ASTM E2192-2007 Standard Guide for Planar Flaw Height Sizing by Ultrasonics《用超声波法测定平面裂纹高度尺寸的标准指南》.pdf

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1、Designation: E 2192 07Standard Guide forPlanar Flaw Height Sizing by Ultrasonics1This standard is issued under the fixed designation E 2192; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in par

2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide provides tutorial information and a descrip-tion of the principles and ultrasonic examination techniques formeasuring the height of plan

3、ar flaws which are open to thesurface. The practices and technology described in this stan-dard guide are intended as a reference to be used whenselecting a specific ultrasonic flaw sizing technique as well asestablishing a means for instrument standardization.21.2 This standard guide does not provi

4、de or suggest accu-racy or tolerances of the techniques described. Parameters suchas search units, examination surface conditions, material com-position, etc. can all have a bearing on the accuracy of results.It is recommended that users assess accuracy and tolerancesapplicable for each application.

5、1.3 This document does not purport to provide instruction tomeasure flaw length.1.4 This standard guide does not provide, suggest, orspecify acceptance standards. After flaw-sizing evaluation hasbeen made, the results should be applied to an appropriate codeor standard that specifies acceptance crit

6、eria.1.5 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 requirements prior to use.2. Refere

7、nced Documents2.1 ASTM Standards:3E 1316 Terminology for Nondestructive Examinations3. Terminology3.1 DefinitionsRelated terminology is defined in Termi-nology E 1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 bi-modalultrasonic examination method that uti-lizes both the longitudinal (

8、L-wave) and shear (S-wave) modesof propagation in order to estimate or measure flaw height.3.2.2 corner reflectorthe reflected ultrasonic energy re-sulting from the interaction of ultrasound with the intersectionof a flaw and the component surface at essentially 90 degrees.3.2.3 doublettwo ultrasoni

9、c signals that appear on thescreen simultaneously and move in unison as search unit ismanipulated toward and away from the flaw. During tip-diffraction flaw sizing, the flaw tip signal and flaw base signal(corner reflector) will appear as a doublet.3.2.4 far-surfacethe surface of the examination pie

10、ceopposite the surface on which the search unit is placed. (Forexample, when examining pipe from the outside surface thefar-surface would be the inside pipe surface).3.2.5 focusthe term as used in this document applies todual crossed-beam search units that have been manufactured sothat they have a m

11、aximum sensitivity at a predetermined depthor sound path in the component. Focusing effect may beobtained with the use of dual-element search units having bothrefracted and roof angles applied to each element.3.2.6 near-surfacethe surface of the examination piece onwhich the search unit is placed. (

12、For example, when examiningpipe from the outside surface the near-surface would be theoutside pipe surface).3.2.7 sizingmeasurement of the through-wall height ordepth dimension of a discontinuity or flaw.3.2.8 30-70-70term that is applied to the technique (andsometimes the search unit) using an inci

13、dent angle thatproduces a nominal 70 L wave in the examination piece.Provided that a parallel far-surface exists, the 30 shear wave,produced simultaneously at the refracting interface, reflects asa 30 shear wave and generates a nominal 70 L wave as aresult of mode conversion off the far-surface. The

14、 70 L wavereflects off a planar flaw and is received by the search unit asa 70 L wave.4. Summary of Guide4.1 This guide describes methods for the following flawsizing techniques.4.1.1 Far-surface creeping wave or mode conversionmethod,4.1.2 Flaw-tip-diffraction method,1This guide is under the jurisd

15、iction of ASTM Committee E07 on Nondestruc-tive Testing and is the direct responsibility of Subcommittee E07.06 on UltrasonicMethod.Current edition approved July 1, 2007. Published July 2007. Originally approvedin 2002. Last previous edition approved in 2002 as E 2192 - 02.2This Standard Guide is ad

16、apted from material supplied toASTM SubcommitteeE07.06 by the Electric Power Research Institute (EPRI).3For 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

17、 Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.3 Dual element bi-modal method, and4.1.4 Dual element, (focused) longitudinal wave or dualelement, (focused) shear wave methods.4.2 In this

18、 guide, ultrasonic sound paths are generallyshown diagrammatically by single lines in one plane thatrepresent the center of the ultrasonic energy.4.3 Additional information on flaw sizing techniques maybe found in the references listed in the Bibliography section.5. Significance and Use5.1 The pract

