Surface Crack Growth in Inconel 718 During Large Unload-Reload Cycles

    Published: Jan 1994

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    Thin Inconel 718 plates with deep (a/t = 0.6 to 0.9) semicircular surface flaws were subjected to different numbers of large load-unload-reload cycles with various minimum and maximum loads and crack mouth displacements. Elastic compliance measurements and marker bands were used to estimate crack lengths at each cycle of interest. Crack growth was analyzed from the perspective of low-cycle fatigue crack propagation using ΔJeff as the correlating parameter. Calculations of ΔJeff were based on a modified version of the reference stress estimate that takes crack closure into account. Results from these tests were correlated consistently with both resistance curve data and baseline small-scale yielding fatigue crack growth data. The development of the crack shape during both single-cycle ductile tearing and multiple-cycle fatigue crack growth was characterized.


    elastic-plastic fracture mechanics, J, integral, resistance curves, surface cracks, fatigue crack growth, ductile tearing, crack shape, crack closure, proof testing

    Author Information:

    McClung, RC
    Group leader and director, Southwest Research Institute, San Antonio, TX

    Hudak, SJ
    Group leader and director, Southwest Research Institute, San Antonio, TX

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP13734S

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