ASTM E1001-21

Standard Practice for Detection and Evaluation of Discontinuities by the Immersed Pulse-Echo Ultrasonic Method Using Longitudinal Waves

SIGNIFICANCE AND USE
6.1 This practice provides guidelines for the application of immersed longitudinal wave examination to the detection and quantitative evaluation of discontinuities in materials.  
6.2 Although not all requirements of this practice can be applied universally to all examination situations and materials, it does provide a basis for establishing contractual criteria between suppliers and purchasers of materials for performing immersed pulse-echo examination, and may be used as a general guide for writing detailed specifications for particular applications.  
6.3 This practice is directed towards the evaluation of discontinuities detectable at normal beam incidence. If discontinuities at other orientations are of concern, alternate scanning techniques are required.
SCOPE
1.1 This practice describes procedures for the ultrasonic examination of bulk materials or parts by transmitting pulsed, longitudinal waves through a liquid couplant into the material and observing the indications of reflected waves (see Fig. 1). It covers only examinations in which one search unit is used as both transmitter and receiver (pulse-echo) and in which the part or material being examined is coupled to the part by a liquid column or is totally submerged in the couplant (either method is considered to be immersion testing). This practice includes general requirements and procedures which may be used for detecting discontinuities and for making a relative or approximate evaluation of the size of discontinuities.
FIG. 1 Basic Immersion Setup  
1.2 This practice replaces Practice E214 and provides more detailed procedures for the selection, standardization, and operation of an examination system and for evaluation of the indications obtained.  
1.3 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2021
• ICS: 19.100 - Non-destructive testing
• Technical Committee: E07 - Nondestructive Testing
• Drafting Committee: E07.06 - Ultrasonic Method

Relations

• Refers: ASTM E1316-24 - Standard Terminology for <?Pub Dtl?>Nondestructive Examinations
• Effective Date: 01-Feb-2024
• Refers: ASTM E1316-19b - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2019
• Refers: ASTM E1316-19 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Mar-2019
• Refers: ASTM E1316-18 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jan-2018
• Refers: ASTM E1316-17a - Standard Terminology for Nondestructive Examinations
• Effective Date: 15-Jun-2017
• Refers: ASTM E1316-17 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2017
• Refers: ASTM E1316-16a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Aug-2016
• Refers: ASTM E1316-16 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Feb-2016
• Refers: ASTM E1316-15a - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2015
• Refers: ASTM E1316-15 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Sep-2015
• Refers: ASTM C1212-98(2015) - Standard Practice for Fabricating Ceramic Reference Specimens Containing Seeded Voids (Withdrawn 2018)
• Effective Date: 01-Jan-2015
• Refers: ASTM E1316-14 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM E1316-14e1 - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Jun-2014
• Refers: ASTM C1336-96(2014) - Standard Practice for Fabricating Non-Oxide Ceramic Reference Specimens Containing Seeded Inclusions (Withdrawn 2018)
• Effective Date: 01-Jan-2014
• Refers: ASTM E1316-13d - Standard Terminology for Nondestructive Examinations
• Effective Date: 01-Dec-2013

Overview

ASTM E1001-21: Standard Practice for Detection and Evaluation of Discontinuities by the Immersed Pulse-Echo Ultrasonic Method Using Longitudinal Waves establishes recognized guidelines for using pulse-echo ultrasonic testing (UT) in immersion, focusing on the detection and evaluation of material discontinuities. Issued by ASTM International, this standard provides a practical foundation for nondestructive testing (NDT) using immersed longitudinal ultrasonic waves, helping suppliers and purchasers define contractual requirements for evaluating bulk materials or parts. The immersion pulse-echo ultrasonic method is especially valued for its ability to detect subsurface flaws in a wide range of materials, contributing to enhanced material quality, safety, and compliance.

Key Topics

• Ultrasonic Immersion Technique: The standard outlines procedures for fully or partially submerging the test piece and ultrasonic search unit in a liquid couplant, ensuring optimal sound transmission and sensitivity when detecting discontinuities.
• Pulse-Echo Method: Focuses on transmitting ultrasonic pulses and receiving echoes through a single search unit, with evaluation based on reflected signals to identify internal flaws.
• Reference Standards and Calibration: Covers the use of reference blocks and artificial reflectors to establish equipment calibration, allowing reliable detection and size estimation of discontinuities.
• System Setup and Scanning Procedures: Provides detailed steps for tank setup, calibration of the system, proper alignment, adjustment of gain settings, and control of scanning parameters such as speed and coverage.
• Evaluation and Acceptance Criteria: Outlines the process for evaluating detected indications, comparative sizing using reference standards, and the criteria for reporting and acceptance.
• Personnel and Agency Qualification: Recommends that NDT practitioners and agencies follow recognized qualification and certification standards (e.g., SNT-TC-1A, ISO 9712).

Applications

ASTM E1001-21 is widely used in industries where the quality and integrity of materials are critical. Practical applications include:

• Aerospace and Defense: Inspection of critical aircraft components, including bar stock, forgings, and plate materials, to ensure the absence of harmful internal flaws.
• Automotive Manufacturing: Non-destructive inspection of engine and structural parts for safety and performance.
• Metallurgy and Heavy Industry: Evaluation of castings, weldments, and rolled products, ensuring product reliability.
• Advanced Ceramics and Composites: Tailoring procedures based on material-specific needs, especially for high-performance and non-metallic materials.
• Quality Assurance in Manufacturing: Enables reliable, repeatable assessment of products prior to delivery, supporting customer and regulatory requirements.

Related Standards

When applying ASTM E1001-21, the following related standards and references are frequently consulted:

• ASTM E127 - Practice for Fabrication and Control of Flat Bottomed Hole Ultrasonic Standard Reference Blocks
• ASTM E214 - Practice for Immersed Ultrasonic Testing by the Reflection Method Using Pulsed Longitudinal Waves (Withdrawn)
• ASTM E317 - Practice for Evaluating Performance Characteristics of Ultrasonic Pulse-Echo Testing Instruments and Systems
• ASTM E543 - Specification for Agencies Performing Nondestructive Testing
• ASTM E1316 - Terminology for Nondestructive Examinations
• ASNT SNT-TC-1A and ISO 9712 - Qualification and certification of NDT personnel

Practical Value

ASTM E1001-21 delivers standardized procedures that enhance the reliability and repeatability of ultrasonic immersion inspections, reduce misinterpretation of results, and provide a basis for clear contractual agreements in material supply chains. Its use promotes safety, regulatory compliance, and improved product quality across multiple industries. By adhering to the procedures and referenced standards, organizations can ensure effective detection and evaluation of subsurface discontinuities, build customer confidence, and minimize the risk of material failure.

