STP631

    Correlation Between the Fatigue-Crack Initiation at the Root of a Notch and Low-Cycle Fatigue Data

    Published: Jan 1977


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    Abstract

    Fatigue-crack initiation was investigated by testing high-strength steels (AFNOR 35 NCD 16 and 35 CD 4) with 0.6-in. (15-mm) thick ASTM compact specimens having various notch-root radii between 0.003 in. (0.07 mm) and 0.04 in. (1 mm).

    Measuring devices were used to detect flaws with a surface area of only a few square millimetres in their propagation planes.

    In order to calculate the number of cycles required to initiate a crack, notch root behavior was investigated through several parameters. − ΔK/ √ρ, from linear-elastic fracture mechanics, which concentrate results when the initiation time is large; − KfEP, an experimental parameter derived from low-cycle fatigue data when Ni<105 cycles. In this case, the ratio between theoretical and experimental values of the initiation time is between one and two for a given nominal stress.

    Keywords:

    crack propagation, cracking (fracturing), fractures (materials), notched specimens


    Author Information:

    Baus, A
    Institut de Recherches de la Sidérurgie Francaise, Saint Germain en Laye,

    Lieurade, HP
    Institut de Recherches de la Sidérurgie Francaise, Saint Germain en Laye,

    Sanz, G
    Institut de Recherches de la Sidérurgie Francaise, Saint Germain en Laye,

    Truchon, M
    Institut de Recherches de la Sidérurgie Francaise, Saint Germain en Laye,


    Paper ID: STP35534S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP35534S


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