1、Designation: E749/E749M 12E749/E749M 17Standard Practice forAcoustic Emission Monitoring During Continuous Welding1This standard is issued under the fixed designation E749/E749M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the
2、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. Scope*1.1 This practice provides recommended guidelines recommendations for acoustic emission (AE) monitoring of weldme
3、ntsduring and immediately following their fabrication by continuous welding processes.1.2 The procedure described in this practice is applicable to the detection and location of AE sources in weldments and in theirheat-affected zone during fabrication, particularly in those cases where the time dura
4、tion of welding is such that fusion andsolidification take place while welding is still in progress.1.3 The effectiveness of acoustic emission to detect discontinuities in the weldment and the heat-affected zone is dependent onthe design of the AE system, the AE system verification procedure, the we
5、ld process, and the material type. Materials that havebeen monitored include low-carbon steels, low-alloy steels, stainless steels, and some aluminum alloys. The system performancemust be verified for each application by demonstrating that the defects of concern can be detected with the desired reli
6、ability.1.4 UnitsThe values stated in either SI units or inch-pound units are to be regarded separately as standard. The values statedin each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining valuesfrom the two systems may result in non-c
7、onformance with the standard.1.5 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 p
8、rior to use.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Ba
9、rriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E543 Specification for Agencies Performing Nondestructive TestingE569 Practice for Acoustic Emission Monitoring of Structures During Controlled StimulationE650 Guide for Mounting Piezoelectric Acoustic Emission SensorsE1316 T
10、erminology for Nondestructive Examinations2.2 ASNT Standards:3SNT-TC-1A Recommended Practice for Nondestructive Testing Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Certification of Nondestructive Testing Personnel2.3 AIA Standard:4NAS-410 Certification an
11、d Qualification of Nondestructive Personnel (Quality Assurance Committee)2.4 ISO Standard:5ISO 9712 Non-Destructive Testing: Qualification and Certification of NDT Personnel1 This practice is under the jurisdiction ofASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Su
12、bcommittee E07.04 on Acoustic EmissionMethod.Current edition approved June 15, 2012June 1, 2017. Published July 2012June 2017. Originally approved in 1980. Last previous edition approved in 20072012 asE749 - 07.E749 -12. DOI: 10.1520/E0749-12.10.1520/E0749-17.2 For referencedASTM standards, visit th
13、eASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate L
14、n., Columbus, OH 43228-0518, http:/www.asnt.org.4 Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http:/www.aia-aerospace.org.5 Available from International Organization for Standardization (ISO), ISO Central Secretaria
15、t, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,Switzerland, http:/www.iso.org.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 po
16、ssible to adequately depict all 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 standardC
17、opyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 DefinitionsFor definitions of terms relating to acoustic emission testing, see Section B of Terminology E1316.4. Significance and Use4.1 Detection and location of AE sou
18、rces in weldments during fabrication may provide information related to the integrity ofthe weld. Such information may be used to direct repair procedures on the weld or as a guide for application of other nondestructiveevaluation (NDE) methods. A major attribute of applying AE for in-process monito
19、ring of welds is the ability of the method toprovide immediate real-time information on weld integrity. This feature makes the method useful to lower weld costs by repairingdefects at the most convenient point in the production process. The AE activity from discontinuities in the weldment is stimula
20、tedby the thermal stresses from the welding process. The AE activity resulting from this stimulation is detected by AE sensors in thevicinity of the weldment, which convert the acoustic waves into electronic signals. The AE instrumentation processes signals andprovides means for immediate display or
21、 indication of AE activity and for permanent recordings of the data.4.2 Items to be considered in preparation and planning for monitoring should include but not be limited to the following:4.2.1 Description of the system or object to be monitored or examined,4.2.2 Extent of monitoring, that is, enti
22、re weld, cover passes only, and so forth,4.2.3 Limitations or restrictions on the sensor mounting procedures, if applicable,4.2.4 Performance parameters to be established and maintained during the AE system verification procedure (sensitivity,location accuracy, and so forth),4.2.5 Maximum time inter
23、val between AE system verification checks,4.2.6 Performance criteria for purchased equipment,4.2.7 Requirements for permanent records of the AE response, if applicable,4.2.8 Content and format of test report, if required, and4.2.9 Operator qualification and certification, if required.5. Basis of App
24、lication5.1 The following items are subject to contractual agreement between the parties using or referencing this practice.5.2 Personnel Qualification:5.2.1 If specified in the contractual agreement, personnel performing examinations to this standard shall be qualified inaccordance with a nationall
25、y or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNTCP-189, SNT-TC-1A, NAS-410, ISO 9712, or a similar document and certified by the employer or certifying agency, as applicable.The practice or standard used and its applicable revision shall be identifie
26、d in the contractual agreement between the using parties.5.3 Qualification of Nondestructive AgenciesIf specified in the contractual agreement, NDT agencies shall be qualified andevaluated as described in Practice E543. The applicable edition of Practice E543 shall be specified in the contractual ag
27、reement.5.4 Procedures and TechniquesThe procedures and techniques to be utilized shall be as specified in the contractual agreement.6. Examination Preparation6.1 The following preparatory procedures should be completed before initiating AE monitoring:6.1.1 Select the location(s) where the sensor(s)
28、 will be acoustically coupled. The sensor(s) should be centrally located near theweldment to provide for optimal AE response from all portions of the weld. If the sensor(s) are piezoelectric, this location shouldbe such that the maximum temperature stays below manufacturersspecifications of the sens
