ASTM E2192-02
(Guide)Standard Guide for Planar Flaw Height Sizing by Ultrasonics
Standard Guide for Planar Flaw Height Sizing by Ultrasonics
SCOPE
1.1 This guide provides tutorial information and a description of the principles and ultrasonic examination techniques for measuring the height of planar flaws which are open to the surface. The practices and technology described in this standard guide are intended as a reference to be used when selecting a specific ultrasonic flaw sizing technique as well as establishing a means for instrument standardization.
1.2 This standard guide does not provide or suggest accuracy or tolerances of the techniques described. Parameters such as search units, examination surface conditions, material composition, etc. can all have a bearing on the accuracy of results. It is recommended that users assess accuracy and tolerances applicable for each application.
1.3 This document does not purport to provide instruction to measure flaw length.
1.4 This standard guide does not provide, suggest, or specify acceptance standards. After flaw-sizing evaluation has been made, the results should be applied to an appropriate code or standard that specifies acceptance criteria.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.
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Designation: E 2192 – 02
Standard Guide for
Planar Flaw Height Sizing by Ultrasonics
This standard is issued under the fixed designation E 2192; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2.2 corner reflector—the reflected ultrasonic energy re-
sulting from the interaction of ultrasound with the intersection
1.1 This guide provides tutorial information and a descrip-
of a flaw and the component surface at essentially 90 degrees.
tionoftheprinciplesandultrasonicexaminationtechniquesfor
3.2.3 creeping wave—a compression wave that travels in a
measuring the height of planar flaws which are open to the
solid immediately adjacent to a free boundary and generates a
surface. The practices and technology described in this stan-
shear mode “headwave” (q.v.) traveling away from the bound-
dard guide are intended as a reference to be used when
ary at the critical angle. (Some users reserve the term lateral
selecting a specific ultrasonic flaw sizing technique as well as
waveforthecreepingwavefollowingaflatparallelsurfaceand
establishing a means for instrument standardization.
the creeping wave is used for those waves following curved
1.2 This standard guide does not provide or suggest accu-
surfaces).
racy or tolerances of the techniques described. Parameters such
3.2.4 doublet—two ultrasonic signals that appear on the
as search units, examination surface conditions, material com-
screen simultaneously and move in unison as search unit is
position, etc. can all have a bearing on the accuracy of results.
manipulated toward and away from the flaw. During tip-
It is recommended that users assess accuracy and tolerances
diffraction flaw sizing, the flaw tip signal and flaw base signal
applicable for each application.
(corner reflector) will appear as a doublet.
1.3 Thisdocumentdoesnotpurporttoprovideinstructionto
3.2.5 echo-dynamic—the amplitude versus time of arrival
measure flaw length.
(or distance through the component) curve created by the
1.4 This standard guide does not provide, suggest, or
ultrasonic signal as the search unit is moved perpendicular to
specify acceptance standards. After flaw-sizing evaluation has
the reflector toward and away from the flaw.
beenmade,theresultsshouldbeappliedtoanappropriatecode
3.2.6 far-surface—the surface of the examination piece
or standard that specifies acceptance criteria.
opposite the surface on which the search unit is placed. (For
1.5 This standard does not purport to address all of the
example, when examining pipe from the outside surface the
safety concerns, if any, associated with its use. It is the
far-surface would be the inside pipe surface).
responsibility of the user of this standard to establish appro-
3.2.7 focus—the term as used in this document applies to
priate safety and health practices and determine the applica-
dualcrossed-beamsearchunitsthathavebeenmanufacturedso
bility of regulatory requirements prior to use.
that they have a maximum sensitivity at a predetermined depth
2. Referenced Documents
or sound path in the component. Focusing effect may be
obtained with the use of dual-element search units having both
2.1 ASTM Standards:
refracted and roof angles applied to each element.
E 1316 Terminology for Nondestructive Examinations
3.2.8 headwave—a shear wave that is generated by mode
3. Terminology
conversionwhenacompressionwavetravelsatagrazingangle
on a free solid surface.
3.1 Definitions—Related terminology is defined in Termi-
3.2.9 insonify—the interrogation of an area in the examina-
nology E 1316.
tion piece with ultrasonic energy.
3.2 Definitions of Terms Specific to This Standard:
3.2.10 near-surface—the surface of the examination piece
3.2.1 bi-modal—ultrasonic examination method that uti-
on which the search unit is placed. (For example, when
lizes both the longitudinal (L-wave) and shear (S-wave) modes
examining pipe from the outside surface the near-surface
of propagation in order to estimate or measure flaw height.
would be the outside pipe surface).
3.2.11 sizing—measurement of the through-wall height or
This guide is under the jurisdiction of ASTM Committee E07 on Nondestruc-
depth dimension of a discontinuity or flaw.
tive Testing and is the direct responsibility of Subcommittee E07.06 on Ultrasonic
3.2.12 time of flight—the sound path measurement of time
Method.
for the reflected or diffracted energy from a flaw.