19、ices referenced in this document are applicableto measuring the height of planar flaws open to the surface thatoriginate on the far-surface or near-surface of the component.These practices are applicable to through-wall sizing of me-chanical or thermal fatigue flaws, stress corrosion flaws, or anyot

20、her surface-connected planar flaws.5.2 The techniques outlined describe proven ultrasonic flawsizing practices and their associated limitations, using refractedlongitudinal wave and shear wave techniques as applied toferritic or austenitic components. Other materials may beexamined using this guide

21、with appropriate standardizationreference blocks. The practices described are applicable to bothmanual and automated examinations.5.3 The techniques recommended in this standard guide useTime of Flight (TOF) or Delta Time of Flight (DTOF) methodsto accurately measure the flaw size. This guide does n

22、ot includethe use of signal amplitude methods to determine flaw size.5.4 Generally, with these sizing methods the volume ofmaterial (or component thickness) to be sized is divided intothirds; the inner13 , the middle13 and the outer13 . Using thefar-surface Creeping Wave Method the user can qualitat

23、ivelysegregate the flaw into the approximate13 zone.5.5 The sizing methods are used in13 zones to quantita-tively size the crack, that is, Tip-diffraction for the inner13 ,Bi-Modal method for the middle13 , and the Focused Longi-tudinal Wave or Focused Shear Wave Methods for the outer13. These13 zon

24、es are generally applicable to most sizingapplications, however, the various sizing methods have appli-cations outside these13 zones provided a proper referenceblock and technique is demonstrated.6. Ultrasonic Flaw Sizing Methods6.1 30-70-70 Mode Conversion or Far-surface CreepingWave MethodThe far-

25、surface Creeping Wave or 30-70-70Mode Conversion method (as illustrated in Fig. 1) providesqualitative additional depth sizing information. This methodhas considerable potential for use when approximating flawsize, or, determining that the flaw is far-surface connected.6.1.1 Excitation of Creeping W

26、avesThe excitation ofrefracted longitudinal waves is always accompanied by re-fracted shear waves. In the vicinity of the excitation, theseparation between these two wave modes is not significantlydistinct. At the surface, a longitudinal wave cannot existindependently of a shear wave because neither

27、 mode cancomply with the boundary conditions for the homogeneouswave equation at the free surface alone; consequently, theso-called headwave is formed. The headwave is always gen-erated if a wave mode with higher velocity (the longitudinalwave) is coupled to a wave mode with lower velocity (thedirec

28、t shear wave) at an interface. The existence of the indirectshear wave, headwave, has also been proven experimentally bySchlieren optics. The longitudinal wave continuously energizesthe shear wave. It can be concluded that the longitudinal wave,which in fact “creeps” along the surface, is completely

29、 attenu-ated a short distance from the location of the excitation. (SeeFig. 2 for generation of the near-side creeping wave). With thepropagation of the near-surface creeping wave and its continu-ous conversion process at each point it reaches, the energyconverted to shear is directed into the mater

30、ial as shown in Fig.3. Thus, the wave front of the headwave includes the head ofthe creeping wave, direct and indirect shear waves.6.1.2 Far-Surface Creeping Wave GenerationWhen theheadwave arrives at the far-surface of the component, the samewave modes will be generated which were responsible forge

31、nerating the shear wave energy, due to the physical law ofreciprocity. Thus, the indirect shear wave and part of the directshear wave will convert into a far-surface creeping wave and a70-degree longitudinal wave. The far-surface creeping wavewill be extremely sensitive to small surface-breaking ref

32、lectorsand the longitudinal wave will be engulfed in a bulk longitu-dinal beam created by beam spread. Additionally, these reflec-tion mechanisms are responsible for a beam offset so that thereis a maximum far-surface creeping wave sensitivity at about 5to 6 mm (0.20 to 0.24 in.) from the ideal conv

33、ersion point onthe far surface. The sensitivity range of the far-surface creepingwave extends from approximately 2 to 13 mm (0.080 to 0.52in.) in front of the index point. The far-surface creeping wave,as reflected from the base of a far-surface notch or flaw, willFIG. 1 Wave Generation for the Far-

34、surface Creeping Wave/30-70-70 Mode-Conversion Search UnitE2192072convert its energy into a headwave since the same principlesapply as established earlier for the near-surface creeping wave.The shear wave will continue to convert at multiple V-paths ifthe material has low attenuation and noise level

