Improved Tank Car Design Development: Ongoing Studies on Sandwich Structures

The Government and industry have a common interest in improving the safety performance of railroad tank cars carrying hazardous materials. Research is ongoing to develop strategies to maintain the structural integrity of railroad tank cars carrying hazardous materials (hazmat) during collisions. This paper describes engineering studies on improved tank car concepts. The process used to formulate these concepts is based on a traditional mechanical engineering design approach. This approach includes initially defining the desired performance, developing strategies that are effective in meeting this performance, and developing the tactics for implementing the strategies. The tactics are embodied in the concept. The tactics and concept evolve through engineering design studies, until a design satisfying all of the design requirements is developed. Design requirements include service, manufacturing, maintenance, repair, and inspection requirements, as well as crashworthiness performance requirements. One of the concepts under development encases the pressurized commodity-carrying tank in a separate carbody. Moreover, this improved tank car concept treats the pressurized commodity-carrying tank as a protected entity. Welded steel sandwich structures are examined as a means to offer protection of the commodity tank against penetrations from impacting objects in the event of a collision. Sandwich structures can provide greater strength than solid plates of equal weight. Protection of the tank is realized through blunting of the impacting object and absorption of the collision energy. Blunting distributes impact loads over a larger area of the tank. Energy absorption reduces the demands on the commodity tank in the event of an impact. In addition, the exterior carbody structure made from sandwich panels is designed to take all of the in-service loads, removing the commodity tank from the load path during normal operations. Design studies described in this paper focus on the protection aspect of using sandwich structures. Studies are conducted to investigate the influence of different parameters, such as sandwich height and core geometry, on the force-deformation behavior of sandwich structures. Calculations are carried out numerically using nonlinear finite element analysis. These analyses are used to examine the crashworthiness performance of the conceptual design under generalized impact scenarios.