1、Designation: E 2192 08Standard 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 () 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 plana
3、r 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 provid
4、e 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.1
5、.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 crite
6、ria.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. Referen
7、ced 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 (L
8、-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 ultrasonic
9、 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 piec
10、eopposite 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 ma
11、ximum 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. (F
12、or 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 incid
13、ent 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 jurisdi
15、ction of ASTM Committee E07 on Nondestruc-tive Testing and is the direct responsibility of Subcommittee E07.06 on UltrasonicMethod.Current edition approved July 1, 2008. Published July 2008. Originally approvedin 2002. Last previous edition approved in 2007 as E 2192 - 07.2This Standard Guide is ada
16、pted 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 practi
19、ces 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 anyoth
20、er 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 w
21、ith 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 no
22、t 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 qualitati
23、velysegregate 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 zone
24、s 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-s
25、urface 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 Wa
26、vesThe 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 (thedirect
28、 shear wave) at an interface. The longitudinal wavecontinuously energizes the shear wave. It can be concluded thatthe longitudinal wave, which in fact “creeps” along the surface,is completely attenuated a short distance from the location ofthe excitation. (See Fig. 2 for generation of the near-sidec
29、reeping wave). With the propagation of the near-surfacecreeping wave and its continuous conversion process at eachpoint it reaches, the energy converted to shear is directed intothe material as shown in Fig. 3. Thus, the wave front of theheadwave includes the head of the creeping wave, direct andind
30、irect 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 forgenerating the shear wave energy, due to the physical law ofreciprocity. Thus, the indirect shear wave and part of
31、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 reflectorsand the longitudinal wave will be engulfed in a bulk longitu-dinal beam created by beam spread. Additional
32、ly, 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 conversion point onthe far surface. The sensitivity range of the far-surface creepingwave extends from approximately
33、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, willconvert its energy into a headwave since the same principlesFIG. 1 Wave Generation for the Far-surface Creeping Wave/30-70-70 Mode-Conversion Search
34、 UnitE2192082apply 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 levels.6.1.3 Typical Echoes of the Far-Surface Creeping Wave/30-70-70 Mode Conversion TechniqueWhen the search unitapp
35、roaches 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 far-surface creeping wave signal, as a result of modeconversion of the indirect shear wave.6.1.3.1 Direct Longitudi
36、nal 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 upper extremity of the flawface, which is very similar to the high-angle longitudinal wavesizing method discussed
37、 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-related position. This mode converted signal resultsfrom the headwave or direct shear wave, which mode convertsthe 70
38、-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. The presence of the mode-converted echo is a strongindication of a flaw with a height greater than 10 to 20 % of th
39、ewall thickness. In the case of smooth or at least open flaws,FIG. 2 Near-Surface Creeping Wave Occurs for a Short Distance in Association with the Incident Longitudinal WaveFIG. 3 Generation of S-Waves (Headwaves) by an L-Wave with Grazing Incidence1Mode-Converted Signal2Far-Surface Creeping-Wave S
40、ignalFIG. 4 Search Unit Index Point PositionE2192083amplitude versus height function curves can give a coarseestimate of flaw height.6.1.3.3 Far-Surface Creeping Wave SignalIf a far-surfaceconnected reflector is within the range of sensitivity (asdescribed above), the far-surface creeping wave will
41、be re-flected and mode converted into the headwave or shear wavedirected to the search unit (Fig. 5). Since the far-surfacecreeping wave is not a surface wave, it will not interact withweld root convexity and will not produce an indication fromthe root as shown by position 1 in Fig. 6. However, if t
42、hesearch 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 inFig. 6. The far-surface creeping wave signal is a clear, sharpsignal with a larger amplitude than the mode conv
43、erted 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 MethodUltrasonic diffraction is a phe-nomenon where ultrasound tends to bend around sharp cornersor ends of an ob
44、ject 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. Sharp edges are diffraction centers tending to radiatespherical or cylindrical wave fronts as though they wereac
45、tually 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 ofthe component. The tip-diffraction method relies on thisprinciple. Although the tip-diffraction concept sounds
46、 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 aflaw, specular reflection from the main plane of the flaw andtexture reflections from flaw surface facets occur
47、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 arrivaltime of the tip-diffracted signal from the top of the flaw andlocates the top of the flaw with respect to
48、 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 surface.6.2.1 Time of Flight (TOF) Sizing TechniqueThe TOFsizing technique is a tip-diffraction technique that takes
49、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 path is possible also. When the search unit is movedaway from the flaw, the tip echo may again be obtained after
copyright@ 2008-2019 麦多课文库（www.mydoc123.com）网站版权所有
备案/许可证编号：苏ICP备17064731号-1