ASTM C1025-15(2020)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1025 − 15 (Reapproved 2020)
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 commonlyproduced to carry current inelectric arc furnaces, as
a consumable item in electrical discharge machining, and as a
1.1 Thistestmethodcoversdeterminationofthemodulusof
structural material in plastic-injection molds.
rupture in bending of specimens cut from graphite electrodes
3.1.2 flexural strength, n—property of solid material that
using a simple square cross section beam in four-point loading
indicates its ability to withstand a flexural or transverse load,
at room temperature.
obtained through a measurement of the ultimate load-carrying
1.2 The values stated in SI units are to be regarded as
capacity of a specified beam in bending.
standard. No other units of measurement are included in this
3.1.3 modulus of rupture in bending, n—the value of maxi-
standard.
mum stress in the extreme fiber of a specified beam loaded to
1.3 This standard does not purport to address all of the
failure in bending.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Significance and Use
priate safety, health, and environmental practices and deter-
4.1 This test method provides a means for determining the
mine the applicability of regulatory limitations prior to use.
modulus of rupture of a square cross section graphite specimen
1.4 This international standard was developed in accor-
machinedfromtheelectrodecoresampleobtainedaccordingto
dance with internationally recognized principles on standard-
Practice C783, with a minimum core diameter of 57 mm. This
ization established in the Decision on Principles for the
test method is recommended for quality control or quality
Development of International Standards, Guides and Recom-
assurance purposes, but should not be relied upon to compare
mendations issued by the World Trade Organization Technical
materials of radically different particle sizes or orientational
Barriers to Trade (TBT) Committee.
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
2.1 ASTM Standards: 4.2 Specimen Size—The maximum particle size and maxi-
mum pore size vary greatly for manufactured graphite
C651 Test Method for Flexural Strength of Manufactured
CarbonandGraphiteArticlesUsingFour-PointLoadingat electrodes, generally increasing with electrode diameter. The
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
C783 Practice for Core Sampling of Graphite Electrodes
results may not agree when a different ratio or specimen size is
E4 Practices for Force Verification of Testing Machines
used.
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
5. Apparatus
3. Terminology
5.1 The testing machine shall conform to the requirements
3.1 Definitions: of Sections 14 and 17 of Practices E4.
3.1.1 electrode graphite, n—a type of manufactured graph-
5.2 The four-point loading fixture shall consist of bearing
ite with less restrictive controls on homogeneity and purity,
blocks or roller assemblies which ensure that forces applied to
the beam are normal only and without eccentricity. (See Test
This test method is under the jurisdiction of ASTM Committee D02 on
Method C651.) The directions of loads and reactions may be
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
maintained parallel by judicious use of linkages, rocker
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products.
bearings, and flexure plates. Eccentricity of loading can be
Current edition approved May 1, 2020. Published June 2020. Originally
avoided by the use of spherical or cylindrical bearings.
approved in 1984. Last previous edition approved in 2015 as C1025 – 15. DOI:
10.1520/C1025-15R20.
Provision must be made in fixture design for relief of torsional
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
loading to less than 5 % of the nominal specimen strength.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Refer to Fig. 1 for a suggested four-point fixture with a
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. semi-articulating roller configuration.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1025 − 15 (2020)
to room temperature and stored in a desiccator or dry environ-
ment and held there prior to testing.
NOTE 1—Water, either in the form of liquid or as humidity in air, can
have an effect on flexural mechanical behavior. Excessive adsorbed water
can result in a reduced failure stress due to a decrease in fracture surface
energy.
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:
FIG. 1 Beam with Four-Point Loading (Not to Scale)
MOR 5 Mc/I
MOR 5 PL/bt 1000
~ !~ !
9.1.2 Maximum bending moment:
5.3 The bearing block diame
...