ASTM C769-15(2020)e1

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.
´1
Designation: C769 − 15 (Reapproved 2020)
Standard Test Method for
Sonic Velocity in Manufactured Carbon and Graphite
Materials for Use in Obtaining an Approximate Value of
Young’s Modulus
This standard is issued under the fixed designation C769; 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.
ε NOTE—Editorially updated 3.1.2 in December 2020.
1. Scope 3. Terminology
1.1 This test method covers a procedure for measuring the 3.1 Definitions:
sonic velocity in manufactured carbon and graphite which can 3.1.1 elastic modulus, n—the ratio of stress to strain, in the
be used to obtain an approximate value of Young’s modulus. stress range where Hooke’s law is valid.
3.1.2 Young’s modulus (E), n—the elastic modulus in ten-
1.2 The values stated in SI units are to be regarded as
sion or compression.
standard. No other units of measurement are included in this
standard.
3.2 Definitions of Terms Specific to This Standard:
1.3 This standard does not purport to address all of the 3.2.1 endcorrectiontime(T ),n—thenon-zerotimeofflight
e
safety concerns, if any, associated with its use. It is the (correction factor), measured in seconds, that may arise by
responsibility of the user of this standard to establish appro- extrapolation of the pulse travel time, corrected for zero time,
priate safety, health, and environmental practices and deter- back to zero sample length.
mine the applicability of regulatory limitations prior to use.
3.2.2 longitudinal sonic pulse, n—asonicpulseinwhichthe
1.4 This international standard was developed in accor-
displacements are in the direction of propagation of the pulse.
dance with internationally recognized principles on standard-
3.2.3 pulse travel time, (T), n—the total time, measured in
t
ization established in the Decision on Principles for the
seconds, required for the sonic pulse to traverse the specimen
Development of International Standards, Guides and Recom-
being tested, and for the associated electronic signals to
mendations issued by the World Trade Organization Technical
traversethetransducercouplingmediumandelectroniccircuits
Barriers to Trade (TBT) Committee.
of the pulse-propagation system.
3.2.4 zero time, (T ), n—the travel time (correction factor),
2. Referenced Documents
measured in seconds, associated with the transducer coupling
2.1 ASTM Standards:
medium and electronic circuits in the pulse-propagation sys-
C559 Test Method for Bulk Density by Physical Measure-
tem.
ments of Manufactured Carbon and Graphite Articles
C747 Test Method for Moduli of Elasticity and Fundamental 4. Summary of Test Method
Frequencies of Carbon and Graphite Materials by Sonic
4.1 The velocity of longitudinal sound waves passing
Resonance
through the test specimen is determined by measuring the
IEEE/ASTM SI 10 Standard for Use of the International
distance through the specimen and dividing by the time lapse,
System of Units (SI) (the Modern Metric System)
3,4
between the transmitted pulse and the received pulse. Pro-
vided the wavelength of the transmitted pulse is a sufficiently
small fraction of the sample lateral dimensions, a value of
This test method is under the jurisdiction of ASTM Committee D02 on
Young’s modulus for isotropic graphite can then be obtained
Petroleum Products, Liquid Fuels, and Lubricantsand is the direct responsibility of
using Eq 1 and Eq 2:
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products.
Current edition approved Nov. 1, 2020. Published December 2020. Originally E 5 C ρV (1)
v
approved in 1980. Last previous edition approved in 2015 as C769 – 15. DOI:
10.1520/C0769-15R20E01.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Schreiber, Anderson, and Soga, Elastic Constants and Their Measurement,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM McGraw-HillBookCo.,1221AvenueoftheAmericas,NewYork,NY10020,1973.
Standards volume information, refer to the standard’s Document Summary page on AmericanInstituteofPhysicsHandbook,3rded.,McGraw-HillBookCo.,1221
the ASTM website. Avenue of the Americas, New York, NY 10020, 1972, pp. 3–98ff.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
C769 − 15 (2020)
the same as the wavelength of the transmitting transducer.
where:
E = Young’s modulus of elasticity, Pa, 5.4 Ifthesampleisonlyafewgrainsthick,theacceptability
ρ = density, kg/m , of the method’s application should be demonstrated by initially
V = longitudinal signal velocity, m/s, and
performing measurements on a series of tests covering a range
C = Poisson’s factor.
v of sample lengths between the proposed test length and a test
length incorporating sufficient grains to adequately represent
The Poisson’s factor, C , is related to Poisson’s ratio, ν,by
ν
the bulk material.
the equation:
11ν 1 2 2ν
~ !~ !
C 5 (2)
6. Apparatus
ν
1 2 ν
6.1 Driving Circuit, consisting of an ultrasonic pulse gen-
If Poisson’s ratio is unknown, it can be assumed as an
erator.
approximation in the method. For nuclear graphites, a typical
6.1.1 The user should select a pulse frequency to suit the
Poisson’s ratio of 0.2 corresponds to a Poisson’s factor of 0.9.
material microstructure and specimen elastic properties and
If the wavelength is not a small fraction of the sample lateral
dimensions being tested. High frequencies are attenuated by
dimensions, and instead is much larger than the specimen
carbon and graphite materials and, while typical practicable
lateral dimensions, then theYoung’s modulus, E is given by Eq
frequencies lie in the range 0.5 MHz to 2.6 MHz, the user may
1 with C set to one rather than being determined by Eq 2.
