STP942: An Update of the Total-Strain Version of Strainrange Partitioning

    Saltsman, JF
    Research Engineer and Senior Research Engineer, NASA-Lewis Research Center, Cleveland, OH

    Halford, GR
    Research Engineer and Senior Research Engineer, NASA-Lewis Research Center, Cleveland, OH

    Pages: 13    Published: Jan 1988


    Abstract

    An updated procedure has been developed for characterizing an alloy and predicting cyclic life by using the total-strain-range version of strainrange partitioning (TS-SRP). The principal feature of the update is a new procedure for determining the intercept of time-dependent elastic-strain-range-versus-cyclic-life lines. The procedure is based on an established relation between failure and the cyclic stress-strain response. The stress-strain response is characterized by empirical equations presented in this report. These equations were determined with the aid of a cyclic constitutive model. The procedures presented herein reduce the testing required to characterize an alloy. Failure testing is done only in the high-strain, short-life regime; cyclic stress-strain response is determined from tests conducted in both the high- and low-strain regimes. These tests are carried out to stability of the stress-strain hysteresis loop but not to failure. Thus both the time and costs required to characterize an alloy are greatly reduced. This procedure was evaluated and verified for two nickel-base superalloys, AF2-1DA and Inconel 718. The analyst can now predict cyclic life in the low-strain, long-life regime without having to conduct expensive failure tests in this regime or resort to questionable larger extrapolations.

    Keywords:

    fatigue (metal), creep-fatigue, life prediction, strainrange partitioning, constitutive modeling, nickel-base superalloys, creep, plasticity, strain fatigue


    Paper ID: STP24490S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24490S


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