ASTM C1025-91(2010)e1

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Designation: C1025 − 91(Reapproved 2010) An American National Standard
Standard Test Method for
Modulus of Rupture in Bending of Electrode Graphite
This standard is issued under the fixed designation C1025; 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.
ε NOTE—Updated units of measurement throughout editorially in May 2010.
1. Scope 3.2 Definitions of Terms Specific to This Standard:
3.2.1 modulus of rupture in bending— the value of maxi-
1.1 Thistestmethodcoversdeterminationofthemodulusof
mum stress in the extreme fiber of a specified beam loaded to
rupture in bending of specimens cut from graphite electrodes
failure in bending computed from the calculations in Section 9.
using a simple square cross section beam in four-point loading
at room temperature.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as
4.1 This test method provides a means for determining the
standard. No other units of measurement are included in this
modulus of rupture of a square cross section graphite specimen
standard.
machinedfromtheelectrodecoresampleobtainedaccordingto
1.3 This standard does not purport to address all of the Practice C783, with a minimum core diameter of 57 mm. This
safety concerns, if any, associated with its use. It is the test method is recommended for quality control or quality
responsibility of the user of this standard to establish appro- assurance purposes, but should not be relied upon to compare
priate safety and health practices and determine the applica- materials of radically different particle sizes or orientational
bility of regulatory limitations prior to use. characteristics. For these reasons as well as those discussed in
4.2 an absolute value of flexural strength may not be obtained.
2. Referenced Documents
4.2 Specimen Size—The maximum particle size and maxi-
2.1 ASTM Standards:
mum pore size vary greatly for manufactured graphite
C651 Test Method for Flexural Strength of Manufactured
electrodes, generally increasing with electrode diameter. The
CarbonandGraphiteArticlesUsingFour-PointLoadingat
test is on a rather short stubby beam, therefore the shear stress
Room Temperature
is not insignificant compared to the flexural stress, and the test
C709 Terminology Relating to Manufactured Carbon and
results may not agree when a different ratio or specimen size is
Graphite
used.
C783 Practice for Core Sampling of Graphite Electrodes
5. Apparatus
E4 Practices for Force Verification of Testing Machines
E691 Practice for Conducting an Interlaboratory Study to
5.1 The testing machine shall conform to the requirements
Determine the Precision of a Test Method
of Sections 14 and 17 of Practices E4.
5.2 The four-point loading fixture shall consist of bearing
3. Terminology
blocks which ensure that forces applied to the beam are normal
3.1 Definitions—For definitions of terms relating to manu-
only and without eccentricity. (See Test Method C651.) The
factured carbon and graphite, see Terminology C709.
directions of loads and reactions may be maintained parallel by
judicious use of linkages, rocker bearings, and flexure plates.
1 Eccentricity of loading can be avoided by the use of spherical
This test method is under the jurisdiction of ASTM Committee D02 on
bearings. Provision must be made in fixture design for relief of
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.F0 on Manufactured Carbon and Graphite Products.
torsional loading to less than 5 % of the nominal specimen
Current edition approved May 1, 2010. Published December 2010. Originally
strength. Refer to Fig. 1 for a suggested four-point fixture.
approvedin1984.Lastpreviouseditionapprovedin2005asC1025–91(2005).DOI:
10.1520/C1025-91R10E01.
5.3 The bearing block diameter shall be between ⁄10 and
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
⁄20 of the specimen support span, 12 mm to 6 mm.Ahardened
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
steel bearing block or its equivalent is necessary to prevent
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. distortion of the loading member.
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C1025 − 91 (2010)
7. Procedure
7.1 Center the specimen in the test fixture. Make sure that
no extraneous torsional loads are being introduced to the
specimen.
7.2 The support span shall be equal to three times the
specimen thickness, 114 mm. The load span shall be one third
the support span, 38 mm. Refer to Fig. 1.
7.3 Apply the breaking load at a maximum rate of
0.02 mm⁄s.
8. Test Data Record
8.1 Measurements to 0.03 mm shall be made to determine
the average width and thickness of the specimen at the section
of failure.
8.2 The load at failure shall be recorded to 61%.
9. Calculation
9.1 If the fracture occurs within the load span, calculate the
modulus of rupture, the maximum bending moment, the
distance from the neutral axis to the location where the fiber
failed, and the moment of inertia of the original cross section
as follows:
9.1.1 Modulus of rupture:
MOR 5 Mc/I
MOR 5 ~PL/bt !~1000!
9.1.2 Maximum bending moment:
M 5 ~P/2!~L/3!
9.1.3 Distance from the neutral axis to the location where
the fiber failed:
c 5 ~t/2!
FIG. 1 Beam with Four-Point Loading (Not to Scale)
9.1.4 Moment of inertia of the original cross-section:
6. Test Specimen
I 5 ~ bt /12!
6.1 Sampling—A core sample (minimum of 57 mm diam-
where:
eter and 165 mm long) shall be obtained from the electrode in
MOR = modulus of rupture, kPa,
accordance with Pr
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