Karina Jacobsen

Train-to-Train Impact Test of Crash-Energy Management Passenger Rail Equipment: Structural Results

On March 23, 2006, a full-scale test was conducted on a passenger rail train retrofitted with newly developed cab and coach car 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 very dangerous modes of deformation: override and large scale lateral buckling. Frames from high-speed movies recorded at the train-to-train test of existing equipment and the train-to-train test of CEM equipment are included in this paper. In the train-to-train test of existing equipment at a closing speed of 30 mph, the colliding cab car crushed by approximately 22 feet. No crush was imparted to any of the trailing equipment. Due to the crippling of the cab car structure, the cab car overrode the conventional locomotive. The space for the operator’s seat and for approximately 47 passenger seats was lost. During the train-to-train test of CEM equipment, at a closing speed of 31 mph, the front of the cab car crushed by approximately 3 feet, and the crush propagated back to all of the unoccupied ends of the trailing passenger cars. The controlled deformation of the cab car prevented override. All of the crew and passenger space was preserved.

Impact tests of crash energy management passenger rail cars: analysis and structural measurements

Two full-scale impact tests were conducted to measure the crashworthiness performance of Crash Energy Management (CEM) passenger rail cars. On December 3, 2003 a single car impacted a fixed barrier at approximately 35 mph and on February 26, 2004, two-coupled passenger cars impacted a fixed barrier at approximately 29 mph. Coach cars retrofitted with CEM end structures, which are designed to crush in a controlled manner were used in the test. These test vehicles were instrumented with accelerometers, string potentiometers, and strain gages to measure the gross motions of each car body in three dimensions, the deformation of specific structural components, and the force-crush characteristic of the CEM end structure. Collision dynamics models were developed to predict the gross motions of the test vehicle. Crush estimates as a function of test speed were used to guide test conditions. This paper describes the results of the CEM single-car and two-car tests and provides results of the structural test. The single-car test demonstrated that the CEM design successfully prevented intrusion into the occupied volume, under similar conditions as the conventional test. During both CEM tests, the leading passenger car crushed approximately three feet, preserving the occupant compartment. In the two-car test, energy dissipation was transferred to the coupled interface, with crush totaling two feet between the two CEM end structures. The pushback of the couplers kept the cars in-line, limiting the vertical and lateral accelerations. In both the conventional tests there was intrusion into the occupant compartment. In the conventional two-car test sawtooth lateral buckling occurred at the coupled connection. Overall, the test results and model show close agreement of the gross motions. The measurements made from both tests demonstrate that the CEM design has improved crashworthiness performance over the conventional design.© 2004 ASME

Impact test of a crash-energy management passenger rail car

On December 3, 2003, a single-car impact test was conducted to assess the crashworthiness performance of a modified passenger rail car. A coach car retrofitted with a crash energy management (CEM) end structure impacted a fixed barrier at approximately 35 mph. This speed is just beyond the capabilities of current equipment to protect the occupants. The test vehicle was instrumented with accelerometers, string potentiometers, and strain gages to measure the gross motions of the car body in three dimensions, the deformation of specific structural components, and the force/crush characteristic of the impacted end of the vehicle. The CEM crush zone is characterized by three structural components: a pushback coupler, a sliding sill (triggering the primary energy absorbers), and roof absorbers. These structural mechanisms guide the impact load and consequent crush through the end structure in a prescribed sequence. Pre-test activities included quasi-static and dynamic component testing, development of finite element and collision dynamics models and quasi-static strength tests of the end frame. These tests helped verify the predicted structural deformation of each component, estimate a force-crush curve for the crush zone, predict the gross motions of the car body, and determine instrumentation and test conditions for the impact test. During the test, the passenger car sustained approximately three feet of crush. In contrast to the test of the conventional passenger equipment, the crush imparted on the CEM vehicle did not intrude into the passenger compartment. However, as anticipated the car experienced higher accelerations than the conventional passenger car. Overall, the test results for the gross motions of the car are in close agreement. The measurements made from both tests show that the CEM design has improved crashworthiness performance over the conventional design. A two-car test is performed to study the coupled interaction of CEM vehicles as well as the occupant environment. The train-to-train test results are expected to show that the crush is passed sequentially down the interfaces of the cars, consequently preserving occupant volume.

