Richard Stringfellow

The development of a rail passenger coach car crush zone

This paper presents information on the design of a rail vehicle crush zone for better occupant protection. The overall design requirements and characteristics are described and the configuration for the various structural subsystems is presented. The paper also includes information on full-scale component tests carried out to support the development of the design, particularly for the primary energy absorbers. Comparisons between test and finite element analysis are presented and there is a discussion of how the test results have affected the design.

Preliminary Development of Locomotive Crashworthy Components

The Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. This paper provides preliminary results of a research program that aims to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler.

A Crush Zone Design for an Existing Passenger Rail Cab Car

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 full-scale 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.Copyright

Development of a passenger rail vehicle crush zone

The use of crush zones in passenger rail vehicles is rapidly growing in the United States and throughout the world. Such crush zones are an important part of the crash energy management philosophy of train occupant protection. The objective of this study was to determine the advantages, disadvantages and issues related to incorporating crush zones at the ends of coach cars for protection in collisions between two trains. The general specifications for the crush zone were selected after consideration of the energy and forces that can be accommodated in such structures. Various designs were considered to meet these requirements and one of these was selected for more detailed development and evaluation. The effort included design layout and nonlinear dynamic finite element analysis to determine crush response.

Analysis of colliding vehicle interactions for the passenger rail train-to-train impact test

A full-scale train-to-train impact test was performed in which a cab car-led passenger train traveling at 30 mph collided with a standing locomotive-led train. During the test, the lead cab car overrode the cab of the standing locomotive, sustaining approximately 20 feet of crush, while the cab of the locomotive remained essentially intact. In this study, a finite element-based analysis of the collision was performed. The first 0.5 seconds of the collision was simulated. Results of the analysis were compared with accelerometer and video test data. Specific comparisons are made between test data and model predictions for: motions of the cab car and the standing locomotive; longitudinal forces arising between the cab car and the standing locomotive and between the respective lead and trailing vehicles; and the mode of deformation of the cab car and the locomotive. The results of the study indicate that the model captures pertinent features of the first 0.3 seconds of the collision, particularly with respect to longitudinal vehicle motions and collision forces. After 0.3 seconds, agreement between model predictions and test data becomes progressively worse. This is attributable to the models inability to capture the massive fracture that occurs at the front of the cab car.

Preliminary Finite Element Analysis of Locomotive Crashworthy Components

The Office of Research and Development of the Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. A research program is being conducted that aims to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler. Preliminary designs for these components have been developed. This paper provides details on the finite element models of the crashworthy components and how the component designs behave in the finite element analyses. The component designs will be evaluated to determine if the requirements have been met, such as the energy absorption capability, deformation modes, and force/crush characteristics.Copyright

Finite element analysis and full-scale testing of locomotive crashworthy components

The Office of Research and Development of the Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. A research program has been conducted to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler. Detailed designs for these components were developed, and the performance of each design was evaluated through large deformation dynamic finite element analysis (FEA). Designs for two test articles that could be used to verify the performance of the component designs in full-scale tests were also developed. The two test articles were fabricated and dynamically tested by means of rail car impact in order to verify certain performance characteristics of the two components relative to specific requirements. The tests were successful in demonstrating the effectiveness of the two design concepts. Test results were consistent with finite element model predictions in terms of energy absorption capability, force-displacement behavior and modes of deformation.Copyright

Rail Vehicle Cab Car Collision and Corner Post Designs According to APTA S-034 Requirements

The American Public Transportation Association standard for rail passenger equipment, S-034, includes requirements for the collision and corner posts of cab cars that are consistent with new federal requirements and substantially different than what has been required in the past. This paper describes the development and evaluation of two cab car end frame designs that were generated to investigate the implications on crashworthiness and operations of the new standards. A review was undertaken of prior cab car crashworthiness research and of existing and planned cab car designs for North American operation. The two designs were then generated and both hand and finite element analysis, including analysis for large deformations, was conducted to demonstrate that the designs meet the requirements. Of particular interest is the issue of providing large deformation capacity of the posts and the implications of eliminating the stairwell to meet the strength requirements.Copyright