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Keywords: ASTM E1001-21, ultrasonic immersion, pulse-echo method, nondestructive testing, longitudinal waves, discontinuity detection, material evaluation, reference standards, quality assurance, NDT personnel qualification.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1001 − 21
Standard Practice for
Detection and Evaluation of Discontinuities by the
Immersed Pulse-Echo Ultrasonic Method Using Longitudinal
Waves
This standard is issued under the fixed designation E1001; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2. Referenced Documents
1.1 This practice describes procedures for the ultrasonic 2.1 ASTM Standards:
examination of bulk materials or parts by transmitting pulsed, C1212 Practice for Fabricating Ceramic Reference Speci-
longitudinal waves through a liquid couplant into the material mens Containing Seeded Voids (Withdrawn 2018)
and observing the indications of reflected waves (see Fig. 1). It C1336 Practice for Fabricating Non-Oxide Ceramic Refer-
covers only examinations in which one search unit is used as ence Specimens Containing Seeded Inclusions (With-
bothtransmitterandreceiver(pulse-echo)andinwhichthepart drawn 2018)
or material being examined is coupled to the part by a liquid E127 Practice for Fabrication and Control of Flat Bottomed
column or is totally submerged in the couplant (either method Hole Ultrasonic Standard Reference Blocks
is considered to be immersion testing). This practice includes E214 Practice for Immersed Ultrasonic Testing by the Re-
general requirements and procedures which may be used for flection Method Using Pulsed Longitudinal Waves (With-
detecting discontinuities and for making a relative or approxi- drawn 2007)
mate evaluation of the size of discontinuities. E317 Practice for Evaluating Performance Characteristics of
Ultrasonic Pulse-Echo Testing Instruments and Systems
1.2 This practice replaces Practice E214 and provides more
without the Use of Electronic Measurement Instruments
detailed procedures for the selection, standardization, and
E543 Specification forAgencies Performing Nondestructive
operation of an examination system and for evaluation of the
Testing
indications obtained.
E1316 Terminology for Nondestructive Examinations
1.3 Units—The values stated in inch-pound units are to be
2.2 ASNT Documents:
regarded as standard. The values given in parentheses are
SNT-TC-1A Recommended Practice for Personnel Qualifi-
mathematical conversions to SI units that are provided for
cation and Certification in Nondestructive Testing
information only and are not considered standard.
ANSI/ASNT-CP-189 for Qualification and Certification of
1.4 This standard does not purport to address all of the
Nondestructive Testing Personnel
safety concerns, if any, associated with its use. It is the
2.3 AIA Document:
responsibility of the user of this standard to establish appro-
NAS-410 Certification and Qualification of Nondestructive
priate safety, health, and environmental practices and deter-
Testing Personnel
mine the applicability of regulatory limitations prior to use.
NOTE 1—For DoD contracts, unless otherwise specified, the issues of
1.5 This international standard was developed in accor-
the documents, which are DoD adopted, are those listed in the issue of the
dance with internationally recognized principles on standard-
DoDISS (Department of Defense Index of Specifications Standards) cited
ization established in the Decision on Principles for the
in the solicitation.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Barriers to Trade (TBT) Committee.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
1 3
This practice is under the jurisdiction of ASTM Committee E07 on Nonde- The last approved version of this historical standard is referenced on
structive Testing and is the direct responsibility of Subcommittee E07.06 on www.astm.org.
Ultrasonic Method. AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
Current edition approved Nov. 1, 2021. Published November 2021. Originally 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
approved in 1984. Last previous edition approved in 2016 as E1001 – 16. DOI: Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
10.1520/E1001-21. WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
*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. United States
E1001 − 21
FIG. 1 Basic Immersion Setup
2.4 ISO Document: 5.2 Personnel Qualification:
ISO 9712 Non-destructive Testing—Qualification and Cer- 5.2.1 If specified in the contractual agreement, personnel
tification for NDT Personnel performing examinations to this practice shall be qualified in
accordance with a nationally or internationally recognized
3. Terminology
NDT personnel qualification practice or standard such as
3.1 Definitions—For definitions of terms used in this ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, ISO 9712, or a
similar document and certified by the employer or certifying
practice, see Terminology E1316.
agency, as applicable. The practice or standard used and its
3.2 Definitions of Terms Specific to This Standard:
applicable revision shall be identified in the contractual agree-
3.2.1 effective beam diameter, n—that distance through
ment between the using parties.
whichasearchunitcanbetraversedacrossareferencereflector
so that the corresponding echo amplitude is at least one half 5.3 Qualification of Nondestructive Agencies—If specified
(-6 dB) of the maximum amplitude. The effective beam diam- in the contractual agreement, NDT agencies shall be qualified
eter is not a characteristic of the search unit alone, but is and evaluated as described in Specification E543. The appli-
dependent on propagating medium, distance to the cable edition of Specification E543 shall be specified in the
discontinuity, reflector geometry, etc. contractual agreement.
3.2.2 scan index, n—the length of the step created by
5.4 Procedures and Techniques—The procedures and tech-
indexing the scan of the search unit over the part, that is
niques to be utilized shall be as specified in the contractual
continuously scanning in one direction, then stepping in the
agreement.
direction perpendicular to the scan or making a linear advance
5.5 Surface Preparation—The pre-examination surface
per rotation (pitch) for rotary scan of cylindrical parts. The
preparation criteria shall be in accordance with 8.1 unless
allowable scan index should be correlated with the search unit
otherwise specified.
effective beam diameter to ensure full coverage of the part as
5.6 Extent of Examination—The extent of examination shall
described in 8.2 below.
be in accordance with 12.3, unless otherwise specified.
3.2.3 transfer, n—a change in scanning gain to compensate
for differences in attenuation of the reference standard and the 5.7 Reporting Criteria/Acceptance Criteria—Reporting cri-
part or material being examined. teriaandacceptancecriteriafortheexaminationresultsshallbe
in accordance with 12.3, unless otherwise specified.
4. Summary of Practice
5.8 Reexamination of Repaired/Reworked Items—
4.1 This practice describes a means for obtaining an evalu-
Reexamination of repaired/reworked items is not addressed in
ation of discontinuities in materials by immersed examination
thispracticeandifrequiredshallbespecifiedinthecontractual
with longitudinal ultrasonic waves. Equipment, reference
agreement.
standards, examination and evaluation procedures, and docu-
mentation are described in detail.
6. Significance and Use
5. Basis of Application 6.1 This practice provides guidelines for the application of
immersed longitudinal wave examination to the detection and
5.1 The following items are subject to contractual agree-
quantitative evaluation of discontinuities in materials.
ment between the parties using or referencing this practice.
6.2 Although not all requirements of this practice can be
applied universally to all examination situations and materials,
Available from International Organization for Standardization (ISO), ISO
it does provide a basis for establishing contractual criteria
Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
Geneva, Switzerland, http://www.iso.org. between suppliers and purchasers of materials for performing
E1001 − 21
immersed pulse-echo examination, and may be used as a 7.4 Alarm—For the examination of parts or material with
general guide for writing detailed specifications for particular regularshapeandparallelsurfaces,suchasplate,machinedbar
applications. stock, and forgings, an audible alarm shall be used in prefer-
ence to a visual alarm, since the examination process can be
6.3 This practice is directed towards the evaluation of
accomplished at a speed which prevents reliable visual moni-
