1、Designation: E 2373 09Standard Practice forUse of the Ultrasonic Time of Flight Diffraction (TOFD)Technique1This standard is issued under the fixed designation E 2373; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice establishes the requirements for develop-ing ultrasonic examination procedures using the ultrasonictechniqu
3、e known as Time-of-Flight Diffraction (TOFD).1.2 Consistent with ASTM Policy, TOFD may be regardedas an ultrasonic test method whereby the qualities and charac-teristics of the item tested are evaluated, measured and in somecases identified. Measurements may be subject to precision andbias that may
4、be determined statistically or as a function ofsome parameter(s) such as wavelength. This practice may beused for applications that would be qualitative and properlyaddressed as examinations as well as quantitative and moreproperly addressed as tests.1.3 The values stated in SI units are to be regar
5、ded asstandard. Inch-pound units are provided for information.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-priate safety and health practices and determine the applica
6、-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E 164 Practice for Contact Ultrasonic Testing of WeldmentsE 543 Specification for Agencies Performing Nondestruc-tive TestingE 1065 Guide for Evaluating Characteristics of UltrasonicSearch UnitsE 1316 Terminolo
7、gy for Nondestructive ExaminationsE 1324 Guide for Measuring Some Electronic Characteris-tics of Ultrasonic Examination Instruments2.2 ASNT Documents:3SNT-TC-1A Recommended Practice for NondestructiveTesting Personnel Qualification and CertificationANSI/ASNT CP-189 Standard for Qualification and Cer
8、ti-fication of Nondestructive Testing Personnel2.3 Aerospace Industries Association Document:4NAS-410 Certification and Qualification of NondestructiveTesting Personnel2.4 Other Documents:BS 7706 (1993) Guide to Calibration and Setting-up of theUltrasonic Time-of-Flight Diffraction (TOFD) Techniquef
9、or Detection, Location and Sizing of Flaws, BritishStandards Institute, 19935Code Case 2235 ASME Boiler and Pressure Vessel Code63. Terminology3.1 DefinitionsRelated terminology is defined in Termi-nology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 B-scan displaya sectional view
10、of the plotted in-spection data formed by the stacking of A-scans. (Some usersrefer to stacked A-scans from non-parallel scans as D-scansand reserve those used with parallel scans as B-scans.)3.2.2 back-wall echoa specular reflection from the back-wall of the component being examined (usually assume
11、d to bea plate).3.2.3 lateral wavea compression wave that travels by themost direct route from the transmitting probe to the receivingprobe in a TOFD configuration.3.2.4 parallel scana scan whereby the probe pair motionis parallel to the ultrasonic beam axis. Also called a B-scan bysome users.1This
12、practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.06 onUltrasonic Method.Current edition approved June 1, 2009. Published July 2009. Originally approvedin 2004. Last previous edition approved in 2004 as E 2373 - 0
13、4.2For 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 fromAmerican Society for NondestructiveTesting (
14、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.5Available from BSI Management Systems, 12110 Sunset Hills
15、Road, Suite 140,Reston VA 20190.6Available from the American Society of Mechanical Engineers, ASME Inter-national, 22 Law Drive, Box 2900, Fairfield, NJ 07007-2900.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.5 PCSabbreviation
16、 for probe center spacing. Refers tothe distance between the marked exit points of a pair of TOFDprobes for a specific application.3.2.6 non-parallel or longitudinal scana scan wherebythe probe pair motion is perpendicular to the ultrasonic beamaxis.3.2.7 RF waveformsthe non-rectified A-scan.4. Sign
17、ificance and Use4.1 This practice provides general principles for the appli-cation of the Time-of-Flight Diffraction Technique as a tool fordetection and sizing of discontinuities.4.2 TOFD is a nondestructive ultrasonic examination tech-nique that is not based on amplitude response. However,sufficie
18、nt sensitivity is required to identify indications forevaluation.4.3 Techniques used are typically applied to welded joints incarbon steel but the principles may be applicable to otherapplications including other materials with suitable validationprocedures agreeable to the contracting parties.4.4 I
19、n addition to a stand-alone ultrasonic detection tech-nique TOFD may be used in conjunction with weld examina-tions such as those described in Practices E 164 and E 1961where it may be used to improve sizing estimates of flawsdetected by the manual or mechanized pulse-echo techniquesand help discrim
