Determining the Potential Drop Calibration of a Fatigue Crack Growth Specimen Subject to Limited Experimental Observations

    Volume 22, Issue 4 (July 1994)

    ISSN: 0090-3973

    CODEN: JTEOAD

    Page Count: 11


    McKeighan, PC
    Research associate/temporary lecturer and reader in engineering materials, Bristol University, Bristol,

    Smith, DJ
    Research associate/temporary lecturer and reader in engineering materials, Bristol University, Bristol,

    (Received 16 November 1993; accepted 26 January 1994)

    Abstract

    Six separate calibration techniques are applied to potential drop (PD) and crack length data from 23 experimental datasets. Five of the techniques use limited experimental input gained during precracking and after test completion to derive the coefficients associated with the calibrations. The datasets include SE(B) and M(T) specimens, fatigue crack growth (FCG) tests and foil analog simulations as well as various aluminum alloys and steel. A comparison of the calibration techniques is undertaken in terms of crack length and the subsequent effect on stress intensity factor errors. The best calibration techniques using two PD and crack length data pairs are the two-point modified and post-test corrected Johnson's equation. Using these methods, 21 of the 23 tests satisfy a criterion based on an acceptable ±2% mean variation in stress intensity factor. If a statistical assessment of the data is made, only 30 to 35% of the tests satisfy this criterion. Finally, the crack length prediction errors that result from the different calibrations can typically cause a 15 to 30% variation in FCG rate da/dN at a given ΔK level. This difference is found to be primarily due to errors in the ΔK calculation.


    Paper ID: JTE11837J

    DOI: 10.1520/JTE11837J

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    Title Determining the Potential Drop Calibration of a Fatigue Crack Growth Specimen Subject to Limited Experimental Observations
    Symposium , 0000-00-00
    Committee E08