discontinuities detectable at normal beam incidence. If discon-
toring of the instrument screen. As a matter of practicality, an
tinuities at other orientations are of concern, alternate scanning
audible alarm should be used in conjunction with visual
techniques are required.
monitoring wherever possible.The alarm shall be adjustable to
allow triggering at any commonly required level of indication
7. Apparatus
amplitude and depth of material. During operation, the audible
7.1 Electronic Equipment—The electronic equipment shall
or visible signal produced by the alarm shall be easily
be capable of producing and processing electronic signals at
detectable by the operator.
frequencies in the range of search unit frequencies being used.
NOTE 3—Alarm requirements are not applicable if recording equipment
The equipment and its display shall be capable of meeting the
is used unless otherwise specified in the contractual agreement.
requirements to be completed in Table 1, as agreed upon
between the supplier and the purchaser, and as measured in 7.4.1 Alarm Gate Synchronization—To ensure that the
accordance with procedures described in Practice E317 or
alarm gate tracks the examination area, the gate shall lock on
equivalent procedures (see Note 2). These requirements are the first interface pulse from the part rather than on the initial
applicable only for the frequencies required for the examina-
pulse from the system. Gating from the initial pulse can result
tion. Also, the equipment, including the search unit, shall be in either partial loss of the examination area from the gate, or
capable of producing echo amplitudes of at least 60 %, of full
the inclusion of the back reflection and interface signal in the
scale, with the noise level no greater than 20 %, from the gated area. This will trigger the gate as would an imperfection.
appropriate reference reflector at a material distance equal to
7.5 Manipulating Equipment shall be provided to ad-
the thickness of the part to be examined.Alternatively, if these
equately support a search tube, containing the search unit, and
conditions can be met at one half the part thickness, the part
to allow angular adjustment so that proper alignment of the
may be examined from both sides.The instrument must have a
sound beam to the part or material surface can be achieved. A
pulser of the sufficient voltage, repetition rate, and waveshape
manipulator may be attached between the search tube and
toprovidetotalvolumecoverageatthedesiredscanningspeed.
search unit to provide the necessary angular adjustments. The
NOTE 2—Significantly higher frequencies than those shown in Table 1 scanningandindexingapparatusshallhavesufficientstructural
(for example, 50 MHz) may be necessary for the smaller critical flaw size
rigidity to provide support for the manipulator and shall allow
of advanced ceramics.
smooth, accurate positioning of the search unit. This apparatus
7.2 Voltage Regulator—If fluctuations in line voltage cause
shall permit control of the scan in accordance with 9.3.1 and
variationsexceeding 65 %oftheverticallimitinanindication
control of the index in accordance with 9.2.1. Also, the
with an amplitude of one half the vertical limit, a voltage
scanning apparatus shall be sufficiently rigid to keep search
regulator should be required on the power source. This
unit backlash to within tolerances as specified in the contrac-
requirement is not applicable to battery-operated units.
tual agreement. Water-path distances shall be continuously
adjustable.
7.3 Search Units—The search unit selected shall be com-
patible with the electronic equipment being used and with the
7.6 Tank—The container or tank shall permit accurate posi-
material to be examined. The search units shall be of the
tioningofthesearchunit,referenceblocks,andpartormaterial
immersion type. Only straight-beam (longitudinal) search
to be examined in accordance with the requirements of Section
units, with flat or focused acoustic lenses, shall be used.
8.
Focused or dual element search units may provide better
7.7 Reference Standards—Ultrasonic reference blocks, or
near-surface resolution and detection of small discontinuities.
reference specimens, are used to standardize the ultrasonic
Generally, round or rectangular search units are used for
equipment and to evaluate the indications received from
examination whereas round search units with symmetrical
discontinuities within the part.The ultrasonic characteristics of
sound beam patterns are used for evaluation.
the reference standards such as attenuation, noise level, surface
condition, and sound velocity, shall be similar to the material
being examined. Metal reference standards should not be used
TABLE 1 Minimum Equipment Requirements (Longitudinal Wave)
for examining ceramics because of the large differences in
Instrument Characteristics: Ultrasonic Test Frequencies 2.25, 5.0, 10.0,
attenuation velocity and acoustic impedance. Standardization
15.0 MHz
(1) verifies that the instrument/search unit combination is
Vertical limit, in. (mm), trace to peak or percent of full screen height
Upper linearity limit, in. (mm), trace to peak or percent of full screen height performingasrequired,and(2)establishesadetectionlevelfor
Lower linearity limit, in. (mm), trace to peak or percent of full screen height
discontinuities.ReferenceblocksasdescribedinPracticeE127
Ultrasonic sensitivity, reflector size, material distance, in. (mm)
have been used as standards for standardizing system
Signal-to-noise ratio
Entry surface resolution, in. (mm) performance, and may continue to be so used in cases where
Back surface resolution, in. (mm)
sufficient empirical evidence has shown that satisfactory ex-
Horizontal limit, in. (mm) or percent of full screen width
aminationresultsareobtained.However,itismoredesirablein
Horizontal linearity range, in. (mm) or percent of full screen width
the general case to use a part identical in shape, dimensions,
E1001 − 21
and material properties to the parts to be examined. The 8.2 Coverage—In all examinations, perform scanning to
procedures established in Practice E127 are recommended for locate discontinuities that are oriented parallel with the entry
selection of reference standard material and manufacturing surface, or that are in a plane approximately normal to the
ultrasonic reference block beam testing. major working direction parallel to the grain flow of the part,
7.7.1 Flat Blocks—The three most commonly used sets of or both. Examine areas of the part, which have not undergone
reference blocks are (1) area-amplitude blocks, containing significant material flow, by methods that will detect randomly
blocks with the same material path and various sizes of oriented discontinuities. To ensure complete coverage of the
reference reflectors; (2) distance-amplitude blocks containing material, it is necessary that the scanning spacing (index) is
blocks with one-size reference reflector at various material less than the effective beam length in the index direction at any
paths;and(3)acombinationincludingbotharea-amplitudeand depth in the material. Furthermore, to ensure repeatable re-
distance-amplitude blocks in one set. These sets are described sponse at the same amplitude from a given length
in Practice E127. However, in general their use is not recom- discontinuity, it is necessary that the scan index not exceed the
mended for system standardization (see 7.7 above) in cases absolute difference between minimum discontinuity length and
where the item under test is not flat. Other types of reference beam length.
blocks may be used when mutually agreed upon between the
8.2.1 Resolution—If entry surface resolution (based on 2:1
supplier and the purchaser. Practices C1212 and C1336 con-
signal-to-noise ratio) is not sufficient to allow detection of the
taining seeded voids and seeded inclusions may be used for
required reference reflectors near the examination surfaces,
ceramics.
perform additional examinations from the opposite side. If
7.7.2 Curved Surfaces—Reference blocks with flat surfaces
surface roughness prevents the required resolution from being
should not be used for establishing gain settings for examina-
obtained, correct the problem before performing the examina-
tions on examination surfaces with radii of curvature less than
tion. Also, for each examination direction, perform examina-
about 8 in. (203 mm). For examination surfaces with radii of
tions from opposite sides when the maximum material travel
curvature less than 8 in. (203 mm), reference blocks shall be
distance is such that the minimum size reference reflector
within10 %oftheradiuscurvatureofthepartbeingexamined.
cannot be detected by examinations applied from only one side
