STP1189: Development of a Fatigue Crack Growth Rate Specimen Suitable for a Multiple Specimen Test Configeration

    Deshayes, FR
    Graduate research assistant and director of Center for Marine Materials, Center for Marine Materials, Florida Atlantic University, Boca Raton, FL

    Hartt, WH
    Graduate research assistant and director of Center for Marine Materials, Center for Marine Materials, Florida Atlantic University, Boca Raton, FL

    Pages: 21    Published: Jan 1993


    Abstract

    A new experimental approach developed by fatigue crack growth rates can be determined for multiple specimens tested in series. This involves a geometry such that the response to cyclic loading in each specimen is mutually independent. Relationships between the stress intensity factor, compliance, and crack length and between direct-current potential drop and crack length have been analytically evaluated for the proposed specimen geometry. An appropriate side-groove depth that avoided crack deviation from the intended plane of extension was determined experimentally, and an analytical expression that accounted for reduced thickness in the crack plane was verified. Calibration curves between crack length and compliance and between crack length and potential drop were experimentally verified as well, and the stress intensity-crack length characteristics for the specimen were confirmed by comparing da/dNKI curves with those for conventional C(T) specimens. A customized, five specimen frame was designed and fabricated in conjunction with a 98-kN MTS actuator and interfaced with a commercially available control system, the hardware and software of which were modified to accommodate multiple-specimen control and data acquisition. The utility of the proposed specimen and test procedure is discussed within the context of threshold and near-threshold crack growth rate determinations where long test times are normally required for data development, particularly for low cyclic frequency applications such as nuclear and offshore.

    Keywords:

    multiple-specimen testing, fatigue crack growth, stress intensity factor, compliance, tapered specimen, elastic analysis, finite element method, direct-current potential drop technique, side grooves, fracture mechanics, fatigue (materials)


    Paper ID: STP24291S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP24291S


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