20、inate between flaws and geometric reflectors.4.5 The technique has proven effective on thicknesses from9 to 300 mm (0.375 to 12 in.). TOFD has been used onthicknesses outside of this range but special considerations arenecessary. Techniques developed outside of this range ofthickness shall be demons
21、trated as capable of meeting therequired detection and sizing requirements of the specificationused.5. Basis of Application5.1 The following items are subject to contractual agree-ment between the parties using or referencing this standard.5.2 Personnel Qualification5.2.1 If specified in the contrac
22、tual agreement, personnelperforming examinations to this standard shall be qualified inaccordance 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 certify
23、ing agency,as applicable. The practice or standard used and its applicablerevision shall be identified in the contractual agreement be-tween the using parties.5.3 Qualification of Nondestructive AgenciesIf specifiedin the contractual agreement, NDT agencies shall be qualifiedand evaluated as describ
24、ed in E 543. The applicable edition ofE 543 shall be specified in the contractual agreement.5.4 Procedures and TechniquesThe procedures and tech-niques to be used shall be as specified in the contractualagreement.5.5 Surface PreparationThe pre-examination surfacepreparation criteria shall be in acco
25、rdance with 6.3 unlessotherwise specified.5.6 Timing of ExaminationThe timing of examinationshall be in accordance with 6.3 unless otherwise specified.5.7 Extent of ExaminationThe extent of examination shallbe in accordance with 6.3 unless otherwise specified.5.8 Reporting Criteria/Acceptance Criter
26、iaReporting cri-teria for the examination results shall be in accordance withSection 8 unless otherwise specified. Since acceptance criteria(for example, for reference radiographs) are not specified inthis practice, they shall be specified in the contractual agree-ment.5.9 Re-examination of Repaired
27、/Reworked ItemsReexamination of repaired/reworked items is not addressed inthis standard and if required shall be specified in the contrac-tual agreement.6. Procedures6.1 Introduction:6.1.1 TOFD is an ultrasonic examination technique that canprovide improved detection and sizing capabilities of disc
28、on-tinuities compared to standard ultrasonic pulse-echo tech-niques. It uses forward scattered tip diffraction and reflection oftransmitted ultrasonic pulses. This document describes therequirements for TOFD equipment and procedures on flat platesurfaces. Guidance for more complex geometries is prov
29、ided intheAppendix. General guidance on TOFD can also be found inBritish Standards BS 7706. Acceptance criteria typical andperformance demonstration requirements that may be usedwith TOFD techniques are found in ASME Code Case 22357.6.1.2 Because phase inversions of signals play an importantrole in
30、the evaluation of TOFD results, all procedures devel-oped using this practice shall require that the equipmentpresentation use and store RF waveforms.6.1.3 Whether motorized or manually-operated, probe mo-tion must be encoded for position and probes held in a fixturethat maintains correct PCS during
31、 scanning. Time basedsampling of data collection is not acceptable.6.1.4 Fig. 1 illustrates the typical probe configuration for aTOFD examination. The figure uses a weld for convenience ofreferences; however, TOFD need not be restricted to just weldexaminations.6.1.5 The lateral wave and back-wall e
32、cho signals provideconvenient references. For most applications mode convertedsignals from flaws are not used and therefore flaw indicationsare usually recognized as occurring between the lateral waveand back-wall echo signals. Although it is more often the caseto use refracted compression mode in t
33、he examination piece,some applications may produce better results when the incidentangle is greater than the first critical angle, thereby providing arefracted transverse shear mode in the examination piece.When using a refracted compression mode in the examinationpiece the direct shear and head wav
34、es also are generated;however, due to their lower acoustic velocities, shear wavesarrive later in time than the back-wall signal.7Reference to ASME CC2235 is made only as an example of an existing codewhere the mutually agreed upon acceptance criteria allowsTOFD to be applied.Thisdoes not suggest th