(see 7.1).
7.8 Reference Reflectors (Targets)—Flat-bottom holes,
(FBH), or other artificial discontinuities, located either directly
8.3 Ultrasonic Frequency—In general, the higher frequen-
in the part or material, in a representative sample of the part or
cies provide a more directive sound beam and provide better
material, or, if previously found to yield satisfactory
depth and lateral resolution. The lower frequencies provide
examination, in reference blocks, shall be used to establish the
better penetration and better detection of misaligned planar
reference echo amplitude or to perform distance-amplitude
discontinuities. For a particular examination, select the fre-
correction, or both. For most examinations, the bottom surface
quency based on the material being examined, the anticipated
ofasuitablediameterflat-bottomholeisthecommonreference
type of discontinuities, and other examination requirements.
reflector. However, other types of artificial discontinuities
(notches, side-drilled holes, etc.) may be used when mutually
9. Examination (Scanning) Procedure
agreed upon between the supplier and the purchaser. Seeded
9.1 System Setup:
voids (Practice C1212), seeded inclusions (Practice C1336),
9.1.1 Tank—Immerse the part to be examined, reference
and laser-drilled holes are common reflectors for advanced
standards, and search unit in a suitable tank filled with liquid
ceramics.
couplant.
8. General Examination Requirements 9.1.1.1 The liquid couplant shall be clean and deaerated to
eliminateattenuationofthesoundbeamandtoimprovesystem
8.1 Material Condition—Perform ultrasonic examination of
signal-to-noise ratio.
parts or material before machining if surface roughness and
9.1.1.2 Care shall be taken to ensure that extraneous indi-
part geometry are within the tolerance specified in the contrac-
cations caused by particulates, air bubbles, etc. in the couplant,
tual agreement. Surfaces may already be sufficiently free of
do not interfere with the examination at the required examina-
roughness and waviness to permit a uniform examination over
tion sensitivity.
the required areas. When it is determined that surface rough-
9.1.1.3 Corrosion inhibitors or wetting agents may be added
ness precludes adequate detection and evaluation of subsurface
as long as they do not affect the material properties.
discontinuities, smooth the areas in question by machining,
9.1.1.4 Residual suspended particulate matter and air
grinding, or other means before the examination is performed.
bubbles that collect on the material and search unit surfaces
Forceramics,careshallbetakentoavoidgeneratingsurfaceor
shall be removed.
near-surfacecracksbythesmoothingoperation.Duringexami-
9.1.2 Reference Standard Selection—The reference stan-
nation and evaluation, ensure that the entry surface and back
surface are free of loose scale, machining, or grinding particles dards shall have the size and type of reference reflectors
or other loose foreign matter. specified in the contractual agreement. A good basic set for
metals is described in Table 2 and in Practice E127 for
distance-amplitude reference blocks.
Beck, K.H., “Limitations to the Use of Reference Blocks for Periodic and
Preinspection Calibration of Ultrasonic Inspection Instruments and Systems,” NOTE 4—The recommendations of paragraphs 9.1.2.1, 9.1.2.2, and
Materials Evaluation, Vol. 57, No. 3, March 1999. 9.1.2.3, which follow are not applicable to ceramics.
E1001 − 21
TABLE 2 Distance Amplitude Reference Block-Metal Path
greater than the thickness of the part (or one half the thickness
Increments, in. (mm)
if the part is examined from both sides).
0.125 (3.2)
9.1.3 Search Unit Adjustment—Normalize the ultrasonic
0.250 (6.4)
beam by adjusting the search unit for maximum echo ampli-
0.375 (9.5)
tude from the front surface of the part or material. This is
0.500 (12.7)
0.625 (15.9)
accomplished by angling the search unit in two directions,
0.750 (19.1)
perpendicular to one another and parallel to the sound-entry
0.875 (22.2)
1.000 (25.4) surface (Note 5). This may be accomplished by use of a
1.250 (31.8)
manipulator with two axes of motion, mutually perpendicular
1.500 (38.1)
to one another, or in the case of curved surfaces, by use of a
1.750 (44.5)
2.000 (50.8) manipulator with one axis of motion and a search tube which
2.250 (57.2)
can be rotated to achieve perpendicularity. During
2.500 (63.5)
examination, monitor either the front-surface or back-surface
2.750 (69.9)
3.000 (76.2) indication. If changes in the shape of the part cause the
3.250 (82.6)
amplitudeofthemonitoredindicationtodecreasebymorethan
3.500 (88.9)
50 %,re-anglethesearchunitasnecessaryoverdifferentzones
3.750 (95.3)
4.000 (101.6) to maintain the beam normal to the examination surface.
4.250 (108.0)
NOTE 5—For focused search units, perform beam normalization so that
4.500 (114.3)
4.750 (120.7) the centerline of the beam is perpendicular to the material entry surface.
5.000 (127.0)
9.1.4 Water Path—The distance from the face of the search
5.250 (133.4)
5.500 (139.7)
unit to the front surface of the material shall be such that the
5.750 (146.1)
second front-surface echo does not appear before the first
6.000 (152.4)
back-surface echo. The water path distance and search unit
focal length will determine whether examination will occur in
the near zone, far zone, or a combination of these. For focused
9.1.2.1 For examination performed only in the near-field
search units, this distance should be such that the search unit
portion of the sound beam, select metal paths from those in
focus is within the material at the depth required to meet
Table 2. The metal paths selected should be in increments so
front-surface resolution requirements.
that the maximum metal path difference between reference
NOTE 6—The permissible variation in the water path depends com-
reflectors does not exceed the requirements described in Table
pletely on the particular system and application (that is, flat or focused
3. This set shall include one reference block with a metal path
search unit, shape of beam profile, etc.). For establishing the distance-
equal to or less than the required front surface resolution, and
amplitude relationship and evaluating discontinuities, maintain the water
one approximately equal to or greater than the thickness of the 1
path to within 6 ⁄8 in. (63.2 mm). During scanning, the maximum
part (or one half the thickness, if the part is examined from variation shall not exceed the amount specified in the contractual
agreement or approved examination procedure.
both sides).
9.1.2.2 For examination performed only in the far-field
9.2 Initial Scanning Standardization:
portionofthesoundbeam,selectatleastthreereferenceblocks
9.2.1 Scan Index Determination—Using the reference
withthefollowingmetalpaths:(1)ametalpathequaltoorless
blocks selected in 9.1.2 and the search unit setup in 9.1.3,
than the required front-surface resolution; (2) a metal path
determine the maximum allowable scan index as follows: (1)
approximately equal to one half the thickness of the part; and
maximize the echo amplitude from the reflector in each
(3) a metal path approximately equal to or greater than the
reference block and adjust the amplitude from 50 to 100 % of
thickness of the part (or the required front-surface resolution,
the upper linearity limit; and (2) determine the total traversing
one quarter, and one half the thickness if the part is examined
distance in the index direction, across each reference target,
from both sides).
through which no less than that percentage of the maximized
9.1.2.3 For examinations which are performed so that part
amplitude is obtained, which corresponds to the allowable
of the thickness of the part is in the near field and part is in the
variation during repeated runs of the reference standard. This
far field, the set of reference block metal paths shall include
distance is dependent on the material travel to the reflector and
blocks which satisfy the above near-field requirements cover-
will vary from one reference target to another. This is the
ing the range from the front-surface resolution to the near-field
effective beam diameter at each material distance. The least of
limit and one reference block with a metal path equal to or
the distances shall be used as the maximum allowable scan
index.
TABLE 3 Reference Block-Metal Path Selection in Near Field 9.2.2 Distance-Amplitude Relationship—The following
paragraph provides a procedure to determine the distance–am-
Maximum Metal Path Difference
Metal Path Range, in. (mm) Between Adjacent Reference plitude relationship for reference blocks described in 9.1.2.
Blocks, in. (mm)
0to0.25(0to6.4) 0.125(3.2)
0.25 to 1.0 (6.4
...

