1、Designation: E 2076 05Standard Test Method forExamination of Fiberglass Reinforced Plastic Fan BladesUsing Acoustic Emission1This standard is issued under the fixed designation E 2076; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision
2、, the year of 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 test method provides guidelines for acoustic emis-sion (AE) examinations of fiberglass reinforced
3、plastic (FRP)fan blades of the type used in industrial cooling towers and heatexchangers.1.2 This test method uses simulated service loading todetermine structural integrity.1.3 This test method will detect sources of acoustic emis-sion in areas of sensor coverage that are stressed during thecourse
4、of the examination.1.4 This test method applies to examinations of new andin-service fan blades.1.5 This test method is limited to fan blades of FRPconstruction, with length (hub centerline to tip) of less than 10ft, and with fiberglass content greater than 15 % by weight.1.6 AE measurements are use
5、d 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 test method.1.7 Values stated in inch-pound units are to be regarded asthe standard. SI units given in paren
6、theses are provided forinformation only.1.8 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
7、limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 543 Practice for Agencies Performing NondestructiveTestingE 650 Guide for Mounting Piezoelectric Acoustic EmissionSensorsE 750 Practice for CharacterizingAcoustic Emission Instru-mentationE 976 Guide for Determining the Reproducib
8、ility of Acous-tic Emission Sensor ResponseE 1067 Practice for Acoustic Emission Examination ofFiberglass Reinforced Plastic Resin (FRP) Tanks/VesselsE 1106 Method for Primary Calibration of Acoustic Emis-sion SensorsE 1316 Terminology for Nondestructive Testing2.2 ASNT Documents:3SNT-TC-1A Recommen
9、ded Practice for NondestructiveTesting Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certi-fication of Nondestructive Testing Personnel2.3 Aerospace Industries Association Document:4NAS 410 Certification and Qualification of NondestructiveTesting Personnel3
10、. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, see Terminology E 1316.4. Summary of Test Method4.1 This test method consists of subjecting individual FRPfan blades to increasing load while monitoring with sensorsthat are sensitive to acoustic emission (transient stress
11、 waves)caused by growing flaws.4.2 This test method provides guidelines to determine thezonal location of structural flaws 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
12、test method is intended to simulate the bendingload. Torsional and centrifugal loads are not simulated by thistest method.1This test method is under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.04 onAcoustic Emission Method.Curr
13、ent edition approved June 1, 2005. Published June 2005. Originallyapproved in 2000. Last previous edition approved in 2000 as E 2076 - 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
14、information, refer to the standards Document Summary page onthe ASTM website.3Available from TheAmerican Society for Nondestructive Testing (ASNT), P.O.Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.4Available from Aerospace Industries Association of America, Inc. (AIA), 1250Eye St., NW, Was
15、hington, DC 20005.1Copyright ASTM International, 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 s
16、tructures via test loading. The damagemechanisms 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 othermeth
17、ods.6. Basis of Application6.1 The following items are subject to contractual agree-ment between the parties using or referencing this test method.6.2 Personnel Qualification6.2.1 If specified in the contractual agreement, personnelperforming examinations to this standard shall be qualified inaccord
18、ance with a nationally or internationally 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 s
19、pecified in the contractual agreement be-tween the using parties.6.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as described in Practice E 543. The applicableedition of Practice E 543 shall be specified in the contra
20、ctualagreement.6.4 Extent of ExaminationThe 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 cr
21、ite-ria, for example, for reference radiographs, are not specified inthis test method, they shall be specified in the contractualagreement.6.6 Reexamination of Repaired/Reworked ItemsReexamination of repaired/reworked items is not addressed inthis test method, and if required, shall be specified in
22、thecontractual agreement.6.7 Personnel TrainingIt 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 component
23、s for AE testing;6.7.5 Data collection and interpretation; and6.7.6 Examination report preparation.7. Apparatus7.1 Essential features of the apparatus required for this testmethod are shown in Fig. 1. Specifications are provided onAnnex A1.7.2 Couplant must be used to acoustically couple sensors tot
24、he blade surface. Adhesives that have acceptable 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 E 650.)7.4 Sensors are to be positioned on the fan mounting drivehub for background no
25、ise detection only; on the blade within 6in. (152.4 mm) of the shank; on the blade midway between theshank and the blade tip; and within 6 in. (152 mm) of the bladetip for background noise detection only. Additional sensorsmay be added when more complete coverage is desired.NOTE 1The sensors indicat
26、ed in Fig. 1 may be placed on either thetop or bottom surface 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
27、real time.(See Practice E 750.) Hit detection is required for eachchannel. An AE hit amplitude measurement is recommendedfor sensitivity verification. Amplitude distributions are recom-mended for flaw characterization.7.6 Preamplifier may be enclosed in the sensor housing or ina separate enclosure.
28、If a separate preamplifier is used, sensorFIG. 1 ApparatusE2076052cable length, between the sensor and the preamplifier, must notresult in a signal loss of greater than 3 dB. Typically, 6 ft (1.8m), is acceptable.7.7 Power/signal cable length (between preamplifier andsignal processor) shall not resu
29、lt in a signal loss of greater than3 dB. Typically, 500 ft (152.4 m) 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 suffic
30、ient speed and capa-bility to independently process data 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 storag
31、e device, such as a magnetic disk, is usedto store data for replay and archiving.7.11 Hard-copy capability should be available from agraphics/line printer or equivalent device.8. Safety Precautions8.1 SafetyAll site safety requirements unique to the testlocation shall be met.9. Calibration and Stand
32、ardization9.1 Annual calibration and verification of AE sensors,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 mus
33、t havecurrent accuracy certification that is traceable to the NationalInstitute 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 i
34、n routine electronic checks. Each signalprocessor channel must 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 r
35、esponse and electronic noiselevel should be recorded. Sensors can be stimulated by a pencillead break in accordance with Guide E 976. 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 sho
36、uld be replaced.9.4 A system performance check must be conducted 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 afla
37、w. System performance checks verify the sensitivity of eachsystem 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 E 976) at a specifieddistance, typically 4
38、in. (101.6 mm) from the sensor.9.4.2 System channels which are found 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 Guidelin
39、esEach fan blade is subjected toprogrammed increasing tip load, up to 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
40、 33 % of test load per minute.10.1.2 Background noise shall be minimized 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
41、 integrity.10.2 LoadingDetermine the test load from the blademanufacturers 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 shal
42、l beapplied. If the blade meets the acceptance criteria on the firstloading 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 SequenceE207605310.2.1 Secure t
43、he shank of the blade in an appropriateholder at its operating 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
44、ofextraneous noise and physical damage to the surface of theblade 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 50-lb (22.7-kg) test load, the fillingrate should not exceed 2 gal (7.6 L)/min (se
45、e 10.1.1).10.2.4 Hold the test load for two minutes and record testresults.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 criteri
46、a proceedwith steps 7 and 8.10.2.7 Immediately replace the empty water 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 Da
47、ta RecordingThe following AE data are to berecorded for each blade examined by this procedure:10.3.1 Maximum dB during loading, or number of hitsabove the high-amplitude threshold. (See Practice E 1067,Annex A2).10.3.2 Number of hits above the low-amplitude threshold(see Practice E 1067,AnnexA2) dur
48、ing two-minute hold at testload.10.3.3 Total number of hits above the 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. Ge
49、nerally, 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 amplitude threshold) is acondition on which accept-reject criteria may be based.11.3 Evaluation based on total hit count above the low-amplitude threshold is important. These hits often are associ-ated with the overall condition of the part, including sec
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