1、Designation: C749 15 An American National StandardStandard Test Method forTensile Stress-Strain of Carbon and Graphite1This standard is issued under the fixed designation C749; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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 the testing of carbon andgraphite in tension to obtain the tensile stress-strain behavi
3、or,to failure, from which the ultimate strength, the strain tofailure, and the elastic moduli may be calculated as may berequired for engineering applications. Table 2 lists suggestedsizes of specimens that can be used in the tests.NOTE 1The results of about 400 tests, on file at ASTM as a researchr
4、eport, show the ranges of materials that have been tested, the ranges ofspecimen configurations, and the agreement between the testers. SeeSection 11.NOTE 2For safety considerations, it is recommended that the chainsbe surrounded by suitable members so that at failure all parts of the loadtrain beha
5、ve predictably and do not constitute a hazard for the operator.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard. Conversions are not p
6、rovidedin the tables and figures.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 limitat
7、ions prior to use.2. Referenced Documents2.1 ASTM Standards:2C565 Test Methods for Tension Testing of Carbon andGraphite Mechanical MaterialsE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical TestingE177 Practice for Use of the Terms Precision and
8、 Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 The terms as related to tension testing as given inTerminology E6 shall be considered as applying to the termsused in this test method.3.1.2 mo
9、dulus of elasticity, nthe ratio of a force applied toa material to the increment of dimensional change along theforce axis, commonly defined as the ratio of tensile stress totensile strain.3.1.3 tensile strength, nproperty of solid material thatindicates its ability to withstand a uniaxial tensile l
10、oad,converted to unit stress based on the original cross-section areaof the tensile test specimen.3.1.4 ultimate tensile strength, nthe maximum tensilestress applied in stretching a specimen to rupture.4. Summary of Test Method4.1 A tensile specimen (Fig. 1) is placed within a load trainassembly mad
11、e up of precision chains and other machinedparts (Fig. 2). A load is applied to the specimen provided withmeans of measuring strain until it is caused to fracture. Thistest yields the tensile strength, elastic constants, and strain tofailure of carbons and graphites.5. Significance and Use5.1 The ro
12、und robin testing on which the precision and biasfor this test method have been determined employed a range ofgraphites (see Table 2) whose grain sizes were of the order of1 mil to14 in. (0.0254 mm to 6.4 mm) and larger. This widerange of carbons and graphites can be tested with uniformgauge diamete
13、rs with minimum parasitic stresses to providequality data for use in engineering applications rather thansimply for quality control. This test method can be easilyadapted to elevated temperature testing of carbons and graphi-tes without changing the specimen size or configuration bysimply utilizing
14、elevated temperature materials for the loadtrain. This test method has been utilized for temperatures ashigh as 4352 F (2400 C). The design of the fixtures (Figs. 2-9and Table 1) and description of the procedures are intended tobring about, on the average, parasitic stresses of less than 5 %.The spe
15、cimens for the different graphites have been designed1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Oct.
16、1, 2015. Published November 2015. Originallyapproved in 1973. Last previous edition approved in 2013 as C749 13. DOI:10.1520/C0749-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume info
17、rmation, 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 Box C700, West Conshohocken, PA 19428-2959. United States1to ensure fracture within the gauge section comm
18、ensurate withexperienced variability in machining and testing care at differ-ent facilities. The constant gauge diameter permits rigorousanalytical treatment.5.2 Carbon and graphite materials exhibit significant physi-cal property differences within parent materials. Exact sam-pling patterns and gra
19、in orientations must be specified in orderto make meaningful tensile strength comparisons. See also TestMethods C565.6. Apparatus6.1 Testing MachineThe machine used for tensile testingshall conform to the requirements of Practices E4. The testingmachine shall have a load measurement capacity such th
