1、Designation: E 1932 07Standard Guide forAcoustic Emission Examination of Small Parts1This standard is issued under the fixed designation E 1932; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers techniques for conducting acousticemission (AE) examinations of small parts. It is confined toexamination objects (or defined
3、 regions of larger objects)where there is low AE signal attenuation throughout theexamination region. This eliminates the consideration of com-plex attenuation factor corrections and multiple sensor andarray placements based on overcoming signal losses overdistances.1.2 The guide assumes a typical A
4、E examination as onewhere there is a controlled or measured stress acting upon thepart being monitored by AE. Particular emphasis is placed onsensor and system selection, sensor placements, stressingconsiderations, noise reduction/rejection techniques, spatialfiltering, location determination, use o
5、f guard sensors, collec-tion of AE data, AE data analysis and report. The purpose ofthe AE examination is to analyze how an object underevaluation is withstanding the applied load.1.3 Possible applications of this guide includes materialscharacterization, quality control of production processes, pro
6、oftesting after fabrication, evaluating regions of interest of largerstructures and retesting after intervals of service. The appliedload may include mechanical forces (tension, compression ortorsional) internal pressure and thermal gradients.1.4 This standard does not purport to address all of thes
7、afety 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.2. Referenced Documents2.1 ASTM Standards:2E 650 Guide for Mounting Piez
8、oelectric Acoustic EmissionSensorsE 750 Practice for CharacterizingAcoustic Emission Instru-mentationE 976 Guide for Determining the Reproducibility of Acous-tic Emission Sensor ResponseE 1316 Terminology for Nondestructive ExaminationsE 2374 Guide for Acoustic Emission System PerformanceVerificatio
9、n3. Terminology3.1 Definitions:3.1.1 Terminology related to acoustic emission is defined inTerminology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 applied loada controlled or known force or stresswhich is applied to an object under examination for the purposeof analyzing the obje
10、cts reaction (by means ofAE monitoring)to that stress.3.2.2 guard sensorssensors whose primary function is theelimination of extraneous noise based on arrival sequences.3.2.3 spatial discriminationthe process of using one ormore (guard and data) sensors to eliminate extraneous noisebased on arrival
11、sequences.3.2.4 spatial filteringability of an AE system or analysisto disregard AE activity based on source location of the AEevent.1This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-tive Testing and is the direct responsibility of Subcommittee E07.04 on AcousticEmission Meth
12、od.Current edition approved July 1, 2007. Published July 2007. Originally approvedin 1998. Last previous edition approved in 2002 as E 1932 - 97(2002)e1.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMSt
13、andards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Significance and Use4.1 The purpose of theAE examination is to analyze how anexamination o
14、bject is withstanding the applied load, or if it issuffering from some latent damage. Consequently the emissionactivity must be evaluated in relation to the applied load.4.2 The applied load (on the examination object) mayinclude mechanical forces (tension, compression or torsional),internal pressur
15、e and thermal gradients. It may be short to long,random or cyclic. The applied load may be controlled by theexaminer or may already exist as part of the process. In eithercase the applied load is measured along with the AE activity.4.3 Possible applications include the determination of partintegrity
16、, quality control assessment of production processes ona sampled or 100 % inspection basis, in-process examinationduring a period of applied load of a fabrication process (forexample, spot welding, bonding, soldering, pressing, etc.),proof-testing after fabrication, monitoring a “region of inter-est
17、” (or concern) of a structure (for example, bridge joint orrepair, vessel, pipe), and reexamination after intervals ofservice.5. Procedure5.1 Preliminary Information:5.1.1 Before examination, the following information, whererelevant, should be obtained by the AE examiner:5.1.1.1 Type of object to be
18、 examined, together with layoutdrawings or sketches.5.1.1.2 Material specifications (including details of heattreatment where possible).5.1.1.3 Proposed or existing applied load specification to-gether with a layout or sketch of the pressure/stress applicationsystem.5.1.1.4 Information regarding the
