STP520

    Threshold for Fatigue Crack Growth in Ferritic Steels at 300 C

    Published: Jan 1973


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    Abstract

    Edge-cracked test specimens of two ferritic steels were subjected to the loading cycle σm ± σa at 300 C. The results showed that whether a crack grows or remains dormant can be predicted from the value of ΔK, the range of stress intensity factor during the fatigue cycle. The threshold value ΔKc necessary for crack growth was slightly greater than that of similar steels at room temperature and depended on the ratio σma. Crack growth data at low rates of crack growth were deduced from an integrated version of the crack growth equation da/dN = BK)m, where B and m are material constants. Crack growth rates at 300 C were similar to those at room temperature. The minimum possible rate of fatigue crack growth appeared to be somewhat greater than one lattice spacing/cycle. The methods used have the advantage that no crack growth monitoring instrumentation is required.

    Keywords:

    fatigue (materials), heat, stress cycling, fatigue tests, structural steels, crack propagation, crack initiation


    Author Information:

    Pook, LP
    Principal scientific officer and higher scientific officer, National Engineering Laboratory, East Kilbride, Glasgow

    Beveridge, AA
    Principal scientific officer and higher scientific officer, National Engineering Laboratory, East Kilbride, Glasgow


    Paper ID: STP38839S

    Committee/Subcommittee: E08.05

    DOI: 10.1520/STP38839S


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