ASTM E2985/E2985M-14(2019)
(Practice)Standard Practice for Determination of Metal Purity Based on Elastic Constant Measurements Derived from Resonant Ultrasound Spectroscopy
Standard Practice for Determination of Metal Purity Based on Elastic Constant Measurements Derived from Resonant Ultrasound Spectroscopy
SIGNIFICANCE AND USE
5.1 Since the beginning of human history, currency has existed in the form of metal coins and bullion. Thieves learned that shaving some precious metal provided a method to change its value. Substitution of common metals for precious metals of higher value was commonplace until weighing methods became so accurate, that it became easily detected. Alloys were also used as substitutes until inexpensive spectrometers became available which ended the counterfeiting practice. The rapid rise in the value of gold inspired the unscrupulous to find a new method. Tungsten was widely used for light bulb filaments until regulations changed that market. The great abundance of tungsten now available, coupled with the almost identical density of gold, presented a new opportunity.
5.2 RUS provides a method to create an unique electronic signature for each piece tested which is operator independent.
SCOPE
1.1 This practice is intended for use with resonant ultrasound spectrometers capable of exciting, measuring, recording, and analyzing multiple whole body mechanical vibration resonant frequencies within parts exhibiting acoustical ringing in the acoustic or ultrasonic, or both, resonant frequency ranges.
1.2 This practice uses Resonant Ultrasound Spectroscopy (RUS) to distinguish conforming parts, as determined from qualified training sets, from those containing significant anomalies in their elastic properties.
1.3 The basic functions of a RUS monitoring system are to detect and classify resonance phenomena. Solid structure resonances are governed by the part’s dimensions, density, and elastic properties. When a material substitution occurs in a precious metal, the chosen metals have almost identical densities and unchanged dimensions, leaving only the elastic properties to affect the resonances.
1.4 This practice can be used to replace destructive methods, which damage the test object through drilling or melting, or both.
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.6 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.
1.7 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
Relations
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: E2985/E2985M − 14 (Reapproved 2019)
Standard Practice for
Determination of Metal Purity Based on Elastic Constant
Measurements Derived from Resonant Ultrasound
Spectroscopy
ThisstandardisissuedunderthefixeddesignationE2985/E2985M;thenumberimmediatelyfollowingthedesignationindicatestheyear
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 1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This practice is intended for use with resonant ultra-
ization established in the Decision on Principles for the
sound spectrometers capable of exciting, measuring, recording,
Development of International Standards, Guides and Recom-
and analyzing multiple whole body mechanical vibration
mendations issued by the World Trade Organization Technical
resonant frequencies within parts exhibiting acoustical ringing
Barriers to Trade (TBT) Committee.
in the acoustic or ultrasonic, or both, resonant frequency
ranges.
2. Referenced Documents
1.2 This practice uses Resonant Ultrasound Spectroscopy
2.1 ASTM Standards:
(RUS) to distinguish conforming parts, as determined from
E543 Specification for Agencies Performing Nondestructive
qualified training sets, from those containing significant
Testing
anomalies in their elastic properties.
E1316 Terminology for Nondestructive Examinations
1.3 The basic functions of a RUS monitoring system are to
E2001 Guide for Resonant Ultrasound Spectroscopy for
detect and classify resonance phenomena. Solid structure Defect Detection in Both Metallic and Non-metallic Parts
resonances are governed by the part’s dimensions, density, and
2.2 Other Referenced Documents:
elastic properties. When a material substitution occurs in a
ANSI/ASNT CP-189 Standard for Qualification and Certifi-
precious metal, the chosen metals have almost identical den-
cation of Nondestructive Testing Personnel
sities and unchanged dimensions, leaving only the elastic
NAS-410 NDT Certification
properties to affect the resonances.
SNT-TC-1A Personnel Qualification and Certification in
Nondestructive Testing
1.4 This practice can be used to replace destructive
methods, which damage the test object through drilling or
3. Terminology
melting, or both.
