STP942

    Evaluation of Life Prediction Methods in High Temperature Fatigue

    Published: Jan 1988


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    Abstract

    A collaborative study supported by the European Community COST 50 program has been conducted on life prediction methods under high-temperature low-cycle fatigue and thermal fatigue cycling in the case of MAR-M509, a cast cobalt-base superalloy. Low-cycle fatigue tests were carried out by the Ecole des Mines de Paris at 900°C in air under longitudinal strain control and included sawtooth triangular shape cycles at three strain rates (frequency range 10−3 to 20 Hz), tensile strain hold cycles, and compressive strain hold cycles. Life to initiation data deduced from a-c potential drop measurements were used to evaluate three types of predictive models: strainrange partitioning, studied by BBC-Baden; creep damage models, studied by the University of Leoben; and an oxidation-fatigue interaction model, studied by the Ecole des Mines de Paris. All the methods have been found to correlate experimental data within a factor of three. However, they range from simple correlating methods with adjustable parameters to be fitted to fully predictive methods with no fitting parameter. Thermal fatigue data on wedge-type specimens (i.e., components instead of laboratory specimens) have been used to check the prediction capability of the various methods and have shown the superiority of oxidation-fatigue interaction models for this material.

    Keywords:

    life prediction, high-temperature low-cycle fatigue, thermal fatigue, cobalt-base superalloy, crack initiation, oxidation


    Author Information:

    L, Rémy
    Centre de Matériaux de l'Ecole des Mines de Paris, EVRY Cédex,

    F, Rezai-Aria
    Centre de Matériaux de l'Ecole des Mines de Paris, EVRY Cédex,

    R, Danzer
    Institut für Metallkunde und Werkstoffprüfung Institut für Physik, Leoben,

    W, Hoffelner
    BBC Brown Boveri, Baden,


    Paper ID: STP24542S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP24542S


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