1、Designation: C651 11C651 13 An 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 C651; the number immediately following the designation indic
2、ates 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.This standard has been approved for use by agencies of
3、the Department of Defense.1. Scope Scope*1.1 This test method covers determination of the flexural strength of manufactured carbon and graphite articles using a simplebeam in four-point loading at room temperature.1.2 The values stated in SI units are to be regarded as standard. No other units of me
4、asurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatoryli
5、mitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C78 Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading)C709 Terminology Relating to Manufactured Carbon and GraphiteC1161 Test Method for Flexural Strength of Advanced Ceramics at Ambient Tempera
6、tureE4 Practices for Force Verification of Testing MachinesE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 DefinitionsFor definitions of terms relating to manu
7、factured carbon and graphite, see Terminology C709.3.2 Definitions of Terms Specific to This Standard:3.2.1 flexural strengtha measure of the ultimate load-carrying capacity of a specified beam in bending.4. Significance and Use4.1 This test method may be used for material development, quality contr
8、ol, characterization, and design data generationpurposes.4.2 This test method determines the maximum loading on a graphite specimen with simple beam geometry in 4point bending,and it provides a means for the calculation of flexural strength at ambient temperature and environmental conditions.5. Appa
9、ratus5.1 The testing machine shall conform to the requirements of Practices E4.5.2 The four-point loading fixture shall consist of bearing blocks or cylindrical bearings spaced in a third-point loadingconfiguration (see Test Method C78).1 This test method is under the jurisdiction of ASTM Committee
10、D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved June 1, 2011Oct. 1, 2013. Published July 2011November 2013. Originally approved in 1970. Last previous edition
11、 approved in 20102011 asC65191(2010)C651 11.1. DOI:10.1520/C065111. DOI:10.1520/C065113.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summar
12、y page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends t
13、hat users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West
14、 Conshohocken, PA 19428-2959. United States15.3 The fixture shall ensure that forces applied to the beam are normal only and without eccentricity through the use of sphericalbearing blocks (see Test Method C78) or articulating roller bearing assemblies (see Test Method C1161).5.3.1 The bearing block
15、 or roller bearing diameter shall be between 1/10 and 1/20 of the specimen support span. A hardenedsteel bearing block or its equivalent is necessary to prevent distortion of the loading member. Support surfaces must be free to pivotor rotate to relieve frictional constraints.5.4 The directions of l
16、oads and reactions may be maintained parallel by judicious use of linkages, rocker bearings, and flexureplates. Eccentricity of loading can be avoided by the use of spherical bearing blocks or articulating roller bearings. Provision mustbe made in fixture design for the relief of torsional loading t
17、o less than 5 % of the nominal specimen strength. Refer to the attachedfigure for a suggested four-point loading fixture.6. Test Specimen6.1 PreparationThe test specimen shall be prepared to yield a parallelepiped of rectangular cross section. The faces shall beparallel and flat within 0.025 mm/mm o
18、f length. In addition, the samples having a maximum particle size less than 0.150 mm indiameter must be finished so that the surface roughness is less than 3 m Ra. Sample edges should be free from visible flaws andchips.NOTE 1For ease of machining to conventional standards, 3 m Ra is equivalent to 1
19、25 in. AA. For finishing of specimens with maximum particlesizes of greater than 0.150 mm, grain structure and porosity can limit the accurate measurement of roughness. In these cases, the surface roughness shouldbe visually equivalent to 3 m Ra as estimated based on the visible surface of the graph
20、ite6.2 SizeThe size of the test specimen shall be selected such that the minimum dimension of the specimen is greater than 5times the largest particle dimension. The test specimen shall have a length to thickness ratio of at least 8, and a width to thicknessratio not greater than 2.6.3 MeasurementsA
21、ll dimensions shall be measured to the nearest 0.5 %.6.4 OrientationThe specimen shall be marked or otherwise identified to denote its orientation with respect to the parent stock.6.5 DryingEach specimen must be dried in a vented oven at 120 to 150C for a period of 2 h. The sample must then be store
22、din a dry environment or a desiccator and held there prior to testing.NOTE 2Water, either in the form of liquid or as humidity in air, can have an effect on flexural mechanical behavior. Excessive adsorbed water canresult in a reduced failure stress due to a decrease in fracture surface energy.7. Pr
23、ocedure7.1 Center the load applying bearing surfaces and the test specimen on the support bearing surfaces. The load span is at leasttwo times the sample thickness, and the support span three times the load span, but not less than 40 mm. The load and supportbearings shall be carefully positioned suc
