1、Designation: E2478 11Standard Practice forDetermining Damage-Based Design Stress for Glass FiberReinforced Plastic (GFRP) Materials Using AcousticEmission1This standard is issued under the fixed designation E2478; the number immediately following the designation indicates the year oforiginal adoptio
2、n or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice details procedures for establishing thedirect stress and she
3、ar stress damage-based design values foruse in the damage-based design criterion for materials to beused in GFRP vessels and other GFRP structures. The practiceuses data derived from acoustic emission examination offour-point beam bending tests and in-plane shear tests (seeASME Section X, Article RT
4、-8).1.2 The onset of lamina damage is indicated by the presenceof significant acoustic emission during the reload portion ofload/reload cycles. “Significant emission” is defined withhistoric index.1.3 UnitsThe values stated in inch-pound units are to beregarded as standard. The values given in paren
5、theses aremathematical conversions to SI units which are provided forinformation only and are not considered standard.1.4 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-pria
6、te safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D790 Test Methods for Flexural Properties of Unreinforcedand Reinforced Plastics and Electrical Insulating MaterialsD4255/D4255M Test Method for In-Plane
7、Shear Propertiesof Polymer Matrix Composite Materials by the Rail ShearMethodD3846 Test Method for In-Plane Shear Strength of Rein-forced PlasticsE543 Specification for Agencies Performing Nondestruc-tive TestingE976 Guide for Determining the Reproducibility of Acous-tic Emission Sensor ResponseE131
8、6 Terminology for Nondestructive ExaminationsE2374 Guide for Acoustic Emission System PerformanceVerification2.2 ASME Documents:3ASME Section X, Article RT-8 Test Method for Determin-ing Damage-Based Design CriterionASME Section V, Article 11 Acoustic Emission Examina-tion of Fiber-Reinforced Plasti
9、c Vessels2.3 Other Standards:ANSI/ASNT-CP-189 Qualification and Certification ofNondestructive Testing Personnel4SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Testing4NAS-410 Certification and Qualification of NondestructiveTest Personnel53. Terminol
10、ogy3.1 Definitions of terms related to conventional acousticemission are in Terminology E1316, Section B.3.2 Definitions of Terms Specific to This Standard:3.2.1 historic indexa measure of the change in MARSE(or other AE feature parameter such as AE Signal Strength)throughout an examination.3.2.2 kn
11、ee in the curvea dramatic change in the slope ofthe cumulative AE (MARSE or Signal Strength) versus timecurve.3.2.3 measured area of the rectified signal envelope(MARSE)a measure of the area under the envelope of therectified linear voltage time signal from the sensor. (see ASMESection V, Article 11
12、)1This 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 Dec. 1, 2011. Published January 2012. Originallyapproved in 2006. Last previous edition approved in 2
13、006 as E2478 - 06a. DOI:10.1520/E2478-11.2For 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 from Amer
14、ican Society of Mechanical Engineers (ASME), ASMEInternational Headquarters, Three Park Ave., New York, NY 10016-5990, http:/www.asme.org.4Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.5Available from
15、Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-
16、2959, United States.3.2.4 significant emissiona level of emission that corre-sponds to the first time during reloading that the historic indexattains a value of 1.4.4. Summary of Practice4.1 This practice uses acoustic emission instrumentationand examination techniques during load/reloading of mater
17、ialsbeing examined, to determine the onset of significant acousticemission. The onset of significant emission is related to thedamage-based design stress by the Felicity ratio.6,75. Significance and Use5.1 The damage-based design approach will permit anadditional method of design for GFRP materials.
