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ASTM D 7779 : 2011

Superseded
Superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

View Superseded by
superseded

A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.

Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature
Available format(s)

Hardcopy , PDF

Superseded date

11-11-2014

Language(s)

English

Published date

01-12-2011

CONTAINED IN VOL. 05.05, 2018 Defines 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.

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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Committee
D 02
DocumentType
Test Method
Pages
9
ProductNote
Reconfirmed 2011
PublisherName
American Society for Testing and Materials
Status
Superseded
SupersededBy

ASTM D 8255 : 2019 Standard Guide for Work of Fracture Measurements on Small Nuclear Graphite Specimens
ASTM C 781 : 2018 Standard Practice for Testing Graphite Materials for Gas-Cooled Nuclear Reactor Components

ASTM E 177 : 2014 : REDLINE Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
IEEE/ASTM SI_10-2010 American National Standard for Metric Practice
ASTM E 337 : 2015 : REDLINE Standard Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
ASTM E 2309 : 2005 Standard Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines

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