24、h that the spans are accurate to within 0.5%. Overlap each end of the specimen by at leastthe specimen thickness. Refer to Fig. 1.7.2 The load applying bearing surfaces shall make contact with the upper surface of the test specimen. Load and support bearingblocks must be parallel to each other and p
25、erpendicular to the test surfaces. Use a loading rate of 1.25 mm/min or less onscrew-driven testing machines. On other test devices, load the part at a uniform rate such that breakage occurs in 5 s or more.8. Test Data Record8.1 Measurements to 0.025 mm shall be made to determine the average width a
26、nd thickness of the specimen.8.2 The load at failure must be recorded to an accuracy of 62 % of the full-scale value.Afull-scale value of 5 kN would requirerecording to an accuracy of 6100 N.9. Calculation9.1 If the fracture occurs within the span length between the load bearing surfaces (that is, w
27、ithin the load span), calculate theflexural strength as follows:S 5 PL/ bd 2where:S = flexural strength, MPa,P = maximum applied load indicated by the testing machine, N,L = support span length, mm,b = average width of specimen, mm, andd = average thickness of specimen, mm.9.2 If the fracture occurs
28、 outside of the span length between load bearing blocks, the location of the fracture shall be recordedas such, and the results of the test shall be reported. Occasional breaks outside the inner load span in 4-point flexure are not unusual,and can often be attributed to large natural flaws in the ma
29、terial.C651 132FIG. 1 Beam with Four-Point LoadingC651 133NOTE 3Angular fractures that effectively traverse the load roller contact point but are determined to have initiated at or inside of the load roller spancan be reasonably attributed to failure at the maximum flexure stress, and should be reco
30、rded as having fractured inside of the span length between theload roller blocks.9.3 If fracture occurs in less than 5 s, the results shall be discarded but reported.9.4 An alternative calculation for flexural strength can be used if the span length between the load bearing surfaces is notaccurately
31、 measured to three times the load span:S 53 Pa/bd2 (1)where:a = distance between the load and support roller, mm.NOTE 4It should be recognized that the above equations do not necessarily give the stress that was acting directly on the origin that caused failure.The equations do not account for subsu
32、rface origins or breaks outside of the load span, nor do they correct for the potential tension/compression inequalityin modulus (behavior that is not linear elastic) commonly accepted in graphite. For conventional Weibull analysis, use the calculated maximum stressin the specimen at failure from th
33、e equations as shown.10. Report10.1 The report of each test shall include the following:10.1.1 Sample identification,10.1.2 Average width to the nearest 0.025 mm,10.1.3 Average thickness to the nearest 0.025 mm,10.1.4 Support span length, (and load span length if accurate third point loading is not
34、measured), mm,10.1.5 Rate of loading, mm/min,10.1.6 Maximum applied load, N,10.1.7 Flexural strength calculated to the nearest 10 kPa,10.1.8 Defects in specimen,10.1.9 Orientation and location of specimen, and10.1.10 Failure location.11. Precision and Bias311.1 PrecisionThe precision statements give
35、n in this section are based on the comparison of the mean strength by the Student“t” test and carrying out the statistical analysis of the data obtained in a round robin as recommended by Practice E691.11.1.1 Comparison of the MeansThe comparison of the means by the Student “t” test leads to the con
36、clusion that the averagestrength values measured by each laboratory can be considered statistically equal to 95 percent confidence level.11.1.2 Repeatability (Single Instrument)The precision within laboratory of two single values of measured strength usingPractice E177 definition with the pooled sta
37、ndard deviation calculated using Practice E691 is:Repeatability within laboratory52Sr!j,which yields a value for the material used in the round robin of 257 psi (1.8 MPa). This value converts into a strength per-centage of 65.5.11.1.3 Repeatability (Multi-Instrument) The precision between laboratori
38、es of two single values of measured strength usingPractice E177 definition with the component of variance between laboratories calculated using Practice E691 is:Repeatability between laboratories52SL! j,which yields a value for the material used in this round robin of 46 psi (0.3 MPa). This converts
39、 into a strength percentage of61.11.2 BiasNo true statement on bias can be made because no reference carbon or graphite material exists.12. Keywords12.1 carbon; flexural strength; graphite3 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research
40、Report RR:C05-1011.C651 134SUMMARY OF CHANGESSubcommittee D02.F0 has identified the location of selected changes to this standard since the last issue(C651 11) that may impact the use of this standard. (Approved Oct. 1, 2013.)(1) Added new Note 3.ASTM International takes no position respecting the v
41、alidity of any patent rights 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 s
42、ubject 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 comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headqu
43、arters. Your comments will 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 stand
44、ard 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).C651 135
