1、Designation: C 769 98 (Reapproved 2005)An American National StandardStandard Test Method forSonic Velocity in Manufactured Carbon and GraphiteMaterials for Use in Obtaining an Approximate YoungsModulus1This standard is issued under the fixed designation C 769; the number immediately following the de
2、signation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a p
3、rocedure for measuring thesonic velocity in manufactured carbon and graphite materialshaving a grain size less than 0.80 mm (132 in.). The sonicvelocity can be used to obtain an approximate value forYoungs modulus.1.2 The values stated in SI units are to be regarded as thestandard.1.3 This standard
4、does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM S
5、tandards:2C 559 Test Method for Bulk Density by Physical Measure-ment of Manufactured Carbon and Graphite ArticlesC 747 Test Method for Moduli of Elasticity and Fundamen-tal Frequencies of Carbon and Graphite Materials by SonicResonanceIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of U
6、nits (SI) (the Modern Metric System)3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 longitudinal sonic pulsea sonic pulse in which thedisplacements are in the direction of propagation of the pulse.3.1.2 pulse travel time, (Tt)the total time, measured inseconds, required for th
7、e sonic pulse to traverse the specimenbeing tested, and for the associated electronic signals totraverse the circuits of the pulse-propagation circuitry.3.1.3 zero time, (To)the travel time (correction factor),measured in seconds, associated with the electronic circuits inthe pulse-propagation syste
8、m.4. Summary of Test Method4.1 The velocity of sound waves passing through the testspecimen is determined by measuring the distance through thespecimen and dividing by the time lapse, between the trans-mitted pulse and the received pulse.3,4An approximate valuefor Youngs modulus can then be obtained
9、 as follows:E 5rv2(1)where:E = Youngs modulus of elasticity, Pa,r = density, kg/m3, andv = signal velocity, m/s.Strictly speaking, the elastic constant given by this measure-ment is not E but C33, provided the sonic pulse is longitudinaland the direction of propagation is along the axis of symme-try
10、.3,45. Significance and Use5.1 Sonic velocity measurements are useful for comparingmaterials.5.2 A value for Youngs modulus can be obtained for manyapplications, which will generally be within 10 % of the valueobtained by other methods, such as in Test Method C 747.6. Apparatus6.1 Driving Circuit, w
11、hich consists of an ultrasonic pulsegenerator capable of producing pulses in a frequency rangefrom 0. 5 to 2.6 MHz.6.2 Transducer, input.6.3 Transducer, output.6.4 Oscilloscope, dual trace with a preamplifier and time-delay circuitry.1This test method is under the jurisdiction of ASTM Committee D02
12、onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products.Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1980. Last previous edition approved in 1998 as C 769 98.2For referenced ASTM standa
13、rds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Schreiber, Anderson, and Soga, Elastic Constants and Their Measurement,McGraw-Hill Book
14、 Co., 1221Avenue of theAmericas, New York, NY 10020, 1973.4American Institute of Physics Handbook, 3rd ed., McGraw-Hill Book Co., 1221Avenue of the Americas, New York 10020, 1972, pp. 398ff.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United St
15、ates.6.5 See Fig. 1 for a typical setup.7. Test Specimen7.1 Selection and Preparation of SpecimensTake specialcare to assure obtaining representative specimens that arestraight, uniform in cross section, and free of extraneousliquids. The specimen end faces shall be perpendicular to thespecimen cyli
16、ndrical surface to within 0.125 mm (0.005 in.)total indicator reading.7.2 Measurement of Weight and DimensionsDeterminethe weight and the average specimen dimensions to within60.5 %.7.3 Limitations on DimensionsThe specimen shall have adiameter and length that is large compared to the wavelength ofs
17、ound in the material under test.8. Procedure8.1 Connect the apparatus as shown in Fig. 1, and refer toequipment manufacturers instructions for hookup precautions.Allow adequate time for equipment warm-up and stabilization.8.2 Provide a suitable coupling medium on transducer faces.NOTE 1Hydroxyethyl
18、cellulose may be used. Petroleum jelly coupleswork well but may be difficult to remove for subsequent tests on the samespecimen.8.3 Bring transducer faces into intimate contact but do notexceed manufacturers recommended contact pressures.8.4 Determine To, the travel time (zero correction) measuredin
