1、Designation:E75107 Designation: E751/E751M 12Standard Practice forAcoustic Emission Monitoring During Resistance Spot-Welding1This standard is issued under the fixed designation E751/E751M; the number immediately following the designation indicates the yearof original adoption or, in the case of rev
2、ision, 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. Scope*1.1 This practice describes procedures for the measurement, processing, and interpretation of the acou
3、stic emission (AE)response associated with selected stages of the resistance spot-welding process.1.2 This practice also provides guidelines for feedback control by utilizing the measured AE response signals during thespot-welding process.1.31.3 UnitsThe values stated in either SI units or inch-poun
4、d 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-conformance with the standard.1.4 This standard does not purport to
5、 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 prior to use.2. Referenced Documents2.1 ASTM Standards:2E543 Specif
6、ication for Agencies Performing Nondestructive TestingE1316 Terminology 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 Nondestructiv
7、e Testing Personnel2.3 AIA Standard:4NAS-410 Certification and Qualification of Nondestructive Personnel (Quality Assurance Committee)3. Terminology3.1 DefinitionsFor definitions of terms relating to acoustic emission testing, see Section B of Terminology E1316.4. Significance and Use4.1The AE produ
8、ced during the production of a spot-weld can be related to weld quality parameters such as the strength andsize of the nugget, the amount of expulsion, and the amount of cracking. Therefore, in-process AE monitoring can be used bothas an examination method, and as a means for providing feedback cont
9、rol. Summary of Practice4.1 The resistance spot-welding process consists of several stages. These are the set-down of the electrodes, squeeze, currentflow, forging, hold time, and lift-off. Various types of acoustic emission signals are produced during each of these stages. Often,these signals can b
10、e identified with respect to the nature of their source. The individual signal elements may be greatly different,or totally absent, in various materials, thicknesses, and so forth. Fig. 1 is a schematic representation showing typical signalelements which may be present in the AE signature from a giv
11、en spot-weld.4.2 Most of the depicted AE signal features can be related to factors of weld quality. The AE occurring during set-down andsqueeze can often be related to the condition of the electrodes and the surface of the parts. The large, often brief, signal at current1This practice is under the j
12、urisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.04 on Acoustic EmissionMethod.Current edition approved Feb.June 15, 2007.2012. Published March 2007.July 2012. Originally approved in 1980. Last previous edition approved in 20012007 asE7
13、51 - 017. DOI: 10.1520/E0751-07.10.1520/E0751-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3Available
14、 from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.4Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http:/www.aia-aerospace.org.1Thi
15、s 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 all changes accurately, ASTM recommends that users consult prior editio
16、ns 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 standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
17、 United States.initiation can be related to the initial resistance, and the cleanliness of the part. For example, burning through of certain oxide layerscontributes to the acoustic emission response during this time.4.2.1 During current flow, plastic deformation, nugget expansion, friction, melting,
18、 and expulsions produce AE signals. Thesignals caused by expulsion (spitting or flashing, or both) generally have large amplitudes and can be distinguished from the restof the acoustic emission associated with nugget formation. Fig. 2 shows typical AE response signals during current flow for bothd-c
19、 and a-c welding.4.2.2 Following termination of the welding current, some materials exhibit appreciableAE noise during solidification which canbe related to nugget size and inclusions. As the nugget cools during the hold period, AE can result from solid-solid phasetransformations and cracking.FIG. 1
20、 Typical AE Response Signals During Resistance Spot WeldingFIG. 2 Typical AE Response Signals During Current FlowE751/E751M 1224.2.3 During the lift-off stage, separation of the electrode from the part produces signals that can be related to the condition ofthe electrode as well as the cosmetic cond
21、ition of the weld.4.3 Using time, and amplitude or energy discrimination, or both, the AE response corresponding to each stage can be separatelydetected and analyzed. Although the AE associated with each stage of the spot-welding process can be relevant to weld quality,this practice only gives detai
22、led consideration to the AE generated by nugget formation and expansion, expulsion, and cracking.5. Significance and Use5.1 The AE produced during the production of a spot-weld can be related to weld quality parameters such as the strength andsize of the nugget, the amount of expulsion, and the amou
23、nt of cracking. Therefore, in-process AE monitoring can be used bothas an examination method, and as a means for providing feedback control.6. Basis of Application5.1The6.1 The following items are subject to contractual agreement between the parties using or referencing this standard.5.26.2 Personne
24、l Qualification:5.2.1If6.2.1 If specified in the contractual agreement, personnel performing examinations to this standard shall be qualified inaccordance with a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNTCP-189, SNT-TC-1A, NAS-410, or
25、a similar document and certified by the employer or certifying agency, as applicable. Thepractice or standard used and its applicable revision shall be identified in the contractual agreement between the using parties.5.36.3 Qualification of Nondestructive AgenciesIf specified in the contractual agr
26、eement, NDT agencies shall be qualified andevaluated as described in Practice E543. The applicable edition of Practice E543 shall be specified in the contractual agreement.5.46.4 Procedures and TechniquesThe procedures and techniques to be utilized shall be as specified in the contractual agreement.
