ASTM_C_769_-_15.pdf

Designation:C76915An American National StandardStandard Test Method forSonic Velocity in Manufactured Carbon and GraphiteMaterials for Use in Obtaining an Approximate Value ofYoungs Modulus1This standard is issued under the fixed designation C769;the number immediately following the designation 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()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This test method covers a procedure for measuring thesonic velocity in manufactured carbon and graphite which canbe used to obtain an approximate value of Youngs modulus.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard 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 Standards:2C559 Test Method for Bulk Density by Physical Measure-ments of Manufactured Carbon and Graphite ArticlesC747 Test Method for Moduli of Elasticity and FundamentalFrequencies of Carbon and Graphite Materials by SonicResonanceIEEE/ASTM SI 10 Standard for Use of the InternationalSystem of Units(SI)(the Modern Metric System)3.Terminology3.1 Definitions:3.1.1 elastic modulus,nthe ratio of stress to strain,in thestress range where Hookes law is valid.3.1.2 Youngs modulus or modulus of elasticity(E),ntheelastic modulus in tension or compression.3.2 Definitions of Terms Specific to This Standard:3.2.1 end correction time(Te)the non-zero time of flight(correction factor),measured in seconds,that may arise byextrapolation of the pulse travel time,corrected for zero time,back to zero sample length.3.2.2 longitudinal sonic pulsea sonic pulse in which thedisplacements are in the direction of propagation of the pulse.3.2.3 pulse travel time,(Tt)the total time,measured inseconds,required for the sonic pulse to traverse the specimenbeing tested,and for the associated electronic signals totraverse the transducer coupling medium and electronic circuitsof the pulse-propagation system.3.2.4 zero time,(T0)the travel time(correction factor),measured in seconds,associated with the transducer couplingmedium and electronic circuits in the pulse-propagation sys-tem.4.Summary of Test Method4.1 The velocity of longitudinal sound waves passingthrough the test specimen is determined by measuring thedistance through the specimen and dividing by the time lapse,between the transmitted pulse and the received pulse.3,4Pro-vided the wavelength of the transmitted pulse is a sufficientlysmall fraction of the sample lateral dimensions,a value ofYoungs modulus for isotropic graphite can then be obtainedusing Eq 1 and Eq 2:E 5 CvV2(1)where:E=Youngs modulus of elasticity,Pa,=density,kg/m3,V=longitudinal signal velocity,m/s,andCv=Poissons factor.The Poissons factor,C,is related to Poissons ratio,bythe equation:C511!1 2 2!1 2(2)1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricantsand is the direct responsibility ofSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Dec.1,2015.Published January 2016.Originallyapproved in 1980.Last previous edition approved in 2009 as C769 09.DOI:10.1520/C0769-15.2For referenced ASTM standards,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 Co.,1221Avenue of theAmericas,NewYork,NY10020,1973.4American Institute of Physics Handbook,3rd ed.,McGraw-Hill Book Co.,1221 Avenue of the Americas,New York,NY 10020,1972,pp.398ff.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 If Poissons ratio is unknown,it can be assumed as anapproximation in the method.For nuclear graphites,a typicalPoissons ratio of 0.2 corresponds to a Poissons factor of 0.9.If the wavelength is not a small fraction of the sample lateraldimensions,and instead is much larger than the specimenlateral dimensions,then the Youngs modulus,E is given by Eq1 with Cset to one rather than being determined by Eq 2.5.Significance and Use5.1 Sonic velocity measurements are useful for comparingmaterials with similar elastic properties,dimensions,andmicrostructure.5.2 Eq 1 provides an accurate value of Youngs modulusonly for isotropic,non-attenuative,and non-dispersive materi-als of infinite dimensions.For non-isotropic graphite,Eq 1 canbe modified to take into account th