The Accident Damage Assessment Guidelines used to make decisions on the safety of damage pressure tank cars were formulated in the 1970s by the Association of American Railroads (AAR) under the auspices of the Federal Railroad Administration. Although these Guidelines have served their purpose, their validity has not been quantitatively established. This report describes an effort by AAR/TTCI and SRI International to examine and refine the Guidelines. Damage mechanics was applied to evaluate the effect of gouges and wheel burns. Notched round bar tensile tests were combined with finite element analysis to predict cleavage failure in the absence of a macroscopic crack. Fracture mechanics was applied to evaluate the stability of a thumbnail crack at a dent root and a through-wall crack. Fracture mechanics was applied to evaluate the stability of a thumbnail crack at a dent root and a through-wall crack. J-resistance tests were used to support the analysis. Laboratory dent/undent tests in which plate was bent then pulled straight in tension were applied to evaluate the effects of denting. The research showed that the present Guidelines are valid, with reasonable factors-of-safety, except for otherwise-undamaged dents that do no involve welds. Consideration of dent root radius should be removed from the Guidelines because radius has little bearing on the likelihood of failure. Tank pressures above 100 psi are sufficient to straighten longitudinal dents and leave them with large root radii. Accordingly, the largest root radii have seen the highest pressures and the most deformation, yet previously were considered the safest. Fortunately, the dent/undent tests showed that otherwise-undamaged dents that do not involve welds fail at loads equal to those for virgin plate.


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    Title :

    Damage Assessment of Railroad Tank Cars Involved in Accidents: Phase II-Modeling and Validation


    Contributors:

    Publication date :

    2002


    Size :

    138 pages


    Type of media :

    Report


    Type of material :

    No indication


    Language :

    English





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