Abstract
Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Two crash energy management (CEM) components that can be integrated into the end structure of a locomotive have been developed: a push-back coupler (PBC) and a deformable anti-climber (DAC). These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating and compromise the occupied space. The objective of this research program is to demonstrate the feasibility of these components in improving crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment.
Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, or may require replacement due to unintentional activation as a result of loads experienced during service and coupling. PBCs are designed with trigger loads which exceed the expected maximum service and coupling loads experienced by conventional couplers. Analytical models are typically used to determine these trigger loads. Two sets of coupling tests have been conducted that validate these models, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive retrofit with a PBC. These tests provide a basis for comparing the coupling performance of a CEM-equipped locomotive with that of a conventional locomotive, as well as confirmation that the PBC triggers at a speed well above typical coupling speeds and at the designed force level. In addition to the two sets of coupling tests, two vehicle-to-vehicle collision tests where one of the vehicles is a CEM-equipped locomotive and a train-to-train collision test are planned. This arrangement of tests allows for evaluation of CEM-equipped locomotive performance, and enables comparison of actual collision behavior with predictions from computer models in a range of collision scenarios.
This paper describes the results of the most recent test in the research program: the first vehicle-to-vehicle impact test. In this test, a CEM-equipped locomotive impacted a stationary conventional locomotive. The primary objective of the test was to demonstrate the effectiveness of the components of the CEM system in working together to absorb impact energy and to prevent override in a vehicle-to-vehicle collision scenario. The target impact speed was 21 mph. The actual speed of the test was 19.3 mph. Despite the lower test speed, the CEM system worked exactly as designed, successfully absorbing energy and keeping the vehicles in-line, with no derailment and no signs of override. The damage sustained during the collision is described. Prior to the tests, a finite element model was developed to predict the behavior of the CEM components and test vehicles during the impact. The test results are compared to pre-test model predictions. The model was updated with the conditions from the test, resulting in good agreement between the updated model and the test results. Plans for future full-scale collision tests are discussed.
Deriving formulations for forecasting the ultimate strength of locally dented ring-stiffened cylinders under combined axial compression and radial pressure loads