STP803V2

    JR-Curve Testing of Large Compact Specimens

    Published: Jan 1983


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    Abstract

    This paper describes experiences and special testing techniques applied to JR-curve development using compact specimens ranging in size by factors up to 20. All specimens were 20 percent side-grooved. The material used was A508 Class 2A and the tests were made at 477 K (400°F). Unloading compliance was used to measure crack growth and a special displacement measuring gage having high sensitivity and linearity was developed to detect minute compliance changes of the order of 0.1 percent. High-temperature creep effects were present but these were readily eliminated from interfering with unloading compliance precision by prior partial unloading to below the creep deformation range. Crack growth was calculated using a differential compliance formula and was usually predicted accurately within ±15 percent of the heat tint indicated growth. This was generally true over a wide range of specimen sizes and initial crack sizes.

    An example JR-curve comparison is given, comparing small-specimen versus large-specimen data. Deviation from a common JR-curve develops when Δap ⩾ 0.06 b0, where b0 is the initial specimen ligament size. For the smallest specimen data, a modified J calculation was applied which reestablishes comparability between large- versus small-specimen JR data, and this can be maintained over crack growth that represents a substantial ligament size change.

    Keywords:

    elastic-plastic fracture, J, R, -curve, key curve, A508 steel


    Author Information:

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

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


    Paper ID: STP36776S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP36776S


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