1、Designation: C 651 91 (Reapproved 2005)e1An American National StandardStandard Test Method forFlexural Strength of Manufactured Carbon and GraphiteArticles Using Four-Point Loading at Room Temperature1This standard is issued under the fixed designation C 651; the number immediately following the des
2、ignation 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.This standard has been approved for use
3、by agencies of the Department of Defense.e1NOTEUnits of measurement were corrected in Section 8 in May 2005.1. Scope1.1 This test method covers determination of the flexuralstrength of manufactured carbon and graphite articles using asimple beam in four-point loading at room temperature.1.2 The valu
4、es stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation only.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-p
5、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C78 Test Method for Flexural Strength of Concrete (UsingSimple Beam with Third-Point Loading)C 709 Terminology Relating to Manufactured Carbon andGraph
6、iteE4 Practices for Force Verification of Testing MachinesE 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1
7、flexural strengtha measure of the ultimate load-carrying capacity of a specified beam in bending.3.2 DefinitionsFor definitions of terms relating to manu-factured carbon and graphite, see Terminology C 709.4. Apparatus4.1 The testing machine shall conform to the requirementsof Practices E4.4.2 The f
8、our-point loading fixture shall consist of bearingblocks which ensure that forces applied to the beam are normalonly and without eccentricity. (See Test Method C78.)4.2.1 The bearing block diameter shall be between 1/10 and1/20 of the specimen support span. A hardened steel bearingblock or its equiv
9、alent is necessary to prevent distortion of theloading member.4.3 The directions of loads and reactions may be maintainedparallel by judicious use of linkages, rocker bearings, andflexure plates. Eccentricity of loading can be avoided by theuse of spherical bearings. Provision must be made in fixtur
10、edesign for relief of torsional loading to less than 5 % of thenominal specimen strength. Refer to the attached figure for asuggested four-point loading fixture.5. Test Specimen5.1 PreparationThe test specimen shall be prepared toyield a parallelepiped of rectangular cross section. The facesshall be
11、 parallel and flat within 0.001 in. (0.025 mm)/in. oflength. In addition, the samples having a maximum particlesize less than 0.006-in. (0.152-mm) diameter must be finishedso that the surface roughness is less than 125 in. AA. Sampleedges should be free from visible flaws and chips.5.2 SizeThe size
12、of the test specimen shall be selectedsuch that the minimum dimension of the specimen is greaterthan 5 times the largest particle dimension. The test specimenshall have a length to thickness ratio of at least 8, and a widthto thickness ratio not greater than 2.5.3 MeasurementsAll dimensions shall be
13、 measured tothe nearest 0.5 %.5.4 OrientationThe specimen shall be marked on the endto denote its orientation with respect to the parent stock.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.F0
14、on Manufactured Carbon and Graphite Products.Current edition approved May 1, 2005. Published May 2005. Originallyapproved in 1970. Last previous edition approved in 2000 as D 651 91 (2000)2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service
15、astm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.5 DryingEach specimen must be dried in a vented ovenat 1
16、20 to 150C for a period of 2 h. The sample must then becooled to room temperature in a desiccator and held there priorto testing.6. Procedure6.1 Center the load applying bearing surfaces and the testspecimen on the bearing blocks. The load span is at least twotimes the sample thickness, and the supp
17、ort span three timesthe load span, but not less than 112 in. (38.1 mm). Overlap eachend of the specimen by at least the specimen thickness. Referto Fig. 1.6.2 The load applying bearing surfaces shall make contactwith the upper surface of the test specimen. Load and supportbearing blocks must be para
18、llel to each other and perpendicularto the test surfaces. Use a loading rate of 0.05 in. (1.27mm)/min or less on screw-driven testing machines. On othertest devices, load the part at a uniform rate such that breakageoccurs in5sormore.7. Test Data Record7.1 Measurements to 0.001 in. (0.025 mm) shall
19、be made todetermine the average width and thickness of the specimen atthe section of failure.7.2 The load at failure must be recorded to an accuracy of62 % of the full-scale value.Afull-scale value of 1000 lb (454kg) would require recording to an accuracy of 620 lb (69.08kg).8. Calculation8.1 If the
20、 fracture occurs within the span length between theload bearing surfaces, calculate the flexural strength as follows:S 5 PL/bd2where:S = flexural strength, psi (MPa),P = maximum applied load indicated by the testing ma-chine, lbf (N),L = support span length, in. (mm),b = average width of specimen, i
21、n. (mm), andd = average thickness of specimen, in. (mm).8.2 If the fracture occurs outside of the span length betweenload bearing blocks, the results of the test shall be discardedbut reported. If fracture occurs in less than 5 s, the results shallbe discarded but reported.8.3 Amultiplying factor of
22、 6.895 may be used to convert ksito MPa.9. Report9.1 The report of each test shall include the following:9.1.1 Sample identification,9.1.2 Average width to the nearest 0.001 in. (0.025 mm),9.1.3 Average thickness to the nearest 0.001 in. (0.025 mm),9.1.4 Span length, in. (mm),9.1.5 Rate of loading,
23、(in./min or ppm),9.1.6 Maximum applied load, lbf (N),9.1.7 Flexural strength calculated to the nearest 10 psi (69kPa),9.1.8 Defects in specimen,9.1.9 Orientation and location of specimen, and9.1.10 Failure mode and location.10. Precision and Bias310.1 PrecisionThe precision statements given in thiss
24、ection are based on the comparison of the mean strength bythe Student “t” test and carrying out the statistical analysis ofthe data obtained in a round robin as recommended by PracticeE 691.10.1.1 Comparison of the MeansThe comparison of themeans by the Student “t” test leads to the conclusion that
25、theaverage strength values measured by each laboratory can beconsidered statistically equal to 95 percent confidence level.10.1.2 Repeatability (Single Instrument)The precisionwithin laboratory of two single values of measured strengthusing Practice E 177 definition with the pooled standarddeviation
26、 calculated using Practice E 691 is:Repeatability within laboratory 5 2 Sr!j,which yields a value for the material used in the round robinof 257 psi (1.8 MPa). This value converts into a strengthpercentage of 65.5.10.1.3 Repeatability (Multi-Instrument) The precision be-tween laboratories of two sin
27、gle values of measured strengthusing Practice E 177 definition with the component of variancebetween laboratories calculated using Practice E 691 is:Repeatability between laboratories 5 2 SL!j,which yields a value for the material used in this round robinof 46 psi (0.3 MPa). This converts into a str
28、ength percentage of61.10.2 BiasNo true statement on bias can be made becauseno reference carbon or graphite material exists.11. Keywords11.1 carbon; flexural strength; graphite; modulus of rupture3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Res
29、earch Report RR: C05-1011.FIG. 1 Beam with Four-Point LoadingC 651 91 (2005)e12ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the vali
30、dity 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 time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comm
31、ents are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have
32、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 ASTM 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).C 651 91 (2005)e13
