Conventional Fuel Tank Blunt Impact Tests: Test and Analysis Results

Abstract

The Federal Railroad Administration's Office of Research and Development is conducting research into fuel tank crashworthiness. A series of impact tests are planned to measure fuel tank deformation under two types of dynamic loading conditions -blunt and raking impacts. This paper describes the results of the first set of blunt impact tests for two retired EMD F-40 locomotive fuel tanks, Tank 232 and Tank 202.On October 8, 2013 and October 9, 2013, the FRA performed impact tests on two conventional passenger locomotive fuel tanks at the Transportation Technology Center (TTC) in Pueblo, Colorado. Each fuel tank was emptied of fluid and mounted on a crash wall with the bottom surface exposed. A rail cart modified with a "rigid" indenter was released to impact the center of the bottom of each fuel tank at about 6 mph. A center-impact on Tank 232 was chosen to impact between two baffles. A center-impact on Tank 202 was chosen to impact on a baffle.In the first test, Tank 232 was impacted by the indenter at 4.5 mph. The maximum residual indentation on the bottom of the tank measured approximately 5 inches. The tank deformed across the middle longitudinal span of the tank forming a diamond-shaped indention. In the second test, Tank 202 was impacted by the indenter at 6.2 mph. The maximum residual indentation on the bottom of the tank measured approximately 1.5 inches. The bottom of the tank deformed with an "X" shape spanning out from the location of square indenter at the center of the tank.Post-test autopsies revealed the deformation of the interior structures, i.e. baffles and attachments. There was no damage to the baffles in Tank 232. Deformation to the interior structure of Tank 202 was limited to the baffle directly beneath the impact location, which folded in the area near the impact location. Material coupons were cut and tensile testing performed to determine the properties of the materials used in each tank.Prior to the test, computer models were developed from measurements taken on the test articles. Material properties were estimated based on Brinell hardness measurements. Computer analyses were conducted to determine the conditions for the test, i.e. instrumentation, location of impact, target impact speeds and to predict the deformation behavior of the tank. Post-test, the resulting stress-strain relationships for the bottom sheets and baffles of both tanks were used to update the finite element models of the two tanks. The models were also updated to reflect the actual geometry of the tanks as confirmed by measurements of the tank interiors. The results of the finite element (FE) models run at the test conditions with the updated tank details are compared with the results from the test itself. Specifically, the deformation progression and the residual dent depth are compared between the tests and the models.In accidents, fuel tanks are subjected to dynamic loading, often including a blunt or raking impact from various components of the rolling stock or trackbed. Current design practice requires...

Results of a Diesel Multiple Unit Fuel Tank Blunt Impact Test

“…The rail cart, equipped with a 12-inch by 12-inch indentor on the front end weighs approximately 14,000 lbs. Additional details of the test setup are described in a paper on tests for tanks 202 and 232 [2]. The test wall mounting setup allows for each test specimen to be mounted through its existing attachment points, as it would to a locomotive or DMU carbody, and positioned to impact the bottom surface of the tank with a rigid indenter at a predetermined location.…”

“…The first two tests were performed at low speeds, 4.5 and 6.2 mph, chosen to impart permanent deformation to the tank and measure the force-deflection characteristics [2,3,4]. These preliminary tests provided valuable initial information on the variance of tank performance based on design details.…”

Results of a Conventional Fuel Tank Blunt Impact Test

“…The rail cart equiped with a 12-inch by 12-inch indentor on the front end weighs approximatley 14,000 lbs. Additional details of the test setup are described in a paper on tests for tanks 202 and 232 [2]. Because of the particular baffle arrangement of tank 234, the tank was mounted to the crash wall and aligned off-center to the track centerline so that the impact was centered between two lateral baffles.…”

“…This FEA featured a model adapted from a previously-described model of tank 232 [2]. Because the test of tank 234 was intended to puncture the tank, the FE model was modified to include material failure and puncture calculation capabilities.…”