STP939

    Cumulative Fatigue and Creep-Fatigue Damage at 350°C on Recrystallized Zircaloy-4

    Published: Jan 1987


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    Abstract

    An experimental program undertaken by CEA, EDF, and FRAGEMA with the aim of characterizing the fatigue and creep-fatigue behavior of Zircaloy-4 following different annealing treatments (recrystallization, stress relief, etc.) is in progress. The results given in this paper concern only recrystallized material. Low-cycle fatigue curves and creep behavior laws under high stresses have been established. Sequential tests of pure fatigue and creep-fatigue were performed.

    The cumulative life fractions at fracture depend on the sequence of loading, stress history, and number of cycles of prestressing. Miner's rule appears to be conservative with regard to a low-high loading sequence, whereas it is not for the reverse high-low loading sequences. Fatigue and creep damage are not interchangeable. Pre-creep improves the fatigue resistance. Pre-fatigue improves the creep strength so long as the beneficial effect of cyclic hardening overcomes the damaging effect of surface cracking. The introduction of a tension hold time into the fatigue cycle slightly increases cyclic hardening and reduces the number of cycles to failure. For hold times of less than 1 h, the sum of fatigue and creep life fractions is close to one.

    Keywords:

    zirconium, Zircaloy, nuclear industry, load follow, creep and fatigue properties, creep-fatigue interaction, stress relaxation, cumulative damage, life fraction


    Author Information:

    Brun, G
    Commissariat à l'Energie Atomique, Saclay,

    Pelchat, J
    Commissariat à l'Energie Atomique, Saclay,

    Floz, JC
    FRAGEMA, Lyon,

    Galimberti, M
    Electricité de France, Lyon,


    Paper ID: STP28146S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP28146S


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