of the structureare monitored. In other applications, only a portion of thestructure may require monitoring.5.6 Reporting Criteria/AcceptanceReporting criteria forthe examination results shall be in accordance with Sec
21、tions10, 11, and 12.5.7 Reexamination of Repaired/Reworked ItemsReexamination of repaired/reworked items is not addressed inthis standard and if required shall be specified in a contractualagreement.6. Examination Preparation6.1 Before the examination begins, make the followingpreparations for AE mo
22、nitoring:6.1.1 Determine the type, number, and placement of sen-sors. This requires knowledge of both material and physicalcharacteristics of the structure and the features of the instru-mentation. This determination is also dependent upon therequired precision and accuracy of the examination.6.1.2
23、Establish communications between the control pointfor the application of the stimulus and the AE examinationcontrol center.6.1.3 Provide a means for continuously recording a measureof the stimulus.6.1.4 Identify potential sources of extraneous acousticnoise, such as vibration, friction, and fluid fl
24、ow. Such sourcesmay require acoustic isolation or control, in order not to maskvalid acoustic emissions.6.1.5 Attach the sensors; both the couplant and sensingdevice must be compatible with the surface conditions and thecomposition of the structural material being examined (seeGuide E 650).6.1.6 Ver
25、ify the AE monitoring system in accordance withSection 8 and Guide E 2374.7. Safety Precautions7.1 When examining vessels, ambient temperature shouldnot be below the ductile-brittle transition temperature of thepressure vessel construction material.8. Calibration and Standardization8.1 Annual calibr
26、ation and verification of pressure trans-ducer, AE sensors, preamplifiers (if applicable), signal proces-sor (particularly the signal processor time reference), and AEelectronic waveform generator should be performed. Equip-ment should be adjusted so that it conforms to equipmentmanufacturers specif
27、ications. Instruments used for calibra-tions must have current accuracy certification that is traceableto the National Institute for Standards and Technology (NIST).8.2 Routine electronic evaluations (verification) must beperformed any time there is concern about signal processorperformance. A wavef
28、orm generator should be used in makingevaluations. Each signal processor channel must respond withpeak amplitude reading within 62 dBV of the electronicwaveform generator output.8.3 A system performance verification (see Guide E 2374)must be conducted immediately before, and immediately after,each e
29、xamination. Performance verifications can also be con-ducted during the examination if there is any suspicion that thesystem performance may have changed. A performance veri-fication uses a mechanical device to induce stress waves intothe structure at a specified distance from each sensor. Inducedst
30、ress waves stimulate a sensor in a manner similar to acousticemission. Performance verifications verify performance of theentire system (including couplant).8.3.1 The preferred technique for conducting a performanceverification is a pencil lead break. Lead should be broken onthe structure at a dista
31、nce of 4 in. (100 to 102 mm) from thesensor centerline. 2H lead, 0.3 mm diameter, 0.1 in. (2 to 3mm) long should be used (see Fig. 4 of Guide E 976). Ifcircumstances require different values to be used, the valuesused shall be documented in the examination report.8.3.2 Location Sensitivity CheckA si
32、mulated AE source iscreated on the surface of the structure in order to check locationsensitivity. Sensor source location sensitivity is determined asfollows.8.3.2.1 Zone Location Sensitivity CheckEach channelshall have the same system examination threshold. The simu-lated AE source generated anywhe
33、re on the vessel shall bedetected by at least one sensor.8.3.2.2 Source Location Algorithm Sensitivity CheckEachchannel shall have the same system examination threshold.Two or more sensors define the structure mounted sensor array.The simulated AE source generated in each structure mountedsensor arr
34、ay shall be detected by the minimum number ofsensors required to locate the source within 65 % of sensorspacing.9. Examination Procedure9.1 Acoustic emission data may be accumulated during orafter stimulation of the structure, or both, as specified in thewritten procedure.9.1.1 During application of
35、 the stimulus, the locations ofacoustic sources are usually determined through analysis of theE569072times of arrival ofAE signals at multiple sensors. Such analysismay be performed through the use of an analysis computer. Thecomputer accumulates and analyzes data over a specifiedparametric range. E
