Evaluation of Fracture Toughness Results and Transferability to Fracture Assessment of Welded Joints

    Published: Jan 1999

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    Fracture mechanics test results for welded joints are affected by the mechanical and metallurgical inhomogeneity in welds. The size of embrittled region encountered by the notch tip and the strength mismatch between the base and weld metals are major factors controlling the fracture resistance of welds. Larger sampling of embrittled region leads to lower fracture toughness of welds. Strength over-matching of the weld metal decreases the HAZ toughness, because the local stress in the HAZ is elevated by the constraint effect of the weld metal. This paper develops the procedure for fracture strength evaluation of welded joints based on the Local Approach. A key idea is the use of the Weibull stress, consisting of stress components in a specific region governing fracture initiation in welds. The concern of this paper is the transferability of toughness results to fracture performance evaluation of welded joints. It is demonstrated that the fracture performance of welded joints can be predicted successfully from 3-point bend test results using the Weibull stress concept. A new procedure for the derivation of fracture toughness requirements has been proposed. It is characterized by the equivalent CTOD, which provides a comparable Weibull stress of both toughness specimen and structural component. The equivalent CTOD concept enables the quantification of fracture toughness requirements to meet design solutions for welded components with mismatched welds.


    fracture mechanics test, fracture toughness, fracture performance, transferability, Local Approach, welded joints, heterogeneity, weld strength mismatch

    Author Information:

    Minami, F
    Associate Professor and Professor, Graduate School of Engineering, Osaka University, Osaka,

    Toyoda, M
    Associate Professor and Professor, Graduate School of Engineering, Osaka University, Osaka,

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP14956S

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