Modeling material failure during cab car end frame impact

New standards have been proposed to increase the strength requirements for cab car end structures and impose further requirements on their ability to absorb energy during a grade-crossing collision [1, 2]. To aid in the development of these new standards, the Federal Railroad Administration (FRA) and the Volpe Center recently completed a set of full-scale tests aimed at assessing the quasi-static and dynamic crush behavior of these end structures. In support of this testing program, end frames designed to meet the new standards were fabricated and retrofitted onto the forward end of an existing cab car. A series of large-deformation quasi-static and explicit dynamic finite element analyses (FEAs) were performed to evaluate the performance of the design. Based on the results of a 2002 full-scale test in which a heavy steel coil impacted the corner post of an end frame built to these new standards, some fracture was expected in certain key end frame components during the tests. For this reason, a material failure model, based on the Bao-Wierzbicki fracture criterion [3], was implemented in the FEA model of the cab car end frame using ABAQUS/Explicit. The FEA model with material failure was used to assess the effect of fracture on the deformation behavior of cab car end structures during quasi-static loading and dynamic impact and, in particular, the ability of such structures to absorb energy. The failure model was implemented in ABAQUS/Explicit for use with shell elements. A series of preliminary calculations were first conducted to assess the effects of element type and mesh refinement on the deformation and fracture behavior of structures similar to those found on cab car end frames, and to demonstrate that the Bao-Wierzbicki failure model can be effectively applied using shell elements. Model parameters were validated through comparison to the results of the 2002 test. Material strength and failure parameters were derived from test data for A710 steel. The model was then used to simulate the three full-scale tests that were conducted during 2008 as part of the FRA program: a collision post impact, and quasi-static loading of both a collision post and a corner post. Analysis of the results of the two collision post tests revealed the need for revisions to both the design of some key end frame components and to key material failure parameters. Using the revised model, pre-test predictions for the outcome of the corner post test were found to be in very good agreement with test results.Copyright

Development and Fabrication of State-of-the-Art End Structures for Budd M1 Cars

The Volpe Center and the Federal Railroad Administration are engaged in active research aimed at improving rail vehicle crashworthiness. One component of this research is focused on improving the performance of passenger train cab cars during collisions with heavy objects at grade crossings. New standards have been approved by the American Public Transportation Association that increase the strength requirements for cab car end structures and impose further requirements on their ability to absorb energy during a collision. The FRA has issued a notice of proposed rulemaking (NPRM) to include these new standards in 49CFR238.211. These standards include requirements for demonstration of energy absorption through either quasi-static or dynamic tests. The intent of each test method is to demonstrate a minimum level of energy absorption—120,000 ft-lbs for a corner post load and 135,000 ft-lbs for a collision post load—while limiting occupied volume intrusion to less than 10 inches. To aid in the development of these new standards, the FRA and Volpe Center are conducting a set of three tests: quasi-static loading of both the collision and corner posts, and dynamic loading of the collision post only. (A dynamic test of the corner post was conducted as part of an earlier program). These tests were developed to illustrate testing methodologies and to demonstrate the feasibility of the new energy absorption and large deformation requirements. In+ each test, the post is loaded 30 inches above the underframe by a proxy object that is 36-inches wide, with a 48-inch diameter cylindrical face. In support of this testing program, the research reported here focused on the design and fabrication of end frames suitable for retrofitting onto the cab end of a Budd M1 cab car. The design of an end frame for retrofit onto the cab end of a Budd Pioneer cab car was modified to account for differences between the two car designs. In addition, reinforcements to the M1 car body and connections from the end frame to the car body were designed and fabricated. An FEA model of the end frame retrofit onto the M1 cab car was developed based upon the detailed design. A series of linear and nonlinear static, quasi-static, and dynamic FEAs were performed to evaluate the performance of the design. Preliminary analyses revealed the need for a few minor modifications to the connections in order to meet design requirements; these were incorporated into the final design for manufacture. Components for the end frame, connections between the end frame and the car body, and reinforcements to the car body were fabricated based on detailed design drawings and then assembled and connected to the reinforced M1 Car, from which the original end frame had been cut off. A successful dynamic test was completed in April, 2008; quasi-static tests are scheduled for summer 2008. The results of FEA model predictions are compared with the results of the dynamic test.© 2008 ASME