Constraint Corrected J-R- Curve and Its Application to Fracture Assessment for X80 Pipelines

    Volume 3, Issue 6 (June 2006)

    ISSN: 1546-962X

    CODEN: JAIOAD

    Published Online: 17 May 2006

    Page Count: 17


    Zhu, X-K
    Senior Research Scientist and Senior Research Leader, Battelle Memorial Institute, Columbus, OH

    Leis, BN
    Senior Research Scientist and Senior Research Leader, Battelle Memorial Institute, Columbus, OH

    (Received 8 April 2005; accepted 6 March 2006)

    Abstract

    Single specimen J-R curve testing for X80 pipeline steel was conducted using single edge notched bend (SENB) and single edge notched tension (SENT) specimens with various crack lengths. Test data indicate that the J-R curves for this steel are strongly constraint dependent. To facilitate transferability of experimental J-R curves to those for actual cracked components, this paper develops a constraint corrected J-R curve for X80 steel. A modified J-Q theory that can consider the global bending stress influence is proposed so as to correctly quantify constraint effect on the crack-tip fields and the J-R curves. Results show that the modified J-Q solution can well match numerical crack-tip fields for bending specimens, with Q being a load-independent constraint parameter under large scale yielding. Based on the experimental data and numerical analysis, a constraint corrected J-R curve is formulated as a function of the parameter Q and crack extension Δa for X80 steel. A general procedure to predict J-R curves for actual cracked components is then outlined. Comparison indicates that the predicted J-R curves developed in this paper agree well with the experimental data for both SENB and SENT specimens. To demonstrate its application in failure assessment, the constraint corrected J-R curve for X80 steel is used to determine failure loads for a surface cracked pipeline. Reasonable agreement to available analytic solution is achieved.


    Paper ID: JAI13209

    DOI: 10.1520/JAI13209

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    Title Constraint Corrected J-R- Curve and Its Application to Fracture Assessment for X80 Pipelines
    Symposium Fatigue and Fracture Mechanics: 35th Volume, 2005-05-20
    Committee E08