1、Designation: C1025 91 (Reapproved 2010)1An American National StandardStandard Test Method forModulus of Rupture in Bending of Electrode Graphite1This standard is issued under the fixed designation C1025; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he 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.1NOTEUpdated units of measurement throughout editorially in May 2010.1. Scope1.1 This test method
3、 covers determination of the modulus ofrupture in bending of specimens cut from graphite electrodesusing a simple square cross section beam in four-point loadingat room temperature.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstan
4、dard.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. Referen
5、ced Documents2.1 ASTM Standards:2C651 Test Method for Flexural Strength of ManufacturedCarbon and Graphite Articles Using Four-Point Loading atRoom TemperatureC709 Terminology Relating to Manufactured Carbon andGraphiteC783 Practice for Core Sampling of Graphite ElectrodesE4 Practices for Force Veri
6、fication of Testing MachinesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsFor definitions of terms relating to manu-factured carbon and graphite, see Terminology C709.3.2 Definitions of Terms Specific to This Standard:3.2
7、.1 modulus of rupture in bending the value of maxi-mum stress in the extreme fiber of a specified beam loaded tofailure in bending computed from the calculations in Section 9.4. Significance and Use4.1 This test method provides a means for determining themodulus of rupture of a square cross section
8、graphite specimenmachined from the electrode core sample obtained according toPractice C783, with a minimum core diameter of 57 mm. Thistest method is recommended for quality control or qualityassurance purposes, but should not be relied upon to comparematerials of radically different particle sizes
9、 or orientationalcharacteristics. For these reasons as well as those discussed in4.2 an absolute value of flexural strength may not be obtained.4.2 Specimen SizeThe maximum particle size and maxi-mum pore size vary greatly for manufactured graphite elec-trodes, generally increasing with electrode di
10、ameter. The test ison a rather short stubby beam, therefore the shear stress is notinsignificant compared to the flexural stress, and the test resultsmay not agree when a different ratio or specimen size is used.5. Apparatus5.1 The testing machine shall conform to the requirementsof Sections 14 and
11、17 of Practices E4.5.2 The four-point loading fixture shall consist of bearingblocks which ensure that forces applied to the beam are normalonly and without eccentricity. (See Test Method C651.) Thedirections of loads and reactions may be maintained parallel byjudicious use of linkages, rocker beari
12、ngs, and flexure plates.Eccentricity of loading can be avoided by the use of sphericalbearings. Provision must be made in fixture design for relief oftorsional loading to less than 5 % of the nominal specimenstrength. Refer to Fig. 1 for a suggested four-point fixture.5.3 The bearing block diameter
13、shall be between110 and120 of the specimen support span, 12 mm to 6 mm.Ahardenedsteel bearing block or its equivalent is necessary to preventdistortion of the loading member.6. Test Specimen6.1 SamplingA core sample (minimum of 57 mm diam-eter and 165 mm long) shall be obtained from the electrode in
14、accordance with Practice C783.6.2 PreparationA test specimen shall be prepared fromthe core to yield a parallelepiped of square cross section. Thefaces shall be parallel and flat within 0.002 mm/mm of length.Specimen edges shall be free from visible flaws and chips. All1This test method is under the
15、 jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products.Current edition approved May 1, 2010. Published December 2010. Originallyapproved in 1984. Last previous edition approved in 200
16、5 as C102591(2005). DOI:10.1520/C1025-91R10E01.2For 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.1Copyright AST
17、M International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.surfaces shall be smooth with a surface texture equivalent tothat obtained from a precision band saw or better.6.3 The square cross section specimen shall be 38 by 38 mmand at least 153 mm long.6.4 M
18、easurementsAll dimensions shall be measured to atleast 0.03 mm.6.5 DryingEach specimen must be dried in an oven atgreater than 110C for 2 h. The specimen must then be cooledto room temperature in a desiccator and held there prior totesting.7. Procedure7.1 Center the specimen in the test fixture. Mak
19、e sure thatno extraneous torsional loads are being introduced to thespecimen.7.2 The support span shall be equal to three times thespecimen thickness, 114 mm. The load span shall be one thirdthe support span, 38 mm. Refer to Fig. 1.7.3 Apply the breaking load at a maximum rate of0.02 mm/s.8. Test Da
