Raking Impact of a Diesel Multiple Unit Fuel Tank: Tests and Anaylsis

Abstract

Abstract The Federal Railroad Administration (FRA) sponsors research on safety topics to address and to improve safety regulations and standards. This paper focuses on the latest research and testing conducted to evaluate passenger locomotive fuel tank integrity. Fuel tank integrity regulations, in the form of a series of static load conditions, currently exist to set a minimum level of protection against an impact to the fuel tank that might puncture the tank and cause the release of diesel fuel. The current research program involves a series of dynamic impact tests and quasi-static tests that measures the forces required to deform a fuel tank and investigate the types of loading conditions experienced by fuel tanks. The objective of the testing program is to establish the baseline puncture resistance of current locomotive fuel tanks under dynamic impact conditions and to develop performance requirements for an appropriate level of puncture resistance in alternative fuel tank designs, such as Diesel Multiple Unit (DMU) fuel tanks. The tests are divided into two loading scenarios identified from accidents: blunt impact and raking impact. The blunt impact scenario in the form of a full-scale dynamic impact test, have been completed on both conventional passenger locomotive fuel tanks and a DMU fuel tank. DMU fuel tank quasi-static tests, conducted in December 2018 and November 2019, are designed to simulate a raking impact scenario of a fuel tank. The Transportation Technology Center Inc. (TTCI), with support from the Volpe Center designed a test setup using a fuel tank mounted to a boxcar placed within the “squeeze frame”. An indenter, shaped like a broken rail, is fixed to the ground and the fuel tank is slowly pushed into the indenter using a series of hydraulic rams. Load cells and string potentiometers are used to measure the force/displacement. Cameras capture the deformation profile of the fuel tank. The Volpe Center develops and performs finite element analysis to evaluate the loading scenario prior to testing. The results of pre-test analyses for the raking impact tests are presented to highlight the critical position on the fuel tank to be impacted. The analysis gives an estimate of the force required to puncture the fuel tank as well as the resultant tear of the fuel tank. Additionally, finite element analysis may be used to evaluate the effect of the fuel on the fuel tank integrity. These results highlight the detailed differences of quasi-static versus dynamic loading of fuel tanks, which supports defining tradeoffs between specifying static load requirements versus scenario-defined performance based standards.