1、Designation: C1025 15 An 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 the case of revisio
2、n, 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 determination of the modulus ofrupture in bending of specimens cut from graphi
3、te 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 thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any,
4、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:2C651 Test Method for Flexural Strength of Manufacture
5、dCarbon and GraphiteArticles Using Four-Point Loading atRoom TemperatureC783 Practice for Core Sampling of Graphite ElectrodesE4 Practices for Force Verification of Testing MachinesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Defin
6、itions:3.1.1 electrode graphite, na type of manufactured graph-ite with less restrictive controls on homogeneity and purity,commonly produced to carry current in electric arc furnaces, asa consumable item in electrical discharge machining, and as astructural material in plastic-injection molds.3.1.2
7、 flexural strength, nproperty of solid material thatindicates its ability to withstand a flexural or transverse load,obtained through a measurement of the ultimate load-carryingcapacity of a specified beam in bending.3.1.3 modulus of rupture in bending, nthe value of maxi-mum stress in the extreme f
8、iber of a specified beam loaded tofailure in bending.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 obtained according toPractice C783, with a minimum core diameter
9、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 or orientationalcharacteristics. For these reasons as well as those discussed in4.2 an absolute value of flexural strengt
10、h may not be obtained.4.2 Specimen SizeThe maximum particle size and maxi-mum pore size vary greatly for manufactured graphiteelectrodes, generally increasing with electrode diameter. Thetest is on a rather short stubby beam, therefore the shear stressis not insignificant compared to the flexural st
11、ress, and the testresults may not agree when a different ratio or specimen size isused.5. Apparatus5.1 The testing machine shall conform to the requirementsof Sections 14 and 17 of Practices E4.5.2 The four-point loading fixture shall consist of bearingblocks or roller assemblies which ensure that f
12、orces applied tothe beam are normal only and without eccentricity. (See TestMethod C651.) The directions of loads and reactions may bemaintained parallel by judicious use of linkages, rockerbearings, and flexure plates. Eccentricity of loading can beavoided by the use of spherical or cylindrical bea
13、rings.Provision must be made in fixture design for relief of torsionalloading to less than 5 % of the nominal specimen strength.Refer to Fig. 1 for a suggested four-point fixture with asemi-articulating roller configuration.5.3 The bearing block diameter shall be between110 and120 of the specimen su
14、pport span, 12 mm to 6 mm. A hardenedsteel bearing block, roller assembly, or its equivalent isnecessary to prevent distortion of the loading member.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility o
15、fSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Oct. 1, 2015. Published November 2015. Originallyapproved in 1984. Last previous edition approved in 2010 as C1025 91(2010)1.DOI: 10.1520/C1025-15.2For referenced ASTM standards, visit the ASTM website, www.as
16、tm.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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Bo
17、x C700, West Conshohocken, PA 19428-2959. United States16. Test Specimen6.1 SamplingA core sample (minimum of 57 mm diam-eter and 165 mm long) shall be obtained from the electrode inaccordance with Practice C783.6.2 PreparationA test specimen shall be prepared fromthe core to yield a parallelepiped
18、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. Allsurfaces shall be smooth with a surface texture equivalent tothat obtained from a precision band saw or better.6.3 The square cross section specimen
19、 shall be 38 mm by38 mm and at least 153 mm long.6.4 MeasurementsAll dimensions shall be measured to atleast 0.03 mm.6.5 DryingEach specimen must be dried in an oven atgreater than 110 C for 2 h. The specimen must then be cooledto room temperature and stored in a desiccator or dry environ-ment and h
20、eld there prior to testing.NOTE 1Water, either in the form of liquid or as humidity in air, canhave an effect on flexural mechanical behavior. Excessive adsorbed watercan result in a reduced failure stress due to a decrease in fracture surfaceenergy.7. Procedure7.1 Center the specimen in the test fi
21、xture. 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. 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.
22、8. Test Data 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 maxim
23、um 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 moment:M 5 P/2!L/3!9.1.3 Distance from the neutral axis to the loca
24、tion 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,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, m
25、m,P = maximum 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
26、shall include 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.FIG. 1 Beam with Four-Point Loading (Not to Scale)C1025 15210.1.6 Maximum applied l
27、oad, N,10.1.7 Modulus of rupture calculated to the nearest 70 kPa,10.1.8 Defects in specimen,10.1.9 Orientation and location of specimen within theparent electrode, and10.1.10 Failure location.11. Precision and Bias311.1 The precision of this test method (see Practice E691)was determined from an AST
28、M round 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 sa
29、mples 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.
30、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 their methodol
31、ogy 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 mea
32、n strength, 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 (with
33、in 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 % confidenc
34、e level. 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
35、 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 mmare tested using this test method.11.5 BiasBias c
36、annot 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 ruptureSUMMARY OF CHANGESSubcommittee D02.F0 has identified the location of selected changes to this standard since the last
37、issue(C1025 91 (2010)1) that may impact the use of this standard. (Approved Oct. 1, 2015.)(1) Revised Section 3, Terminology.(2) Revised Section 5.(3) Revised subsection 6.5; added new Note 1.ASTM International takes no position respecting the validity of any patent rights asserted in connection wit
38、h 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 time by the responsible techn
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40、on 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 International, 100 Barr Har
41、bor 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
42、.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:C05-1009.C1025 153
