1、Designation: C 1025 91 (Reapproved 2005)An American National StandardStandard Test Method forModulus of Rupture in Bending of Electrode Graphite1This standard is issued under the fixed designation C 1025; the number immediately following the designation indicates the year oforiginal adoption or, in
2、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 determination of the modulus ofrupture in bending of specim
3、ens 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 as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafet
4、y 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:2C 651 Test Method for Flexural St
5、rength of ManufacturedCarbon and Graphite Articles Using Four-Point Loading atRoom TemperatureC 709 Terminology Relating to Manufactured Carbon andGraphiteC 783 Practice for Core Sampling of Graphite ElectrodesE4 Practices for Force Verification of Testing MachinesE 691 Practice for Conducting an In
6、terlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions: For definitions of terms relating to manu-factured carbon and graphite, see Terminology C 709.3.2 Definitions of Terms Specific to This Standard:3.2.1 modulus of rupture in bending the value of maxi-mum stre
7、ss 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 graphite specimenmachined from the electrode core sample ob
8、tained according toPractice C 783, with a minimum core diameter of 57 mm (2.25in.) This test method is recommended for quality control orquality assurance purposes, but should not be relied upon tocompare materials of radically different particle sizes ororientational characteristics. For these reas
9、ons as well as thosediscussed in 4.2 an absolute value of flexural strength may notbe obtained.4.2 Specimen Size The maximum particle size and maxi-mum pore size vary greatly for manufactured graphite elec-trodes, generally increasing with electrode diameter. The test ison a rather short stubby beam
10、, 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 17 of Practices E4.5.2 The four-point loading fi
11、xture shall consist of bearingblocks which ensure that forces applied to the beam are normalonly and without eccentricity. (See Test Method C 651.) Thedirections of loads and reactions may be maintained parallel byjudicious use of linkages, rocker bearings, and flexure plates.Eccentricity of loading
12、 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 shall be between110 and120 of the specimen supp
13、ort span, 12 mm (0.50 in.) to 6 mm(0.25 in.). A hardened steel bearing block or its equivalent isnecessary to prevent distortion of the loading member.6. Test Specimen6.1 SamplingA core sample (minimum of 57 mm(2.25 in.) diameter and 165 mm (6.50 in.) long) shall beobtained from the electrode in acc
14、ordance with Practice C 783.6.2 Preparation A 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 (0.002 in./1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and L
15、ubricants and is the direct responsibility of SubcommitteeD02.F0 on Manufactured Carbon and Graphite Products.Current edition approved June 1, 2005. Published August 2005. Originallyapproved in 1984. Last previous edition approved in 2000 as C 102591(2000).2For referenced ASTM standards, visit the A
16、STM 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 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Uni
17、ted States.in.) of length. Specimen edges shall be free from visible flawsand chips. All surfaces shall be smooth with a surface textureequivalent to that obtained from a precision band saw or better.6.3 The square cross section specimen shall be 38 by 38 mm(1.50 by 1.50 in.) and at least 153 mm (6.
18、0 in.) long.6.4 MeasurementsAll dimensions shall be measured to atleast 0.03 mm (0.001 in.).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 spec
19、imen in the test fixture. Make 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 (4.5 in.). The load span shall beone third the support span, 38 mm (1.50 in.). Refer to Fig. 1.7.3 Apply the brea
20、king load at a maximum rate of0.02 mm/s (0.05 in./min).8. Test Data Record8.1 Measurements to 0.03 mm (0.001 in.) shall be made todetermine the average width and thickness of the specimen atthe section of failure.8.2 The load at failure shall be recorded to 61%.9. Calculation9.1 If the fracture occu
21、rs within the load span, calculate themodulus of rupture, the maximum bending 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
22、moment:M 5 P/2!L/3!9.1.3 Distance from the neutral axis to the location wherethe 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 (psi 103),M = maximum bending moment, N mm (lbf in),c = distance from the neutral axis to the loc
23、ation wherethe fiber failed, mm (in.),I = moment of inertia of the original cross-section, mm(in.),P = maximum applied load indicated by the testingmachine, N (lbf),L = support span length, mm (in.),b = average width of the specimen, mm (in.), andt = average thickness of the specimen, mm (in.).9.2 I
24、f the fracture occurs outside of the load span, thisobservation shall be reported.FIG. 1 Beam with Four-Point Loading (Not to Scale)C 1025 91 (2005)29.3 A multiplying factor of 0.145 may be used to convertkPa to psi.10. Report10.1 The report of each test shall include the following:10.1.1 Sample ide
25、ntification,10.1.2 Average width to the nearest 0.03 mm (0.001 in.),10.1.3 Average thickness to nearest 0.03 mm (0.001 in.),10.1.4 Support span length, mm (in.),10.1.5 Rate of loading, mm (in.)/min. or N (lb)/min.10.1.6 Maximum applied load, N (lb),10.1.7 Modulus of rupture calculated to the nearest
26、 70 kPa(10 psi),10.1.8 Defects in specimen,10.1.9 Orientation and location of specimen within theparent electrode, and10.1.10 Failure mode and location.11. Precision and Bias311.1 The precision of this test method (see Practice E 691)was determined from an ASTM round robin test on 38-mm(1.50-in.) sq
27、uare cross section specimens which were cut froma 153-mm (6.0-in.) thick slab from a 610 mm (24.0 in.)diameter premium grade electrode having a maximum particlesize less than 6 mm (0.25 in.). Since this round robin was adestructive test, each participating laboratory tested only theirsamples. The sa
28、mples sent to each laboratory were selected soas to represent the slab of graphite; that is, samples fromdifferent radial locations within the 610-mm (24.0-in.) diam-eter slab. Hence the stated precision not only represents thevariations within the test itself but also the variations within thesampl
29、ed electrode.11.2 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 t
30、heir methodology 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 anddensi
31、ty. Their mean strength, corrected by regression to themean density, was 225.4 kPa (1550 psi) with a standarddeviation of 4.3 kPa (110 psi). Plotted on probability paper,their distribution appeared normal with no significant skewnessor kurtosis. Tested by analysis of variation with degrees offreedom
32、 5 (between groups) and 24 (within groups against thenull hypothesis and the random effects hypothesis), a differ-ence between labs was barely discernible. The null hypothesiswas satisfied at 90 % confidence level. The confidence band onthe ratio of variances (between labs to within labs) includedze
33、ro at the two-sided 80 % confidence level. Best estimates forthe standard deviations are:11.3.1 Between Laboratories:sb5 6.76 kPa 47 psi!with 5 df.11.3.2 Within Laboratories:sw5 14.6 kPa 100 psi!with 24 df.11.3.3 Mean Value:x 5 225.4 kPa 1550 psi!11.3.4 It can also be safely concluded that the withi
34、n-labvariability is largely due 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 mm(0.25 in.) are tested
35、using this test method.11.5 BiasBias cannot 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 right
36、s 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 t
37、ime 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 will
38、 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 ASTM
39、 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).3Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:C05-1009.C 1025 91 (2005)3