36、xamples of parameters are pressure, time,and stress. Each channel shall have the same system examina-tion threshold. As the stimulus is applied, record the numberand location of emitting sources and the amount ofAE detectedfrom each source. The AE rate at one or more sensors may bemonitored and disp
37、layed in real time during stimulation. If theacoustic emission activity indicates a critically intense source,the AE operator shall stop the examination and notify theowner of the structure or his designee immediately. The causeof the AE increase shall be investigated before continuing thestimulatio
38、n schedule.9.1.2 Continuous emission from any leak in a structurestimulated by pressure can mask acoustic emission fromsources near the leak. Effects of leaks on acoustic emissionmeasurements should be eliminated to adequately examinepressure boundaries. Knowledge of attenuation in the structureand
39、the response of sensors affected by leak noise may helplocalize the leak.9.1.3 Following the examination, repeat the performanceverification in accordance with 8.3.10. Examination Records10.1 All system performance verification data and instru-ment adjustments, including equipment description and pe
40、rfor-mance data, shall be included in the records of the examinationwith all pertinent qualification/certification records and besigned by the responsible AE examiner. The informationrecorded should be sufficient to permit complete reanalysis ofthe results. This information should include, but not b
41、e limitedto:10.1.1 Location of AE examination, material, physical char-acteristics of the structure, and manufacturers data sheet or tagdata.10.1.2 Sensor specifications, including size, sensitivity, fre-quency response, method of attachment, type of couplant, typeand length of connecting cables.10.
42、1.3 Sensor locations.10.1.4 Functional descriptions of signal conditioners, pro-cessors, and display equipment.10.1.5 Stimulation schedule, AE monitoring procedures,and results of all sensitivity checks.10.1.6 Method of stimulation and examination schedule.10.1.7 Permanent data record of the measure
43、d AE signalparameters, in analog or digital form.10.1.8 Stimulation medium temperature, ambient air tem-perature.11. Interpretation of Results11.1 All results shall be summarized on an appropriatelayout map, displayed or tabulated, or both, for ready referenceand interpretation. This layout or tabul
44、ation shall display thelocation and classification of each source with pertinent com-ments.11.1.1 Source LocationAll location data resulting fromanalysis shall be presented in a manner consistent with thepreviously established calibration accuracy.11.1.2 Source ClassificationSources are usually clas
45、sifiedwith respect to their acoustic activity and intensity.11.1.2.1 A sources acoustic activity is normally measuredby event count or emission count. A source is considered to beactive if itsAE activity continues to increase with increasing orconstant stimulus. A source is considered to be critical
46、ly activeif the rate of change of its AE activity with respect to thestimulus, consistently increases with increasing stimulation, orif the rate of change of its AE activity with respect to time,consistently increases with time under constant stimulus (seeFig. 1).11.1.2.2 Preferred intensity measure
47、s of a source are its:average detected energy per event, average emission count perhit, or average amplitude per hit. A source is considered to beintense if it is active and its intensity measure consistentlyexceeds, by a specified amount, the average intensity of activesources. The intensity of a s
48、ource can be calculated forincrements of the stimulus or of hits. It is noted that, if there isonly one active source, the intensity measure of the source isNOTE 1To the right of the vertical line, Source 1 is inactive, Source 2 is active, and Source 3 is critically active.FIG. 1 Schematic Represent
49、ation of Three Different Source TypesE569073the average intensity of all sources, and therefore the intrinsiccomparison no longer is applicable. In this case, it is necessaryto classify the source through comparison with results fromsimilar examinations. (See Fig. 2.)11.1.2.3 When using source location algorithms, in additionto activity and intensity, another characteristic of each detectedAE source that should be considered for source classification isthe size of the “region” of the located source. The clustering ofthe located events from a sharp discontinuity,