This 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. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E1001 − 16 E1001 − 21
Standard Practice for
Detection and Evaluation of Discontinuities by the
Immersed Pulse-Echo Ultrasonic Method Using Longitudinal
Waves
This standard is issued under the fixed designation E1001; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This practice describes procedures for the ultrasonic examination of bulk materials or parts by transmitting pulsed, longitudinal
waves through a liquid couplant into the material and observing the indications of reflected waves (see Fig. 1). It covers only
examinations in which one search unit is used as both transmitter and receiver (pulse-echo) and in which the part or material being
examined is coupled to the part by a liquid column or is totally submerged in the couplant (either method is considered to be
immersion testing). This practice includes general requirements and procedures which may be used for detecting discontinuities
and for making a relative or approximate evaluation of the size of discontinuities.
1.2 This practice replaces Practice E214 and provides more detailed procedures for the selection, standardization, and operation
of an examination system and for evaluation of the indications obtained.
1.3 Units—The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C1212 Practice for Fabricating Ceramic Reference Specimens Containing Seeded Voids (Withdrawn 2018)
C1336 Practice for Fabricating Non-Oxide Ceramic Reference Specimens Containing Seeded Inclusions (Withdrawn 2018)
E127 Practice for Fabrication and Control of Flat Bottomed Hole Ultrasonic Standard Reference Blocks
E214 Practice for Immersed Ultrasonic Testing by the Reflection Method Using Pulsed Longitudinal Waves (Withdrawn 2007)
This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.06 on Ultrasonic Method.
Current edition approved Dec. 1, 2016Nov. 1, 2021. Published December 2016November 2021. Originally approved in 1984. Last previous edition approved in 20112016
as E1001 - 11.E1001 – 16. DOI: 10.1520/E1001-16.10.1520/E1001-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
*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. United States
E1001 − 21
FIG. 1 Basic Immersion Setup
E317 Practice for Evaluating Performance Characteristics of Ultrasonic Pulse-Echo Testing Instruments and Systems without the
Use of Electronic Measurement Instruments
E428 Practice for Fabrication and Control of Metal, Other than Aluminum, Reference Blocks Used in Ultrasonic Testing
(Withdrawn 2019)
E543 Specification for Agencies Performing Nondestructive Testing
E1158 Guide for Material Selection and Fabrication of Reference Blocks for the Pulsed Longitudinal Wave Ultrasonic Testing
of Metal and Metal Alloy Production Material (Withdrawn 2019)
E1316 Terminology for Nondestructive Examinations
2.2 ASNT Documents:
SNT-TC-1A Recommended Practice for Personnel Qualification and Certification in Nondestructive Testing
ANSI/ASNT-CP-189 for Qualification and Certification of Nondestructive Testing Personnel
2.3 Aerospace Industries Association AIA Document:
NAS-410 Certification and Qualification of Nondestructive Testing Personnel
NOTE 1—For DoD contracts, unless otherwise specified, the issues of the documents, which are DoD adopted, are those listed in the issue of the DoDISS
(Department of Defense Index of Specifications Standards) cited in the solicitation.
2.4 ISO DocumentsDocument:
ISO 9712 Non-destructive Testing—Qualification and Certification for NDT Personnel
3. Terminology
3.1 Definitions—For definitions of terms used in this practice, see Terminology E1316.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 effective beam diameter—diameter, n—that distance through which a search unit can be traversed across a reference reflector
so that the corresponding echo amplitude is at least one half (-6 dB) (-6 dB) of the maximum amplitude. The effective beam
diameter is not a characteristic of the search unit alone, but is dependent on propagating medium, distance to the discontinuity,
reflector geometry, etc.
3.2.2 scan index—index, n—the length of the step created by indexing the scan of the search unit over the part, that is continuously
scanning in one direction, then stepping in the direction perpendicular to the scan or making a linear advance per rotation (pitch)
for rotary scan of cylindrical parts. The allowable scan index should be correlated with the search unit effective beam diameter to
ensure full coverage of the part as described in 8.2 below.
3.2.3 transfer—transfer, n—a change in scanning gain to compensate for differences in attenuation of the reference standard and
the part or material being examined.
Available from American Society for Nondestructive Testing (ASNT), P.O. Box 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Available from Aerospace Industries Association of America, Inc. (AIA), 1000 Wilson Blvd., Suite 1700, Arlington, VA 22209-3928, http://www.aia-aerospace.org.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva,
Switzerland, http://www.iso.org.
E1001 − 21
4. Summary of Practice
4.1 This practice describes a means for obtaining an evaluation of discontinuities in materials by immersed examination with
longitudinal ultrasonic waves. Equipment, reference standards, examination and evaluation procedures, and documentation are
described in detail.
5. Basis of Application
5.1 The following items are subject to contractual agreement between the parties using or referencing this standard.practice.
5.2 Personnel Qualification:
5.2.1 If specified in the contractual agreement, personnel performing examinations to this standardpractice shall be qualified in
accordance with a nationally or internationally recognized NDT personnel qualification practice or standard such as ANSI/ASNT-
CP-189, SNT-TC-1A, NAS-410, ISO 9712, or a similar document and certified by the employer or certifying agency, as applicable.
The practice or standard used and its applicable revision shall be identified in the contractual agreement between the using parties.
5.3 Qualification of Nondestructive Agencies—If specified in the contractual agreement, NDT agencies shall be qualified and
evaluated as described in Specification E543. The applicable edition of Specification E543 shall be specified in the contractual
agreement.
5.4 Procedures and Techniques—The procedures and techniques to be utilized shall be as specified in the contractual agreement.
5.5 Surface Preparation—The pre-examination surface preparation criteria shall be in accordance with 8.1 unless otherwise
specified.