20、at thebreaking load of the test specimen falls between 10 % and90 % of the scale or load cell capacity. This range must belinear to within 1 % over 1 % increments either by design or bycalibration.6.2 Strain Measurements:6.2.1 The axial strain can be measured at room temperatureby the use of strain
21、gauges, mechanical extensometers, Tuck-erman gauges, optical systems, or other devices applied dia-metrically opposite in the gauge length portion of the speci-men. Two opposing gauges provide some compensation forbending and some assurance that it was not severe. Differentgraphites require differen
22、t attachment procedures and extremecare is necessary. A proven device for mounting the specimenwith minimum damage and for enabling the specimen toreceive different extensometers is shown in Fig. 9. Whenattaching strain gauges, the modification of the surface mayTABLE 1 List of Materials Shown in Fi
23、g. 2Assembly Item Quantity Name, Description, Material1A 101 2 Crosshead attachment yoke1 diax4long416 or 440 S.S.12 in.AgripsB,C102 2 Chain316 dia, 700 pound tensile limit, 10 links longCarbon Steel103 4 Chain journal916 dia x12 long416 or 440 S.S.D104 4 Pin316 dia x 1Std Dowel105 2 Grip attachment
24、 yoke1 dia x 258 long416 or 440 S.S.D106 2 Pin14 shank dia with12 dia x34 long knurled head, total length212, taper first half inch at 10416 or 440 S.S.D107 2 Grip sleeve112 diax2516 long416 or 440 S.S.D108 2 Split sleeve1 diax1long416 or 440 S.S.D109 1 Specimen0.510 dia x 434 longCarbon110 Not Used
25、1B . . . 2 Item 101Crosshead attachment yoke34 in.Agrips . . . 2 Item 102Chain. . . 4 Item 103Chain journal. . . 4 Item 104Pin. . . 2 Item 105Grip attachment yoke. . . 2 Item 106Pin111 2 Grip sleeve112 diax2516 long416 or 440 S.S.D112 2 Split sleeve1 diax1long416 or 440 S.S.D113 1 Specimen0.760 dia
26、x 434 longCarbon114 Not Used1C 115 2 Crosshead attachment yoke112 diax4long416 or 440 S.S.D114 in.Agrips 116 2 Chain38 dia, 5100 pound tensile limit, 10 links longCarbon Steel117 4 Chain journal58 dia x58 long416 or 440 S.S.D118 4 Pin38 diax112 longStd Dowel119 2 Grip attachment yoke112 diax258 long
27、416 or 440 S.S.D120 2 Pin12 shank dia with34 dia x34 long knurled head, total length414, taper first half inch at 10416 or 440 S.S.D121 2 Grip sleeve178 diax358 long416 or 440 S.S.D122 2 Split sleeve112 diax214 long416 or 440 S.S.D123 1 Specimen114 diax934 longCarbon124 Not Used1D . . . 2 Item 115Cr
28、osshead attachment yoke2in.Agrips . . . 2 Item 116Chain. . . 4 Item 117Chain journal. . . 4 Item 118Pin125 2 Grip attachment yoke214 diax258 long416 or 440 S.S.D126 2 Pin12 shank dia with34 dia x34 long knurled head, total length414, taper first half inch at 10416 or 440 S.S.D127 2 Grip sleeve234 di
29、ax512 long416 or 440 S.S.D128 2 Split sleeve214 diax4long416 or 440 S.S.D129 1 Specimen2.000 dia x 1438 longCarbon130 Not UsedA1 in. is equal to 25.4 mm.BPreload chain to yield using a load time recording.CCommercially available.DOr alternative high strength stainless steel.C749 152result in a glue-
30、graphite composite at the skin and thus theresulting strain values may be erroneous and typically low.When using clip-on extensometers, the knife edges can initiatefracture. Record, but do not include the fractures at theattachments in the averages. If more than 20 % of the failuresoccur at the atta
31、chment location, change the strain monitoringsystem or attachment device.6.2.2 The circumferential strain can be measured at roomtemperature by use of strain gauges applied circumferentially.Knowledge of the anisotropy in the billet and orientation of thespecimen is necessary in order to properly pl
32、ace the strain-measuring device. Generally, one can expect three values ofPoissons ratio for a nonisotropic material. Hence, the strainsensing devices must be sized and positioned carefully. Notethe limitations on strain gauges mentioned in 6.2.1.6.2.3 The diametral strains can be measured by most o
33、f thedevices with limitations mentioned in 6.2.1 and 6.2.2.6.3 Parasitic Stress MonitorAn optional parasitic stressmonitor can be inserted as an extension of one of the grips. Itshall be a steel rod about 4 in. long with strain gauges mountedat 90 angles to monitor axial bending moments on the rod a
34、ndthus on the specimen. The rod shall be sized so that the bendingmoment applied to the specimen being used can be detected towithin a 5 % parasitic stress in the outer fiber of the specimen.The parasitic stress shall be calculated elastically by translatingthe moment and assuming that the specimen
