Correlating Material Properties to Puncture Resistance to Enhance the Safety and Security of Tank Cars

In the Next Generation Railroad Tank Car Project, testing and analysis were performed on TC128B material as well as other tank car steels (e.g. A1011, A516-70). In a similar material evaluation effort, the Chlorine Institute sponsored a program to characterize other high strength low alloy (HSLA) candidate steel materials (A710, HPS 70, and HPS 100). In this study, this past data is used and augmented by additional testing and analysis to evaluate the impact and puncture resistance performance of candidate materials that could be used in tank car structure (both shell and jacket). Understanding the appropriate form of material damage and failure models, predicting structural performance and linking behavior to basic material properties, will allow design optimization and selection of the most appropriate material for the tank structures.

The research program included detailed characterizations of various steel material samples (including a number of different TC128B variants). These detailed material characterizations included assessing tensile stress-strain properties as well as mechanical behavior of notched samples. As part of the research, detailed constitutive and damage models were developed for each material and the models were used to simulate the corresponding tests.

This report presents estimates and formulas for conditional probabilities of release (CPR) for all common tank car configurations and components in service today, given that the tank car is involved in an FRA-reportable accident, as well as distributions of the quantity of lading lost in the event of a release. The study was funded by the industry partners of the Advanced Tank Car Collaborative Research Program, using data provided by the RSI-AAR Railroad Tank Car Safety Research and Test Project. The study updates and expands upon an earlier Tank Car Safety Project report: RA-05-02, “Safety Performance of Tank Cars in Accidents: Probabilities of Lading Loss”, published in 2006.

The purposes of revising the RA-05-02 CPR estimates were to take advantage of data from more recent accidents, and to incorporate factors in the modeling of tank car performance that were not addressed by the earlier report. The new estimates are more reflective of current and future tank cars and accident environments.

CPR estimates for the more recent time period are generally lower than the RA-05-02 estimates for any given car. Some of the newly analyzed variables were revealed to be significant.

Over the last decade, there has been significant ongoing research to develop strategies for improving railroad tank cars so they can maintain tank integrity for more severe accident conditions. Beginning in 2006 and continuing through 2009, Dow Chemical Company, Union Pacific Railroad, and Union Tank Car Company assembled a joint project team to drive forward a holistic process for the development of a next generation rail tank car. This work was performed under the Next Generation Railroad Tank Car (NGRTC) Program and completed in cooperation with U.S. Department of Transportation, Federal Railroad Administration (DOT – FRA), Transport Canada (TC), and U.S. Department of Homeland Security Transportation Security Administration (DHS - TSA) and addressed safety, security, emergency response and operational challenges. The NGRTC program developed a database of both full-scale impact testing on tank cars and tank heads as well as a significant database on characterization of tank car materials and laboratory scale component tests (e.g. panel punch tests). An additional effort in the NGRTC Program was the development and validation of detailed finite element tank impact models and tank car steel constitutive and failure models which can be used to accurately predict the puncture resistance under different impact conditions.

Subsequent to the NGRTC Program, the Advanced Tank Car Collaborative Research Program (ATCCRP) was initiated to coordinate research efforts to enhance the safety and security of rail tank car shipments of toxic inhalation hazard (TIH) materials. The ATCCRP builds on the prior and ongoing research conducted by the NGRTC Project, the Chlorine Institute (CI) tank car safety research [2-4], and the RSI-AAR Tank Car Safety Research and Test Project [5, 6]. The ATCCRP is a joint effort comprised of the following groups: shippers of tank cars carrying toxic inhalation hazard (TIH) materials [represented by the American Chemistry Council (ACC), CI, and the Fertilizer Institute (TFI)]; railroads that transport hazardous materials [represented by the Association of American Railroads (AAR)]; and rail tank car builders and lessors [represented by the Railway Supply Institute (RSI)]. In addition, Memoranda of Cooperation (MOC) were developed to formalize cooperation agreements between ATCCRP participants and the DOT - FRA, TC, DHS - TSA and the DHS Science and Technology Directorate (DHS - S&T).