5.6 Extent of Examination—The extent of examination shall be in accordance with 12.3, unless otherwise specified.
5.7 Reporting Criteria/Acceptance Criteria—Reporting criteria and acceptance criteria for the examination results shall be in
accordance with 12.3, unless otherwise specified.
5.8 Reexamination of Repaired/Reworked Items—Reexamination of repaired/reworked items is not addressed in this standard-
practice and if required shall be specified in the contractual agreement.
6. Significance and Use
6.1 This practice provides guidelines for the application of immersed longitudinal wave examination to the detection and
quantitative evaluation of discontinuities in materials.
6.2 Although not all requirements of this practice can be applied universally to all examination situations and materials, it does
provide a basis for establishing contractual criteria between suppliers and purchasers of materials for performing immersed
pulse-echo examination, and may be used as a general guide for writing detailed specifications for particular applications.
6.3 This practice is directed towards the evaluation of discontinuities detectable at normal beam incidence. If discontinuities at
other orientations are of concern, alternate scanning techniques are required.
7. Apparatus
7.1 Electronic Equipment—The electronic equipment shall be capable of producing and processing electronic signals at
frequencies in the range of search unit frequencies being used. The equipment and its display shall be capable of meeting the
requirements to be completed in Table 1, as agreed upon between the supplier and the purchaser, and as measured in accordance
with procedures described in Practice E317 or equivalent procedures (see Note 2). These requirements are applicable only for the
frequencies required for the examination. Also, the equipment, including the search unit, shall be capable of producing echo
amplitudes of at least 60 %, of full scale, with the noise level no greater than 20 %, from the appropriate reference reflector at a
material distance equal to the thickness of the part to be examined. Alternatively, if these conditions can be met at one half the
E1001 − 21
TABLE 1 Minimum Equipment Requirements (Longitudinal Wave)
Ultrasonic Test
Frequency, MHz
Instrument Characteristics
2.25 5.0 10.0 15.0
Instrument Characteristics: Ultrasonic Test Frequencies 2.25, 5.0, 10.0,
15.0 MHz
Vertical limit, in. (mm), trace to peak or percent of full screen height
Upper linearity limit, in. (mm), trace to peak or percent of full screen height
Lower linearity limit, in. (mm), trace to peak or percent of full screen height
Ultrasonic sensitivity, reflector size, material distance, in. (mm)
Signal-to-noise ratio
Entry surface resolution, in. (mm)
Back surface resolution, in. (mm)
Horizontal limit, in. (mm) or percent of full screen width
Horizontal linearity range, in. (mm) or percent of full screen width
part thickness, the part may be examined from both sides. The instrument must have a pulser of the sufficient voltage, repetition
rate, and waveshape to provide total volume coverage at the desired scanning speed.
NOTE 2—Significantly higher frequencies than those shown in Table 1 (for example, 50 MHz) may be necessary for the smaller critical flaw size of
advanced ceramics.
7.2 Voltage Regulator—If fluctuations in line voltage cause variations exceeding 65 % of the vertical limit in an indication with
an amplitude of one half the vertical limit, a voltage regulator should be required on the power source. This requirement is not
applicable to battery-operated units.
7.3 Search Units—The search unit selected shall be compatible with the electronic equipment being used and with the material
to be examined. The search units shall be of the immersion type. Only straight-beam (longitudinal) search units, with flat or focused
acoustic lenses, shall be used. Focused or dual element search units may provide better near-surface resolution and detection of
small discontinuities. Generally, round or rectangular search units are used for examination whereas round search units with
symmetrical sound beam patterns are used for evaluation.
7.4 Alarm—For the examination of parts or material with regular shape and parallel surfaces, such as plate, machined bar stock,
and forgings, an audible alarm shall be used in preference to a visual alarm, since the examination process can be accomplished
at a speed which prevents reliable visual monitoring of the instrument screen. As a matter of practicality, an audible alarm should
be used in conjunction with visual monitoring wherever possible. The alarm shall be adjustable to allow triggering at any
commonly required level of indication amplitude and depth of material. During operation, the audible or visible signal produced
by the alarm shall be easily detectable by the operator.
NOTE 3—Alarm requirements are not applicable if recording equipment is used unless otherwise specified in the contractual agreement.
7.4.1 Alarm Gate Synchronization—To ensure that the alarm gate tracks the examination area, the gate shall lock on the first
interface pulse from the part rather than on the initial pulse from the system. Gating from the initial pulse can result in either partial
loss of the examination area from the gate, or the inclusion of the back reflection and interface signal in the gated area. This will
trigger the gate as would an imperfection.
7.5 Manipulating Equipment shall be provided to adequately support a search tube, containing the search unit, and to allow angular
adjustment in two mutually perpendicular, vertical planes. so that proper alignment of the sound beam to the part or material
surface can be achieved. A manipulator may be attached between the search tube and search unit to provide the necessary angular
adjustments. The scanning and indexing apparatus shall have sufficient structural rigidity to provide support for the manipulator
and shall allow smooth, accurate positioning of the search unit. This apparatus shall permit control of the scan in accordance with
9.3.1 and control of the index in accordance with 9.2.1. Also, the scanning apparatus shall be sufficiently rigid to keep search unit
backlash to within tolerances as specified in the contractual agreement. Water-path distances shall be continuously adjustable.
7.6 Tank—The container or tank shall permit accurate positioning of the search unit, reference blocks, and part or material to be
examined in accordance with the requirements of Section 8.
7.7 Reference Standards—Ultrasonic reference blocks, or reference specimens, are used to standardize the ultrasonic equipment
E1001 − 21
