STP770

    Growth of Short Cracks During High Strain Fatigue and Thermal Cycling

    Published: Jan 1982


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    Abstract

    Research in high-temperature fatigue usually concerns either crack initiation and endurance of smooth specimens in high strain fatigue (HSF) or the growth of long cracks in the nominally elastic regime described by linear elastic fracture mechanics. This review shows that the relatively unfamiliar growth rates in HSF can be linked to those in stress-intensity controlled growth, and so can be used satisfactorily for predicting component failure. Either a strain-based intensity parameter or a J-integral method may be used, and several examples are given. Integrated HSF growth rates are also shown to be consistent with smooth specimen endurance from (1) striation measurements, (2) direct measurement, and (3) the predictions of the shear decohesion model.

    Empirical HSF growth relations are summarized and the effects of temperature, environment, tension dwells, and microstructural damage are assessed in several alloys. The greatest correction that has to be made to the experimental and theoretical growth relations arises from the accelerating effects of creep during dwell.

    Keywords:

    high temperature alloys, thermal cycling, thermal shock, thermomechanical test, high strain fatigue, cyclic crack growth relation, linear elastic fracture mechanics, strain intensity, J-integral, creep-fatigue interaction, tension dwell, frequency, total endurance, integrated endurance, striation spacing, growth models, crack tip opening displacement, transgranular and intergranular crack, microstructural damage, aging, environment, laboratory specimen, component, plastic strain range


    Author Information:

    Skelton, RP
    Central Electricity Research Laboratories, Central Electricity Generating Board, Leatherhead, Surrey,


    Paper ID: STP32436S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP32436S


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