1、Designation: E2374 10E2374 15Standard Guide forAcoustic Emission System Performance Verification1This standard is issued under the fixed designation E2374; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 System performance verification methods launch stress waves into the examination article on which the sensor is mounted.The re
3、sulting stress wave travels in the examination article and is detected by the sensor(s) in a manner similar to acousticemission.1.2 This guide describes methods which can be used to verify the response of an Acoustic Emission system including sensors,couplant, sensor mounting devices, cables and sys
4、tem electronic components.1.3 Acoustic emission system performance characteristics, which may be evaluated using this document, include somewaveform parameters, and source location accuracy.1.4 Performance verification is usually conducted prior to beginning the examination.1.5 Performance verificat
5、ion can be conducted during the examination if there is any suspicion that the system performance mayhave changed.1.6 Performance verification may be conducted after the examination has been completed.1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are
6、 included in this standard.1.8 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 determine the applicability of regulatorylimitations pri
7、or to use.2. Referenced Documents2.1 ASTM Standards:2E750 Practice for Characterizing Acoustic Emission InstrumentationE976 Guide for Determining the Reproducibility of Acoustic Emission Sensor ResponseE1316 Terminology for Nondestructive ExaminationsE1419 Practice for Examination of Seamless, Gas-F
8、illed, Pressure Vessels Using Acoustic EmissionE1781 Practice for Secondary Calibration of Acoustic Emission Sensors3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 examination articlethe item which is being examined with AE and to which AE sensors are attached.3.1.2 velocityth
9、e measured velocity of a stress wave, traveling in the examination article, using specified AE systemparameters and components. Velocity is often used in triangulation calculations to determine the position of the AE source.3.1.3 auto sensor test (AST)an electronic means by which a sensor can be fed
10、 an electronic pulse to excite the examinationarticle. The resulting stress wave in the examination article can be measured by the same sensor or by other sensors that are onthe same examination article. See 3.1.4 and 3.1.5.3.1.4 auto sensor test-self test modea means by which an AST sensor may be u
11、sed to check its own performance.1 This guide 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 Jan. 1, 2010Dec. 1, 2015. Published February 2010December 2015. Original
12、ly approved in 2004. Last previous edition approved in 20042010as E2374 - 04.E2374 - 10. DOI: 10.1520/E2374-10.10.1520/E2374-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information
13、, refer to the standards Document Summary page on the ASTM website.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 version. Becauseit may not be technically possible to adequately depict a
14、ll 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 section appears at the end of this standardCopyright ASTM International,
15、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.5 auto sensor test-near neighbor modea means by which an AST sensor may be used to determine the sensitivity of oneor more neighboring sensors on the same examination article.4. Significance and Use4.1 Acoustic E
16、mission data acquisition can be affected by numerous factors associated with the electronic instrumentation,cables, sensors, sensor holders, couplant, the examination article on which the sensor is mounted, background noise, and the userssettings of the acquisition parameters (for example, threshold
17、).4.2 This guide is not intended to replace annual (or semi-annual) instrumentation calibration (see Practice E750) or sensorrecertification (see Practice E1781).4.3 This guide is not intended to replace routine electronic evaluation ofAE instrumentation or routine sensitivityreproducibilityverifica
18、tion of AE sensors (see Guide E976).4.4 This guide is not intended to verify the maximum processing capacity or speed of an AE system.4.5 This guide does not purport to address all of the safety concerns, if any associated with its use. It is the responsibility ofthe user of this guide to establish
19、appropriate safety and health practices and determine the applicability of regulatory limitationsprior to use.5. Apparatus5.1 To determine system performance a sensor must be subjected to a stress wave traveling in the examination article. Transientstress waves are launched by mechanical or electrom