18、 This is a veryuseful technique to determine the performance of differenttypes of resins and composition of GFRP materials in order todevelop a damage tolerant and reliable design. This AE-basedmethod is not unique, other damage-sensitive evaluation meth-ods can also be used.5.2 This practice involv
19、es the use of acoustic emissioninstrumentation and examination techniques as a means ofdamage detection to support a destructive test, in order toderive the damage-based design stress.5.3 This practice is not intended as a definitive predictor oflong-term performance of GFRP materials (such as those
20、 usedin vessels). For this reason, codes and standards require cyclicproof testing of prototypes (for example, vessels) which are nota part of this practice.5.4 Other design methods exist and are permitted.6. Basis of Application6.1 The following items are subject to contractual agree-ment between t
21、he parties using or referencing this practice:6.1.1 Personnel QualificationIf specified in the contrac-tual agreement, personnel performing examinations to thispractice shall be qualified in accordance with a nationally orinternationally recognized NDT personnel qualification prac-tice or standard s
22、uch as ANSI/ASNT-CP-189, SNT-TC-1A,NAS-410, or a similar document and certified by the employeror certifying agency, as applicable. The practice or standardused and its applicable revision shall be identified in thecontractual agreement between the using parties.6.1.2 Qualification of Nondestructive
23、 AgenciesIf speci-fied in the contractual agreement, NDT agencies shall bequalified and evaluated as described in Practice E543. Theapplicable revision of Practice E543 shall be specified in thecontractual agreement.6.1.3 Procedure and TechniquesThe procedures and tech-niques to be utilized shall be
24、 as specified in the contractualagreement.6.1.4 Timing of ExaminationThe timing of examinationshall be in accordance with 12.4 unless otherwise specified.6.1.5 Extent of ExaminationThe extent of examinationshall be in accordance with Sections 9 and 10 unless otherwisespecified.6.1.6 Reporting Criter
25、iaReporting criteria for the exami-nation results shall be in accordance with 15.1 unless otherwisespecified.7. ApparatusNOTE 1Refer to Fig. 1 for AE system block diagram showing keycomponents of the AE system. It is recommended to use two AE sensorsto monitor the specimen, evaluated on a per channe
26、l basis.7.1 AE Sensors7.1.1 AE sensors shall be resonant in a 100 to 300 kHzfrequency band.7.1.2 Sensors shall have a peak sensitivity greater than 77dB (referred to 1 volt per microbar, determined by face-to-faceultrasonic examination) within the frequency range 100 to 300kHz. Sensitivity within th
27、e 100 to 300 kHz range shall not varymore than 3 dB within the temperature range of intended use.7.1.3 Sensors shall be shielded against electromagneticinterference through proper design practice or differential(anti-coincidence) element design, or both.7.1.4 Sensors shall have omni-directional resp
28、onse, withvariations not exceeding 2 dB from the peak response.7.2 Couplant7.2.1 Commercially available couplants for ultrasonic flawdetection may be used. Silicone-based high-vacuum grease hasbeen found to be particularly suitable. Adhesives may also beused.7.2.2 Couplant selection should be made t
29、o minimizechanges in coupling sensitivity during a complete examination.Consideration should be given to the time duration of theexamination and maintaining consistency of coupling through-out the examination.7.3 Sensor-Preamplifier Cable7.3.1 The cable connecting the sensor to the preamplifiershall
30、 not attenuate the sensor peak voltage in the 100 to 300kHz frequency range more than 3 dB (6 ft (1.8 m) is a typicallength). Integral preamplifier sensors meet this requirement.They have inherently short, internal, signal cables.7.3.2 The sensor-preamplifier cable shall be shielded againstelectroma
31、gnetic interference. Standard low-noise coaxial cableis generally adequate.7.4 Preamplifier7.4.1 The preamplifier shall have a noise level no greaterthan five microvolts rms (referred to a shorted input) within the100 to 300 kHz frequency range.7.4.2 Preamplifier gain shall vary no more than 61dBwit
32、hin the 100 to 300 kHz frequency band and temperaturerange of use.7.4.3 Preamplifiers shall be shielded from electromagneticinterference.7.4.4 Preamplifiers of differential design shall have a mini-mum of 40 dB common-mode rejection.7.4.5 Preamplifiers shall include a bandpass filter with aminimum b
33、andwidth of 100 kHz to 300 kHz. Note that thecrystal resonant characteristics provide additional filtering asdoes the bandpass filter in the signal conditioner.6Ramirez, G., Ziehl, P., Fowler, T., 2004, “Nondestructive Evaluation of FRPDesign Criteria with Primary Consideration to Fatigue Loading”,