Rail car impact tests with steel coil: collision dynamics

Two full-scale oblique grade-crossing impact tests were conducted in June 2002 to compare the crashworthiness performance of alternative corner post designs on rail passenger cab cars. On June 4, 2002 a cab car fitted with an end structure built to pre-1999 requirements impacted a steel coil at approximately 14 mph. Following, on June 7, 2002 a cab car fitted with an end structure built to current requirements underwent the same test. Each car was equipped with strain gauges, string potentiometers and accelerometers to measure the deformation of specific structural elements, and the longitudinal, lateral and vertical displacements of the car body. The gross motions of the cars and steel coil, the force/crush behavior of the end structures, and the deformation of major elements in the end structures were measured during the tests. During the first test, the car fitted with the 1990s design end structure acquired more than 20 inches of longitudinal deformation causing failure at the corner post and resulting in the loss of operator survival space. During the second test, the corner post on the car fitted with the state-of-the-art design deformed longitudinally by about 8 inches, causing no failure and consequently preserving the survivable operator volume. In both cases, the steel coil was thrown to the side of the train after impacting the end structure. Prior to the tests, the crush behaviors of the cars and their dynamic responses were simulated with car crush and collision dynamics models. The car crush model was used to determine the force/crush characteristics of the corner posts, as well as their modes of deformation. The collision dynamics model was used to predict the extent of crush of the corner posts as functions of impact velocity, as well as the three-dimensional accelerations, velocities, and displacements of the cars and coil. Both models were used in determining the instrumentation and its locations. This paper describes the collision dynamics model and compares predictions for the gross motions of the cars and coils made with this model with measurements from the tests. A companion paper describes the car crush model and compares predictions made of car crush with measurements from the test. The collision dynamics was analyzed using a lumped-parameter model, with nonlinear stiffness characteristics. The suspension of the car is included in the model in sufficient detail to predict derailment. The model takes the force/crush characteristic developed in the car crush analysis as input, and includes the lateral force that develops as the corner post is loaded longitudinally. The results from the full-scale grade-crossing impact tests largely agree with and confirm the preliminary results of the three-dimensional lumped parameter computer model of the collision dynamics. The predictions of the model for the three-dimensional accelerations, velocities, and displacements of the car and the coil are in very close agreement with the measurements made in the tests of both cars, up to the time of failure of the corner post. The cars remained on the track in both tests, as predicted with the model.

Effectiveness of alternative rail passenger equipment crashworthiness strategies

Crashworthiness strategies, which include crash energy management (CEM), pushback couplers, and push/pull operation, are evaluated and compared under specific collision conditions. Comparisons of three strategies are evaluated in this paper: push versus pull operation (cab car led versus locomotive led consists); conventional versus CEM consists; and incremental CEM versus full-CEM. Rail cars that incorporate CEM are designed to absorb collision energy through crushing of unoccupied structures within the car. Pushback couplers are designed to recede into the draft sill under collision loads and enable the car ends to come into contact, minimizing the likelihood of lateral buckling. Push/pull operation refers to operating either a locomotive (pull mode) or a cab car (push mode) at the leading end of the train. Five cases using combinations of these three strategies are evaluated. The basic collision scenario for each case analyzed in this paper is a train-to-train collision between like trains. Each train has a locomotive, four coach cars, and a cab car. The impact velocity ranges from 10 to 40 mph. The following five cases are evaluated: (1) all conventional cars with a cab car leading (baseline case); (2) all conventional cars with a locomotive leading; (3) conventional coach cars with pushback couplers, with CEM cab car leading; (4) all CEM cars with a cab car leading: (5) all CEM cars with a locomotive leading. A one-dimensional lumped-mass collision dynamics model is used to evaluate the effectiveness of each strategy, or combination of strategies, in terms of preserving survivable space for occupants and minimizing secondary impact velocity (SIV). Test data is used to correlate SIV with head, chest, and neck injury. Probability of serious injuries and fatalities are calculated based on calculated car crush and injury values. The maximum crashworthy speed, or the maximum impact speed at which everyone is expected to survive, is calculated for each case. Of the five cases evaluated, the scenario of a cab car led conventional consist represents the baseline level of crashworthiness. The highest levels of crashworthiness are achieved by a consist of all CEM cars with a locomotive leading, followed by all CEM cars with a cab car leading. The results indicate that incremental improvements in collision safety can be made by judiciously applying different combinations of these crashworthiness strategies. A CEM cab car leading conventional cars that are modified with pushback couplers enhances the level of crashworthiness over a conventional cab car led consist and provides a level of crashworthiness equal to a locomotive leading conventional passenger cars

