ASTM C749-08(2010)e1
(Test Method)Standard Test Method for Tensile Stress-Strain of Carbon and Graphite
Standard Test Method for Tensile Stress-Strain of Carbon and Graphite
SIGNIFICANCE AND USE
The round robin testing on which the precision and bias for this test method have been determined employed a range of graphites (see Table 2) whose grain sizes were of the order of 1 mil to ¼ in. (0.0254 to 6.4 mm) and larger. This wide range of carbons and graphites can be tested with uniform gauge diameters with minimum parasitic stresses to provide quality data for use in engineering applications rather than simply for quality control. This test method can be easily adapted to elevated temperature testing of carbons and graphites without changing the specimen size or configuration by simply utilizing elevated temperature materials for the load train. This test method has been utilized for temperatures as high as 4352°F (2400°C). The design of the fixtures (Figs. 2-9 and Table 1) and description of the procedures are intended to bring about, on the average, parasitic stresses of less than 5 %. The specimens for the different graphites have been designed to ensure fracture within the gauge section commensurate with experienced variability in machining and testing care at different facilities. The constant gauge diameter permits rigorous analytical treatment.
5.2 Carbon and graphite materials exhibit significant physical property differences within parent materials. Exact sampling patterns and grain orientations must be specified in order to make meaningful tensile strength comparisons. See also Test Methods C565.
SCOPE
1.1 This test method covers the testing of carbon and graphite in tension to obtain the tensile stress-strain behavior, to failure, from which the ultimate strength, the strain to failure, and the elastic moduli may be calculated as may be required for engineering applications. Table 2 lists suggested sizes of specimens that can be used in the tests.
Note 1—The results of about 400 tests, on file at ASTM as a research report, show the ranges of materials that have been tested, the ranges of specimen configurations, and the agreement between the testers. See Section 11.
Note 2—For safety considerations, it is recommended that the chains be surrounded by suitable members so that at failure all parts of the load train behave predictably and do not constitute a hazard for the operator.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. Conversions are not provided in the tables and figures.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
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´1
Designation: C749 − 08(Reapproved 2010) An American National Standard
Standard Test Method for
Tensile Stress-Strain of Carbon and Graphite
This standard is issued under the fixed designation C749; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
´ NOTE—Updated units scope statement and Table 1 editorially in May 2010.
1. Scope E6 Terminology Relating to Methods of Mechanical Testing
E177 Practice for Use of the Terms Precision and Bias in
1.1 This test method covers the testing of carbon and
ASTM Test Methods
graphite in tension to obtain the tensile stress-strain behavior,
E691 Practice for Conducting an Interlaboratory Study to
to failure, from which the ultimate strength, the strain to
Determine the Precision of a Test Method
failure, and the elastic moduli may be calculated as may be
required for engineering applications. Table 2 lists suggested
3. Terminology
sizes of specimens that can be used in the tests.
NOTE 1—The results of about 400 tests, on file at ASTM as a research 3.1 Definitions—The terms as related to tension testing as
report, show the ranges of materials that have been tested, the ranges of
given inTerminology E6 shall be considered as applying to the
specimen configurations, and the agreement between the testers. See
terms used in this test method. See also Terminology C709.
Section 11.
NOTE 2—For safety considerations, it is recommended that the chains
4. Summary of Test Method
be surrounded by suitable members so that at failure all parts of the load
train behave predictably and do not constitute a hazard for the operator.
4.1 Atensile specimen (Fig. 1) is placed within a load train
1.2 The values stated in inch-pound units are to be regarded
assembly made up of precision chains and other machined
as standard. The values given in parentheses are mathematical
parts (Fig. 2).Aload is applied to the specimen provided with
conversions to SI units that are provided for information only
means of measuring strain until it is caused to fracture. This
and are not considered standard. Conversions are not provided
test yields the tensile strength, elastic constants, and strain to
in the tables and figures.
failure of carbons and graphites.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5. Significance and Use
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 5.1 The round robin testing on which the precision and bias
for this test method have been determined employed a range of
bility of regulatory limitations prior to use.