Current edition approved April 10, 2002. Published June 2002.
ThisStandardGuideisadaptedfrommaterialsuppliedtoASTMSubcommittee
E07.06 by the Electric Power Research Institute (EPRI).
Annual Book of ASTM Standards, Vol 03.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2192–02
3.2.13 30-70-70—term that is applied to the technique (and 5.4 Generally, with these sizing methods the volume of
sometimes the search unit) using an incident angle that material (or component thickness) to be sized is divided into
1 1 1
produces a nominal 70° L wave in the examination piece.
thirds; the inner ⁄3 , the middle ⁄3 and the outer ⁄3 . Using the
Provided that a parallel far-surface exists, the 30° shear wave,
far-surface Creeping Wave Method the user can qualitatively
produced simultaneously at the refracting interface, reflects as
segregate the flaw into the approximate ⁄3 zone.
a 30° shear wave and generates a nominal 70° L wave as a
5.5 The sizing methods are used in ⁄3 zones to quantita-
result of mode conversion off the far-surface. The 70° L wave
tively size the crack, that is, Tip-diffraction for the inner ⁄3 ,
reflects off a planar flaw and is received by the search unit as
Bi-Modal method for the middle ⁄3 , and the Focused Longi-
a 70° L wave.
tudinal Wave or Focused Shear Wave Methods for the outer ⁄3
. These ⁄3 zones are generally applicable to most sizing
4. Summary of Guide
applications, however, the various sizing methods have appli-
4.1 This guide describes methods for the following flaw
cations outside these ⁄3 zones provided a proper reference
sizing techniques.
block and technique is demonstrated.
4.1.1 Far-surface creeping wave or mode conversion
method,
6. Ultrasonic Flaw Sizing Methods
4.1.2 Flaw-tip-diffraction method,
6.1 30-70-70 Mode Conversion or Far-surface Creeping
4.1.3 Dual element bi-modal method, and
Wave Method—The far-surface Creeping Wave or 30-70-70
4.1.4 Dual element, (focused) longitudinal wave or dual
Mode Conversion method (as illustrated in Fig. 1) provides
element, (focused) shear wave methods (see 3.2.8).
qualitative additional depth sizing information. This method
4.2 In this guide, ultrasonic sound paths are generally
has considerable potential for use when approximating flaw
shown diagrammatically by single lines in one plane that
size, or, determining that the flaw is far-surface connected.
represent the center of the ultrasonic energy.
6.1.1 Excitation of Creeping Waves—The excitation of
4.3 Additional information on flaw sizing techniques may
refracted longitudinal waves is always accompanied by re-
be found in the references listed in the Bibliography section.
fracted shear waves. In the vicinity of the excitation, the
5. Significance and Use separation between these two wave modes is not significantly
distinct. At the surface, a longitudinal wave cannot exist
5.1 The practices referenced in this document are applicable
independently of a shear wave because neither mode can
to measuring the height of planar flaws open to the surface that
comply with the boundary conditions for the homogeneous
originate on the far-surface or near-surface of the component.
wave equation at the free surface alone; consequently, the
These practices are applicable to through-wall sizing of me-
so-called headwave is formed. The headwave is always gen-
chanical or thermal fatigue flaws, stress corrosion flaws, or any
erated if a wave mode with higher velocity (the longitudinal
other surface-connected planar flaws.
wave) is coupled to a wave mode with lower velocity (the
5.2 The techniques outlined describe proven ultrasonic flaw
direct shear wave) at an interface. The existence of the indirect
sizingpracticesandtheirassociatedlimitations,usingrefracted
shearwave,headwave,hasalsobeenprovenexperimentallyby
longitudinal wave and shear wave techniques as applied to
Schlierenoptics.Thelongitudinalwavecontinuouslyenergizes
ferritic or austenitic components. Other materials may be
the shear wave. It can be concluded that the longitudinal wave,
examined using this guide with appropriate standardization
which in fact “creeps” along the surface, is completely attenu-
referenceblocks.Thepracticesdescribedareapplicabletoboth
ated a short distance from the location of the excitation. (See
manual and automated examinations.
5.3 The techniques recommended in this standard guide use Fig. 2 for generation of the near-side creeping wave). With the
Time of Flight (TOF) or Delta Time of Flight (· TOF) methods propagation of the near-surface creeping wave and its continu-
toaccuratelymeasuretheflawsize.Thisguidedoesnotinclude ous conversion process at each point it reaches, the energy
the use of signal amplitude methods to determine flaw size. converted to shear is directed into the material as shown in Fig.
