STP1505

    Fracture Toughness of Hydrided Zircaloy-4 Sheet under through-Thickness Crack Growth Conditions

    Published: Jan 2009


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    Abstract

    The susceptibility of fuel cladding to failure in the case of a postulated reactivity-initiated accident may be determined by crack initiation within a hydride blister or rim and subsequent crack growth through the thickness of the cladding. This study has determined the fracture toughness of hydrided cold-worked stress relieved Zircaloy-4 sheet subject to through-thickness crack growth at both 25 and 300°C. The experimental approach utilizes a novel procedure in which a narrow linear strip of brittle hydride blister across the specimen width creates a well-defined precrack upon initial loading. The subsequent crack growth resistance is then characterized by four-point bending of the specimen and an elastic-plastic fracture mechanics analysis. At room temperature, the through-thickness fracture toughness (Kq) is sensitive to the orientation of the hydride platelets and Kq≅25 MPa√m for crack growth through a mixed in-plane/out-of-plane hydride field. In contrast, Kq is much nigher (≅75 MPa√m) when the hydride platelets are oriented predominantly in the plane of the sheet and therefore normal to both the crack plane and the crack growth direction. At 300°C, the material exhibits greater ductility as the hydride particles within the matrix resist fracture such that Kq≅83 MPa√m, despite the much lower flow stress of the material.

    Keywords:

    Zircaloy, hydrides, fracture toughness


    Author Information:

    Raynaud, P. A.
    The Pennsylvania State University, University Park, PA

    Koss, D. A.
    The Pennsylvania State University, University Park, PA

    Motta, A. T.
    The Pennsylvania State University, University Park, PA

    Chan, K. S.
    Southwest Research Institute, San Antonio, TX


    Paper ID: STP48135S

    Committee/Subcommittee: B10.02

    DOI: 10.1520/STP48135S


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