ASTM C749-2008 Standard Test Method for Tensile Stress-Strain of Carbon and Graphite.pdf

1、Designation: C 749 08An American National StandardStandard Test Method forTensile Stress-Strain of Carbon and Graphite1This standard is issued under the fixed designation C 749; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y

2、ear 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 behav

3、ior,to failure, from which the ultimate strength, the strain tofailure, and the elastic moduli may be calculated as may berequired for engineering applications. Table 1 lists suggestedsizes of specimens that can be used in the tests.NOTE 1The results of about 400 tests, on file at ASTM as a research

4、report, 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 beh

5、ave 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.1.3 This standard doe

6、s 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. Referenced Documents2.1 ASTM Stan

7、dards:2C 565 Test Methods for Tension Testing of Carbon andGraphite Mechanical MaterialsC 709 Terminology Relating to Manufactured Carbon andGraphiteE4 Practices for Force Verification of Testing MachinesE6 Terminology Relating to Methods of Mechanical Test-ingE 177 Practice for Use of the Terms Pre

8、cision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 DefinitionsThe terms as related to tension testing asgiven in Terminology E6shall be considered as applying to theterms used in this test method. See

9、also Terminology C 709.4. Summary of Test Method4.1 A tensile specimen (Fig. 1) is placed within a load trainassembly made 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

10、 the tensile strength, elastic constants, and strain tofailure of carbons and graphites.5. Significance and Use5.1 The round robin testing on which the precision and biasfor this test method have been determined employed a range ofgraphites (see Table 1) whose grain sizes were of the order of1 mil t

11、o14 in. (0.0254 to 6.4 mm) and larger. This wide rangeof carbons and graphites can be tested with uniform gaugediameters with minimum parasitic stresses to provide qualitydata for use in engineering applications rather than simply forquality control. This test method can be easily adapted toelevated

12、 temperature testing of carbons and graphites withoutchanging the specimen size or configuration by simply utilizingelevated temperature materials for the load train. This testmethod has been utilized for temperatures as high as 4352F(2400C). The design of the fixtures (Figs. 2-9 and Table 2) anddes

13、cription of the procedures are intended to bring about, onthe average, parasitic stresses of less than 5 %. The specimensfor the different graphites have been designed to ensurefracture within the gauge section commensurate with experi-enced variability in machining and testing care at differentfaci

14、lities. The constant gauge diameter permits rigorous ana-lytical treatment.1This test method is under the 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 approve

15、d July 1, 2008. Published August 2008. Originallyapproved in 1973. Last previous edition approved in 2002 as C 74992(2002).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, re

16、fer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 Carbon and graphite materials exhibit significant phy

17、si-cal property differences within parent materials. Exact sam-pling patterns and grain orientations must be specified in orderto make meaningful tensile strength comparisons. See also TestMethods C 565.6. Apparatus6.1 Testing MachineThe machine used for tensile testingshall conform to the requireme

18、nts of Practices E4. The testingmachine shall have a load measurement capacity such that thebreaking load of the test specimen falls between 10 and 90 %of the scale or load cell capacity. This range must be linear towithin 1 % over 1 % increments either by design or bycalibration.6.2 Strain Measurem

19、ents:6.2.1 The axial strain can be measured at room temperatureby the use of strain 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 forTA

20、BLE 1 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 by31634 by149326A

21、 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 by14AGR 0.250 25, rou

22、nds, 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 by31612 by14ABased on Re

23、search Report RR:C05-1000 (see Section 11).BIdentity of suppliers available from ASTM International Headquarters.CGas-bearings.NOTEStandard Specimen:r1= r2,A1= A2/1.2,l1= D2/2, andl2= 2 in. (51 mm) or 8 D1, whichever is greater.FIG. 1 Double Reduction Used to Minimize Radii-FracturesC749082bending a

24、nd some assurance that it was not severe. Differentgraphites require different 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. 10. Whenattaching strain ga

25、uges, the modification of the surface mayresult in a glue-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 av

26、erages. If more than 20 % of the failuresoccur at the attachment 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 orien

27、tation of thespecimen is necessary in order to properly place 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

28、.2.1.FIG. 2 Tensile Load Train AssemblyC7490836.2.3 The diametral strains can be measured by most of 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 ab

29、out 4 in. long with strain gauges mountedat 90 angles to monitor axial bending moments on the rod andthus 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 parasi

30、tic stress shall be calculated elastically by translatingthe moment and assuming that the specimen 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 te

31、st.6.5 General Test ArrangementThe general arrangementof the specimen, flexible linkages, and crossheads 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. 9. The selection of the proper ratio ofshank to gaug

32、e diameter is important to prevent excessivehead-pops or fracture of the specimen at the groove in theshanks. The ratios shown in Table 1 have been found satisfac-tory for this use. It is acceptable to double reduce gaugediameters as necessary (see Fig. 1) to eliminate head pops (orout-of-gauge frac

33、tures) or reduce them to an acceptable 20 %maximum of the total fractures. However, the reducing radiusmust be maintained near the values shown or excessive radiibreaks will be obtained.Also, the gauge diameter should not bereduced to less than three to five times the maximum particlessize in the ma

34、terial, or the failure mode may be atypical.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

35、 or grinding is acceptable.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 f

