STP1428

    Using Fracture Mechanics Concepts for a Mechanism-Based Prediction of Thermomechanical Fatigue Life

    Published: Jan 2003


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    Abstract

    An extensive database on the isothermal and thermomechanical fatigue behavior of high-temperature titanium alloy IMI 834 and dispersoid-strengthened aluminum alloy X8019 in SiC particle-reinforced as well as non-reinforced condition was used to evaluate both the adaptability of fracture mechanics approaches to TMF and the resulting predictive capabilities of determining material life by crack propagation consideration. Emphasis was put on the selection of the correct microstructural concepts, then adjusting them using data from independent experiments in order to avoid any sort of fitting. It is shown that the cyclic J-integral (ΔJeff concept) is suitable to predict the cyclic lifetime for conditions where the total crack propagation rate is approximately identical to plain fatigue crack growth velocity. In the case that crack propagation is strongly affected by creep, the creep-fatigue damage parameter DCF introduced by Riedel can successfully be applied. If environmental effects are very pronounced the accelerating influence of corrosion on fatigue crack propagation can no longer implicitly be taken into account in the fatigue crack growth law. Instead, a linear combination of the crack growth rate contributions from plain fatigue (determined in vacuum) and from environmental attack was assumed and found to yield a satisfactory prediction, if the relevant corrosion process is taken into account.

    Keywords:

    High-temperature titanium alloy, IMI 834, high-temperature aluminum alloy, X8019, metal matrix composite, fracture mechanics, fatigue crack propagation, cyclic life, environmental damage, thermomechanical fatigue, life prediction


    Author Information:

    Christ, H-J
    Professor and Graduate Research Assistant, Universität Siegen, Siegen,

    Teteruk, R
    Professor and Graduate Research Assistant, Universität Siegen, Siegen,

    Jung, A
    Professor and Graduate Research Assistant, Universität Siegen, Siegen,

    Maier, HJ
    Professor, Universität Paderborn, Paderborn,


    Paper ID: STP11432S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP11432S


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