FUEL TANK INTEGRITY RESEARCH: FUEL TANK ANALYSES AND TEST PLANS

The Federal Railroad Administration’s Office of Research and Development is conducting research into fuel tank crashworthiness. Fuel tank research is being performed to determine strategies for increasing the fuel tank impact resistance to mitigate the threat of a post-collision or postderailment fire. 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 that fuel tanks have minimum properties adequate to sustain a prescribed set of static load conditions. Current research is intended to increase understanding of the impact response of fuel tanks under dynamic loading. Utilizing an approach that has been effective in increasing the structural crashworthiness of railcars, improved strategies can be developed that will address the types of loading conditions which have been observed to occur in a collision or derailment event. U.S. rail accident surveys reveal the types of threats fuel tanks are exposed to during collisions, derailments and other events. These include blunt impacts and raking impacts to any exposed side of the tank. This research focuses on evaluating dynamic impact conditions for fuel tanks and investigating how fuel tank design features affect the collision performance of the tank. Research activities will include analytical modeling of fuel tanks under dynamic loading conditions, dynamic impact testing of fuel tank articles, and recommendations for improved fuel tank protection strategies. This paper describes detailed finite element analyses that have been developed to estimate the behavior of three different fuel tanks under a blunt impact. These analyses are being used to understand the deformation behavior of different tanks and prepare for planned testing of two of these tanks. Observations are made on the influence of stiffeners, baffles, and other design details relative to the distance from impact. This paper subsequently describes the preliminary test plans for the first set of tests on conventional passenger locomotive fuel tanks. The first set of tests is designed to measure the deformation behavior of the fuel tanks with a blunt impact of the bottom face of the tanks. The test articles are fuel tanks from two retired EMD F-40 locomotives. A blunt impact will be conducted by securing the test articles to a crash wall and impacting them with an indenter extending from a test cart. This set of tests is targeted for late summer 2013 at the Transportation Technology Center (TTC) in Pueblo, Colorado. Both blunt and raking impact conditions will be evaluated in future research. Tests are also being planned for DMU fuel tanks under dynamic loads.

A Dynamic Test of a Collision Post of a State-of-the-Art End Frame Design

In support of the Federal Railroad Administration’s (FRA) Railroad Equipment Safety Program, a full-scale dynamic test of a collision post of a state-of-the-art (SOA) end frame was conducted on April 16, 2008. The purpose of the test was to evaluate the dynamic method for demonstrating energy absorption and graceful deformation of a collision post. The post aims to protect the operators and passengers in the event of a collision where only the superstructure, not the underframe, is loaded. Methods for improving the performance of collision and corner posts were prompted by accidents such as the fatal collision in Portage, Indiana in 1998, where a coil of steel sheet metal penetrated the cab car through the collision post. The improvements made for the SOA end frame structure include more substantial corner and collision posts, robust post connections to the buffer beam and anti-telescoping (AT) beam, and corner and collision posts integrated with a shelf and bulkhead sheet. Full length side sills improved support for the end frame. This test focused on one collision post because of its critical position in protecting the operator and passengers in an impact with an object at a grade-crossing. For the test, a 14,000-lb cart impacted a standing cab car at a speed of 18.7 mph. The cart had a rigid coil shape mounted on the leading end that concentrated the impact load on the collision post. The requirements for protecting the operator’s space state that there will be no more than 10 inches of longitudinal crush and none of the attachments of any of the structural members separate. During the test, the collision post deformed approximately 7.4 inches and absorbed approximately 138,000 ft-lb of energy. The attachment between the post and the AT beam remained intact. The connection between the post and the buffer beam did not completely separate, however the forward flange and both side webs fractured. The post itself did not completely fail. There was material failure in the back and the sides of the post at the impact location. Overall, the end frame was successful in absorbing energy and preserving space for the operators and the passengers.© 2008 ASME

Conventional locomotive coupling tests

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. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. 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. These components are designed to improve 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, and may require replacement due to unintentional activation as a result of service loads. Push-back couplers are designed with trigger loads meant to exceed the expected maximum service loads experienced by conventional couplers. Analytical models are typically used to determine these required trigger loads. Two sets of coupling tests are planned to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive equipped with a push-back coupler. These tests will allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests.This paper describes the results of the coupling tests of conventional equipment. In this set of tests, a moving locomotive was coupled to a standing cab car. The coupling speed for the first test was 2 mph, the second test 4 mph, and the tests continued with the speed incrementing by 2 mph until the last test was conducted at 12 mph. The damage observed resulting from the coupling tests is described. The lowest coupling speed at which damage occurred was 6 mph. Prior to the tests, a one-dimensional lumped-mass model was developed for predicting the longitudinal forces acting on the equipment and couplers. The model predicted that damage would occur for coupling speeds between 6 and 8 mph. The results of these conventional coupling tests compare favorably with pre-test predictions. Next steps in the research program, including future full-scale dynamic tests, are discussed.

