1、Designation: E2076/E2076M 10Standard Practice forExamination of Fiberglass Reinforced Plastic Fan BladesUsing Acoustic Emission1This standard is issued under the fixed designation E2076/E2076M; the number immediately following the designation indicates the yearof original adoption or, in the case of
2、 revision, the year of last 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. Scope1.1 This practice provides guidelines for acoustic emission(AE) examinations of fiberglass reinforc
3、ed plastic (FRP) fanblades of the type used in industrial cooling towers and heatexchangers.1.2 This practice uses simulated service loading to deter-mine structural integrity.1.3 This practice will detect sources of acoustic emission inareas of sensor coverage that are stressed during the course of
4、the examination.1.4 This practice applies to examinations of new and in-service fan blades.1.5 This practice is limited to fan blades of FRP construc-tion, with length (hub centerline to tip) of less than 3 m 10 ft,and with fiberglass content greater than 15 % by weight.1.6 AE measurements are used
5、to detect emission sources.Other nondestructive examination (NDE) methods may beused to evaluate the significance of AE sources. Procedures forother NDE methods are beyond the scope of this practice.1.7 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as st
6、andard. 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.1.8 This standard does not purport to address all of thesafety concerns, if any,
7、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:2E543 Specification for Agencies Performing Nondestruc
8、-tive TestingE650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE750 Practice for Characterizing Acoustic Emission Instru-mentationE976 Guide for Determining the Reproducibility of Acous-tic Emission Sensor ResponseE1067 Practice for Acoustic Emission Examination of Fi-berglass Reinforced
9、 Plastic Resin (FRP) Tanks/VesselsE1106 Test Method for Primary Calibration of AcousticEmission SensorsE1316 Terminology for Nondestructive Examinations2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for
10、Qualification and Certi-fication of Nondestructive Testing Personnel2.3 Aerospace Industries Association Document:4NAS 410 Certification and Qualification of NondestructiveTesting Personnel3. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, see Terminology E1316.4. Summary
11、of Practice4.1 This practice consists of subjecting individual FRP fanblades to increasing load while monitoring with sensors thatare sensitive to acoustic emission (transient stress waves)caused by growing flaws.4.2 This practice provides guidelines to determine the zonallocation of structural flaw
12、s in FRP fan blades.4.3 The test load, applied at the blade tip is calculated toprovide 100 % of the maximum allowable operating (bending)load at the blade-hub interface.4.4 This practice is intended to simulate the bending load.Torsional and centrifugal loads are not simulated by thispractice.1This
13、 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, 2010. Published July 2010. Originally approvedin 2000. Last previous edition approved in 2005 as E2
14、076 - 05. DOI: 10.1520/E2076_E2076M-10.2For 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 ASTM website.3Available fromAmerica
15、n 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-aerospace.org.1Copyright ASTM Inter
16、national, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.5 Structurally insignificant flaws may produce acousticemission.5. Significance and Use5.1 The AE examination method detects structurally signifi-cant flaws in FRP structures via test loading. The damagem
17、echanisms that are detected in FRP include resin cracking,fiber debonding, fiber pullout, fiber breakage, delamination,and secondary bond failure.5.2 Flaws in unstressed areas will not generate detectableAE.5.3 Flaws located with AE may be examined by othermethods.6. Basis of Application6.1 The foll
18、owing items are subject to contractual agree-ment between the parties using or referencing this practice.6.2 Personnel Qualification6.2.1 If specified in the contractual agreement, personnelperforming examinations to this practice shall be qualified inaccordance with a nationally or internationally
19、recognizedNDT personnel qualification practice or standard such asANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, or a similardocument and certified by the employer or certifying agency,as applicable. The practice or standard used and its applicablerevision shall be specified in the contractual agreement be-t