and to evaluate the indications received from discontinuities within the part. The ultrasonic characteristics of the reference
standards such as attenuation, noise level, surface condition, and sound velocity, shall be similar to the material being examined.
Metal reference standards should not be used for examining advanced ceramics because of the large differences in attenuation
velocity and acoustic impedance. Standardization (1) verifies that the instrument/search unit combination is performing as required,
and (2) establishes a detection level for discontinuities. Reference blocks as described in PracticesPractice E127 and E428have
been used as standards for standardizing system performance, and may continue to be so used in cases where muchsufficient
empirical evidence has shown that satisfactory examination results are obtained. However, it is more desirable in the general case
to use a part identical in shape, dimensions, and material properties to the parts to be examined. (See Ref. (1) .) The procedures
established in GuidePractice E1158E127 are recommended for selection of reference standard material and manufacturing
ultrasonic reference block beam testing.
7.7.1 Flat Blocks—The three most commonly used sets of reference blocks are (1) area-amplitude blocks, containing blocks with
the same material path and various sizes of reference reflectors; (2) distance-amplitude blocks containing blocks with one-size
reference reflector at various material paths; and (3) a combination including both area-amplitude and distance-amplitude blocks
in one set. These sets are described in Practice E127. However, in general their use is not recommended for system standardization
(see 7.7 above). above) in cases where the item under test is not flat. Other types of reference blocks may be used when mutually
agreed upon between the supplier and the purchaser. Practices C1212 and C1336 containing seeded voids and seeded inclusions
may be used for advanced ceramics.
7.7.2 Curved Surfaces—Reference blocks with flat surfaces should not be used for establishing gain settings for examinations on
examination surfaces with radii of curvature less than about 8 in. (200(203 mm). For examination surfaces with radii of curvature
less than 8 in. (203.2(203 mm), reference blocks shall be within 10%10 % of the radius curvature of the part being examined.
7.8 Reference Reflectors (Targets)—Flat-bottom holes, (FBH), or other artificial discontinuities, located either directly in the part
or material, in a representative sample of the part or material, or, if previously found to yield satisfactory examination, in reference
blocks, shall be used to establish the reference echo amplitude or to perform distance-amplitude correction, or both. For most
examinations, the bottom surface of a suitable diameter flat-bottom hole is the common reference reflector. However, other types
of artificial discontinuities (notches, side-drilled holes, etc.) may be used when mutually agreed upon between the supplier and the
purchaser. Seeded voids (Practice C1212), seeded inclusions (Practice C1336), and laser-drilled holes are common reflectors for
advanced ceramics.
8. General Examination Requirements
8.1 Material Condition—Perform ultrasonic examination of parts or material before machining if surface roughness and part
geometry are within the tolerance specified in the contractual agreement. Surfaces may already be sufficiently free of roughness
and waviness to permit a uniform examination over the required areas. When it is determined that surface roughness precludes
adequate detection and evaluation of subsurface discontinuities, smooth the areas in question by machining, grinding, or other
means before the examination is performed. For advanced ceramics, care shall be taken to avoid generating surface or near-surface
cracks by the smoothing operation. During examination and evaluation, ensure that the entry surface and back surface are free of
loose scale, machining, or grinding particles or other loose foreign matter.
8.2 Coverage—In all examinations, perform scanning to locate discontinuities that are oriented parallel with the entry surface, or
that are in a plane approximately normal to the major working direction parallel to the grain flow of the part, or both. Examine
areas of the part, which have not undergone significant material flow, by methods that will detect randomly oriented discontinuities.
To ensure complete coverage of the material, it is necessary that the scanning spacing (index) is less than the effective beam length
in the index direction at any depth in the material. Furthermore, to insureensure repeatable response at the same amplitude from
a given length discontinuity, it is necessary that the scan index not exceed the absolute difference between minimum discontinuity
length and beam length. This is known as “invariant worst case interception”. (See Ref. (2).) Note that conformance to this
paragraph does not accomplish examination of the entire volume of the material. Uninspectable zones due to limitations in entry
surface resolution and back surface resolution prevent complete volumetric examination.
8.2.1 Resolution—If entry surface resolution (based on 2:1 signal-to-noise ratio) is not sufficient to allow detection of the required
reference reflectors near the examination surfaces, perform additional examinations from the opposite side. If surface roughness
prevents the required resolution from being obtained, correct the problem before performing the examination. Also, for each
The boldface numbers in parentheses refer to a list of references at the end of this standard.Beck, K.H., “Limitations to the Use of Reference Blocks for Periodic and
Preinspection Calibration of Ultrasonic Inspection Instruments and Systems,” Materials Evaluation, Vol. 57, No. 3, March 1999.
E1001 − 21
examination direction, perform examinations from opposite sides when the maximum material travel distance is such that the
minimum size reference reflector cannot be detected by examinations applied from only one side (see 7.1).
8.3 Ultrasonic Frequency—In general, the higher frequencies provide a more directive sound beam and provide better depth and
lateral resolution. The lower frequencies provide better penetration and better detection of misaligned planar discontinuities. For
a particular examination, select the frequency based on the material being examined, the anticipated type of discontinuities, and
other examination requirements.
9. Examination (Scanning) Procedure
9.1 System Setup:
9.1.1 Tank—Immerse the part to be examined, reference standards, and search unit in a suitable tank filled with liquid couplant.