FIG. 1 Wave Generation for the Far-surface Creeping Wave/30-70-70 Mode-Conversion Search Unit
E2192–02
FIG. 2 Near-Surface Creeping Wave Occurs for a Short Distance in Association with the Incident Longitudinal Wave
3. Thus, the wave front of the headwave includes the head of 6.1.3.1 Direct Longitudinal Wave Signal—If the flaw ex-
the creeping wave, direct and indirect shear waves. tends to within approximately 0.375 to 0.625 in. (9.5 to 15.9
6.1.2 Far-Surface Creeping Wave Generation—When the mm) of the scanning surface (near surface), the direct longitu-
headwave arrives at the far-surface of the component, the same dinal wave will reflect from the upper extremity of the flaw
wave modes will be generated which were responsible for face, which is very similar to the high-angle longitudinal wave
generating the shear wave energy, due to the physical law of sizing method discussed later.
reciprocity. Thus, the indirect shear wave and part of the direct 6.1.3.2 Mode Converted Signal—If the flaw exceeds a
shear wave will convert into a far-surface creeping wave and a height of 10 to 20 % of the wall thickness, an indication from
70-degree longitudinal wave. The far-surface creeping wave the mode converted signal will occur at a typical wall
will be extremely sensitive to small surface-breaking reflectors thickness-related position. This mode converted signal results
and the longitudinal wave will be engulfed in a bulk longitu- from the headwave or direct shear wave, which mode converts
dinal beam created by beam spread. Additionally, these reflec- the 70-degree longitudinal wave that impinges on the reflector
tion mechanisms are responsible for a beam offset so that there at its highest part; it is reflected as a 70-degree longitudinal
is a maximum far-surface creeping wave sensitivity at about 5 wave back to the search unit as depicted by position 1 in Fig.
to 6 mm (0.20 to 0.24 in.) from the ideal conversion point on 4. The presence of the mode-converted echo is a strong
thefarsurface.Thesensitivityrangeofthefar-surfacecreeping indicationofaflawwithaheightgreaterthan10to20 %ofthe
wave extends from approximately 2 to 13 mm (0.080 to 0.52 wall thickness. In the case of smooth or at least open flaws,
in.) in front of the index point. The far-surface creeping wave, amplitude versus height function curves can give a coarse
as reflected from the base of a far-surface notch or flaw, will estimate of flaw height.
convert its energy into a headwave since the same principles 6.1.3.3 Far-Surface Creeping Wave Signal—If a far-surface
apply as established earlier for the near-surface creeping wave. connected reflector is within the range of sensitivity (as
The shear wave will continue to convert at multiple V-paths if described above), the far-surface creeping wave will be re-
the material has low attenuation and noise levels. flected and mode converted into the headwave or shear wave
6.1.3 Typical Echoes of the Far-Surface Creeping Wave/30- directed to the search unit (Fig. 5). Since the far-surface
70-70 Mode Conversion Technique—When the search unit creeping wave is not a surface wave, it will not interact with
approaches a far-surface connected reflector, three different weld root convexity and will not produce an indication from
signalswilloccurinsequence:(1)70-degreelongitudinalwave the root as shown by position 1 in Fig. 6. However, if the
direct reflection; (2) 30-70-70 mode-converted signal; and (3) search unit is moved too far toward the weld centerline, the
A far-surface creeping wave signal, as a result of mode direct shear wave beam could result in a root signal, but there
conversion of the indirect shear wave. is at least 5 mm (0.2 in.) difference in positioning as shown in
FIG. 3 Generation of S-Waves (Headwaves) by an L-Wave with Grazing Incidence
E2192–02
1—Mode-Converted Signal
2—Far-Surface Creeping-Wave Signal
FIG. 4 Search Unit Index Point Position
FIG. 5 Generation of Far-Surface Creeping Wave Signal
Fig. 6. The far-surface creeping wave signal is a clear, sharp diffraction and mode conversions. There are two standardiza-
signal with a larger amplitude than the mode converted signal.
tion and measuring techniques for tip-diffraction sizing: (1)
It does not have as smooth an echo-dynamic behavior as does
The Time of Flight (TOF) technique that measures the arrival
the mode converted signal, and it cannot be observed over as
time of the tip-diffracted signal from the top of the flaw and
long a distance as shown in Fig. 7.
locates the top of the flaw with respect to the near surface; and
6.2 Tip-Diffraction Method—Ultrasonic diffraction is a phe-
(2) The Delta Time of Flight (· TOF) technique that measures
nomenon where ultrasound tends to bend around sharp corners
the difference in arrival time of the tip-diffracted signal and the
or ends of an object placed in its path, as illustrated in Fig. 8.
corner reflector signal at the far surface.
While the flaw tends to cast a shadow, diffraction occurs at the
6.2.1 Time of Flight (TOF) Sizing Technique—The TOF
flaw tips and ultrasonic energy is bent to fill part of the shadow
sizing technique is a tip-diffraction technique that takes advan-
region. Sharp ed
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