19、 measuring or recording ofthe applied load must also be obtained in order to determine thecompatibility with the AE equipment.5.1.1.5 Potential sources of background noise and the iso-lating mechanisms applied thereto.5.1.1.6 Previous history, including the maximum appliedload to which the object or
20、 system has been subjected.5.1.1.7 Where possible, locations of known discontinuitiesand the general results of earlier AE or other NDE examina-tions.5.1.1.8 Results of earlier examinations on similar objects.5.1.2 Before examination, the AE examiner should considerthe following information. Some de
21、tails need to be coordinatedwith the on-site management or responsible personnel:5.1.2.1 The Type of AE Equipment to be UsedConsiderations should include the number of channels, thefrequency range of the instruments filters, the real-time dataprocessing rates for the type of application, its locatio
22、n/guard/spatial filtering capabilities, the type of data being collected(for example, RMS, ASL, AE feature based or waveformbased) and the compatibility of the system to monitor andrecord the applied load during the AE examination. Theseitems must be able to perform at the anticipated levels ofperfo
23、rmance expected during the examination. In addition,consideration should be given to the data analysis, display andreplay capabilities of the equipment to assure its ability toprocess the stored data in a way needed to arrive at asatisfactory conclusion and examination result.5.1.2.2 Application of
24、LoadConsideration should begiven to the application of the load in relation to the integrityof the examination object and achieving a successful AEexamination result. In cases where the applied load is part ofthe process being monitored, a suitable time forAE monitoringneeds to be determined where p
25、rocess noise is low and appliedload (for AE examination purposes) maximum. Sometimes (ifneeded) the applied loading can be altered to achieve thiswithout compromising the process (for example, inserting ashort load hold at maximum load).(1) In cases where the applied load is controlled with theexami
26、nation, then consideration should be given to design theloading schedule to appropriately stress the examination objectin order to excite “latent flaws” without over-stressing ordamaging the object. In addition, the loading schedule shouldbe designed to provide best insight into the integrity of the
27、 part(for example, implementing a load schedule to evaluate the“Kaiser effect”).5.1.2.3 Sensor TypesConsiderations that should guide theuser into proper selection include the sensors frequency range,size (including sensor height, diameter and weight), maximumor minimum temperature specification, the
28、 sensors sensitivityand frequency response, and acoustic impedance matching ofthe sensor and part.5.1.2.4 Location of Sensors and Placement StrategyConsiderations need to be given to the number of sensorsrequired for the examination, their placement strategy andlocation on the part to be monitored.(
29、1) In cases where background noise can be controlled ordoes not exist, then a single sensor near the expected source ofthe AE is sufficient.(2) In cases where there are a limited number of backgroundnoise sources (such as the grips in a tension test), a single AEdata sensor near the expected source
30、of AE and the use of aguard sensor near each background source will effectivelyblock noises that emanate from a region closer to the guardsensors than to the AE data sensor. Alternatively, a group oftwo or more sensors can be strategically placed to performspatial discrimination of background noise
31、and allow process-ing of AE events.(3) In cases where extraneous noise cannot be controlled andcould be emanating from any or all directions, a multiple-sensor location strategy (such as linear or planar location)should be considered. In this situation, enough sensors shouldbe specified to allow for
32、 an accurate source location, andmeans should be available to allow for the application ofspatial filtering and/or spatial discrimination so that only dataemanating from the region of interest is processed as relevantAE data.5.1.2.5 Data to be RecordedThe AE examiner shouldknow in advance the data a
33、nd information to be recorded andhave all the necessary equipment, hardware, accessories andsoftware to acquire, store, and process this information. Otherthan the equipment forAE monitoring, appropriate sensors anddevices are required for measuring and recording the appliedload and other load or co
34、ndition related parametric data.E1932072Details of any interfaces may need to be coordinated with theexamination site management and personnel.5.1.2.6 Applicability and possible limitations of the methodfor the particular examination.5.1.2.7 Any preconditions necessary for conducting the AEexaminati
