ASTM E1816-18(2022)

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: E1816 − 18 (Reapproved 2022)
Standard Practice for
Measuring thickness by Pulse-Echo Electromagnetic
Acoustic Transducer (EMAT) Methods
This standard is issued under the fixed designation E1816; 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.
1. Scope E494 Practice for Measuring Ultrasonic Velocity in Materi-
als by Comparative Pulse-Echo Method
1.1 This practice provides guidelines for measuring the
E543 Specification for Agencies Performing Nondestructive
thickness of materials using Electromagnetic Acoustic Trans-
Testing
ducers (EMAT), a non-contact pulse-echo method, at tempera-
E587 Practice for Ultrasonic Angle-Beam Contact Testing
tures not to exceed 1200°F [650°C].
E797 Practice for Measuring Thickness by Manual Ultra-
1.2 This practice is applicable to any electrically conductive
sonic Pulse-Echo Contact Method
or ferromagnetic material, or both, in which ultrasonic waves
E1316 Terminology for Nondestructive Examinations
will propagate at a constant velocity throughout the part, and
E1774 Guide for Electromagnetic Acoustic Transducers
from which back reflections can be obtained and resolved.
(EMATs)
1.3 Units—The values stated in either SI units or inch- 2.2 ASNT Standards:
pound units are to be regarded separately as standard. The SNT-TC-1A Recommended Practice for Personnel Qualifi-
values stated in each system may not be exact equivalents; cations and Certification in Nondestructive Testing
therefore,eachsystemshallbeusedindependentlyoftheother. ANSI/ASNT CP-189 Standard for Qualification and Certifi-
Combining values from the two systems may result in noncon- cation of Nondestructive Testing Personnel
formance with the standard. 2.3 Aerospace Industries Association Standard:
NAS 410 Certification and Qualification of Nondestructive
1.4 This standard does not purport to address all of the
Test Personnel
safety concerns, if any, associated with its use. It is the
2.4 International Standards Organization (ISO):
responsibility of the user of this standard to establish appro-
ISO 9712 Qualification and Certification of NDT Personnel
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
3. Terminology
1.5 This international standard was developed in accor-
3.1 Definitions: Related terminology is defined inTerminol-
dance with internationally recognized principles on standard-
ogy E1316.
ization established in the Decision on Principles for the
3.2 Definitions of Terms Specific to This Standard:
Development of International Standards, Guides and Recom-
3.2.1 bulk wave—an ultrasonic wave, either longitudinal or
mendations issued by the World Trade Organization Technical
shear horizontal mode, used in nondestructive testing to
Barriers to Trade (TBT) Committee.
interrogate the volume of a material.
2. Referenced Documents
3.2.2 butterfly (double elongated racetrack) coil—an EMAT
coil consisting of two coils wound on an elongated racetrack
2.1 ASTM Standards:
shape, placed side by side, and connected so the current on the
E114 Practice for Ultrasonic Pulse-Echo Straight-Beam
conductors in the middle section flows in only one direction.
Contact Testing
3.2.3 electromagnetic acoustic transducer (EMAT)—an
electromagnetic device for converting electrical energy into
acoustical energy in the presence of a magnetic field.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
structive Testing and is the direct responsibility of Subcommittee E07.06 on
Ultrasonic Method.
Current edition approved Dec. 1, 2022. Published December 2022. Originally AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
approved in 1996. Last previous edition approved in 2018 as E1816 – 18. DOI: 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
10.1520/E1816-18R22. Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
For referenced ASTM standards, visit the ASTM website, www.astm.org, or WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Available from International Organization for Standardization (ISO), ISO
Standards volume information, refer to the standard’s Document Summary page on Central Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,
the ASTM website. Geneva, Switzerland, http://www.iso.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1816 − 18 (2022)
3.2.4 Lorentz forces—forces exerted on a charged particle different instruments, including range, sweep, material
by electric currents when placed in a magnetic field. Lorentz standardize, or velocity.
forces are perpendicular to both the direction of the magnetic
4.7 The timing circuits in different instruments use various
field and the current direction. Lorentz forces are the forces
conversion schemes. A common method is the so-called
responsible behind the principle of electric motors.
time/analog conversion in which the time measured by the
3.2.5 magnetostrictive forces—forces arising from magnetic
instrumentisconvertedintoaproportionald-cvoltagewhichis
domain wall movements within a magnetic material during
then applied to the readout device. Another technique uses a
magnetization.
veryhigh-frequencyoscillatorthatismodulatedorgatedbythe
appropriate echo indications, the output being used either
3.2.6 meander coil—an EMAT coil consisting of periodic,
directlytosuitabledigitalreadoutsorconvertedtoavoltagefor
winding, nonintersecting, and usually evenly spaced conduc-
other presentation.
tors.