20、ween the using parties.6.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E543. The applicableedition of Practice E543 shall be specified in the contractualagreement.6.4 Extent of ExaminationThe
21、extent of examination shallbe in accordance with 10.2 unless otherwise specified.6.5 Reporting Criteria/Acceptance CriteriaReporting cri-teria for the examination results shall be in accordance withSection 12 unless otherwise specified. Since acceptance crite-ria, for example, for reference radiogra
22、phs, are not specified inthis practice, they shall be specified in the contractual agree-ment.6.6 Reexamination of Repaired/Reworked ItemsReexamination of repaired/reworked items is not addressed inthis practice, and if required, shall be specified in the contrac-tual agreement.6.7 Personnel Trainin
23、gIt is recommended that personnelperforming the examination have additional training on thefollowing topics:6.7.1 Basic technology of AE from FRP;6.7.2 Failure mechanism of FRP;6.7.3 AE instrument and sensor checkout on FRP;6.7.4 Loading of FRP components for AE testing;6.7.5 Data collection and int
24、erpretation; and6.7.6 Examination report preparation.7. Apparatus7.1 Essential features of the apparatus required for thispractice are shown in Fig. 1. Specifications are provided onAnnex A1.7.2 Couplant must be used to acoustically couple sensors tothe blade surface. Adhesives that have acceptable
25、acousticproperties and ultrasonic couplants are acceptable.7.3 Sensors may be held in place with elastic straps,adhesive tape, or other mechanical means. (See Guide E650.)7.4 Sensors are to be positioned on the fan mounting drivehub for background noise detection only; on the blade within150 mm 6 in
26、. of the shank; on the blade midway between theshank and the blade tip; and within 150 mm 6 in. of the bladetip for background noise detection only. Additional sensorsmay be added when more complete coverage is desired.NOTE 1The sensors indicated in Fig. 1 may be placed on either thetop or bottom su
27、rface of the blade.7.5 Instrumentation shall be capable of recording AE hitsabove a low-amplitude threshold, AE hits above a high-amplitude threshold (both within a specific frequency range)and have sufficient channels to localizeAE sources in real time.(See Practice E750.) Hit detection is required
28、 for each channel.An AE hit amplitude measurement is recommended for sensi-tivity verification. Amplitude distributions are recommendedfor flaw characterization.7.6 Preamplifiers may be enclosed in the sensor housing orin a separate enclosure. If a separate preamplifier is used,FIG. 1 ApparatusE2076
29、/E2076M 102sensor cable length, between the sensor and the preamplifier,must not result in a signal loss of greater than 3 dB. Typically,2 m 6 ft, is acceptable.7.7 Power/signal cable length (between preamplifier andsignal processor) shall not result in a signal loss of greater than3 dB. Typically,
30、150 m 500 ft is acceptable.7.8 Signal processors are computerized instruments withindependent channels that filter, measure, and convert analoginformation into digital form for display and permanent stor-age. A signal processor must have sufficient speed and capa-bility to independently process data
31、 from all sensors simulta-neously. The signal processor should provide capability to filterdata for replay.7.9 A video monitor is used to display processed data invarious formats. Display format may be selected by theexaminer.7.10 A data storage device, such as a hard disk, is used tostore data for
32、replay and archiving.7.11 Hard-copy capability should be available from a graph-ics printer or equivalent device.8. Safety Precautions8.1 SafetyAll site safety requirements unique to the testlocation shall be met.9. Calibration and Standardization9.1 Annual calibration and verification of AE sensors
33、,preamplifiers, if applicable, signal processor, andAE electronicwaveform generator should be performed. Equipment shouldbe adjusted so that it conforms to the equipment manufactur-ers specifications. Instruments used for calibration must havecurrent accuracy certification that is traceable to the N
34、ationalInstitute for Standards and Technology (NIST).9.2 Routine electronic checks must be performed on amonthly basis or at any time there is concern about signalprocessor performance. An AE electronic waveform generatorshould be used in routine electronic checks. Each signalprocessor channel must
35、respond with peak amplitude readingswithin 62 dB of the electronic waveform generator output.9.3 Routine sensor checks must be performed on a monthlybasis or at any time that there is concern about the sensorperformance. Peak amplitude response and electronic noiselevel should be recorded. Sensors c
