STP676

    Cyclic Relaxation Response Under Creep-Fatigue Conditions

    Published: Jan 1979


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    Abstract

    The path and history dependence of elevated-temperature, time-dependent deformation response is investigated for three alloy steels—2¼Cr-1Mo steel, Type 304 stainless steel, and Type 316 stainless steel. The scope is limited to uniaxial loading under isothermal conditions. Relaxation data are evaluated for several prior cyclic (fatigue) loading histories. Results of these evaluations are compared with creep data for the same histories. To analyze stress relaxation data, creep equations are chosen and integrated using the time-hardening rule to develop closed-form expressions for relaxation response. Coefficients for these relaxation expressions are obtained using nonlinear least squares techniques. The appropriateness of using linearized transformations compared with direct nonlinear approaches is treated. For tensile hold-time creep-fatigue tests, the dependence of the coefficients on initial stress level is evaluated. Finally, the dramatic effects of both loading sequence and strain (both monotonic and cyclic) are discussed for one particular experimental case.

    Keywords:

    creep, fatigue (materials), stress relaxation, austenitic stainless steel, ferritic low-alloy steel, stresses, strains, hardening


    Author Information:

    Laflen, JH
    General Electric Company, Cincinnati, Ohio

    Jaske, CE
    Senior research scientist, Battelle's Columbus Laboratories, Columbus, Ohio


    Paper ID: STP37424S

    Committee/Subcommittee: E28.11

    DOI: 10.1520/STP37424S


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