20、echanical devices that produce a waveform with fast rise-time, short durationand repeatable peak amplitude. Steady state (continuous) stress waves are launched by mechanical or electromechanical devicesthat produce a waveform with long duration constant amplitude. Various apparatus can be used as ve
21、rification sources includingthe following:5.1.1 Pencil Lead Break (PLB)A mechanical pencil technique whereby lead is pushed against the examination articlessurface with sufficient force to break the lead. When the lead breaks, there is a sudden release of stress on the surface. (See GuideE976, subse
22、ction 4.3.3 and Fig. 4.)5.)5.1.1.1 The distance between the PLB and the sensor must be specified and kept consistent.5.1.1.2 The “Hsu pencil source” uses a mechanical pencil with a 2.5 mm lead extension, 2H hardness and 0.3 mm or 0.5 mmdiameter (0.3 mm is preferred).5.1.1.3 The “Nielsen shoe” can ai
23、d in breaking the lead consistently.5.1.1.4 The pencil should be held at an angle of 30 degrees to the surface.5.1.1.5 Three to five lead breaks are generally conducted to show a consistent result.5.1.1.6 Application standards (for example, Test Method E1419, Table X1.2) specify the minimum signal a
24、mplitude that mustbe measured by the AE instrumentation.5.1.1.7 Channels which are found to have unacceptably low or high sensitivity can be re-coupled (that is, replace couplant),repaired (that is, replace sensor, or cable, or both), or replaced to the examination article (that is, exchanged for an
25、other channel),or both.5.1.1.8 PLB can be used to determine the apparent velocity in the examination article (apparent velocity = sensorspacing/time-of-flight). “Time-of-flight” is the time required for a stress wave to travel the sensor-spacing distance5.1.2 Independent Piezoelectric PulserAn elect
26、romechanical device held against the examination article and used inconjunction with an electronic signal or pulse generator. The electrical signal from the signal/pulse generator is converted into amechanical displacement by the transducers crystal. (See Guide E976, subsection 4.3.1.) One significa
27、nt advantage of thistechnique is that the output of the electronic signal/pulse generator can be adjusted in numerous ways (for example, amplitude andrepetition rate).5.1.2.1 The independent pulser can be used to excite the receiving AE sensor before, during and after an examination asverification t
28、hat there were no changes in coupling or sensor response. The independent pulser technique is particularly usefulwhen there is limited access to the examination article that would preclude the use of manual techniques (for example, PLB).5.1.2.2 The independent pulser technique is particularly useful
29、 in continuous monitoring situations where sensors will be on theexamination article for a long period of time. In this situation the independent pulser is left in place and used periodically to assuresystem performance.5.1.3 AST Capable Integrated Pulser/SensorAnAE sensor that has been designed to
30、accept an electronic signal/pulse into itscrystal. The mechanical displacement of the crystal excites the examination article. The stress wave generated in the examinationarticle can be detected by other sensors on the same examination article. With certain realizations of the AST function (self tes
31、tmode), it can also be detected by the exciting sensor.5.1.3.1 Auto Sensor Test: Near Neighbor ModeAn integrated pulser/sensor can be used to measure sensitivity andtime-of-flight (that is, the time required for a stress wave to travel the sensor-spacing distance) for neighboring sensors on the same
32、examination article. The time-of-flight can be used to calculate the apparent velocity of the stress wave (apparent velocity = sensorspacing/time-of-flight).E2374 1525.1.3.2 Auto Sensor Test: Self Test ModeAn integrated pulser/sensor can be used to verify the performance of the sensorcoupling and th
33、e sensor and channel electronics to which it is attached by establishing a baseline duration (or energy) measuredfrom the AST pulse using a sensor that is known to be operating properly and mounted optimally on the examination article. Thebaseline duration number (for example, 10 000 s) can then be
34、compared with theAST duration measurements from each channelon the examination article. Channels, which produce AST duration measurements that are low compared to the baseline, shouldbe recoupled, repaired or replaced as necessary.5.1.4 Spring Loaded Center PunchAspring loaded device that imparts a
35、mechanical impact force, creating a very large stresswave on the examination article. The spring assures a consistent and repeatable force.5.1.4.1 The spring-loaded center punch is of particular advantage when AE sensors are distributed over large distances on anexamination article, as the imparted
