ASTM D7775-11
(Guide)Standard Guide for Measurements on Small Graphite Specimens
Standard Guide for Measurements on Small Graphite Specimens
SIGNIFICANCE AND USE
The purpose of this guide is to report considerations, which should be included in testing nonstandard specimens that lie outside the constraints imposed on size/volume in existing ASTM standards for graphite (noting that there are some generic ASTM standards with no such constraints). These constraints may be real or may be an artifact of the round-robin test program that supported the standard. It is the responsibility of the user to demonstrate that the application of a standard outside any specified constraints is valid and reasonably provides properties of the bulk material from which the nonstandard specimen was extracted.
SCOPE
1.1 This guide covers best practice for properties measurements on small (nonstandard) graphite specimens and requirements for representing properties of the bulk material. This guide is aimed specifically at measurements required on nuclear graphites, where there may be constraints on the geometry or volume of the test specimen, or both.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
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Designation:D7775–11
Standard Guide for
Measurements on Small Graphite Specimens
This standard is issued under the fixed designation D7775; 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 tal Frequencies of Carbon and Graphite Materials by Sonic
Resonance
1.1 This guide covers best practice for properties measure-
C748 Test Method for Rockwell Hardness of Graphite
ments on small (nonstandard) graphite specimens and require-
Materials
ments for representing properties of the bulk material. This
C749 Test Method for Tensile Stress-Strain of Carbon and
guide is aimed specifically at measurements required on
Graphite
nuclear graphites, where there may be constraints on the
C769 Test Method for Sonic Velocity in Manufactured
geometry or volume of the test specimen, or both.
Carbon and Graphite Materials for Use in Obtaining
1.2 The values stated in SI units are to be regarded as
Young’s Modulus
standard. No other units of measurement are included in this
C781 Practice for Testing Graphite and Boronated Graphite
standard.
Materials for High-Temperature Gas-Cooled Nuclear Re-
1.3 This standard does not purport to address all of the
actor Components
safety concerns, if any, associated with its use. It is the
C886 Test Method for Scleroscope Hardness Testing of
responsibility of the user of this standard to establish appro-
Carbon and Graphite Materials
priate safety and health practices and determine the applica-
C1161 Test Method for Flexural Strength of Advanced
bility of regulatory limitations prior to use.
Ceramics at Ambient Temperature
2. Referenced Documents
C1259 Test Method for Dynamic Young’s Modulus, Shear
Modulus, and Poisson’s Ratio for Advanced Ceramics by
2.1 ASTM Standards:
Impulse Excitation of Vibration
C559 Test Method for Bulk Density by Physical Measure-
E228 Test Method for Linear Thermal Expansion of Solid
ments of Manufactured Carbon and Graphite Articles
Materials With a Push-Rod Dilatometer
C565 Test Methods for Tension Testing of Carbon and
E1461 Test Method for Thermal Diffusivity by the Flash
Graphite Mechanical Materials
Method
C611 Test Method for Electrical Resistivity of Manufac-
tured Carbon and Graphite Articles at Room Temperature
3. Summary of Guide
C651 Test Method for Flexural Strength of Manufactured
3.1 There is currently a suite of ASTM standards (see 2.1)
Carbon and GraphiteArticles Using Four-Point Loading at
that can be applied to graphite covering a range of physical,
Room Temperature
mechanical, electrical and thermal property measurements.
C695 Test Method for Compressive Strength of Carbon and
Each of these standards has been developed with the objective
Graphite
ofoptimizingthemethodofmeasurementintheabsenceofany
C714 Test Method for Thermal Diffusivity of Carbon and
constraints on test specimen production. Without exception,
Graphite by Thermal Pulse Method
these standards specify limits on the ratio between test speci-
C747 Test Method for Moduli of Elasticity and Fundamen-
mendimensionsandcokeandfillergrainsizesorprescribetest
specimen geometries or size ranges, or both. The default
position for any user should be to follow these standards
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
exactly as described. However, in some applications, available
Products and Lubricants and is the direct responsibility of Subcommittee D02.F0 on
test material or experiment design constraints on test specimen
Manufactured Carbon and Graphite Products.
sizes may result in noncompliance. The objective of this guide
Current edition approved Dec. 1, 2011. Published January 2012. DOI: 10.1520/
D7775–11.
