ASTM D7779-20
(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
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.
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 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
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 IEEE/ASTM SI 10.
1.7 This standard does no...
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Standards Content (Sample)
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: D7779 − 20
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* 1.4 This test method gives fracture toughness values, K
Ic
and critical strain energy release rate, G for specific condi-
Ic
1.1 This test method covers and provides a measure of the
tions of environment, deformation rate, and temperature. Frac-
resistance of a graphite to crack extension at ambient tempera-
ture toughness values for a graphite grade can be functions of
ture and atmosphere expressed in terms of stress-intensity
environment, deformation rate, and temperature.
factor, K, and strain energy release rate, G.These crack growth
resistance properties are determined using beam test specimens
1.5 This test method is divided into two major parts. The
with a straight-through sharp machined V-notch.
first major part is the main body of the standard, which
provides general information on the test method, the applica-
1.2 This test method determines the stress intensity factor,
bility to materials comparison and qualification, and require-
K, from applied force and gross specimen deflection measured
ments and recommendations for fracture toughness testing.
away from the crack tip. The stress intensity factor calculated
The second major part is composed of annexes, which provide
at the maximum applied load is denoted as fracture toughness,
information related to test apparatus and test specimen geom-
K , and is known as the critical stress intensity factor. If the
Ic
etry.
resolution of the deflection gauge is sensitive to fracture
behavior in the test specimen and can provide a measure of the
Main Body Section
Scope 1
specimen compliance, strain energy release rate, G, can be
Referenced Documents 2
determined as a function of crack extension.
Terminology 3
Summary of Test Method 4
1.3 This test method is applicable to a variety of grades of
Significance and Use 5
graphite which exhibit different types of resistance to crack Apparatus 6
Test Specimen 7
growth, such as growth at constant stress intensity (strain
Procedure 8
energy release rate), or growth with increasing stress intensity
Specimen Dryness 9
(strain energy release rate), or growth with decreasing stress Calculation of Results 10
Report 11
intensity (strain energy release rate). It is generally recognized
Precision and Bias 12
that because of the inhomogeneous microstructure of graphite,
Keywords 13
the general behavior will exhibit a mixture of all three during Annex Annex A1
the test. The crack resistance behavior exhibited in the test is
1.6 The values stated in SI units are to be regarded as
usually referred to as an “R-curve.”
standard. No other units of measurement are included in this
standard.
NOTE 1—One difference between the procedure in this test method and
test methods such as Test Method E399, which measure fracture
1.6.1 Measurementunitsexpressedinthesetestmethodsare
toughness, K , by one set of specific operational procedures, is that Test
Ic
in accordance with IEEE/ASTM SI 10.
Method E399 focuses on the start of crack extension from a fatigue
precrackformetallicmaterials.Thistestmethodforgraphitemakesuseof
1.7 This standard does not purport to address all of the
a machined notch with sharp cracking at the root of the notch because of
safety concerns, if any, associated with its use. It is the
the nature of graphite. Therefore, fracture toughness values determined
responsibility of the user of this standard to establish appro-
with this method may not be interchanged with K as defined in Test
Ic
Method E399. priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.8 This international standard was developed in accor-
1 dance with internationally recognized principles on standard-
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
ization established in the Decision on Principles for the
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products.
Development of International Standards, Guides and Recom-
Current edition approved Oct. 1, 2020. Published December 2020. Originally
mendations issued by the World Trade Organization Technical
approved in 2011. Last previou
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7779 − 11 (Reapproved 2015) D7779 − 20
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 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, K , and
Ic
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, K ,
Ic
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 K as defined in Test Method E399.
Ic
1.4 This test method gives fracture toughness values, K and critical strain energy release rate, G for specific conditions of
Ic Ic
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.
1
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.F0 on Manufactured Carbon and Graphite Products.
Current edition approved June 1, 2015Oct. 1, 2020. Published July 2015December 2020. Originally approved in 2011. Last previous edition approved in 20112015 as
D7779 – 11.D7779 – 11 (2015). DOI:10.1520/D7779-11R15.DOI:10.1520/D7779-20.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D7779 − 20
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
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 IEEE/ASTM SI 10.
1.7 This standard does not purport to address all of
...
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