graphites (see Table 2) whose grain sizes were of the order of
2. Referenced Documents
1 mil to ⁄4 in. (0.0254 to 6.4 mm) and larger. This wide range
of carbons and graphites can be tested with uniform gauge
2.1 ASTM Standards:
diameters with minimum parasitic stresses to provide quality
C565 Test Methods for Tension Testing of Carbon and
data for use in engineering applications rather than simply for
Graphite Mechanical Materials
quality control. This test method can be easily adapted to
C709 Terminology Relating to Manufactured Carbon and
elevated temperature testing of carbons and graphites without
Graphite
changingthespecimensizeorconfigurationbysimplyutilizing
E4 Practices for Force Verification of Testing Machines
elevated temperature materials for the load train. This test
method has been utilized for temperatures as high as 4352°F
(2400°C).Thedesignofthefixtures(Figs.2-9andTable1)and
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
description of the procedures are intended to bring about, on
D02.F0 on Manufactured Carbon and Graphite Products.
the average, parasitic stresses of less than 5 %. The specimens
Current edition approved May 1, 2010. Published May 2010. Originally
for the different graphites have been designed to ensure
approved in 1973. Last previous edition approved in 2008 as C749 – 08. DOI:
10.1520/C0749-08R10E01.
fracture within the gauge section commensurate with experi-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
enced variability in machining and testing care at different
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
facilities. The constant gauge diameter permits rigorous ana-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. lytical treatment.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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C749 − 08 (2010)
TABLE 1 List of Materials Shown in Fig. 2
Assembly Item Quantity Name, Description, Material
1A 101 2 Crosshead attachment yoke—1 diax4long—416 or 440 S.S.
A B,C
1 3
⁄2 in. grips 102 2 Chain— ⁄16 dia, 700 pound tensile limit, 10 links long—Carbon
Steel
D
9 1
103 4 Chain journal— ⁄16 dia x ⁄2 long—416 or 440 S.S.
104 4 Pin— ⁄16 dia x 1—Std Dowel
D
105 2 Grip attachment yoke—1 dia x 2 ⁄8 long—416 or 440 S.S.
1 1 3
106 2 Pin— ⁄4 shank dia with ⁄2 dia x ⁄4 long knurled head, total length
D
2 ⁄2, taper first half inch at 10°—416 or 440 S.S.
D
1 5
107 2 Grip sleeve—1 ⁄2 diax2 ⁄16 long—416 or 440 S.S.
D
108 2 Split sleeve—1 diax1long—416 or 440 S.S.
109 1 Specimen—0.510 dia x 4 ⁄4 long—Carbon
110 Not Used
1B . . . 2 Item 101—Crosshead attachment yoke
A
⁄4 in. grips . . . 2 Item 102—Chain
. . . 4 Item 103—Chain journal
. . . 4 Item 104—Pin
. . . 2 Item 105—Grip attachment yoke
. . . 2 Item 106—Pin
1 5 D
111 2 Grip sleeve—1 ⁄2 diax2 ⁄16 long—416 or 440 S.S.
D
112 2 Split sleeve—1 diax1long—416 or 440 S.S.
113 1 Specimen—0.760 dia x 4 ⁄4 long—Carbon
114 Not Used
D
1C 115 2 Crosshead attachment yoke—1 ⁄2 diax4long—416 or 440 S.S.
A
1 3
1 ⁄4 in. grips 116 2 Chain— ⁄8 dia, 5100 pound tensile limit, 10 links long—Carbon Steel
D
5 5
117 4 Chain journal— ⁄8 dia x ⁄8 long—416 or 440 S.S.
3 1
118 4 Pin— ⁄8 diax1 ⁄2 long—Std Dowel
D
1 5
119 2 Grip attachment yoke—1 ⁄2 diax2 ⁄8 long—416 or 440 S.S.
1 3 3
120 2 Pin— ⁄2 shank dia with ⁄4 dia x ⁄4 long knurled head, total length
D
4 ⁄4, taper first half inch at 10°—416 or 440 S.S.
D
7 5
121 2 Grip sleeve—1 ⁄8 diax3 ⁄8 long—416 or 440 S.S.
D
1 1
122 2 Split sleeve—1 ⁄2 diax2 ⁄4 long—416 or 440 S.S.
1 3
123 1 Specimen—1 ⁄4 diax9 ⁄4 long—Carbon
124 Not Used
1D . . . 2 Item 115—Crosshead attachment yoke
A
2in. grips . . . 2 Item 116—Chain
. . . 4 Item 117—Chain journal
. . . 4 Item 118—Pin
D
1 5
125 2 Grip attachment yoke—2 ⁄4 diax2 ⁄8 long—416 or 440 S.S.
1 3 3
126 2 Pin— ⁄2 shank dia with ⁄4 dia x ⁄4 long knurled head, total length
D
4 ⁄4, taper first half inch at 10°—416 or 440 S.S.
D
3 1
127 2 Grip sleeve—2 ⁄4 diax5 ⁄2 long—416 or 440 S.S.