35、at application of ASME CC2235 would be appropriate in allcases. It should be recognized that the high sensitivity of the TOFD technique couldresult in indications from reflectors in plate materials that meet all plate ultrasonicspecification requirements. Such indications should not be considered un
36、acceptableunless they fail to meet the acceptance criteria agreed upon in 8.1.E23730926.1.6 Fig. 2 is a sketch of a typical presentation for anon-parallel scan of a butt weld in a plate with an imbeddedflaw. The right side of Fig. 2 illustrates a waveform extractedfrom a B-scan display showing the l
37、ateral wave, upper tipdiffracted, lower tip diffracted and the back-wall echo signals.The left side of Fig. 2 indicates the probe placement withrespect to the weld (upper left) and relative motion of theprobes (a non-parallel scan is indicated).6.1.7 Fig. 3 illustrates an actual TOFD scan with fivei
38、ndications (identified on the left) and an extractedA-scan fromone of the indications.6.2 Written ProcedureA documented examination strat-egy or scan plan shall be provided showing probe placement,movement, and component coverage that provides a standard-ized and repeatable methodology for component
39、 acceptance.The scan plan shall also include ultrasonic beam angle(s) used,beam directions with respect to some reference such as a weldcenterline, and volume examined.6.3 Examination Materials and Surface Preparation:6.3.1 TOFD technique can be applied to both metals andnonmetals. Best results are
40、had on fine-grained isotropicmaterials with low attenuation including some finer grainedaustenitic alloys and aluminum. With suitable validation pro-cedures, agreeable to the contracting parties, coarser-grainedand anisotropic materials may also be examined using TOFD.These usually require additiona
41、l modifications to frequenciesand digital signal processing.6.3.2 The scanning area shall be clear of weld spatter andother conditions which may interfere with the movement of theprobes, the coupling liquid, or the transmission of acousticenergy into the material. Any surface condition such asgeomet
42、ry, coating, and so forth, impeding the ultrasonicexamination shall be noted for corrective action prior toscanning.6.3.3 The TOFD technique may be used with immersion,contact or gap techniques. Single element or phased arraypiezoelectric probes may be used. EMAT or other non-standardprobes may also
43、 be used with suitable validation proceduresagreeable to the contracting parties.6.3.4 The acoustic coupling shall be obtained by using amedium suitable for the purpose and compatible with thematerial being examined. Water, coupling gels or pastes,greases and oils are typically used. Water additives
44、 such asenvironmentally-safe wetting agent and corrosion inhibitorsmay be used to enhance acoustic coupling and protect theexamination piece. For examination where ambient tempera-tures are below 0C (32F) methyl alcohol or similar mediamay be used. For examination at elevated temperatures theexamina
45、tion surface or probes may require cool-down orspecially designed high-temperature couplants. The couplingmedium selected shall provide uniform and reliable examina-tion in the temperature range of intended use. Couplant andscanning conditions, including temperature, used for standard-ization shall
46、be the same as that used in the examination.FIG. 1 TOFD Configuration and Signal OriginsFIG. 2 Schematic Representation of TOFD Scan (Left) and DataDisplay (Right)E23730936.3.5 Examination should occur after welding when thesurface temperature is cooled to less than 40C (100F).Surface preparation sh
47、all be adequate to provide surface accessto examine the entire weld volume and heat affected zones.6.4 Qualification and Certification of PersonnelIf speci-fied in the contractual agreement, personnel performing exami-nations to this practice shall be qualified in accordance with anationally-recogni
48、zed NDT personnel qualification standardand certified by the employer or certifying agency as appli-cable. The practice or standard used and its applicable versionshall be identified in the contractual agreement between theusing parties and should include a requirement for trainingspecific to TOFD.6
49、.5 Equipment RequirementsAn ultrasonic system forTOFD shall provide a means of transmitting, receiving, stor-ing, displaying and analyzing ultrasonic signals. As well, itshall provide a fixed spacing between the transmitting andreceiving probes and ensure that probe motion is encoded andits position maintained within prescribed tolerances with re-spect to a reference position such as the weld centerline.6.5.1 Electronics:6.5.1.1 The instrument shall provide a linear “A” scanpresentation for both setting up scan parameters and for signalanalysis. Instrument line
