ASTM C1025-91(2005)

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An American National Standard
Designation:C1025–91 (Reapproved 2005)
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.
1. Scope 4. Significance and Use
1.1 Thistestmethodcoversdeterminationofthemodulusof 4.1 This test method provides a means for determining the
rupture in bending of specimens cut from graphite electrodes modulus of rupture of a square cross section graphite specimen
using a simple square cross section beam in four-point loading machinedfromtheelectrodecoresampleobtainedaccordingto
at room temperature. Practice C783, with a minimum core diameter of 57 mm (2.25
1.2 The values stated in SI units are to be regarded as in.) This test method is recommended for quality control or
standard. The values given in parentheses are for information quality assurance purposes, but should not be relied upon to
only. compare materials of radically different particle sizes or
1.3 This standard does not purport to address all of the orientational characteristics. For these reasons as well as those
safety concerns, if any, associated with its use. It is the discussed in 4.2 an absolute value of flexural strength may not
responsibility of the user of this standard to establish appro- be obtained.
priate safety and health practices and determine the applica- 4.2 Specimen Size— The maximum particle size and maxi-
bility of regulatory limitations prior to use. mum pore size vary greatly for manufactured graphite elec-
trodes, generally increasing with electrode diameter.The test is
2. Referenced Documents
on a rather short stubby beam, therefore the shear stress is not
2.1 ASTM Standards: insignificant compared to the flexural stress, and the test results
C651 Test Method for Flexural Strength of Manufactured
may not agree when a different ratio or specimen size is used.
Carbon and GraphiteArticles Using Four-Point Loading at
5. Apparatus
Room Temperature
C709 Terminology Relating to Manufactured Carbon and 5.1 The testing machine shall conform to the requirements
Graphite of Sections 14 and 17 of Practices E4.
C783 Practice for Core Sampling of Graphite Electrodes 5.2 The four-point loading fixture shall consist of bearing
E4 Practices for Force Verification of Testing Machines blocks which ensure that forces applied to the beam are normal
E691 Practice for Conducting an Interlaboratory Study to only and without eccentricity. (See Test Method C651.) The
Determine the Precision of a Test Method directions of loads and reactions may be maintained parallel by
judicious use of linkages, rocker bearings, and flexure plates.
3. Terminology
Eccentricity of loading can be avoided by the use of spherical
3.1 Definitions: For definitions of terms relating to manu- bearings. Provision must be made in fixture design for relief of
factured carbon and graphite, see Terminology C709.
torsional loading to less than 5 % of the nominal specimen
3.2 Definitions of Terms Specific to This Standard: strength. Refer to Fig. 1 for a suggested four-point fixture.
3.2.1 modulus of rupture in bending— the value of maxi-
5.3 The bearing block diameter shall be between ⁄10 and
mum stress in the extreme fiber of a specified beam loaded to ⁄20 of the specimen support span, 12 mm (0.50 in.) to 6 mm
failure in bending computed from the calculations in Section 9.
(0.25 in.). A hardened steel bearing block or its equivalent is
necessary to prevent distortion of the loading member.
This test method is under the jurisdiction of ASTM Committee D02 on
6. Test Specimen
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
D02.F0 on Manufactured Carbon and Graphite Products.
6.1 Sampling—A core sample (minimum of 57 mm
Current edition approved June 1, 2005. Published August 2005. Originally
(2.25 in.) diameter and 165 mm (6.50 in.) long) shall be
approvedin1984.Lastpreviouseditionapprovedin2000asC1025–91(2000).DOI:
obtained from the electrode in accordance with Practice C783.
10.1520/C1025-91R05.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.2 Preparation— A test specimen shall be prepared from
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
the core to yield a parallelepiped of square cross section. The
Standards volume information, refer to the standard’s Document Summary page on
faces shall be parallel and flat within 0.002 mm/mm (0.002 in./
the ASTM website.
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C1025–91 (2005)
FIG. 1 Beam with Four-Point Loading (Not to Scale)
in.) of length. Specimen edges shall be free from visible flaws distance from the neutral axis to the location where the fiber
and chips. All surfaces shall be smooth with a surface texture failed, and the moment of inertia of the original cross section
equivalent to that obtained from a precision band saw or better. as follows:
6.3 Thesquarecrosssectionspecimenshallbe38by38mm
9.1.1 Modulus of rupture:
(1.50 by 1.50 in.) and at least 153 mm (6.0 in.) long.
MOR 5 Mc/I
6.4 Measurements—All dimensions shall be measured to at
MOR 5 ~PL/bt !~1000!
least 0.03 mm (0.001 in.).
6.5 Drying—Each specimen must be dried in an oven at
9.1.2 Maximum bending moment:
greater than 110°C for 2 h. The specimen must then be cooled
M 5 ~P/2!~L/3!
to room temperature in a desiccator and held there prior to
9.1.3 Distance from the neutral axis to the location where
testing.
the fiber failed:
7. Procedure
c 5 ~t/2!
7.1 Center the specimen in the test fixture. Make sure that
9.1.4 Moment of inertia of the original cross-section:
no extrane
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