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ASTM D7779-11

(Test Method)

Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature

Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature

SIGNIFICANCE AND USE
This test method may be used for guidance for material development to improve toughness, material comparison, quality assessment, and characterization.
The fracture toughness value provides information on the initiation of fracture in graphite containing a straight-through notch; the information on stress intensity factor beyond fracture toughness as a function of crack extension provides information on the crack propagation resistance once a fracture crack has been initiated to propagate through the test specimen.
SCOPE
1.1 This test method covers and provides a measure of the resistance of a graphite to crack extension at ambient temperature and atmosphere expressed in terms of stress-intensity factor, K, and strain energy release rate, G. These crack growth resistance properties are determined using beam test specimens with a straight-through sharp machined V-notch.
1.2 This test method determines the stress intensity factor, K, from applied force and gross specimen deflection measured away from the crack tip. The stress intensity factor calculated at the maximum applied load is denoted as fracture toughness, KIc, and is known as the critical stress intensity factor. If the resolution of the deflection gauge is sensitive to fracture behavior in the test specimen and can provide a measure of the specimen compliance, strain energy release rate, G, can be determined as a function of crack extension.
1.3 This test method is applicable to a variety of grades of graphite which exhibit different types of resistance to crack growth, such as growth at constant stress intensity (strain energy release rate), or growth with increasing stress intensity (strain energy release rate), or growth with decreasing stress intensity (strain energy release rate). It is generally recognized that because of the inhomogeneous microstructure of graphite, the general behavior will exhibit a mixture of all three during the test. The crack resistance behavior exhibited in the test is usually referred to as an “R-curve.”
Note 1—One difference between the procedure in this test method and test methods such as Test Method E399, which measure fracture toughness, KIc, by one set of specific operational procedures, is that Test Method E399 focuses on the start of crack extension from a fatigue precrack for metallic materials. This test method for graphite makes use of a machined notch with sharp cracking at the root of the notch because of the nature of graphite. Therefore, fracture toughness values determined with this method may not be interchanged with KIc as defined in Test Method E399.
1.4 This test method gives fracture toughness values, KIc and critical strain energy release rate, GIc for specific conditions of environment, deformation rate, and temperature. Fracture toughness values for a graphite grade can be functions of environment, deformation rate, and temperature.
1.5 This test method is divided into two major parts. The first major part is the main body of the standard, which provides general information on the test method, the applicability to materials comparison and qualification, and requirements and recommendations for fracture toughness testing. The second major part is composed of annexes, which provide information related to test apparatus and test specimen geometry. Main BodySection Scope1 Referenced Documents2 Terminology3 Summary of Test Method4 Significance and Use5 Apparatus6 Test Specimen7 Procedure 8 Specimen Dryness9 Calculation of Results10 Report11 Precision and Bias12 Keywords13 AnnexAnnex A1
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6.1 Measurement units expressed in these test methods are in accordance with .
1.7 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 appr...

General Information

Status
Historical
Publication Date
30-Nov-2011
ICS
59.100.20 - Carbon materials
Technical Committee
D02 - Petroleum Products, Liquid Fuels, and Lubricants
Drafting Committee
D02.F0 - Manufactured Carbon and Graphite Products
Current Stage
Ref Project

Relations

Referred By
ASTM D7775-21 - Standard Guide for Measurements on Small Graphite Specimens
Effective Date
01-Dec-2011
Referred By
ASTM C781-20 - Standard Practice for Testing Graphite Materials for Gas-Cooled Nuclear Reactor Components
Effective Date
01-Dec-2011
Referred By
ASTM D8289-20 - Standard Test Method for Tensile Strength Estimate by Disc Compression of Manufactured Graphite
Effective Date
01-Dec-2011
Referred By
ASTM D8255-19 - Standard Guide for Work of Fracture Measurements on Small Nuclear Graphite Specimens
Effective Date
01-Dec-2011