Collision Scenarios for Assessing Crashworthiness of Passenger Rail Equipment

In June 2009, at the request of the Federal Railroad Administration (FRA), the Railroad Safety Advisory Committee established the Engineering Task Force (ETF). The ETF is comprised of government, railroads, suppliers, and labor organizations and their consultants. The ETF was tasked with recommending a process for assessing alternative Tier I passenger rail equipment, i.e., passenger equipment that is operated at speeds up to 125 mph on the general railroad system. The final product of the ETF is a document outlining criteria and procedures for demonstrating crashworthiness performance of passenger rail equipment built to alternative design standards and proposed for operation in the US. The results provide a means of assessing whether an alternative design compares to designs compliant with the FRA’s Tier I crashworthiness requirements. This paper focuses on the criteria and procedures developed for scenario-based requirements. The principle collision scenario describes the minimum train-level crashworthiness performance required in a train-to-train collision of an alternatively designed passenger train with a conventional locomotive-led passenger train. For cab car-led and MU locomotive-led operations, the impact speed is prescribed at 20 mph. For locomotive led operations, the impact speed is prescribed at 25 mph. Criteria for evaluating this scenario include intrusion limits for the passengers and engineer, and occupant protection measures. Other scenario-based requirements discussed in this paper include colliding equipment override, connected equipment override, and truck attachment.© 2010 ASME

Results of a Conventional Fuel Tank Blunt Impact Test

The Federal Railroad Administration’s Office of Research and Development is conducting research into passenger locomotive fuel tank crashworthiness. A series of impact tests is being conducted to measure fuel tank deformation under two types of dynamic loading conditions – blunt and raking impacts. This program is intended to result in a better understanding of design features that improve the puncture resistance of passenger locomotive fuel tanks. One reason for performing this program is to aid in development of appropriate standards for puncture resistance to be applied to alternativelydesigned fuel tanks, such as on diesel multiple unit (DMU) passenger rail equipment. This paper describes the results of the third blunt impact test of retired F-40 locomotive fuel tanks. The test setup was designed for the Transportation Technology Center (TTC) in Pueblo, Colorado, to impart blunt impacts to the bottom of each fuel tank specimen. The specimens tested to date are from FRA-owned retired F-40 passenger locomotives. To conduct the test, each tank was emptied of fluid and mounted on a crash wall with the bottom surface exposed. A rail cart modified with a “rigid” indenter measuring 12 inches by 12 inches, was released to impact the bottom of fuel tank at a target impact speed. The first two tests, conducted on October 8 and 9, 2013, were designed to impact the center of two different tank designs. Tests were conducted at impact speeds of 4.5 and 6.2 mph and caused maximum residual dents of 5 inches and 1.5 inches, respectively. On August 20, 2014 the test of fuel tank 234 was conducted to impact the tank off-center between two baffles. Forcedeformation measurements were collected for each tank during the three tests. The series of tests provide information regarding the influence of tank design on puncture resistance. In the test of tank 234, the target impact speed was 12.5 mph, and the actual impact occurred at 11.2 mph. The test resulted in a residual dent depth of approximately 9 inches, and buckling of several internal baffles. The impact did not result in puncture of the tank. Following the test, the tank was cut open to permit examination of the baffles. This examination revealed a different baffle geometry than was modeled based on pre-test measurements. Finite element analysis (FEA) was used to predict the behavior of the tank during the test. The FE model of the tank required several material properties to be defined in order to capture puncture behavior. The combination of metal plasticity, ductile failure, and element removal would permit the model to simulate puncture for this tank. Following the test, the tank was cut open, revealing a different baffle arrangement than had been initially thought. The post-test FE model was then updated to include the actual baffle arrangement of tank 234. With the actual baffle arrangement included in the model, the FE results are in fairly good agreement with the test. Additional changes to the ductile failure criterion were also made in the post-test model. The objective of this research program is to establish the baseline puncture resistance of current passenger locomotive fuel tanks under dynamic impact conditions and to develop performance requirements to ensure an appropriate level of puncture resistance in alternative fuel tank designs, such as DMU fuel tanks.