27、6.Ordering Information6.1If the spot-weld monitoring or process control methods described in this practice are performed as a service, the followingitems should be addressed in the purchase specification, and are subject to agreement between the purchaser and the supplier:6.1.1Description of the wel
28、ded parts in terms of geometry, dimensions, number and position of welds, and materials.6.1.2Description of the welding machine, type and dimensions of the electrodes, type of weld controller, welding schedule, anddistance between the welding head and the controller.6.1.3Location and mounting method
29、 for the acoustic emission sensors, and design of the mounting fixture, as appropriate.6.1.4In the event that the process is actually controlled by acoustic emission, the circuit requirements associated with theelectronic interface to the weld controller to ensure synchronous operation.6.1.5The perf
30、ormance and limiting AE parameters which were predetermined.6.1.6Method of recording or reporting (that is, form and content of the report), if applicable.6.1.7Technical qualifications of the personnel performing the examination. These should be based on a documented program thatcertifies personnel
31、for conducting AE examinations.7. Principles of Application7.1The resistance spot-welding process consists of several stages. These are the set-down of the electrodes, squeeze, currentflow, forging, hold time, and lift-off. Various types of acoustic emission signals are produced during each of these
32、 stages. Often,these signals can be identified with respect to the nature of their source. The individual signal elements may be greatly different,or totally absent, in various materials, thicknesses, and so forth. Fig. 1 is a schematic representation showing typical signalelements which may be pres
33、ent in the AE signature from a given spot-weld.7.2Most of the depicted AE signal features can be related to factors of weld quality. The AE occurring during set-down andsqueeze can often be related to the condition of the electrodes and the surface of the parts. The large, often brief, signal at cur
34、rentinitiation can be related to the initial resistance, and the cleanliness of the part. For example, burning through of certain oxide layerscontributes to the acoustic emission response during this time.7.2.1During current flow, plastic deformation, nugget expansion, friction, melting, and expulsi
35、ons produce AE signals. Thesignals caused by expulsion (spitting or flashing, or both) generally have large amplitudes and can be distinguished from the restof the acoustic emission associated with nugget formation. Fig. 2 shows typical AE response signals during current flow for bothd-c and a-c wel
36、ding.7.2.2Following termination of the welding current, some materials exhibit appreciable AE noise during solidification which canbe related to nugget size and inclusions. As the nugget cools during the hold period, AE can result from solid-solid phasetransformations and cracking.7.2.3During the li
37、ft-off stage, separation of the electrode from the part produces signals that can be related to the condition ofthe electrode as well as the cosmetic condition of the weld.7.3Using time, and amplitude or energy discrimination, or both, the AE response corresponding to each stage can be separatelydet
38、ected and analyzed. Although the AE associated with each stage of the spot-welding process can be relevant to weld quality,E751/E751M 123this practice only gives detailed consideration to the AE generated by nugget formation and expansion, expulsion, and cracking.Ordering Information7.1 If the spot-
39、weld monitoring or process control methods described in this practice are performed as a service, the followingitems should be addressed in the purchase specification, and are subject to agreement between the purchaser and the supplier:7.1.1 Description of the welded parts in terms of geometry, dime
40、nsions, number and position of welds, and materials.7.1.2 Description of the welding machine, type and dimensions of the electrodes, type of weld controller, welding schedule, anddistance between the welding head and the controller.7.1.3 Location and mounting method for the acoustic emission sensors
41、, and design of the mounting fixture, as appropriate.7.1.4 In the event that the process is actually controlled by acoustic emission, the circuit requirements associated with theelectronic interface to the weld controller to ensure synchronous operation.7.1.5 The performance and limiting AE paramete
42、rs which were predetermined.7.1.6 Method of recording or reporting (that is, form and content of the report), if applicable.7.1.7 Technical qualifications of the personnel performing the examination. These should be based on a documented programthat certifies personnel for conducting AE examinations
43、.8. Apparatus8.1 Acoustic Emission System:8.1.1 The AE sensor should be a contacting type having an appropriate frequency response within the range from 0.1 to 1.0MHz. Free resonances associated with electrode vibrations may necessitate the use of sensors with a frequency response in therange from 0
44、.30 to 1.0 MHz.8.1.2 The electronic instrument should contain adjustable amplification (gain) over the range from 40 to 100 dB, or anequivalent dynamic range and adjustable threshold. The instrument should be capable of performing time and amplitude or energydiscrimination. Using some timing referen
45、ce, it is necessary to detect the AE contained within a certain time interval and withina certain signal or energy amplitude range. This is required for each characteristic stage of the AE signal that is to be separatelymeasured. Thus, the instrument should contain one or more signal amplitude or en
46、ergy level detectors, timing gates, and counters.It should also contain a comparator and signaling output if it is used for on-line monitoring.8.1.3 If feedback control is to be used, the instrument should facilitate the selection of an optimum AE level, and it shouldgenerate an appropriate control
47、signal whenever this level is exceeded. This control signal should terminate the weldingsynchronously with the zero-crossing points of the weld current.8.2 Support EquipmentA waveform recorder is normally used for performing measurements. A means for detecting currentinitiation independent from the
48、AE signals should be available.8.3 Data-Recording Devices (optional) If it is desired to permanently record processed AE data, the AE instrument shouldbe capable of this function.8.4 Audio or Visual AlarmAn alarm can be used in applications where the acceptability of individual spot welds is to bede
49、termined in real-time, and where no record of rejected welds is necessary.8.5 Print-out DeviceA print-out device may be used to provide a permanent record, and it is usually employed as follows:8.5.1 Whenever a permanent record is necessary to document the quality of individual welds, the printer should print out suchinformation as is necessary to segregate and identify rejectable welds.8.5.2 When the joined parts contain a large number of spot-welds, and the integrity of the product does not depend on the qualityof individual welds but rather on the number of unacceptabl
