STP1450: A Methodology for Assessing Fatigue Crack Growth Reliability of Railroad Tank Cars

    Zhao, W
    Research Professor and Carolina Distinguished Professor, University of South Carolina, Columbia, SC

    Sutton, MA
    Research Professor and Carolina Distinguished Professor, University of South Carolina, Columbia, SC

    Penã, J
    Mechanical Engineer, Federal Railroad Administration, Washington, DC,

    Pages: 15    Published: Jan 2004


    Abstract

    A methodology for assessing structural reliability of railroad tank cars undergoing fatigue crack growth is being developed. A three-degree-of freedom (3-dof) surface crack is employed to account for an asymmetric stress field existing at a fatigue critical location in tank car structures. A fatigue life prediction program using the Walker equation to account for stress ratio effects is developed for the 3-dof surface crack model. A component reliability problem is formulated as a limit state function and solved using a first-order reliability method along with importance sampling method within the commercial reliability software, STRUREL. The methodology is demonstrated using illustrative railroad tank car examples. The results show that: (a) failure probability, Pf, increases as tank car mileage increases; (b) welding residual stresses in the tank structure can significantly increase Pf ; (c) uncertainty in the stress amplitude also has a significant effect on Pf; and (d) the correlation between initial crack depth and initial crack aspect ratio is an important parameter.

    Keywords:

    structural reliability, fatigue crack growth, railroad tank car, surface crack


    Paper ID: STP11290S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP11290S


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