D
128 2 Split sleeve—2 ⁄4 diax4long—416 or 440 S.S.
129 1 Specimen—2.000 dia x 14 ⁄8 long—Carbon
130 Not Used
A
1 in. is equal to 25.4 mm.
B
Preload chain to yield using a load time recording.
C
Commercially available.
D
Or alternative high strength stainless steel.
5.2 Carbon and graphite materials exhibit significant physi- metrically opposite in the gauge length portion of the speci-
cal property differences within parent materials. Exact sam- men. Two opposing gauges provide some compensation for
pling patterns and grain orientations must be specified in order
bending and some assurance that it was not severe. Different
tomakemeaningfultensilestrengthcomparisons.SeealsoTest graphites require different attachment procedures and extreme
Methods C565.
care is necessary. A proven device for mounting the specimen
with minimum damage and for enabling the specimen to
6. Apparatus
receive different extensometers is shown in Fig. 10. When
6.1 Testing Machine—The machine used for tensile testing
attaching strain gauges, the modification of the surface may
shall conform to the requirements of Practices E4. The testing
result in a glue-graphite composite at the skin and thus the
machine shall have a load measurement capacity such that the
resulting strain values may be erroneous and typically low.
breaking load of the test specimen falls between 10 and 90 %
When using clip-on extensometers, the knife edges can initiate
of the scale or load cell capacity. This range must be linear to
fracture. Record, but do not include the fractures at the
within 1 % over 1 % increments either by design or by
attachments in the averages. If more than 20 % of the failures
calibration.
occur at the attachment location, change the strain monitoring
system or attachment device.
6.2 Strain Measurements:
6.2.1 The axial strain can be measured at room temperature 6.2.2 The circumferential strain can be measured at room
by the use of strain gauges, mechanical extensometers, Tuck- temperature by use of strain gauges applied circumferentially.
erman gauges, optical systems, or other devices applied dia- Knowledge of the anisotropy in the billet and orientation of the
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C749 − 08 (2010)
A
TABLE 2 Sample Sizes Used in Round-Robin Tests (Suggested Specimen Size)
Recommended
Max Grain Size, Specimen Shank and
B
Material Sample, in.
in. Size, in. Maximum Gauge,
in.
1 C 1 3
AXM-50 0.001 5 by 5 by 5, molded ⁄2 by 0.200 ⁄2 by ⁄16
3 1
⁄4 by ⁄4
1 1
9326 0.001 20 by 10 by 2, molded ⁄2 by ⁄4
⁄4 by 0.3
C
1 3
⁄2 by ⁄16
1 3
⁄2 by ⁄16
3 1
⁄4 by ⁄4
1 1 1 3
9326A 0.001 20 by 10 by 2, molded ⁄2 by ⁄4 ⁄2 by ⁄16
3 3
⁄4 by ⁄8
3 3
⁄4 by 0.3 ⁄4 by 0.3
3 3
⁄4 by ⁄8
1 1 1 1
ATJ 0.006 13, rounds, molded ⁄2 by ⁄4 ⁄2 by ⁄4
3 3 3 1
⁄4 by ⁄8 ⁄4 by ⁄4
3 3 3 1
⁄4 by ⁄8 ⁄4 by ⁄4
3 3
⁄4 by ⁄8
1 1 3 3
HLM 0.033 molded, 10 by 18 by 25 ⁄2 by ⁄4 ⁄4 by ⁄8
3 3
⁄4 by ⁄8
3 3
⁄4 by ⁄8
3 3
⁄4 by ⁄8
CS 0.030 10, rounds, extruded 2 by 1
3 3 3 3
⁄4 by ⁄8 ⁄4 by ⁄8
1 1
⁄2 by ⁄4
1 1
⁄2 by ⁄4
AGR 0.250 25, rounds, extruded 2 by 1 2 by 1
1 5
2by1 1 ⁄4 by ⁄8
2by1
1 5
1 ⁄4 by ⁄8
CGE 0.265 14, rounds, extruded 2 by 1 ⁄4
3 1
⁄4 by ⁄2 2by1
3 1 3 1
Graphitar . . . carbon-graphite, resin impregnated ⁄4 by ⁄4 ⁄4 by ⁄4
C
1 1 1
Grade 86 ⁄2 by ⁄4 ⁄2 by 0.2
1 1
⁄2 by ⁄4
3 1 3 1
Purebon P-59 . . . carbon-graphite, copper treated ⁄4 by ⁄4 ⁄4 by ⁄4
C
1 1 1 3
⁄2 by ⁄4 ⁄2 by ⁄16
1 1
⁄2 by ⁄4
A
Based on Research Report RR:C05-1000 (see Section 11).