36、an be stimulated by a pencillead break in accordance with Guide E976. Sensors which arefound to have peak amplitudes or electronic noise more than 3dB greater than the average of the group of sensors to be usedduring the examination should be replaced.9.4 A system performance check must be conducted
37、 imme-diately before and immediately after each examination. Asystem performance check utilizes a mechanical device toinduce stress waves into the structure. The induced stresswaves must be nondestructive and simulate emission from aflaw. System performance checks verify the sensitivity of eachsyste
38、m channel (including the couplant).9.4.1 The preferred technique for conducting a systemperformance check utilizes a pencil lead break. Lead should bebroken on the surface (see Fig. 4 of Guide E976) at a specifieddistance, typically 100 mm 4 in. from the sensor.9.4.2 System channels which are found
39、to have performanceoutside of specified values should be repaired or replaced.Values should be specified such that the sensitivity of channelsused in the same test differ by no more than 6 dB.10. Test Procedure10.1 General GuidelinesEach fan blade is subjected toprogrammed increasing tip load, up to
40、 a predetermined maxi-mum value (test load), while being monitored by sensors thatdetect acoustic emission (stress waves) caused by growingstructural flaws.10.1.1 Blade tip load shall be controlled so as to not exceeda load rate of 33 % of test load per minute.10.1.2 Background noise shall be minimi
41、zed and identified.Excessive background noise is cause for suspension of theloading. In the analysis of examination results, backgroundnoise should be properly discounted, if the source is deter-mined to be irrelevant to mechanical integrity.10.2 LoadingDetermine the test load from the blademanufact
42、urers specifications. The blade may be loaded onceor twice depending upon the outcome of the first loading. If theacoustic emission activity generated by the first loading ex-ceeds the criteria then an immediate second loading shall beapplied. If the blade meets the acceptance criteria on the firstl
43、oading then the second loading is not required. Fig. 2 showsthe recommended loading sequence. The following is a prac-tical way to achieve the desired blade tip load.FIG. 2 Graph of Fan Blade Testing SequenceE2076/E2076M 10310.2.1 Secure the shank of the blade in an appropriateholder at its operatin
44、g pitch (blade parallel to the floor). Thiswill usually be the blade manufacturers drive hub arrangement(see also Fig. 1).10.2.2 Suspend an empty water container at the tip end ofthe blade. Padding is recommended to reduce the possibility ofextraneous noise and physical damage to the surface of theb
45、lade tip.10.2.3 Fill the water container with a sufficient amount ofwater to equal the maximum desired test load at the blade tip.For example, for a typical 25-kg 50-lb test load, the fillingrate should not exceed 7.5 L 2 gal/min (see 10.1.1).10.2.4 Hold the test load for two minutes and record test
46、results.10.2.5 Remove the load from the blade tip.10.2.6 Evaluate the acoustic emission activity in accordancewith Section 11. If the blade meets the acceptance criteria, nofurther testing is required. If it fails to meet the criteria proceedwith steps 7 and 8.10.2.7 Immediately replace the empty wa
47、ter container andrefill the container with water equal to the maximum desiredtest load at the blade tip. Filling rate should not exceed therequirement in 10.1.1.10.2.8 Hold the test load for two minutes and record testresults.10.3 Data RecordingThe following AE data are to berecorded for each blade
48、examined by this procedure:10.3.1 Maximum dB during loading, or number of hitsabove the high-amplitude threshold. (See Practice E1067,Annex A2).10.3.2 Number of hits above the low-amplitude threshold(see Practice E1067, Annex A2) during two-minute hold at testload.10.3.3 Total number of hits above t
49、he low-amplitude thresh-old during loading.10.3.4 Indicate most active sensor location.11. Evaluation11.1 Evaluation based on emissions during load hold isparticularly significant. Continuing emissions indicate continu-ing damage. Generally, background noise will be at a minimumduring load hold. Emissions continuing during load holdperiods is a condition on which accept-reject criteria may bebased.11.2 Evaluation based on high-amplitude hits is important.These hits often are associated with major structural damage.High-amplitude hits (above the high
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