ASTM C769-98

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An American National Standard
Designation:C769–98
Standard Test Method for
Sonic Velocity in Manufactured Carbon and Graphite
Materials for Use in Obtaining an Approximate Young’s
Modulus
This standard is issued under the fixed designation C 769; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 This test method describes a procedure for measuring 4.1 The velocity of sound waves passing through the test
the sonic velocity in manufactured carbon and graphite mate- specimen is determined by measuring the distance through the
rials having a grain size less than 0.80 mm ( ⁄32in.). The sonic specimen and dividing by the time lapse, between the trans-
4,5
velocity can be used to obtain an approximate value for mitted pulse and the received pulse. An approximate value
Young’s modulus. for Young’s modulus can then be obtained as follows:
1.2 This standard does not purport to address all of the
E5rv (1)
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
where:
priate safety and health practices and determine the applica- E = Young’s modulus of elasticity, Pa,
r = density, kg/m , and
bility of regulatory limitations prior to use.
v = signal velocity, m/s.
2. Referenced Documents
Strictly speaking, the elastic constant given by this measure-
ment is not E but C , provided the sonic pulse is longitudinal
2.1 ASTM Standards:
C 559 Test Method for Bulk Density by Physical Measure- and the direction of propagation is along the axis of symme-
4,5
try.
ment of Manufactured Carbon and Graphite Articles
C 747 Test Method for Moduli of Elasticity and Fundamen-
5. Significance and Use
tal Frequencies of Carbon and Graphite Materials by Sonic
5.1 Sonic velocity measurements are useful for comparing
Resonance
materials.
IEEE/ASTM SI 10 Standard for Use of the International
5.2 A value for Young’s modulus can be obtained for many
System of Units (SI) (the Modern Metric System)
applications, which will generally be within 10 % of the value
3. Terminology
obtained by other methods, such as in Test Method C 747.
3.1 Definitions of Terms Specific to This Standard:
6. Apparatus
3.1.1 longitudinal sonic pulse—a sonic pulse in which the
6.1 Driving Circuit, which consists of an ultrasonic pulse
displacements are in the direction of propagation of the pulse.
generator capable of producing pulses in a frequency range
3.1.2 pulse travel time, (T)—the total time, measured in
t
from 0. 5 to 2.6 MHz.
seconds, required for the sonic pulse to traverse the specimen
6.2 Transducer, input.
being tested, and for the associated electronic signals to
6.3 Transducer, output.
traverse the circuits of the pulse-propagation circuitry.
6.4 Oscilloscope, dual trace with a preamplifier and time-
3.1.3 zero time, (T )—the travel time (correction factor),
o
delay circuitry.
measured in seconds, associated with the electronic circuits in
6.5 See Fig. 1 for a typical setup.
the pulse-propagation system.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of D02.F on
Manufactured Carbon and Graphite Products.
CurrenteditionapprovedMarch10,1998.PublishedSeptember1998.Originally Schreiber, Anderson, and Soga, Elastic Constants and Their Measurement,
published as C 769 – 80. Last previous edition C 769 – 80 (Reapproved 1989). McGraw-Hill Book Co., 1221Avenue of theAmericas, NewYork, NY10020, 1973.
2 5
Annual Book of ASTM Standards, Vol 05.05. American Institute of Physics Handbook,3rded.,McGraw-HillBookCo.,1221
Annual Book of ASTM Standards, Vol 14.02. Avenue of the Americas, New York 10020, 1972, pp. 3–98ff.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C769
8.5 Measure and weigh the test specimen as in 7.2.
8.6 Calculate the density of the test specimen in accordance
with Test Method C 559.
8.7 Lightly grease the faces of the test specimens that will
contact the transducers or provide another suitable medium for
this purpose. Place the transducers against the test specimen
end faces.
8.8 Tune the signal generator to transducer frequency, and
adjust the electronic components to give good visual amplitude
resolution on the oscilloscope.
8.9 Determine T, the total traverse time from the oscillo-
t
scope traces, as illustrated in Fig. 2, preferably by using
time-delay circuitry.
9. Calculation
9.1 Velocity of Signal:
L
v 5 (2)
T 2 T
t o
where:
v = velocity of signal, m/s,
L = specimen length, m,
T = traverse time, s, and
t
T = travel time, s.
o
9.2 Since graphites are not isotropic, the value of Young’s
modulus cannot be determined by a velocity measurement in
only one direction. However, an approximation to Young’s
modulus is obtained as follows:
E5rv (3)
FIG. 1 Equipment Setup
E = Young’s modulus, Pa (approximate),
7. Test Specimen
r = density, kg/m , and
7.1 Selection and Preparation of Specimens—Take special
v = velocity of sound, m/s.
care to assure obtaining representative specimens that are
9.3 Conversion Factors—See Practice
...