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ASTM D 7779 : 2020

Current

Current

The latest, up-to-date edition.

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

Available format(s)

Hardcopy , PDF

Language(s)

English

Published date

09-12-2020

€56.53
Excluding VAT

Committee
D 02
DocumentType
Test Method
Pages
9
PublisherName
American Society for Testing and Materials
Status
Current
Supersedes

1.1This 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.

1.2This 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.

1.3This 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.

1.4This 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.

1.5This 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

1.6The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6.1Measurement units expressed in these test methods are in accordance with IEEE/ASTM SI 10.

1.7This 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.

1.8This 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.

ASTM E 1823 : 2024 Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 177 : 1990 : REV A : R1996 Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods
ASTM E 1823 : 2024 : REV A Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 399 : 2024 Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
ASTM C 1161 : 2018 : R2023 Standard Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature
ASTM E 337 : 2015 : R2023 Standard Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
ASTM E 337 : 2015 Standard Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)
ASTM E 691 : 2020 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM E 1823 : 2024 : REV B Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 399 : 2020 : REV A Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
ASTM E 691 : 2019 : EDT 1 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM E 691 : 2023 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM E 399 : 2023 Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
ASTM E 1823 : 2021 Standard Terminology Relating to Fatigue and Fracture Testing
ASTM C 1161 : 2018 Standard Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature
ASTM E 691 : 2022 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM E 691 : 2009 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM E 561 : 2020 Standard Test Method for <emph type="bdit">K<inf>R</inf></emph> Curve Determination
ASTM E 561 : 2022 Standard Test Method for <emph type="bdit">K<inf>R</inf></emph> Curve Determination
ASTM E 4 : 2021 Standard Practices for Force Calibration and Verification of Testing Machines
ASTM E 691 : 2021 Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
ASTM C 1421 : 2018 Standard Test Methods for Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature
ASTM C 1161 : 1994 : R1996 Standard Test Method for Flexural Strength of Advanced Ceramics at Ambient Temperature
ASTM E 1823 : 2024 : REV C Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 1823 : 2023 Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 561 : 2023 Standard Test Method for <emph type="bdit">K<inf>R</inf></emph> Curve Determination
ASTM E 399 : 2022 Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness of Metallic Materials
ASTM E 561 : 2021 Standard Test Method for <emph type="bdit">K<inf>R</inf></emph> Curve Determination
ASTM E 1823 : 2020 : REV B Standard Terminology Relating to Fatigue and Fracture Testing
ASTM E 4 : 2024 Standard Practices for Force Calibration and Verification of Testing Machines

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