19、 seconds, associated with the electronic circuits in thepulse-propagation instrument and coupling.8.5 Measure and weigh the test specimen as in 7.2.8.6 Calculate the density of the test specimen in accordancewith Test Method C 559.8.7 Lightly grease the faces of the test specimens that willcontact t
20、he transducers or provide another suitable medium forthis purpose. Place the transducers against the test specimenend faces.8.8 Tune the signal generator to transducer frequency, andadjust the electronic components to give good visual amplituderesolution on the oscilloscope.8.9 Determine Tt, the tot
21、al traverse time from the oscillo-scope traces, as illustrated in Fig. 2, preferably by usingtime-delay circuitry.9. Calculation9.1 Velocity of Signal:v 5LTt2 To(2)where:v = velocity of signal, m/s,L = specimen length, m,Tt= traverse time, s, andTo= travel time, s.9.2 Since graphites are not isotrop
22、ic, the value of Youngsmodulus cannot be determined by a velocity measurement inonly one direction. However, an approximation to Youngsmodulus is obtained as follows:E 5rv2(3)E = Youngs modulus, Pa (approximate),r = density, kg/m3, andv = velocity of sound, m/s.9.3 Conversion FactorsSee IEEE/ASTM SI
23、 10.10. Report10.1 The report shall include the following:FIG. 1 Equipment Setup FIG. 2 Typical Oscilloscope DisplayC 769 98 (2005)210.1.1 Specimen dimensions, weight, and test specimenorientation with respect to forming direction;10.1.2 Sonic velocity for each specimen;10.1.3 Density of each specim
24、en, if calculated;10.1.4 Youngs modulus of each specimen, if calculated;10.1.5 It is recommended that average and standard devia-tion values be included for each group of specimens;10.1.6 Environmental conditions of test, including tempera-ture, humidity, and special atmosphere (if used);10.1.7 Freq
25、uency of transducers used and sonic velocityequipment identification;10.1.8 Method of coupling the transducers to the specimen;and10.1.9 As available, complete identification of the materialbeing tested including manufacturer, grade identification, lotnumber and grain orientation, original billet si
26、ze, and specimensampling plan.11. Precision and Bias511.1 Around-robin series of sonic velocity measurements asperformed on four different materials by two laboratories.Twelve samples of each material were measured. In all, foursets of measurements were made on each group of twelvesamples for a tota
27、l of sixteen sets of data. The averagecoefficient of variance for the sixteen sets was 3.8 %, which isindicative of the sample-to-sample and measurement-to-measurement variation in each set of twelve.11.2 There was a difference between the moduli measuredon a given material by the two laboratories r
28、anging from 0 to14 %, which suggests that the methods used are materialdependent.11.3 Also included in the round-robin were resonant-bar-modulus (see Test Method C 747) and stress-strain modulusmeasurements. Differences between the resonant-bar modulusand the sonic velocity modulus were also signifi
29、cant, being ashigh as 10 %. Although most of the resonant-bar moduli arelower than the sonic velocity moduli, in one material, thereverse was true. Thus a simple correction factor cannot beapplied.11.4 The systematic differences between laboratories andmaterials and methods can occur for several rea
30、sons:11.4.1 Frequency of the wave used.11.4.2 Sample size-to-wavelength ratio.11.4.3 Interpretation of the breakaway point on the receivedsignal.11.4.4 Coupling factors, such as transducer pressure.11.4.5 Different modes of propagation for the differentsample configuration used in the tests.11.5 The
31、 value of Youngs modulus obtained by this methodmust not be construed as accurate or absolute to better thanabout 10 % as evidenced by the interlaboratory differences.However, in a given laboratory setup, a relatively high degreeof precision is obtainable and might be construed as anaccurate value.
32、For comparative purposes in a given material,the method is adequate, but from one material to another, themodulus comparison must be considered approximate.12. Keywords12.1 carbon; graphite; sonic; velocity; Youngs ModulusASTM International takes no position respecting the validity of any patent rig
33、hts asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any
34、 time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments wi
35、ll receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by AS
36、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).5Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: C05-1001.C 769 98 (2005)3