B
Identity of suppliers available from ASTM International Headquarters.
C
Gas-bearings.
NOTE 1—Standard Specimen:
r = r ,
1 2
A = A /1.2,
1 2
l = D /2, and
1 2
l = 2 in. (51 mm) or 8 D , whichever is greater.
2 1
FIG. 1 Double Reduction Used to Minimize Radii-Fractures
specimen is necessary in order to properly place the strain- 6.3 Parasitic Stress Monitor—An optional parasitic stress
measuring device. Generally, one can expect three values of monitor can be inserted as an extension of one of the grips. It
Poisson’s ratio for a nonisotropic material. Hence, the strain shall be a steel rod about 4 in. long with strain gauges mounted
sensing devices must be sized and positioned carefully. Note at 90° angles to monitor axial bending moments on the rod and
the limitations on strain gauges mentioned in 6.2.1. thusonthespecimen.Therodshallbesizedsothatthebending
6.2.3 The diametral strains can be measured by most of the moment applied to the specimen being used can be detected to
devices with limitations mentioned in 6.2.1 and 6.2.2. within a 5 % parasitic stress in the outer fiber of the specimen.
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C749 − 08 (2010)
FIG. 2 Tensile Load Train Assembly
Theparasiticstressshallbecalculatedelasticallybytranslating 7. Test Specimens
the moment and assuming that the specimen is a free-end
7.1 Test specimens shall be produced to the general con-
beam.
figurations shown in Fig. 9.The selection of the proper ratio of
6.4 Gripping Devices—Gripping devices that conform to
shank to gauge diameter is important to prevent excessive
those shown in Fig. 2 shall be used. The centerlines of all
head-pops or fracture of the specimen at the groove in the
connectionsmustaligntowithinthetolerancesshownthrough-
shanks. The ratios shown in Table 2 have been found satisfac-
out the test.
tory for this use. It is acceptable to double reduce gauge
6.5 General Test Arrangement—Thegeneralarrangementof diameters as necessary (see Fig. 1) to eliminate head pops (or
out-of-gauge fractures) or reduce them to an acceptable 20 %
the specimen, flexible linkages, and crossheads shall be as
shown in the schematic of Fig. 3. maximum of the total fractures. However, the reducing radius
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C749 − 08 (2010)
Item
Dimensions,
in. (mm)
101 115
0.250 ± 0.001 0.312 ± 0.001
A
(6.35 ± 0.03) (7.92 ± 0.03)
0.500 ± 0.001 0.625 ± 0.001
B
(12.70 ± 0.03) (15.88 ± 0.03)
C 1.000 (25.40) 1.500 (38.10)
3 3
D ⁄16 (4.76) ⁄8 (9.52)
NOTE 1—Refer to Fig. 2, Items 101 and 115.
FIG. 4 Crosshead Attachment Yoke
7.4 To determine the cross-sectional area, the diameter of
thespecimenatthesmallerorconstantdiameterregionshallbe
used. The dimension shall be recorded to the nearest 0.001 in.
(0.0254 mm).
FIG. 3 Schematic of Tensile System for Carbon and Graphite
8. Procedure
8.1 Calibration—Calibrate the micrometres that are to be
used for measurement of diameters by measuring the dimen-
must be maintained near the values shown or excessive radii
sions of blocks provided by the NBS that are accurate within
breakswillbeobtained.Also,thegaugediametershouldnotbe
60.0001 in. (0.00254 mm). Calibrate all instrumentation and
reduced to less than three to five times the maximum particles
establish shunt calibration for each recorded and each param-
size in the material, or the failure mode may be atypical.
eter. Zero all recorders.
7.2 Improperly prepared test specimens often cause unsat-
8.2 Specimen—Adapt to the specimen the appropriate strain
isfactory test results. It is important, therefore, that care be
instrumentation by bonding strain gauges to its surface,
exercised in the preparation of specimens both in minimizing
adapting, or any other strain measuring system so that strain
end and side thrusts and in providing a quality surface. Either
can be measured during the test. Place the specimen within the
tool cutting or grinding is acceptable.
load train. Make sure all instrumentation is properly calibrated
7.3 The gauge length of the specimen will be measured and zeroed.
from the axial center of the specimen. Gauge marks can be
8.3 Loading—Apply the load at a predetermined constant
applied with ink or layout dope but no scratching, punchin
...
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