34、ASME Journal ofPressure Vessel Technology, Vol. 126, pp. 113.7Ziehl, P. and Fowler, T., 2003, “Fiber Reinforced Polymer Vessel Design witha Damage Approach”, Journal of Composite Structures, Vol. 61, Issue 4, pp.395-411.E2478 1127.4.6 It is preferred that the preamplifier be mounted insidethe sensor
35、 housing.7.5 Power-Signal Cable7.5.1 The cable and connectors that provide power topreamplifiers, and that conduct amplified signals to the mainprocessor, shall be shielded against electromagnetic interfer-ence. Signal loss shall be less than 3 dB over the length of thecable.7.6 Power Supply7.6.1 As
36、table, grounded, power supply that meets the signalprocessor manufacturers specification shall be used.7.7 Main Signal Processor7.7.1 The main processor shall have circuitry through whichsensor data will be processed. It shall be capable of processinghits, hit arrival time, duration, counts, peak am
37、plitude, andMARSE (or similar AE feature parameters such as SignalStrength) on each channel.7.7.2 Electronic circuitry shall be stable within 61dBinthetemperature range 40 to 100F (4 to 38C).7.7.3 Threshold shall be accurate within 61 dB.7.7.4 MARSE shall be measured on a per channel basis andshall
38、have a resolution of 1 % of the value obtained from a onemillisecond duration, 150 kHz sine burst having an amplitude25 dB above the data analysis threshold. Usable dynamic rangeshall be a minimum of 40 dB.NOTE 2Instead of MARSE, other AE feature parameters such as“Signal Strength” may be used.7.7.5
39、 Amplitude shall be measured in decibels referenced to0 dB as 1 microvolt at the preamplifier input. Usable systemdynamic range shall be a minimum of 60 dB with 1 dBresolution over the frequency band of 100 to 300 kHz, and thetemperature range of 40 to 100F (4 to 38C). Not more than61 dB variation i
40、n peak detection accuracy shall be allowedover the stated temperature range.7.7.6 Hit duration (AE signal duration) shall be accurate to65 s and is measured from the first threshold crossing to thelast threshold crossing of the AE signal.7.7.7 Hit arrival time shall be recorded globally for eachchan
41、nel accurate to within one millisecond, minimum.7.7.8 The system deadtime of each channel of the systemshall be no greater than 200 s.7.7.9 The hit definition time shall be 400 s.7.7.10 The examination threshold shall be set at 40 dB(depending on background noise of the system setup whensubjected to
42、 a constant load of 10 % or less of the estimatedfailure load). Threshold should remain constant during theentire examination.8. Calibration and Verification8.1 Annual calibration and verification of AE sensors,preamplifiers (if applicable), signal processor, and AE elec-tronic waveform generator (o
43、r simulator) should be performed.Equipment should be adjusted so that it conforms to equipmentmanufacturers specifications. Instruments used for calibra-tions must have current accuracy certification that is traceableto the National Institute for Standards and Technology (NIST).8.2 Routine electroni
44、c evaluations must be performed anytime there is concern about signal processor performance. AnAE electronic waveform generator or simulator, should be usedin making evaluations. Each signal processor channel mustFIG. 1 AE System Block DiagramE2478 113respond with peak amplitude reading within 62dBo
45、ftheelectronic waveform generator output.8.3 A system performance verification must be conductedimmediately before, and immediately after, each examination.A performance verification uses a mechanical device to inducestress waves into the material under examination, at a specifieddistance from each
46、sensor. Induced stress waves stimulate asensor in the same way as emission from a flaw. Performanceverifications verify performance of the entire system (includingcouplant). (Refer to Guide E2374 for AE system performanceverification techniques).8.3.1 The preferred technique for conducting a perform
47、anceverification is a pencil lead break (PLB). Lead should bebroken on the material surface at a specified distance from eachsensor. The 2H lead, 0.012-in. (0.3-mm) diameter, and0.0790.118-in. (2 to 3-mm) long should be used (see Fig. 5 ofGuide E976 and Guide E2374).8.3.2 Auto Sensor Test (AST)An el
48、ectromechanical devicesuch as a piezoelectric pulser (and sensor which contains thisfunction) can be used in conjunction with pencil lead break(8.3.1) as a means to assure system performance. This devicecan be used to replace the PLB post examination, systemperformance verification (8.3). (Refer to
49、Guide E2374.)9. Test Methods9.1 The evaluation setup, loading arrangement, and speci-men dimensions for the flexure test shall be in accordance withProcedure B of Test Methods D790. Specimen thickness maybe dictated by the type of laminate being tested. Otherwise,specimens will be typically38-in. (9.5-mm) thick and shallhave sufficient width, clearance, and overhang to permitmounting of an acoustic emission sensor. Sensors should not bemounted in the middle third of the specimen.9.2 The evaluation setup, loading arrangement, and speci-men dimensions for