35、s.6.1.3 Typical Echoes of the Far-Surface Creeping Wave/30-70-70 Mode Conversion TechniqueWhen the search unitapproaches a far-surface connected reflector, three differentsignals will occur in sequence: (1) 70-degree longitudinal wavedirect reflection; (2) 30-70-70 mode-converted signal; and (3)A fa

36、r-surface creeping wave signal, as a result of modeconversion of the indirect shear wave.6.1.3.1 Direct Longitudinal Wave SignalIf the flaw ex-tends to within approximately 0.375 to 0.625 in. (9.5 to 15.9mm) of the scanning surface (near surface), the direct longitu-dinal wave will reflect from the

37、upper extremity of the flawface, which is very similar to the high-angle longitudinal wavesizing method discussed later.6.1.3.2 Mode Converted SignalIf the flaw exceeds aheight of 10 to 20 % of the wall thickness, an indication fromthe mode converted signal will occur at a typical wallthickness-rela

38、ted position. This mode converted signal resultsfrom the headwave or direct shear wave, which mode convertsthe 70-degree longitudinal wave that impinges on the reflectorat its highest part; it is reflected as a 70-degree longitudinalwave back to the search unit as depicted by position 1 in Fig.4. Th

39、e presence of the mode-converted echo is a strongindication of a flaw with a height greater than 10 to 20 % of thewall thickness. In the case of smooth or at least open flaws,amplitude versus height function curves can give a coarseestimate of flaw height.6.1.3.3 Far-Surface Creeping Wave SignalIf a

40、 far-surfaceconnected reflector is within the range of sensitivity (asdescribed above), the far-surface creeping wave will be re-flected and mode converted into the headwave or shear waveFIG. 2 Near-Surface Creeping Wave Occurs for a Short Distance in Association with the Incident Longitudinal WaveF

41、IG. 3 Generation of S-Waves (Headwaves) by an L-Wave with Grazing Incidence1Mode-Converted Signal2Far-Surface Creeping-Wave SignalFIG. 4 Search Unit Index Point PositionE2192073directed to the search unit (Fig. 5). Since the far-surfacecreeping wave is not a surface wave, it will not interact withwe

42、ld root convexity and will not produce an indication fromthe root as shown by position 1 in Fig. 6. However, if thesearch unit is moved too far toward the weld centerline, thedirect shear wave beam could result in a root signal, but thereis at least 5 mm (0.2 in.) difference in positioning as shown

43、inFig. 6. The far-surface creeping wave signal is a clear, sharpsignal with a larger amplitude than the mode converted signal.It does not have as smooth an echo-dynamic behavior as doesthe mode converted signal, and it cannot be observed over aslong a distance as shown in Fig. 7.6.2 Tip-Diffraction

44、MethodUltrasonic diffraction is a phe-nomenon where ultrasound tends to bend around sharp cornersor ends of an object placed in its path, as illustrated in Fig. 8.While the flaw tends to cast a shadow, diffraction occurs at theflaw tips and ultrasonic energy is bent to fill part of the shadowregion.

45、 Sharp edges are diffraction centers tending to radiatespherical or cylindrical wave fronts as though they wereactually ultrasonic point or line sources. If the screen signalscorrelating to these diffraction centers are identified, it ispossible to determine their positions relative to the thickness

46、 ofthe component. The tip-diffraction method relies on thisprinciple. Although the tip-diffraction concept sounds simple,there are many other signals that may complicate screeninterpretation. This is due to the fact that the ultrasound/planarflaw interaction is very complex. When ultrasound strikes

47、aflaw, specular reflection from the main plane of the flaw andtexture reflections from flaw surface facets occur in addition todiffraction and mode conversions. There are two standardiza-tion and measuring techniques for tip-diffraction sizing: (1)The Time of Flight (TOF) technique that measures the

48、 arrivaltime of the tip-diffracted signal from the top of the flaw andlocates the top of the flaw with respect to the near surface; and(2) The Delta Time of Flight (DTOF) technique that measuresthe difference in arrival time of the tip-diffracted signal and thecorner reflector signal at the far surf

49、ace.6.2.1 Time of Flight (TOF) Sizing TechniqueThe TOFsizing technique is a tip-diffraction technique that takes advan-tage of uniquely locating the flaw tip. The signal from the flawtip is peaked (maximized), and its arrival time or sound path ismeasured without regard to the arrival time of other signals.This time of flight or sound path is then a direct measurementof the remaining ligament (material) above the flaw, or thedistance from the flaw tip to the examination surface. Thistechnique is illustrated in Fig. 9. Note that here the secondhalf-V