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ASTM D7779-11 - Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient TemperatureASTM D7779-11 - Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature
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ASTM D7779-11 - Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7779 − 11 AnAmerican National Standard
Standard Test Method for
Determination of Fracture Toughness of Graphite at
1
Ambient Temperature
This standard is issued under the fixed designation D7779; 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 tions of environment, deformation rate, and temperature. Frac-
ture toughness values for a graphite grade can be functions of
1.1 This test method covers and provides a measure of the
environment, deformation rate, and temperature.
resistance of a graphite to crack extension at ambient tempera-
ture and atmosphere expressed in terms of stress-intensity 1.5 This test method is divided into two major parts. The
factor, K, and strain energy release rate, G.These crack growth first major part is the main body of the standard, which
resistancepropertiesaredeterminedusingbeamtestspecimens provides general information on the test method, the applica-
with a straight-through sharp machined V-notch. bility to materials comparison and qualification, and require-
ments and recommendations for fracture toughness testing.
1.2 This test method determines the stress intensity factor,
The second major part is composed of annexes, which provide
K, from applied force and gross specimen deflection measured
information related to test apparatus and test specimen geom-
away from the crack tip. The stress intensity factor calculated
etry.
at the maximum applied load is denoted as fracture toughness,
Main Body Section
K , and is known as the critical stress intensity factor. If the
Ic
Scope 1
resolution of the deflection gauge is sensitive to fracture
Referenced Documents 2
behavior in the test specimen and can provide a measure of the
Terminology 3
Summary of Test Method 4
specimen compliance, strain energy release rate, G, can be
Significance and Use 5
determined as a function of crack extension.
Apparatus 6
Test Specimen 7
1.3 This test method is applicable to a variety of grades of
Procedure 8
graphite which exhibit different types of resistance to crack
Specimen Dryness 9
Calculation of Results 10
growth, such as growth at constant stress intensity (strain
Report 11
energy release rate), or growth with increasing stress intensity
Precision and Bias 12
(strain energy release rate), or growth with decreasing stress
Keywords 13
Annex Annex A1
intensity (strain energy release rate). It is generally recognized
that because of the inhomogeneous microstructure of graphite,
1.6 The values stated in SI units are to be regarded as
the general behavior will exhibit a mixture of all three during
standard. No other units of measurement are included in this
the test. The crack resistance behavior exhibited in the test is
standard.
usually referred to as an “R-curve.”
1.6.1 Measurementunitsexpressedinthesetestmethodsare
in accordance with IEEE/ASTM SI 10.
NOTE 1—One difference between the procedure in this test method and
test methods such as Test Method E399, which measure fracture
1.7 This standard does not purport to address all of the
toughness, K , by one set of specific operational procedures, is that Test
Ic
safety concerns, if any, associated with its use. It is the
Method E399 focuses on the start of crack extension from a fatigue
responsibility of the user of this standard to establish appro-
precrackformetallicmaterials.Thistestmethodforgraphitemakesuseof
priate safety and health practices and determine the applica-
a machined notch with sharp cracking at the root of the notch because of
the nature of graphite. Therefore, fracture toughness values determined bility of regulatory limitations prior to use.
with this method may not be interchanged with K as defined in Test
Ic
Method E399. 2. Referenced Documents
2
1.4 This test method gives fracture toughness values, K 2.1 ASTM Standards:
Ic
and critical strain energy release rate, G for specific condi-
C709 Terminology Relating to Manufactured Carbon and
Ic
Graphite
1
This test method is under the jurisdiction of ASTM Committee D02 on
2
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved Dec. 1, 2011. Published March 2012. DOI:10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D7779-11. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United Stat
...

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SIGNIFICANCE AND USE
5.1 This test method may be used for guidance for material development to improve toughness, material comparison, quality assessment, and characterization.  
5.2 The fracture toughness value provides information on the initiation of fracture in graphite containing a straight-through notch; the information on stress intensity factor beyond fracture toughness as a function of crack extension provides information on the crack propagation resistance once a fracture crack has been initiated to propagate through the test specimen.
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1.1 This test method covers and provides a measure of the resistance of a graphite to crack extension at ambient temperature and atmosphere expressed in terms of stress-intensity factor, K, and strain energy release rate, G. These crack growth resistance properties are determined using beam test specimens with a straight-through sharp machined V-notch.  
1.2 This test method determines the stress intensity factor, K, from applied force and gross specimen deflection measured away from the crack tip. The stress intensity factor calculated at the maximum applied load is denoted as fracture toughness, KIc, and is known as the critical stress intensity factor. If the resolution of the deflection gauge is sensitive to fracture behavior in the test specimen and can provide a measure of the specimen compliance, strain energy release rate, G, can be determined as a function of crack extension.  
1.3 This test method is applicable to a variety of grades of graphite which exhibit different types of resistance to crack growth, such as growth at constant stress intensity (strain energy release rate), or growth with increasing stress intensity (strain energy release rate), or growth with decreasing stress intensity (strain energy release rate). It is generally recognized that because of the inhomogeneous microstructure of graphite, the general behavior will exhibit a mixture of all three during the test. The crack resistance behavior exhibited in the test is usually referred to as an “R-curve.”  
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Main Body  
Section  
Scope  
1  
Referenced Documents  
2  
Terminology  
3  
Summary of Test Method  
4  
Significance and Use  
5  
Apparatus  
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Test Specimen  
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Report  
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Keywords  
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Annex  
Annex A1  
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Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature

SIGNIFICANCE AND USE
5.1 This test method may be used for guidance for material development to improve toughness, material comparison, quality assessment, and characterization.  
5.2 The fracture toughness value provides information on the initiation of fracture in graphite containing a straight-through notch; the information on stress intensity factor beyond fracture toughness as a function of crack extension provides information on the crack propagation resistance once a fracture crack has been initiated to propagate through the test specimen.
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1.1 This test method covers and provides a measure of the resistance of a graphite to crack extension at ambient temperature and atmosphere expressed in terms of stress-intensity factor, K, and strain energy release rate, G. These crack growth resistance properties are determined using beam test specimens with a straight-through sharp machined V-notch.  
1.2 This test method determines the stress intensity factor, K, from applied force and gross specimen deflection measured away from the crack tip. The stress intensity factor calculated at the maximum applied load is denoted as fracture toughness, KIc, and is known as the critical stress intensity factor. If the resolution of the deflection gauge is sensitive to fracture behavior in the test specimen and can provide a measure of the specimen compliance, strain energy release rate, G, can be determined as a function of crack extension.  
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Main Body  
Section  
Scope  
1  
Referenced Documents  
2  
Terminology  
3  
Summary of Test Method  
4  
Significance and Use  
5  
Apparatus  
6  
Test Specimen  
7  
Procedure  
8  
Specimen Dryness  
9  
Calculation of Results  
10  
Report  
11  
Precision and Bias  
12  
Keywords  
13  
Annex  
Annex A1  
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SIGNIFICANCE AND USE
5.1 Sonic velocity measurements are useful for comparing materials with similar elastic properties, dimensions, and microstructure.  
5.2 Eq 1 provides an accurate value of Young’s modulus only for isotropic, non-attenuative, non-dispersive materials of infinite dimensions. For non-isotropic graphite Eq 1 can be modified to take into account the Poisson’s ratios in all directions. As graphite is a strongly attenuative material, the value of Young’s modulus obtained with Eq 1 will be dependent on specimen length. If the specimen lateral dimensions are not large compared with the wavelength of the propagated pulse, then the value of Young’s modulus obtained with Eq 1 will be dependent on the specimen lateral dimensions. The accuracy of the Young’s modulus calculated from Eq 1 will also depend upon uncertainty in Poisson’s ratio and its impact on the evaluation of the Poisson’s factor in Eq 2. However, a value for Young’s modulus Eq 1 or Eq 7) can be obtained for many applications, which is often in good agreement with the value obtained by other more accurate methods, such as in Test Method C747. The technical issues and typical values of corresponding uncertainties are discussed in detail in STP 1578.6  
5.3 If the grain size of the carbon or graphite is greater than or about equal to the wavelength of the sonic pulse, the method may not provide a value of the Young’s modulus representative of the bulk material. Therefore it would be desirable to test a lower frequency (longer wavelength) to demonstrate that the range of obtained velocity values are within acceptable levels of accuracy. Significant signal attenuation should be expected when grain size of the material is greater than or about equal to the wavelength of the transmitted sonic pulse or the material is more porous than would be expected for as-manufactured graphite.
Note 1: Due to frequency dependent attenuation in graphite, the wavelength of the sonic pulse through the test specimen is not necessaril...
SCOPE
1.1 This test method covers a procedure for measuring the longitudinal and transverse (shear) sonic velocities in manufactured carbon and graphite which can be used to obtain approximate values for the elastic constants: Young’s modulus (E), the shear modulus (G), and Poisson’s ratio (v).  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 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.

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ASTM
ASTM D8289-20(Test Method)
Standard Test Method for Tensile Strength Estimate by Disc Compression of Manufactured Graphite

SIGNIFICANCE AND USE
4.1 By definition, the tensile strength of manufactured graphite is obtained by the direct uniaxial tensile test (Test Method C749). The C749 tensile test specimen is relatively large and is frequently incompatible with available irradiation capsule volumes, or oxidation apparatus (Test Method D7542). The splitting tensile test provides an alternate means of testing tensile properties on specimens that have severe geometric constraints and otherwise cannot meet the prescribed testing geometries of Test Method C749. By loading a disc-shaped specimen, on edge, under a compressive load, the resulting tensile stresses transverse to the loading axis provide an indication of the tensile strength properties of graphite. To obtain consistent and meaningful values of a splitting tensile strength, it is vital that the fracture initiate in the center of the disk and not along an edge. This standard test helps to ensure that the disk specimens break diametrally along the loading diameter due to tensile stresses that are perpendicular to the loading axis and that the fracture initiates at the center of the disk.  
4.2 The stress determined using the diametral compression test is the maximum tensile stress at the center of the disk when loaded under the prescribed conditions and the fracture initiates at the center of the disk. It should be understood that this tensile stress value is obtained with the specimen in a complex biaxial stress condition. When the test is performed carefully and consistently these tensile stress values are comparable to each other, but the performers of this test should validate the values obtained. Any bias when comparing values with this standard to the uniaxial tensile stress values obtained using Test Method C749 should be identified and reported. Validation shall be performed on the same material and may not be applicable to other states of the same material (for example, oxidized, irradiated). Guidance on small specimen testing can be found in G...
SCOPE
1.1 This test method covers testing apparatus, specimen preparation, and testing procedures for determining the splitting tensile strength of graphite by diametral line compression of a disk. This small specimen geometry (Test Method D7779) is specifically intended for irradiation capsule use. Users are cautioned to use Test Method C749 if possible for measuring tensile strength properties of graphite.  
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.3 All dimension and force measurements and stress calculations shall conform to the guidelines for significant digits and rounding established in Practice D6026.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

  • Standard
    5 pages
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  • Standard
    5 pages
    English language
    sale 15% off