On March 23, 2006, a full-scale test was conducted on a passenger rail train retrofitted with newly developed cab end and non-cab end crush zone designs. This test was conducted as part of a larger testing program to establish the degree of enhanced performance of alternative design strategies for passenger rail crashworthiness. The alternative design strategy is referred to as crash energy management (CEM), where the collision energy is absorbed in defined unoccupied locations throughout the train in a controlled progressive manner. By controlling the deformations at critical locations the CEM train is able to protect against two dangerous modes of deformation: override and large-scale lateral buckling.The CEM train impacted a standing locomotive-led train of equal mass at 31 mph on tangent track. The interactions at the colliding interface and between coupled interfaces performed as expected. Crush was pushed back to subsequent crush zones and the moving passenger train remained in-line and upright on the tracks with minimal vertical and lateral motions.The added complexity associated with this test over previous full-scale tests of the CEM design was the need to control the interactions at the colliding interface between the two very different engaging geometries. The cab end crush zone performed as intended because the locomotive coupler pushed underneath the cab car buffer beam, and the deformable anti-climber engaged the uneven geometry of the locomotive anti-climber and short hood. Space was preserved for the operator as the cab end crush zone collapsed.The coupled interfaces performed as predicted by the analysis and previous testing. The conventional interlocking anti-climbers engaged after the pushback couplers triggered and absorbed the prescribed amount of energy. Load was transferred through the integrated end frame, and progressive controlled collapsed was contained to the energy absorbers at the roof and floor level. The results of this full-scale test have clearly demonstrated the significant enhancement in safety for passengers and crew members involved in a push mode collision with a standing locomotive train.
As part of the passenger equipment crashworthiness research, sponsored by the Federal Railroad Administration and supported by the Volpe Center, passenger coach and cab cars have been tested in inline collision conditions. The purpose of these tests was to establish baseline levels of crashworthiness performance for the conventional equipment and demonstrate the minimum achievable levels of enhancement using performance based alternatives.The alternative strategy pursued is the application of the crash energy management design philosophy. The goal is to provide a survivable volume where no intrusion occurs so that passengers can safely ride out the collision or derailment. In addition, lateral buckling and override modes of deformation are prevented from occurring. This behavior is contrasted with that observed from both full scale tests recently conducted and historical accidents where both lateral buckling and/or override occurs for conventionally designed equipment.A prototype crash energy management coach car design has been developed and successfully tested in two full-scale tests. The design showed significant improvements over the conventional equipment similarly tested. The prototype design had to meet several key requirements including: it had to fit within the same operational volume of a conventional car, it had to be retrofitted onto a previously used car, and it had to be able to absorb a prescribed amount of energy within a maximum allowable crush distance. To achieve the last requirement, the shape of the force crush characteristic had to have tiered force plateaus over prescribed crush distances to allow for crush to be passed back from one crush zone to another. The distribution of crush along the consist length allows for significantly higher controlled energy absorption which results in higher safe closing speeds.
A Crash Energy Management (CEM) cab car crush zone design has been developed for retrofit onto an existing Budd M1 cab car. This design is to be used in the upcoming fullscale train-to-train test of a CEM consist impacting a standing freight consist of comparable weight. The cab car crush zone design is based upon the coach car crush zone design that has been previously developed and tested.The integrated system was developed after existing national and international CEM systems were reviewed. A detailed set of design requirements was then drafted, and preliminary designs of sub-assemblies were developed. The preliminary designs were analyzed using detailed large deformation finite element software. Performance of the cab car crush zone under ideal and non-ideal loading conditions was analyzed prior to development of the final design.The key components of the design include: a long stroke push-back coupler capable of accommodating the colliding locomotive coupler, a deformable anti-climber to manage the colliding interface interaction, an integrated end frame on which the deformable anti-climber is attached, a set of primary energy absorbers designed to crush in a controlled manner while absorbing the majority of the collision energy, and a survivable space for the operator which pushes back into an electrical closet.The cab car crush zone is designed to control both lateral and vertical vehicle motions that can promote lateral buckling of the train and override of the impacting equipment. The design is capable of managing the colliding interface interaction with a freight locomotive and passing crush back to successive crush zones. Detailed fabrication drawings have been developed and submitted to a fabrication shop. In addition, existing Budd M1 cars are being prepared to receive the retrofit components.
Two grade-crossing impact tests were conducted in June 2002 at the Federal Railroad Administration’s (FRA’s) Transportation Technology Center in Pueblo, Colorado as part of the FRA’s research into passenger equipment crashworthiness. In both of these tests a cab car moving at approximately 14 mph impacted a standing coil of steel supported by a frangible table. The coil was positioned such that the left-side corner post of the cab car sustained the brunt of the impact. The cars were instrumented to measure the accelerations of the carbody, the displacements of the suspensions, the displacements of the corner posts, and the strains in selected structural members. The coil was instrumented to measure its three-dimensional acceleration, including yaw, pitch, and roll. On-board and wayside high-speed film and video cameras were used to record the impact. On June 4, 2002 a cab car compliant with general industry practice circa 1999 was tested and on June 7, 2002 a cab car compliant with current FRA regulations and American Public Transportation Association (APTA) Standards and Recommended Practices for Rail Passenger Equipment was tested. The tests themselves were conducted in response to a recommendation from the APTA Passenger Rail Equipment Safety Standards (PRESS) Committee to measure the crashworthiness performance of alternative cab car end structures. During the test of the 1990’s design, the corner post failed, eliminating the survival space for the operator. During the test of the state-of-the-art design cab car, the corner post remained attached and deformed less than 9 inches, preserving space for the operator. Prior to the test, crush analyses were conducted to determine the force/crush characteristics of the two end structure designs, as well as their modes of deformation. Collision dynamics analyses were also conducted to determine the extent of crush and the gross motion of the car and coil. This paper describes the analysis of the crush behaviors of the two different end structure designs. A companion paper describes the results of the collision dynamics analyses. The crush of the cars was analyzed using detailed finite-element models. The impact end of each car was modeled, including approximately 1/4 of the length of the car. The back end of the cab car model was fixed, and its end structure was impacted by an initially moving cylinder with the same mass and dimensions as the steel coil used in the tests. Prior to the tests, runs were made with the models with and without material failure. This approach allowed calculation of an upper bound and a lower bound on the force/crush characteristics. The pre-test predictions of the analysis of the state-of-the art car including material failure very closely match the results of the test for the force/crush characteristic, strains at the measured locations, the geometry of the deformed structure, and the locations and extent of material failure. The pre-test predictions of the analysis of the 1990’s design also closely match the test measurements, however, the extent of material failure predicted was slightly less than observed in the test; failure of the corner post was predicted to occur at a speed of a 1.6 mph (approximately 10%) greater than the test speed. A more sophisticated implementation of the material failure modeling helped bring the model results into very close agreement with the test measurements.
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