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Standard Test Method for Determination of Fracture Toughness of Graphite at Ambient Temperature
NORMA vydaná dňa 1.10.2020
Označenie normy: ASTM D7779-20
Dátum vydania normy: 1.10.2020
Kód tovaru: NS-1013181
Počet strán: 9
Približná hmotnosť: 27 g (0.06 libier)
Krajina: Americká technická norma
Kategória: Technické normy ASTM
fracture toughness, graphite, notched beam, strain energy release rate, three-point bend,, ICS Number Code 59.100.20 (Carbon materials)
|Significance and Use|
5.1This test method may be used for guidance for material development to improve toughness, material comparison, quality assessment, and characterization.
5.2The 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.
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, 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 1.4This test method gives fracture toughness values, KIc and critical strain energy release rate, 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.
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 .
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.
|2. Referenced Documents|
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