36、racture within 0.1 in. (2.5mm). The total gauge length is defined as that section with thesmaller 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

37、50 % of the specimens shouldfracture within the uniform diameter or the specimen should beredesigned and the system checked. Acceptable fracture loca-tions are shown in Fig. 11.FIG. 3 Schematic of Tensile System for Carbon and GraphiteDimensions,in. (mm)Item101 115A0.250 6 0.001 0.312 6 0.001(6.35 6

38、 0.03) (7.92 6 0.03)B0.500 6 0.001 0.625 6 0.001(12.70 6 0.03) (15.88 6 0.03)C 1.000 (25.40) 1.500 (38.10)D316 (4.76)38 (9.52)NOTERefer to Fig. 2, Items 101 and 115.FIG. 4 Crosshead Attachment YokeC749084Dimensions,in. (mm)Item103 117E916 (14.29)58 (15.88)F516 (7.94)12 (12.7)G 0.250 6 0.001 (6.35 6

39、0.03) 0.3126 0.001 (7.92 6 0.03)H 0.500 (12.70) 0.625 (15.88)J316 (4.76)38 (9.52)K18 (3.18)316 (4.76)NOTERefer to Fig. 2, Items 103 and 117.FIG. 5 Chain JournalDimensions,in. (mm)Item107 111 121 127S14 (6.35)14 (6.35)12 (12.7)12 (12.7)T 1.000 6 0.001 (25.40 6 0.03) 1.000 6 0.001 (25.40 6 0.03) 1.500

40、 6 0.001 (38.10 6 0.03) 2.250 6 0.001 (57.15 6 0.03)U 1.500 (38.10) 1.500 (38.10) 1.875 (47.62) 2.750 (69.85)V2516 (58.74) 2516 (58.74) 358 (92.07) 512 (139.70)WA632 632 1032 1032X 0.500 + 0.002 0.000 0.750 + 0.002 0.000 1.250 + 0.002 0.000 2.000 + 0.002 0.000(12.70 + 0.05 0.00) (19.05 + 0.05 0.00)

41、(31.75 + 0.05 0.00) (50.80 + 0.05 0.00)AScrew size.NOTERefer to Fig. 2, Items 107, 109, 111, 113, 121, 123, and 129.FIG. 6 Grip SleeveC7490857.4 To determine the cross-sectional area, the diameter ofthe specimen at the smaller or constant diameter region shall beused. The dimension shall be recorded

42、 to the nearest 0.001 in.(0.0254 mm).8. Procedure8.1 CalibrationCalibrate the micrometres that are to beused for measurement of diameters by measuring the dimen-sions of blocks provided by the NBS that are accurate within60.0001 in. (0.00254 mm). Calibrate all instrumentation andestablish shunt cali

43、bration for each recorded and each param-eter. Zero all recorders.8.2 SpecimenAdapt to the specimen the appropriate straininstrumentation by bonding strain gauges to its surface, adapt-ing, or any other strain measuring system so that strain can bemeasured during the test. Place the specimen within

44、the loadtrain. Make sure all instrumentation is properly calibrated andzeroed.8.3 LoadingApply the load at a predetermined constantstress rate by following the appropriate load time curve eithermanually or automatically. Continuously apply the load untilfracture is induced.8.4 RecordingDuring the en

45、tire load application duration,record the output of the load cell on the vertical axis of an X-Yrecorder and the strain on the horizontal axis, and obtain apermanent record of the stress-strain curve for the specimenbeing tested during the entire test.8.5 Post TestObserved the specimen fracture surf

46、ace. Ifthe specimen failed outside the gauge length as defined in 6.3(including head pops), the strength value measured must bereported but not included in the average.9. Calculation9.1 Calculate the strength as follows:sult5PmaxA(1)where:sult= tensile strength, psi (Pa),Pmax= maximum load, lbf (N),

47、 andA = cross-sectional area of the specimen in the constantdiameter region or gauge section, in.2(m2).9.1.1 The cross-sectional area is given by the equation:A 5pD24(2)where:D = average diameter of the constant diameter region(gauge section) of the specimen, in. (m).Dimensions of Specimen,in. (mm)I

48、tem109 and 113(14 and38)123( 0.625)129( 1.000)Dimensions of GripAttachment Yoke,in. (mm)Item105 119 125L316 (4.76)38 (9.52)38 (9.52)M 1.000 (25.4) 1.500 (38.10) 1.500 (38.10)N 0.250 6 0.001 (6.35 6 0.03) 0.312 6 0.001(7.92 6 0.03) 0.312 6 0.001 (7.92 6 0.03)O 0.500 6 0.001 (12.70 6 0.03) 0.625 6 0.0

49、01 (15.88 6 0.03) 0.625 6 0.001 (15.88 6 0.03)P14 (6.35)12 (12.7)12 (12.7)R 0.996 6 0.001 (25.30 6 0.03) 1.496 6 0.001 (38.00 6 0.03) 2.246 6 0.001 (57.05 6 0.03)NOTERefer to Fig. 2, Items 105, 109, 113, 119, 123, 125, and 129.FIG. 7 Grip Attachment YokeC7490869.2 Calculate modulus of elasticity of the specimen from thestress-strain curve as follows:E 5 initial slope of stress2strain curve 5DsD(3)where:E = modulus of elasticity,