ISSN: 1546-962X
CODEN: JAIOAD
Published Online: 30 August 2004
Page Count: 15

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, US Department of Transportation, Federal Railroad Administration, Washington, DC

(Received 16 September 2002; accepted 11 July 2003)

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, P_f, increases as tank car mileage increases; (b) welding residual stresses in the tank structure can significantly increase P_f; (c) uncertainty in the stress amplitude also has a significant effect on P_f; 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: JAI11574
DOI: 10.1520/JAI11574
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