20、ta Record8.1 Measurements to 0.03 mm shall be made to determinethe average width and thickness of the specimen at the sectionof failure.8.2 The load at failure shall be recorded to 61%.9. Calculation9.1 If the fracture occurs within the load span, calculate themodulus of rupture, the maximum bending
21、 moment, thedistance from the neutral axis to the location where the fiberfailed, and the moment of inertia of the original cross sectionas follows:9.1.1 Modulus of rupture:MOR 5 Mc/IMOR 5 PL/bt2!1000!9.1.2 Maximum bending moment:M 5 P/2!L/3!9.1.3 Distance from the neutral axis to the location where
22、the fiber failed:c 5 t/2!9.1.4 Moment of inertia of the original cross-section:I 5 bt3/12!where:MOR = modulus of rupture, kPa,M = maximum bending moment, N mm,c = distance from the neutral axis to the location wherethe fiber failed, mm,I = moment of inertia of the original cross-section,mm,P = maxim
23、um applied load indicated by the testingmachine, N,L = support span length, mm,b = average width of the specimen, mm, andt = average thickness of the specimen, mm.9.2 If the fracture occurs outside of the load span, thisobservation shall be reported.10. Report10.1 The report of each test shall inclu
24、de the following:10.1.1 Sample identification,10.1.2 Average width to the nearest 0.03 mm,10.1.3 Average thickness to nearest 0.03 mm,10.1.4 Support span length, mm,10.1.5 Rate of loading, mm/min. or N/min.10.1.6 Maximum applied load, N,10.1.7 Modulus of rupture calculated to the nearest 70 kPa,10.1
25、.8 Defects in specimen,10.1.9 Orientation and location of specimen within theparent electrode, and10.1.10 Failure location.FIG. 1 Beam with Four-Point Loading (Not to Scale)C1025 91 (2010)1211. Precision and Bias311.1 The precision of this test method (see Practice E691)was determined from an ASTM r
26、ound robin test on 38-mmsquare cross section specimens which were cut from a 153-mmthick slab from a 610 mm diameter premium grade electrodehaving a maximum particle size less than 6 mm. Since thisround robin was a destructive test, each participating labora-tory tested only their samples. The sampl
27、es sent to eachlaboratory were selected so as to represent the slab of graphite;that is, samples from different radial locations within the610-mm diameter slab. Hence the stated precision not onlyrepresents the variations within the test itself but also thevariations within the sampled electrode.11.
28、2 The referenced ASTM round robin test was a multi-purpose test and only that portion of the test data accumulatedon four-point bending tests on square cross section specimenswas analyzed to arrive at the stated precision. Six laboratoriesparticipated in the test to the extent that their methodology
29、 andtest fixtures conform to, but may not be identical to, thismethod and the fixture shown in Fig. 1.11.3 The six sets of data contained all of the specimens ofthe stated test geometry, and form a homogeneous population.The data also exhibited a correlation between strength anddensity. Their mean s
30、trength, corrected by regression to themean density, was 225.4 kPa with a standard deviation of4.3 kPa. Plotted on probability paper, their distribution ap-peared normal with no significant skewness or kurtosis. Testedby analysis of variation with degrees of freedom 5 (betweengroups) and 24 (within
31、groups against the null hypothesis andthe random effects hypothesis), a difference between labs wasbarely discernible. The null hypothesis was satisfied at 90 %confidence level. The confidence band on the ratio of variances(between labs to within labs) included zero at the two-sided80 % confidence l
32、evel. Best estimates for the standard devia-tions are:11.3.1 Between Laboratories:sb5 6.76 kPawith 5 degrees of freedom.11.3.2 Within Laboratories:sw5 14.6 kPawith 24 degrees of freedom.11.3.3 Mean Value:x 5 225.4 kPa11.3.4 It can also be safely concluded that the within-labvariability is largely du
33、e to materials variability for which nodata was available for correlation. Known effects includeorientation and disparate flaws.11.4 The stated precision of this test will probably worsen ifelectrodes having a maximum particle size larger than 6 mmare tested using this test method.11.5 BiasBias cann
34、ot be determined as this is a destruc-tive test and no standard specimens are available.12. Keywords12.1 carbon; electrode graphite; flexural strength; graphite;modulus of ruptureASTM International takes no position respecting the validity of any patent rights asserted in connection with any item me
35、ntionedin 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 time by the responsible technical committe
36、e 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 will receive careful consideration at a meeti
37、ng 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 ASTM International, 100 Barr Harbor Drive, PO
38、 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/).3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:C05-1009.C1025 91 (2010)13