is to provide advice on how the application of selected
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
standards under noncompliant conditions can be tested for
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
suitability.The ultimate objective is to provide guidance on the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. use of each of the ASTM standards listed. The 2011 issue of
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7775–11
this guide addresses eight standards: Test Method C559 for largerelativetotheflashsourceasthefrontsurfaceneedstobe
Bulk Density by Physical Measurement of Manufactured heated uniformly. The specimen thickness must be selected
Carbon and GraphiteArticles, Test Method C611 for Electrical such that t/t is smaller than 0.02, where t is the pulse time
1/2
Resistivity of Manufactured Carbon and Graphite Articles at and t is the time for the rear surface temperature to rise to
1/2
RoomTemperature,TestMethodC747forModuliofElasticity one half of its maximum value.
and Fundamental Frequencies of Carbon and Graphite Mate- 5.7 Test Method C747—Applies to slender rod or bar
rials by Sonic Resonance, Test Method C769 for Sonic
geometries. The test specimen length to thickness ratio should
Velocity in Manufactured Carbon and Graphite Materials for lie in the range 5 to 20:1.
Use in Obtaining Young’s Modulus, Test Method C749 for
5.8 Test Method C748—Applies to flat specimens of mini-
Tensile Stress-Strain of Carbon and Graphite and Practice
mum thickness 6.35 mm. The grain size of the test material
C781 for Testing Graphite and Boronated Graphite Materials
should be less than 0.8 mm, with a hardness range 0 to 120
for High-Temperature Gas-Cooled Nuclear Reactor Compo-
Rockwell L.
nents, Test Method E228 for Linear Thermal Expansion of
5.9 Test Method C749—Applies to reduced-diameter uni-
Solid Materials with a Push-Rod Dilatometer, andTest Method
axial tensile test geometries as defined in Fig. 9 of that
E1461 for Thermal Diffusivity by the Flash Method.
standard. Gage diameter must be greater than 3 to 5 times the
maximum grain size.
4. Significance and Use
5.10 Test Method C769—Applies to right cylinder geom-
4.1 The purpose of this guide is to report considerations,
etry. The user should minimize attenuation of the sonic pulse
which should be included in testing nonstandard specimens
by selecting a wavelength appropriate to the grain size of the
that lie outside the constraints imposed on size/volume in
test material. If the test specimen is a few grains thick,
existing ASTM standards for graphite (noting that there are
acceptability of application should be tested over a range of
some generic ASTM standards with no such constraints).
lengths. Specimen should have a diameter of at least a factor of
These constraints may be real or may be an artifact of the
two and ideally a factor of five greater than the wavelength of
round-robin test program that supported the standard. It is the
sound within the material.
responsibility of the user to demonstrate that the application of
5.11 Test Method C886—Can be applied to any convenient
a standard outside any specified constraints is valid and
testspecimensize,buttestsurfacessmallerthan5by5mmare
reasonably provides properties of the bulk material from which
not recommended. The material must have a grain size less
the nonstandard specimen was extracted.
than 0.8 mm. The minimum specimen thickness is 5 mm.
5.12 Test Method E228—Applies to right cylinder (prefer-
5. Test Specimen Volume/Size Constraints in Current
able) or slab geometries. Ideally, test specimens should be 25
Standards
to 60 mm long and 5 to 10 mm in diameter or equivalent
5.1 Test Method C559—Applies to test specimens with
(although there is no fundamental limitation provided the
rectangular parallelepiped or right circular cylinder geometry.
instrument controls the maximum thermal gradient to better
The minimum test volume is specified as 500 mm . The
than 62°C/50 mm). The specimen length should be such that
minimum test specimen dimension should be 10 times the
the accuracy of determining the expansion DL/L is at least
length of the largest visible grain.
620 mm/m.
5.2 Test Methods C565—Applies to reduced diameter uni-
5.13 Test Method E1461—Applies to thin circular disk
axial tensile specimens. Grain size must be smaller than 0.79
specimens with the front surface area less than that of the
mm; while not specified, it is assumed that this refers to
energy beam. Typically, test specimens should be 10 to 12.5
average grain size. The acceptable fracture zone shall be 19
mm in diameter and 1 to 6 mm in thickness.
mm long with the centre of the zone at the point of minimum
5.14 Test Method C1259—Can be applied to graphite test
diameter. The ratio of specimen diameter to grain size or flaw
specimens with both round and rectangular cross sections. The
size must be greater than 5.
ratio of test specimen length to minimal cross-sectional dimen-
5.3 Test Method C611—Applies to strip, rod, bar or tube
sion should be greater than 10, and preferably greater than 20.
geometries. Specimen length to maximum cross-sectional di-
For shear modulus measurements, the test specimen width to
mension should be 6:1. No dimension should be smaller than 5
thickness ratio should be greater than 5.
times the length of the largest visible grain.