3.1 Definitions—Thedefinitionsoftermsrelatingtoconven-
1.5 The values stated in either SI units or inch-pound units
tional ultrasonic examination can be found in Terminology
are to be regarded separately as standard. The values stated in
E1316.
each system may not be exact equivalents; therefore, each
3.2 Resonant ultrasound spectroscopy (RUS)—Basic RUS
system shall be used independently of the other. Combining
was originally applied in fundamental research applications in
values from the two systems may result in non-conformance
physics and materials science.Afew other recognizable names
with the standard.
include acoustic resonance spectroscopy, acoustic resonant
1.6 This standard does not purport to address all of the
inspection, and resonant inspection. Guide E2001 documents
safety concerns, if any, associated with its use. It is the
RUS extensively.Anondestructive examination method which
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. 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- Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
structive Testing and is the direct responsibility of Subcommittee E07.06 on 4th Floor, New York, NY 10036, http://www.ansi.org.
Ultrasonic Method. Available fromAerospace IndustriesAssociation ofAmerica, Inc. (AIA), 1000
Current edition approved May 1, 2019. Published June 2019. Originally WilsonBlvd.,Suite1700,Arlington,VA22209-3928,http://www.aia-aerospace.org.
approved in 2014. Last previous edition approved in 2014 as E2985/E2985M – 14. AvailablefromAmericanSocietyforNondestructiveTesting(ASNT),P.O.Box
DOI: 10.1520/E2985_E2985M-14R19. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2985/E2985M − 14 (2019)
employs the measurement and analysis of acoustic or ultra- many different samples to observe the differences from differ-
sound resonance patterns, or both, for the identification of ent mints and geometries. A RUS examination of doped
acceptablevariationsinthephysicalcharacteristicsoftestparts samples is then used to illustrate spectral differences and
in production environments. In this procedure an isolated, rigid establish detection limits.
partiscausedtoresonate.Certainresonancesaremeasuredand
5. Significance and Use
compared to a previously defined acceptable pattern combina-
tion of resonances. Based on this comparison the part is judged
5.1 Since the beginning of human history, currency has
to be acceptable or, if it does not conform to the established
existed in the form of metal coins and bullion. Thieves learned
pattern, to be unacceptable.
that shaving some precious metal provided a method to change
itsvalue.Substitutionofcommonmetalsforpreciousmetalsof
4. Summary of Practice
higher value was commonplace until weighing methods be-
came so accurate, that it became easily detected. Alloys were
4.1 Reports indicating that gold bullion is being physically
also used as substitutes until inexpensive spectrometers be-
hollowed and replaced with similar density metals, such as
came available which ended the counterfeiting practice. The
tungsten, are surfacing. While not a huge concern for the
rapid rise in the value of gold inspired the unscrupulous to find
original manufacturer, the secondary exchange market can
a new method. Tungsten was widely used for light bulb
experience disruption if the integrity of the asset comes into
filaments until regulations changed that market. The great
question. Verifying the sample purity is critical and must be
abundance of tungsten now available, coupled with the almost
performed quickly and nondestructively. Several potential test
identical density of gold, presented a new opportunity.
methods are applicable, but most are not good solutions for
expense and technical reasons. 5.2 RUS provides a method to create an unique electronic
signature for each piece tested which is operator independent.
4.2 In physics, resonance is the tendency of a system to
oscillate at a greater amplitude at some frequencies than at
6. Basis of Application
others. These are known as the system’s resonance frequencies
6.1 The following items are subject to contractual agree-
and are generally functions of the square root of the stiffness
ment between the parties using or referencing this practice.
over the mass. Since each unique metal has a set of defined
elastic constants, the stiffness of any two metals will always be 6.2 Personnel Qualification
different, meaning that the resonances produced from any 6.2.1 If specified in the contractual agreement, personnel
driving forces will be different and easily measured. Reso- performing examinations to this standard shall be qualified in
nances can be produced from any swept sine spectrometer
accordance with a nationally and internationally recognized
(preferred) or with an impulse function (striking with a NDT personnel qualification practice or standard such as
hammer). Independent of how the resonance spectrum is
ANSI/ASNT CP-189, SNT-TC-1A, NAS-410, or similar as
created, it can be measured and compared with known good applicable. The practice or standard used and its applicable
samples to observe whether or not it has been altered as
revision shall be identified in the contractual agreement be-
described in 4.4. tween the using parties.
4.3 RUS, as defined in Guide E2001, describes a sample 6.3 Qualification of Nondestructive Testing Agencies—If
specified in the contractual agreement, NDT agencies shal
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