Session: Track 2-1: Rolling Stock and Dynamics

Paper Number: 131837

131837 - Improving Crash Energy Management of Tank Cars 

Increasing volume of rail transport inevitably leads to an increased number of accidents, which raises safety concerns and challenges related to hazmat transportation. In the event of an accident or derailment, the puncture resistance of the tank is key to prevention of hazmat release and escalation of the incident.

The objective of this FRA funded research effort was to investigate mitigation solutions aimed at improving the puncture resistance of hazmat tank cars. This was achieved by first developing and validating a finite element (FE) model of a full-scale tank car subject to shell impact. The effectiveness of different mitigation solutions was then evaluated by exercising the validated FE model.

The side impact test of a water-filled DOT-105 tank car was used for the validation exercise and established as the baseline condition. The tank car that featured a 0.775-inch-thick TC128-B steel shell was physically tested at 15.16 mph with puncture of the shell occurring. A survival speed of 13.0 mph was subsequently calculated using the validated FE model.

A new low-carbon version of TC128-B steel developed by ArcelorMittal was then assessed. The new steel featured higher ductility and reduced strength and had been predicted by AM to provide in the region 12 – 14% improvement in puncture energy. Using information published by AM the performance of this new steel was evaluated in reference to the baseline discussed above. The calculated improvement in puncture energy was very similar to that estimated by AM, representing an incremental improvement in the puncture resistance of tank cars.

Within the available tank car space and weight constraints one of the simplest solutions is to increase the thickness of the tank shell. Clearly, this applies to the design of new tank cars only and is a solution that has been adopted by the tank car industry in generational improvements in which the head and shell thickness have been increased. This solution was investigated here by increasing the tank shell thickness to 1.5 inches and calculating the tank car response to side impact. A survival speed of ~22 to 23 mph was achieved. This utilized ~90% of the available weight.

Recognizing the challenges related to manufacturing a tank car with 1.5-inch-thick shell, a parametric study was conducted to investigate the effect of increased ductility and strength. In both cases, the puncture energy approximately doubled, with survival speeds increasing to 19 mph and 20 mph for the high ductility and high strength materials respectively. These findings are consistent with those of previous researchers.

Implementing a multi-layer, or tank-within-a-tank, solution was also considered. The results indicated that in various configurations the survival speed could approximately match that of the 1.5-inch-thick-shell provided that the total steel thickness was the same. It was noted that splitting the outer plates into a series of rings did not significantly change the puncture resistance. One significant benefit the multi-layer solution offers is the use of increased strength or ductility steels for the outer layers. Additionally, a numerical investigation of the effect of plate thickness on ductility showed that increasing the thickness can significantly reduce ductility in bending. Applying a multi-layer solution allows avoiding this ductility penalty.

An internal tank car liner was also investigated and shown to be potentially effective purely as a containment mechanism in the event of puncture. Mitigation solutions aimed at blunting the indenter were also considered, with the effectiveness similar to increasing the shell thickness, but with significant added complexity and cost. Therefore, pursuing mitigation solutions aimed primarily at blunting is not recommended.

In summary, the most promising mitigation solution is likely to be the multi-layer solution, in which different steel grades can be used for the outer layers with the specific purpose of enhancing the overall puncture resistance of the tank car.

Presenting Author: Pawel Woelke Thornton Tomasetti

Presenting Author Biography: Pawel Woelke co-leads the Applied Science Practice at Thornton Tomasetti and is responsible for tackling the most challenging engineering problems in automotive, rail, shipping and other industries. He specializes in assessment of characterization of extreme loading conditions such as explosion, fire, impact etc. and their effects on structures, materials and mechanical systems. Pawel has also contributed to and led a number of vulnerability studies for critical infrastructure in the New York metropolitan area, including bridges, tunnels, buildings, storage facilities and retaining walls, as well as elements of non-load-bearing building envelope.
Over the last several years, Pawel has been focusing on decarbonization efforts and enabling energy transition through improving safety of the energy storage systems, hydrogen, nuclear reactors and facilities, carbon dioxide transportation and storage and other hazardous materials.

Authors:

Philip Taylor Thornton Tomasetti
Juan Londono Thornton Tomasetti
Pawel Woelke Thornton Tomasetti
David Jeong Independent Consultant
David Tyrell Independent Consultant
John W. Hutchinson Independent Consultant