5.15 Test Method C1161—Applies to rectangular parallel-
5.4 Test Method C651—Applies to rectangular parallelepi-
epiped geometries and can be adapted for graphite. The
ped geometries. The minimum dimension should be greater
average grain size should be less than 2% of the beam
than 5 times largest grain dimension. Test specimen length to
thickness. For beam lengths of 25, 45, and 90 mm, specified
thickness should be greater than 8. The ratio of test specimen
widths are 2, 4, and 8 mm, respectively, and specified depths
width to thickness should be less than or equal to 2.
are 1.5, 3, and 6 mm, respectively.
5.5 Test Method C695—Applies to right cylinder geometry.
The test specimen diameter should be greater than 10 times the
6. General Principle for Measurements Outside Specified
maximum grain size. The test specimen height to diameter
Specimen Volume/Size Constraints in Current
ratio should be in the range 1.9 to 2.1. The minimum test size
Standards
is specified as 9.5 mm diameter and 19.1 mm height.
5.6 Test MethodC714—Appliestocirculardisks,2to4mm 6.1 The default position for any user should be to follow
thickand6to12mmindiameter.Thediametermustnotbetoo these standards exactly as described.
D7775–11
6.2 Specimen size and volume constraints may be set by a at the centre of each long face in the case of the rectangular
particular measurement technique and hence apply to any test parallelepiped or 90° apart on the periphery of the circular end
material, but some may depend upon the microstructure and faces in the case of the right cylinder. For the rectangular
composition of the material. In such cases, it is preferable to parallelepiped, width and thickness at each end and at two
provide technical data and basis to support the choice of the intermediate points along the length are required. For the right
adapted measurement technique and test specimen dimensions cylinder, two sets of diameter measurements are required, each
used. set consisting of four measurements, one at each end and two
6.3 A simple, general principle should be applied to any at two intermediate points along an axial line.
proposed measurements that are noncompliant with respect to
7.2 The accuracy of contact measuring devices must be
volume/size.
assessed in the context of point and flat contact options.
6.3.1 The user must first specify the level of accuracy
7.3 Principal sources of mensuration error will arise from
required for the measurements together with tolerable repeat-
geometry irregularity and from surface condition.
ability, tolerance, and bias uncertainties associated with the
7.4 For specimens of regular geometry, mensuration could
measured properties. This may need to take into account the
be carried out with automated multi-measurement contact
number of specimens used for the measurements.
devices that record and analyze results for prescribed measure-
6.3.2 These qualifying measurement criteria must be dem-
ment patterns.
onstrated using representative material in a manner compliant
7.5 Non-contact scanning devices can also be used to
with the ASTM standard. The user should take account of
determine volumes of both regular and non-regular geometry
in-service changes to test material (for example, irradiation,
specimens. Such devices need careful qualification before use
oxidation) when selecting representative material for such a
to ensure the detectors respond consistently for graphite
demonstration; as-manufactured material may not be suffi-
surfaces. The calibration and accuracy of the device must be
ciently representative for such purposes.
tested on volume standards made from materials that respond
6.3.3 The measurements should then be repeated on the
to the scanning beam in a simple manner to graphite.
same material, progressively reducing the volume/size of the
7.6 Bulk density can also be determined usingArchimedes’
specimen and repeating the measurements. Ideally, this proce-
Principle, as an alternative to mensuration techniques. The
dure would involve the successive re-sizing of the starting
specimen immersed in a fluid is subject to an upwards
specimen. This would ensure that no specimen to specimen
buoyancyforceequaltotheweightofthefluiddisplacedbythe
variability affected the results. Consideration should be given
specimen.Bymeasuringtheweightoftheimmersedspecimen,
to within specimen variability and any potential effects of
the buoyancy force can be deduced, and by using the measured
specimen preparation that might affect the property measure-
mass of the dry specimen the density can be calculated. This
ment. This process should be continued until there are suffi-
“immersion” method has the advantage of being applicable to
cient compliant data to benchmark the measurement technique
non-regular specimen geometries. For a porous material, the
against the material; there should be sufficient data at and
method depends upon a constant level of penetration of the
below the desired test specimen geometry to characterize the
open pores by the fluid. The level of penetration is not
dependenceofthemeasuredpropertyuponvolume/size.Itmay
important provided it is reproducible between repeat immer-
be necessary to study more than one parameter and these
sions.
should be varied singly in order not to confound the results.
7.7 An application of the i
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