An Evaluation of the JR-Curve Method for Fracture Toughness Characterization

    Published: Jan 1983

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    This program involved the testing of compact specimens made from A508 Class 2A tube plate material. The objective of the program was to study specimen size and plan view dimension effects on the upper-shelf [204°C(400°F)] JR-curve toughness behavior. Low upper-shelf Charpy toughness relative to typical reactor vessel materials was preferred.

    The basis material was a 330-cm-diameter (130 in.) by 61-cm-thick (24 in.) slab of tube plate that had been rejected from service after ultrasonic inspection. There was some unwanted variability in strength and toughness properties and a careful specimen sampling plan did not entirely eliminate material variability from the test matrix. Therefore, a dimensional analysis in the form of key curves was used to categorize the material before attempting to decipher specimen geometry effects on the JR-curve behavior. It was then possible to show that specimens of all sizes from 1T to 10T that had equal conditions of constraint would develop the same JR-curve. The principal limitation on small specimens was that they simply lacked sufficient ligament size to sustain crack growth for full JR-curve development.

    The omega (ω) criterion was evaluated with the hope of identifying when J—Δap data from specimens with short ligaments could be expected to depart from the specimen-size-independent JR-curve. This was not successful herein from the standpoint that few specimens had sufficiently small ligaments to display this deviation. When deviation did in fact occur, it was not distinctly associated with a given value of ω.

    A comparison was made between the load-displacement behavior of two 1T compact specimens having equal Charpy (CVN) toughness and JR-curves but unequal strength properties (88 RB versus 99 RB). This was possible because of uniquely variable metallurgical conditions. The high-hardness specimen showed 40 percent greater load-bearing capacity. This was a good demonstration of why more than just JR-curve behavior should be used to judge the suitability of materials for given applications. Material strength properties are contained in crack drive representations which are curves that are compared with JR-curves. From such comparisons it is possible to predict load versus displacement and crack instability in untested configurations. Hence, part of the material flow property effect is not considered when comparing just JR-curves.


    elastic-plastic fracture, J, R, -curve, A50B steel

    Author Information:

    McCabe, DE
    Senior engineer, advisory engineer, and senior engineer, Westinghouse R&D Center, Pittsburgh, Pa.

    Landes, JD
    Senior engineer, advisory engineer, and senior engineer, Westinghouse R&D Center, Pittsburgh, Pa.

    Ernst, HA
    Senior engineer, advisory engineer, and senior engineer, Westinghouse R&D Center, Pittsburgh, Pa.

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP36786S

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