5. Significance and Use
4. Summary of Practice
5.1 The methods described provide indirect measurement of
4.1 Determining the thickness (T) of a material, when
the thickness of sections of materials not exceeding tempera-
measured by the pulse-echo ultrasonic method, is a product of
tures of 1200°F [650°C]. Measurements are made from one
the velocity of sound in the material (V) and the transit time (t)
side of the object, without requiring access to the rear surface.
divided by two due to round trip through the material.
5.2 Ultrasonic thickness measurements are used extensively
T 5 Vt⁄2 (1)
on basic shapes and products of many materials, on precision
4.2 The pulse-echo ultrasonic instrument measures the tran-
machined parts, and to determine wall thinning in process
sit time of the ultrasonic pulse travelling through the part.
equipment caused by corrosion and erosion.
4.3 The velocity in the material being measured is a
5.3 Recommendations for determining the capabilities and
function of the material physical properties. It is usually
limitations of ultrasonic thickness gages for specific applica-
assumed to be uniform for a given class of materials and its
tions can be found in the cited references (1,2).
approximate value can be obtained fromTable X3.1 in Practice
E494, from other references, or can be estimated experimen-
6. Basis of Application
tally. Different alloys of steel, aluminum, or other metals can
have differences in velocity enough to make your reading 6.1 The following items are subject to contractual agree-
ment between the parties using or referencing this standard.
outside of its accuracy requirements. Extreme care must be
taken when selecting calibration block materials.
6.2 Personnel Qualification:
6.2.1 If specified in the contractual agreement, personnel
4.4 One or more reference blocks are required having
performing examinations to this standard shall be qualified in
known velocity or, preferably, being of the same alloy material
accordance with a nationally- or internationally-recognized
as that being examined, and having thicknesses accurately
NDT personnel qualification practice or standard such as
measured, and which are in the range of thicknesses to be
ANSI/ASNT-CP-189, SNT-TC-1A, NAS-410, ISO 9712, or a
measured. It is generally desirable that the thicknesses be
similar document and certified by the employer or certifying
“round numbers” rather than miscellaneous odd values. One
agency, as applicable. The practice or standard used and its
block should have a thickness value near the maximum
applicable revision shall be identified in the contractual agree-
thickness of the range of interest and another block near the
ment between the using parties. Instruments with direct read
minimum thickness.
thickness displays, including automated thickness
4.5 Thickness measurements of materials at high-
measurement, may be used by personnel only trained in the
temperature can be performed with specially designed search
thickness measurement procedure if initial programing of the
units with high temperature compensation. Normalization of
instrument is done by personnel trained in accordance with one
apparent thickness readings for elevated temperatures is re-
of the standards mentioned above.
quired. A rule of thumb mentioned in Practice E797 and often
used is as follows: The apparent thickness reading obtained 6.3 Qualification of Nondestructive Agencies—If specified
in the contractual agreement, NDT agencies shall be qualified
from steel walls having elevated temperatures is high (too
thick) by a factor of about 1 % per 100°F (55°C). Thus, if the and evaluated as described in Specification E543. The appli-
cable edition of Specification E543 shall be specified in the
instrument was standardized on a piece of similar material at
68°F (20°C), and if the reading was obtained with a surface contractual agreement.
temperature of 860°F (460°C), the apparent reading should be
6.4 Procedures and Techniques—The procedures and tech-
reduced by 8 %. This correction is an average one for many
niques to be used shall be as described in this practice unless
types of steel. Other corrections would have to be determined
otherwisespecified.Specifictechniquesmaybespecifiedinthe
empirically for other materials.
contractual agreement.
4.6 The display element (A-scan display, meter, or digital
display) of the instrument must be adjusted to present conve-
nie
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