35、is a free-endbeam.6.4 Gripping DevicesGripping devices that conform tothose shown in Fig. 2 shall be used. The centerlines of allconnections must align to within the tolerances shown through-out the test.6.5 General Test ArrangementThe general arrangement ofthe specimen, flexible linkages, and cross
36、heads shall be asshown in the schematic of Fig. 3.7. Test Specimens7.1 Test specimens shall be produced to the general con-figurations shown in Fig. 1. The selection of the proper ratio ofshank to gauge diameter is important to prevent excessivehead-pops or fracture of the specimen at the groove in
37、theshanks. The ratios shown in Table 2 have generally been foundsatisfactory for this use. For some grades of graphite (see Note3), the gauge size ratios of Table 2 still may not be satisfactoryto eliminate excessive head-pops. In this case, a reduction ofgauge dimension “KK” by up to 8 % of the Tab
38、le 2 value whileTABLE 2 Sample Sizes Used in Round-Robin Tests (Suggested Specimen Size)AMaterialBMax Grain Size,in.Sample, in.SpecimenSize, in.RecommendedShank andMaximum Gauge,in.AXM-50 0.001 5 by 5 by 5, molded12 by 0.200C 12 by31634 by149326 0.001 20 by 10 by 2, molded12 by1434 by 0.312 by316C12
39、 by31634 by149326A 0.001 20 by 10 by 2, molded12 by1412 by31634 by3834 by 0.334 by 0.334 by38ATJ 0.006 13, rounds, molded12 by1412 by1434 by3834 by1434 by3834 by1434 by38HLM 0.033 molded, 10 by 18 by 2512 by1434 by3834 by3834 by3834 by38CS 0.030 10, rounds, extruded 2 by 134 by3834 by3812 by1412 by1
40、4AGR 0.250 25, rounds, extruded 2 by 1 2 by 12by1 114 by582by1114 by58CGE 0.265 14, rounds, extruded 2 by 11434 by12 2by1Graphitar . . . carbon-graphite, resin impregnated34 by1434 by14Grade 8612 by14C 12 by 0.212 by14Purebon P-59 . . . carbon-graphite, copper treated34 by1434 by1412 by14C 12 by3161
41、2 by14ABased on Research Report RR:C05-1000 (see Section 11).BIdentity of suppliers available from ASTM International Headquarters.CGas-bearings.C749 153maintaining the same radius “LL” is allowable. An acceptablealternative method is to double reduce gauge diameters asnecessary (see Fig. 10) to eli
42、minate head pops (or out-of-gaugefractures) or reduce them to an acceptable 20 % maximum ofthe total fractures. However, the reducing radius must bemaintained near the values shown or excessive radii breaks willbe obtained. Also, the gauge diameter should not be reduced toless than three to five tim
43、es the maximum particles size in thematerial, or the failure mode may be atypical.NOTE 3Grades that exhibit higher comparative strengths or arecharacterized by increased notch sensitivity may be particularly suscep-tible to head pops. This failure mode has been observed more commonlyin finer grained
44、 grades of graphite.7.2 Improperly prepared test specimens often cause unsat-isfactory test results. It is important, therefore, that care beexercised in the preparation of specimens both in minimizingend and side thrusts and in providing a quality surface. Eithertool cutting or grinding is acceptab
45、le.7.3 The gauge length of the specimen will be measuredfrom the axial center of the specimen. Gauge marks can beapplied with ink or layout dope but no scratching, punching, ornotching of the specimen is permissible. The gauge length is tobe used in referencing the point of fracture within 0.1 in.(2
46、.5 mm). The total gauge length is defined as that section withthe smaller uniform diameter extending from radius tangent toradius tangent plus 10 %. The additional 10 % is intended toaccommodate the normal statistics of fracture for a materiallike graphite. However, at least 50 % of the specimens sh
47、ouldfracture within the uniform diameter or the specimen should beredesigned and the system checked. Acceptable fracture loca-tions are shown in Fig. 11.7.4 To determine the cross-sectional area, the diameter ofthe specimen at the smaller or constant diameter region shall beused. The dimension shall
48、 be recorded to the nearest 0.001 in.(0.0254 mm).Dimensions,in. (mm)Item109 113 123 129HH0.510 + 0.000 0.002 0.760 + 0.000 0.002 1.250 + 0.000 0.002 2.000 + 0.000 0.002(12.95 + 0.00 0.05) (19.30 + 0.00 0.05) (31.75 + 0.00 0.05) (50.80 + 0.00 0.05)JJ 0.390 (9.91) 0.640 (16.26) 0.990 (25.15) 1.490 (37
49、.85)KK 0.250 0.002 (6.35 0.05) 0.375 0.002 (9.52 0.05) 0.625 0.002 (15.88 0.05) 1.000 0.002 (25.40 0.05)LL 1 (25.4) 1 (25.4) 2 (50.8) 2 (50.8)MM 0.635 (16.13) 0.635 (16.13) 1.250 (31.75) 1.500 (38.10)NN 0.125 (31.75) 0.125 (31.75) 0.255 (6.48) 0.505 (12.83)OO 238 (60.32) 238 (60.32) 478 (123.82) 7316 (182.56)PP78 (22.22)78 (22.22) 114 (31.
