STP1207

    Evaluation of the Relationship Between C*, δ5, and δt during Creep Crack Growth

    Published: Jan 1994


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    Abstract

    The relationships between C*, δ5 and δt, during creep crack growth are explored analytically and experimentally in this paper. The experimental part of the program used a Cr-Mo-V steel that exhibits a creep-ductile behavior, a Ti-6242Si alloy containing an equiaxed microstructure that is on the borderline of creep-ductile and creep-brittle behavior, and a Ti-6242Si-alloy containing a lamellar microstructure that exhibits an essentially creep-brittle behavior. It is shown that for creep-ductile materials, the rate of creep component of δ5, δ5C, and δt, are essentially similar for crack extensions smaller than 15% of the initial crack size. Either parameter is able to correlate creep crack growth rates in the extensive creep regime in these materials. It is recommended that, for limited amounts of crack extension, δ5C be used as an operational definition of δt, in creep-ductile materials.

    For high crack growth rates in the creep-brittle materials, a correlation between da/dt and δ5 is found. However, it is analytically shown that δ5 values are dominated by crack growth under these conditions, therefore, this correlation is not of any significant value and should not be used for structural life predictions.

    Keywords:

    creep, cracks, C, * integral, crack tip opening displacement (CTOD), C, t, parameter


    Author Information:

    Saxena, A
    Professor and director, School of Materials Engineering, Georgia Institute of Technology, Atlanta, GA

    Dogan, B
    Group head and institute head, GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht,

    Schwalbe, K-H
    Group head and institute head, GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht,


    Paper ID: STP13724S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP13724S


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