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    S-N Curve for Crack Initiation and an Estimate of Fatigue Crack Nucleus Size

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    A study of fatigue life prediction was made for ASTM A533 Grade B nuclear pressure vessel steel. The objectives of the study were to predict the S-N curve, representing crack initiation, and to estimate the average crack nucleus size using an engineering approach. The plastic replica method was used to monitor crack initiation and growth from well-polished specimens under uniaxial tension-tension stressing.

    Two methods were used to estimate crack nucleus size: (1) backcalculating crack length via the da/dN versus ΔK relationship, and (2) evaluating an assumed relationship between the endurance limit and the threshold stress intensity factor range. Crack nucleus size estimated by these two methods are fairly consistent when the effects of crack closure and plastic zone correction are taken into account.


    crack closure, small cracks, crack initiation, crack nucleus size, crack shape, fatigue crack growth, S-N, curve, replication method

    Author Information:

    Yang, CY
    ESBU, Pittsburgh, PA

    Liaw, PK
    The University of Tennessee, Knoxville, TN

    Palusamy, SS
    ESBU, Pittsburgh, PA

    Ren, W
    The University of Tennessee, Knoxville, TN

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP16243S