STP1372

    A Size Effect on the Fatigue Crack Growth Rate Threshold of Alloy 718

    Published: Jan 2000


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    Abstract

    Fatigue crack growth rate (FCGR) tests were conducted on Nickel-based uperalloy 718 in the solution annealed and aged condition at room temperature. In each test, the FCGR threshold was measured using the K-decreasing constant R method. Initial testing was at two facilities, one of which used C(T) specimens with W = 127 mm. Previous data at the other facility had been obtained with specimens with W = 50.8 mm. A comparison of test results at R = 0.1 showed that the threshold for the 127 mm specimen was considerably higher than that of the 50.8 mm specimen. A check showed that this difference was not due to a heat-to-heat or lab-to-lab variation. Additional tests were conducted on specimens with W = 25.4 mm and at other R values. Data for the various specimens is presented along with parameters usually used to describe threshold behavior.

    Keywords:

    Alloy 718, crack propagation, crack closure, specimen size effect, fatigue crack growth rate threshold, Biaxiality ratio, T stress, constraint


    Author Information:

    Garr, KR
    Engineering Specialist, The Boeing Company, Rocketdyne Propulsion & Power, Canoga Park, CA

    Hresko, GC
    Fracture Systems Research, Allentown, PA


    Paper ID: STP13432S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP13432S


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