Volume 17, Issue 1 (January 1989)

    Fatigue Crack Propagation Threshold

    (Received 16 November 1987; accepted 15 July 1988)

    CODEN: JTEOAD

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    Abstract

    Service-type fatigue loading conditions are critically analyzed with respect to their relevance for a fatigue crack growth threshold. It was found that a threshold should be experimentally determined as a function of the monotonic-plastic zone size (i.e., as a function of Kmax). For each Kmax the cyclic-plastic zone size depends on the applied ΔK and threshold testing should cover the range ΔK ≈ ΔKth and ΔK (R = 0) for tension fatigue. For a given plastic zone, Kmax and ΔK fixed, the threshold ΔKth could occur anywhere between Kmax and Kmin. This study presents experimental procedures and furnishes results for Inconel 617 and a Ti-6A1-4V alloy which allow one to analyze the influence of the three parameters cited above. It demonstrates the following:

    • The threshold decreases “linearly” with increasing monotonic-plastic zone size; this confirms existing data.

    • The cyclic-plastic zone has minimal influence on the fatigue threshold with Ti-6A1-4V, while this influence is substantial in the case of Inconel 617.

    • A shift of threshold between Kmax and Kmin does not alter the magnitude of the threshold.


    Author Information:

    Marci, G
    Branch Head, Graduate Student, and Senior Research Engineer, Fracture and Mechanical Property Branch, Institute for Materials Research, DFVLR, German Aerospace Research Establishment, Köln 90,

    Castro, DE
    Branch Head, Graduate Student, and Senior Research Engineer, Fracture and Mechanical Property Branch, Institute for Materials Research, DFVLR, German Aerospace Research Establishment, Köln 90,

    Bachmann, V
    Branch Head, Graduate Student, and Senior Research Engineer, Fracture and Mechanical Property Branch, Institute for Materials Research, DFVLR, German Aerospace Research Establishment, Köln 90,


    Stock #: JTE11530J

    ISSN: 0090-3973

    DOI: 10.1520/JTE11530J

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    Author
    Title Fatigue Crack Propagation Threshold
    Symposium , 0000-00-00
    Committee E08