36、force is so strong it can be detected easily.5.1.4.2 The spring-loaded center punch is readily available and easy to apply anywhere on the examination article, at any time.5.1.4.3 To avoid damage to the surface, it is desirable to apply the center punch through an intermediate interface such as a th
37、insheet of metal or coin.metal.5.1.5 ProjectileAn object which is launched or projected to impact the surface of the examination article. Examples includea steel ball dropped onto the surface, a BB gun fired at the surface or a mass at the end of a pendulum. In most cases the energybeing imparted on
38、to the surface can be determined.5.1.6 Gas JetA gas jet forces a gas through a nozzle at high pressure onto the surface of the examination article beinginstrumented. The gas jet is controlled by an electronic valve with the ability of being turned on momentarily to create a transientsurface wave or
39、kept on to create a continuous surface wave.5.1.6.1 The gas jet is usually used in an industrial environment where compressed air or gas is readily available.5.1.6.2 The gas jet is usually used in places that are inaccessible so that system verification can be carried out remotely fromthe sensor.5.1
40、.6.3 The gas jet is a good device for creating a simulated, continuous leak-type, AE signal.5.1.7 Electrical Spark DischargeA spark struck between two electrodes near the surface of the examination article generatesstress waves that propagate in a manner similar to acoustic emission. The technique c
41、an be used in a similar manner to a pencillead break or independent piezoelectric pulser. The advantage of an electrical spark discharge is its short duration and impulse typeresponse, providing a wideband frequency response.5.1.8 Mechanical CrackerA mechanically loaded device which is embrittled or
42、 subjected to chemical attack (which causesit to crack at a rate controlled by the applied mechanical load). When coupled to the surface of the examination article, the deviceproduces true AE signals of varying amplitude. This method truly generates acoustic emission and is useful in characterizing
43、theAE system response to a brittle crack.5.1.9 Laser SourceA pulsed laser, (such as a “Nd-YAG” laser), can be used to create a high energy, short duration pulse thatimpinges on the surface of the test object, creating mechanical waves that travel through the test object to the neighboring sensors.Th
44、e pulse energy needs to be adjusted low enough to avoid surface ablation (melting or vaporization) damage. Surface damagecan be eliminated by using aluminum tape at the target site. This allows for multiple laser pulses at the same target site.6. Procedure6.1 The procedure for accomplishing system p
45、erformance verification utilizes one of the devices listed in Section 5 to producea stress wave on the examination article. The sensor(s), mounted a specified distance from the verification device detects the stresswave and the acoustic emission system processes the information for display and stora
46、ge. The operator of the acoustic emissionsystem examines the data to determine if they are within the limits specified in the written test procedure. Note that two operatorsmay be required: one to operate the verification device (for example, PLB) and a second to read the data and record the results
47、.6.1.1 Verification of Acoustic Emission transient signal parameters (or AE features)Waveform parameters/features that arenecessary for achieving the desired examination results are typically required to be measured, within a specified degree ofaccuracy, during system performance verification.These
48、parameters and the required degree of accuracy are specified in the writtentest procedure.TABLE 1 Example of Peak Amplitude Performance VerificationNOTE 1Specific values are found in Test Method E1419, AppendixX1.2. At a specified distance of greater than 100 mm from each sensor aPLB verification de
49、vice is used. The acoustic emission system mustrespond with a specified peak amplitude reading of greater than 70 dBAE.Waveform parameter to be verified Peak amplitudeSpecified acceptable range 70 dBAEVerification device PLBLead diameter 0.3 mmLead hardness 2HLead length 2.5 mmPLB distance 100 mm, specifyE2374 1536.1.1.1 An example of this process is provided in Table 1 and Fig. 1 where peak amplitude from each sensor is used to verifysystem performance. The accuracy requirements used in this example are found in Test Method E1419, Table X1.2.6.1.2 Verificati
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