29、or(s). Take care in selecting the sensormounting locations to avoid contact or disturbance, or both, of the sensor by any of the welding or structural positioning equipment.Typical distances from 150 to 300 mm 6 to 12 in. from the heat-affected zone of the weld are usually satisfactory. Typical fixe
30、dsensor placement patterns that have been successfully used are shown in Figs. 1-3.6.1.1.1 If a fixed contact sensor(s) is used, clean the area(s) where attachment will be made to eliminate loose scale, weldingflux, or other debris, and attach the sensor in accordance with Guide E650.6.1.1.2 If movi
31、ng sensors are used, clean the coupling path so that uniform sensitivity is maintained as the sensor moves. Fig.4 shows side and top views of a typical configuration for moving sensors.FIG. 1 Typical Sensor Placement for Single Channel AE Monitoring of a Linear WeldE749/E749M 1726.1.2 Position and r
32、oute the signal cables connecting the sensor(s) to the AE instrumentation to avoid contacting the hot weldbead or entangling the welding and positioning equipment.6.1.3 Adjustment of Apparatus:6.1.3.1 After all sensors are mounted, connected, and operational (without objectionable background noise),
33、 theAE monitoringsystem can then be adjusted using an AE simulator.6.1.3.2 Gain AdjustmentTo set or select the overall gain for a channel (if necessary), locate the acoustic emission simulatorat a selected distance adjacent to the sensor. Monitor the response to the simulated emission, and adjust th
34、e overall channel gainto a specified amplitude level. Repeat this procedure two times, placing the simulator at the same distance from the sensor but atdifferent azimuthal positions relative to the original simulator positions (see Fig. 5). Record the average gain for the three simulatorpositions. R
35、epeat the entire procedure for eachAE sensor on the structure, and adjust the gains. The average gains for all channelsshould give responses to the simulator that have peak voltages identical to within 63 dB.6.1.4 Determination of Source-Location AccuracyCheck the operation of the AE source-location
36、 function by analyzingsimulatedAE signals from several random locations in the weld and on the structure, as well as from any specific critical locations.For each placement of the simulator, determine and record the precision and accuracy of the AE location function. It should benoted that the accur
37、acy of locating the simulator source will not necessarily be the same as for locating a real AE source. Duringtrial welding in multipassmulti-pass configurations, it should be verified that location accuracy is maintained during weld buildup.Experiments indicate that location accuracy depends on the
38、 percentage completion of multipassmulti-pass welds.6.2 Check the integrity of the welding ground return system to eliminate the possibility of diverting the weld currents to theAEinstrumentation ground.7. Apparatus7.1 The AE apparatus normally consists of sensors, preamplifiers, and electronic inst
39、rumentation with display and recordingcapabilities. Acoustic emission monitoring during welding places many specialized requirements on AE apparatus due to severeenvironmental factors and interfering noise sources. The following criteria provide guidelines to aid in minimizing these interferingfacto
40、rs, and maximizing the effectiveness of the monitoring process:7.1.1 Sensors should be used that are capable of operating in the temperature range to be encountered. Use of “high-temperature” sensors or waveguides to isolate conventional sensors may be necessary for multipass,multi-pass, high heat i
41、nputwelds, or welds maintained at elevated preheat temperatures. The sensors should be electrically insulated from the structure undertest to ensure that the weld current or welder ground is not coupled into the AE instrumentation. If the weld current is pulsed orhas a significant transient componen
42、t, differential sensors may aid in suppressing interference.7.1.2 Frequency Bandpass Filters are recommended to minimize background noise interference during AE monitoring ofwelding. A low-frequency limit to the passband in the vicinity of 100 kHz will aid in minimizing background noise due tomechan
43、ical noise sources such as grinding, chipping, and manipulation of the structure under test. Radio frequency interferencedue to contactors and heavy electrical machinery, as well as the welding arc, may be minimized by use of a high-frequency limitto the passband ranging from 100 kHz to 1 MHz. The s
44、ensor operating frequency range should be compatible with the aboveconsiderations.7.2 The Welding Arc is a low-level continuous source of AE. To minimize interference from the welding arc, the sensitivity ofthe AE monitoring apparatus should be adjusted so that arc noise is below the trigger thresho
45、ld. This sensitivity is the maximumFIG. 2 Typical Sensor Placement for Two-Channel AE Monitoring of a Linear WeldFIG. 3 Typical Sensor Placement for Three-Channel AE Monitoring of a Circular WeldE749/E749M 173usableAE sensitivity for weld monitoring and varies with different welding methods. Table 1
46、 indicates overall gain for a particularFIG. 4 Moving Sensor Configuration with Sensor Position Fixed Relative to Weld HeadFIG. 5 AE Simulator Positions During Sensor CalibrationTABLE 1 Gain For AE System Utilizing Typical CommerciallyAvailable Piezoelectric Sensors Monitoring Typical Weld MethodsWe
47、ld Method AE System GainRange, dBSubmerged arc (single or tandem wire 800 to 1000 A) 35 to 45Submerged arc (single wire 400 to 500 A) 45 to 55Submerged arc (single wire 200 to 400 A) 55 to 65Gas shielded metal arc (MIG or short arc 150 to 400 A) 50 to 70Gas shielded tungsten arc (TIG 75 to 250 A) 60
48、 to 80E749/E749M 174system monitoring welding methods and using typical commercial piezoelectric transducers. This table is for general guidelinepurposes and not for direct reference.7.3 Single-Channel AE Instrumentation employing a single sensor may provide information on the presence of discontinu
49、itiesin a weld. For low-heat input welds, where the delay time between fusion and AE activity is short, discontinuities may also belocated in the weld by noting the presence of unusualAE activity and recording the position of the welding head when such activityoccurs. As the weld heat input increases, the delay time between fusion and AE activity usually increases, thus making use ofmultichannel arrival time interval measurements necessary for AE source location.7.4 The AE apparatus should be capable of providing output signals that are proportional to overall acoust