35、on such as surface preparation or limitation ofpressurization rate needs to be coordinated with theexamination-site management or responsible personnel.5.2 Sensor InstallationThe methods and procedures usedin mounting AE sensors can have significant effects upon theperformance of those sensors. Opti
36、mum and reproducibledetection of AE requires both appropriate sensor-mountingfixtures and consistent sensor-mounting procedures. Refer toGuide E 650.5.3 Calibration and Verification:5.3.1 Annual calibration and verification of pressure trans-ducer, AE sensors, preamplifiers (if applicable), signal p
37、roces-sor (particularly the signal processor time reference), and AEelectronic simulator (waveform generator) should be per-formed. Equipment should be adjusted so that it conforms tothe equipment manufacturers specifications. Instruments usedfor calibrations must have current accuracy certification
38、 that istraceable to the National Institute for Standards and Technol-ogy (NIST).5.3.2 Routine electronic evaluations should be performedany time there is concern about signal processor performance.An AE electronic simulator (waveform generator) should beused in making evaluations. Each signal proce
39、ssor channelmust respond with peak amplitude reading within 62 dBV ofthe electronic waveform generator output. Guide E 750 de-scribes other measurements for characterizing AE equipment.5.3.3 A system performance verification should be con-ducted immediately before, and immediately after, each AEexam
40、ination. In addition, a system performance verificationcan be conducted during the examination if there is anysuspicion that the system performance may have changed. Aperformance check uses a mechanical device to induce stresswaves into the examination object at a specified distance fromeach sensor
41、(see Guide E 2374). Induced stress waves stimu-late a sensor in a manner similar to an acoustic emission.Performance checks verify performance of the entire system(including couplant).5.3.3.1 The preferred technique for conducting a perfor-mance check is a pencil lead break. Lead should be broken on
42、the examination object surface at a prescribed distance fromthe sensor. 2H lead, 0.3mm or 0.5 mm diameter, 2.5 mm longshould be used (see 4.3.3 in Guide E 976). In establishing thedetails of the lead break technique, care should be taken toavoid saturating the electronics.5.4 Examination:5.4.1 Pre-E
43、xamination RequirementsBefore the AE ex-amination, the following requirements should be completed.5.4.1.1 Visually examine the examination object, the acous-tic sensors and other instrumentation, to verify that the equip-ment is securely mounted and isolated from controllablesources of acoustic and
44、electrical noise.5.4.1.2 Review the examination object to identify all poten-tial sources of background noise such as rubbing surfaces(friction), pump or other vibration, valve stroking, personnelmovement, fluid flow and turbulence. Evaluate backgroundnoise by monitoring the AE for a short period wi
45、thout theapplied load or under slight loading conditions (if possible).Identified sources may require acoustic isolation or control, sothat they will not mask relevant acoustic emission sourceswithin the object being examined.5.4.1.3 Test spatial filtering, or other applied discriminationfacilities,
46、 to prove its/their capability to reject extraneousburst-type noise.5.4.2 Collection of AE Data:5.4.2.1 Begin monitoring and recordingAE data and subjectthe examination object to the applied load.5.4.2.2 During AE examination, whenever circumstancesallow, the noise at each sensor should be monitored
47、 periodi-cally to ensure that background noise remains acceptable forcontinued AE examination. The magnitude of the noise, thetimes of any specific noise incidents and the effect of the noiseon the AE examination, shall be recorded.5.4.2.3 The applied load or other parameters, or both,should be moni
48、tored and recorded to the extent necessary toallow correlation with the AE data.5.4.2.4 Acoustic emission data should be collected continu-ously during load applications as well as during holds andunloading.5.5 Data AnalysisThe AE signals should be analyzed todetermine the integrity of examination o
49、bjects after loading.This analysis should be made over ranges of a relevantparameters such as pressure (applied load), time, stress andtemperature. If location or spatial filtering facilities are used,only AE signals which were generated within the region ofinterest should be analyzed.5.5.1 Emission ActivityAE activity of the part(s) beingexamined may be determined as the cumulative AE or eventcount, or derived from parameters of detected AE signals orotherwise. The analysis techniques should be uniform andrepeatable.5.5.2 Evaluation CriteriaEvaluating the emission a
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