ν
show that frequencies outside this range are acceptable.
5. Significance and Use
6.2 Transducer, input, with suitable coupling medium (see
8.5).
5.1 Sonic velocity measurements are useful for comparing
materials with similar elastic properties, dimensions, and
6.3 Transducer, output, with suitable coupling medium (see
microstructure.
8.5).
6.3.1 The signal output will depend upon the characteristics
5.2 Eq 1 provides an accurate value of Young’s modulus
of the chosen transducers and pulser-receiver and the test
only for isotropic, non-attenuative, and non-dispersive materi-
material.Itisrecommendedthattheuseranalysestheinputand
als of infinite dimensions. For non-isotropic graphite, Eq 1 can
output frequency spectra to determine optimum conditions.
be modified to take into account the Poisson’s ratios in all
Band pass filters and narrow band transducers may be used to
directions. As graphite is a strongly attenuative material, the
simplify the signal output which could improve the measure-
value of Young’s modulus obtained with Eq 1 will be depen-
ment of the time of flight.
dentonspecimenlength.Ifthespecimenlateraldimensionsare
not large compared to the wavelength of the propagated pulse,
6.4 Computer, with analogue to digital converter, or
then the value of Young’s modulus obtained with Eq 1 will be
oscilloscope, and external trigger from driving circuit.
dependentonthespecimenlateraldimensions.Theaccuracyof
6.5 See Fig. 1 for a typical schematic setup.
the Young’s modulus calculated from Eq 1 will also depend
upon the uncertainty in Poisson’s ratio and its impact on the NOTE 2—Some manufacturers combine items 6.1 and 6.4 into a single
package with direct time readout. Such apparatus can operate
evaluationofthePoisson’sfactorinEq2.However,avaluefor
satisfactorily, provided the frequency of the propagated pulse is already
Young’s modulus can be obtained for many applications,
known, in order to check that wavelength requirements for the method are
which is often in good agreement with the value obtained by
satisfied.
other more accurate methods, such as in Test Method C747.
The technical issues and typical values of corresponding
7. Test Specimen
uncertainties are discussed in detail in STP 1578.
7.1 Selection and Preparation of Specimens—Take special
5.3 If the grain size of the carbon or graphite is greater than
care to assure obtaining representative specimens that are
or about equal to the wavelength of the sonic pulse, the method
straight, uniform in cross section, and free of extraneous
may not be providing a value of Young’s modulus representa-
liquids. The specimen end faces shall be perpendicular to the
tive of the bulk material. Therefore, it would be recommended
specimencylindricalsurfacetowithin0.125 mmtotalindicator
to test a lower frequency (longer wavelength) to demonstrate
reading.
that the range of obtained velocity values are within an
7.2 Measurement of Weight and Dimensions—Determine
acceptable level of accuracy. Significant signal attenuation
the weight and the average specimen dimensions to within
should be expected when the grain size of the material is
60.2 %.
greaterthanoraboutequaltothewavelengthofthetransmitted
sonic pulse or the material is more porous than would be 7.3 Limitations on Dimensions—These cannot be precisely
expected for an as-manufactured graphite. specified as they will depend upon the properties of the
material being tested and the experimental setup (for example,
NOTE 1—Due to frequency dependent attenuation in graphite, the
transducer frequency). In order to satisfy the theory that
wavelength of the sonic pulse through the test specimen is not necessarily
supports Eq 1, as a guide, the specimen should have a diameter
that is at least a factor five, greater than the wavelength of
ASTM Selected Technical Papers, STP 1578, Graphite Testing for Nuclear
sound in the material under test. In practice, the length of the
Applications: The Significance of Test Specimen Volume and Geometry and the
specimen will be determined taking account of the comments
Statistical Significance of Test Specimen Population, 2014, edited by Tzelepi and
Carroll. in 5.3 and 5.4.
´1
C769 − 15 (2020)
FIG. 1 Basic Experimental Arrangement for the Ultrasonic Pulsed-Wave Transit Time Technique
cellulose, petroleum jelly, high vacuum greases and water-based ultra-
7.4 Limitations on Ultrasonic Pulse Frequency—Generally
sonic couplants. However these may be difficult to remove subsequently.
speaking, a better accuracy of time of flight will be obtained at
Distilled water can provide a very satisfactory coupling medium without
higher frequencies. However, attenuation increases at higher
significantendeffects,andsurfacewatermayberemovedsubsequentlyby
frequencies leading to weak and distorted signals.
drying. Manufacturers offer rubber-tipped transducers suitable for nonin-
vasive measurements. With these transducers either good load control or
8. Procedure
accurate determination of the rubber length is essential during measure-
ment if good reproducibility is to be achieved.
8.1 For any given apparatus and choice of coupling
medium, it is necessary to follow procedures to quantify the 8.6 Bring transducer faces into intimate contact but do not
zerotime,T ,andendcorrectiontime,T ,correctionfactors.T
exceed manufacturer’s recommended contact pressures.
0 e 0
will be dependent upon the type of transducers and their
8.7 Followthevendor’sinstructionstoadjusttheinstrumen-
performance over time and should be regularly checked (see
tation to match the transducer frequency to give good visual
8.8).Itmustbequantifiedifthetestsetupischanged.T should
e
amplitude resolution.
be small and reflects the interaction between the coupling
medium
...