9.1.1.1 The liquid couplant shall be clean and deaerated to eliminate attenuation of the sound beam and to improve system
signal-to-noise ratio.
9.1.1.2 Care shall be taken to ensure that extraneous indications caused by particulates, air bubbles, etc. in the couplant, do not
interfere with the examination at the required examination sensitivity.
9.1.1.3 Corrosion inhibitors or wetting agents may be added as long as they do not affect the material properties.
9.1.1.4 Residual suspended particulate matter and air bubbles that collect on the material and search unit surfaces shall be
removed.
9.1.2 Reference Standard Selection—The reference standards shall have the size and type of reference reflectors specified in the
contractual agreement. A good basic set for metals is described in Table 2 and in Practice E127 for distance-amplitude reference
blocks.
NOTE 4—The recommendations of paragraphs 9.1.2.1, 9.1.2.2, and 9.1.2.3, which follow are not applicable to advanced ceramics.
9.1.2.1 For examination performed only in the near-field portion of the sound beam, select metal paths from those in Table 2. The
metal paths selected should be in increments so that the maximum metal path difference between reference reflectors does not
TABLE 2 Distance Amplitude Reference Block-Metal Path
Increments, in. (mm)
0.125 (3.2)
0.250 (6.4)
0.375 (9.5)
0.500 (12.7)
0.625 (15.9)
0.750 (19.1)
0.875 (22.2)
1.000 (25.4)
1.250 (31.8)
1.500 (38.1)
1.750 (44.5)
2.000 (50.8)
2.250 (57.2)
2.500 (63.5)
2.750 (69.9)
3.000 (76.2)
3.250 (82.6)
3.500 (88.9)
3.750 (95.3)
4.000 (101.6)
4.250 (108.0)
4.500 (114.3)
4.750 (120.7)
5.000 (127.0)
5.250 (133.4)
5.500 (139.7)
5.750 (146.1)
6.000 (152.4)
E1001 − 21
exceed the requirements described in Table 3. This set shall include one reference block with a metal path equal to or less than
the required front surface resolution, and one approximately equal to or greater than the thickness of the part (or one half the
thickness, if the part is examined from both sides).
9.1.2.2 For examination performed only in the far-field portion of the sound beam, select at least three reference blocks with the
following metal paths: (1) a metal path equal to or less than the required front-surface resolution; (2) a metal path approximately
equal to one half the thickness of the part; and (3) a metal path approximately equal to or greater than the thickness of the part
(or the required front-surface resolution, one quarter, and one half the thickness if the part is examined from both sides).
9.1.2.3 For examinations which are performed so that part of the thickness of the part is in the near field and part is in the far field,
the set of reference block metal paths shall include blocks which satisfy the above near-field requirements covering the range from
the front-surface resolution to the near-field limit and one reference block with a metal path equal to or greater than the thickness
of the part (or one half the thickness if the part is examined from both sides).
9.1.3 Search Unit Adjustment—Normalize the ultrasonic beam by adjusting the search unit for maximum echo amplitude from the
front surface of the part or material. This is accomplished by angling the search unit in two directions, perpendicular to one another
and parallel to the sound-entry surface (Note 5). This may be accomplished by use of a manipulator with two axes of motion,
mutually perpendicular to one another, or in the case of curved surfaces, by use of a manipulator with one axis of motion and a
search tube which can be rotated to achieve perpendicularity. During examination, monitor either the front-surface or back-surface
indication. If changes in the shape of the part cause the amplitude of the monitored indication to decrease by more than 50 %,
re-angle the search unit as necessary over different zones to maintain the beam normal to the examination surface.
NOTE 5—For focused search units, perform beam normalization so that the centerline of the beam is perpendicular to the material entry surface.
9.1.4 Water Path—The distance from the face of the search unit to the front surface of the material shall be such that the second
front-surface echo does not appear before the first back-surface echo. The water path distance and search unit focal length will
determine whether examination will occur in the near zone, far zone, or a combination of these. For focused search units, this
distance should be such that the search unit focus is within the material at the depth required to meet front-surface resolution
requirements.
NOTE 6—The permissible variation in the water path depends completely on the particular system and application (that is, flat or focused search unit, shape
of beam profile, etc.)etc.). For establishing the distance-amplitude relationship and evaluating discontinuities, maintain the water path to within 6 ⁄8 in.
(63.2 mm). During scanning, the maximum variation shall not exceed the amount specified in the contractual agreement or approved examination
procedure.
9.2 Initial Scanning Standardization:
9.2.1 Scan Index Determination—Using the reference blocks selected in 9.1.2 and the search unit setup in 9.1.3, determine the
maximum allowable scan index as follows: (1) maximize the echo amplitude from the reflector in each reference block and adjust
the amplitude from 50 to 100 % of the upper linearity limit; and (2) determine the total traversing distance in the index direction,
across each reference target, through which no less than that percentage of the maximized amplitude is obtained, which
corresponds to the allowable variation during repeated runs of the reference standard.(See Ref. (2 ).) This distance is dependent
on the material travel to the reflector and will vary from one reference target to another. This is the effective beam diameter at each
material distance. The least of the distances shall be used as the maximum allowable scan index.
TABLE 3 Reference Block-Metal Path Selection in Near Field
Maximum Metal Path Difference
Metal Path Range, in. (mm) Between Adjacent Reference
Blocks, in. (mm)
0 to 0.25 (0 to 6.4) 0.125 (3.2)
0.25 to 1.0 (6.4 to 25.4) 0.250 (6.4)
1.0 to 3.0 (25.4 to 76.2) 0.500 (12.7)
Over 3.0 (over 76.2) 1.000 (25.4)
Beck, K. H., “Effect of Ultrasonic Transducer Beam Profile on Accuracy of Discontinuity Detection During Scanning,” Materials Evaluation, Vol. 64, No. 2, Feb. 2006,
pp. 102–105.
E1001 − 21
9.2.2 Distance-Amplitude Relationship—The following paragraph provides a procedure to determine the distance–amplitude
relationship for reference blocks described in section 9.1.2. This procedure is not mandatory, but is recommended when using
electronic equipment lacki
...