STP1114

    Experience in Using Direct Current Electric Potential to Monitor Crack Growth in Ductile Metals

    Published: Jan 1991


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    Abstract

    The direct-current electric potential (d-c EP) method is receiving increasing attention as an alternative to the unloading compliance method for monitoring crack initiation and growth during fracture toughness testing of ductile metals. Advantages of the d-c EP method include uninterrupted tests, continuous monitoring of crack extension, ability to accurately measure relatively large amounts of crack growth, and ability to be used at high displacement rates in many materials. The principal shortcoming of the d-c EP method (as with most other methods) is the uncertainty in defining the point of crack initiation in some tests.

    This paper describes Battelle's experience in using the d-c EP method to monitor crack initiation and growth in compact (tension) specimens machined from various pipes used in cooling systems of nuclear reactors. Among the materials investigated are carbon steel pipes (base metal and weld metal) and extremely ductile austenitic stainless steel pipes (base metal and weld metal). Discussed in the paper are: (1) estimation of the crack-initiation point from d-c EP data, (2) ability of the d-c EP method to accurately predict large amounts of crack growth in highly ductile metals, (3) modification of the Johnson equation to improve the accuracy of the d-c EP method for large crack growth, and (4) use of the d-c EP method at high displacement rates.

    Keywords:

    electric potential method, crack initiation, crack growth


    Author Information:

    Landow, MP
    Research scientist and senior research scientist, Battelle, Columbus, OH

    Marschall, CW
    Research scientist and senior research scientist, Battelle, Columbus, OH


    Paper ID: STP16853S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP16853S


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