Mathematical Simulation of Air Suspension Failure and Derailment

Air suspensions are a commonly used component of modern transit and passenger vehicle suspensions. New vehicle performance specifications usually require testing and analyses with the air suspension inflated and also deflated. However, the tests and analyses usually do not include the dynamic effects that may occur at the instant of deflation. Transportation Technology Center, Inc. (TTCI) recently investigated a revenue service flange climb derailment for a large North American transit system. The derailment occurred on the diverging route of a No. 10 turnout. Initial investigation by the transit system did not identify any track or equipment that showed significant deviations from their normal practices; no obvious cause for the derailment was identified, although the air suspension had been deflated after the derailment. To assist in determining potential contributing factors for the derailment, TTCI conducted NUCARS® simulations of the car negotiating the turnout, using these parameters: • Vehicle dynamic response to local track geometry conditions, including motions of the air suspension; • Sudden deflation of the air suspension; • Wheel and rail profiles. This paper presents the methods used to represent sudden component failures in the NUCARS simulations, including the air suspension deflation. The simulation results show how the sudden deflation of the air suspension combined with local track geometry and wheel/rail contact conditions could contribute to a flange climb derailment.

Development of Performance Requirements for a Rail Passenger Workstation Table Safety Standard

The American Public Transportation Association’s (APTA) Construction and Structural committee, a railroad industry group, with the support of the Federal Railroad Administration (FRA) and the John A. Volpe National Transportation Systems Center (Volpe Center), is creating an industry safety standard for an energy absorbing table. Workstation tables in passenger trains are an increasingly popular seating configuration both in the United States and abroad. Although a well-attached table can provide convenience and compartmentalization for the occupant, there is a risk of abdominal injury during a rail accident. In Fact, there have been several accidents in the United States in which impacts with workstation tables have severely or fatally injured occupants. In 2006, in response to these injuries, an FRA sponsored program developed a prototype table that distributed load over a wider area of the abdomen and absorbed energy during a collision. This table design was tested with specialized anthropomorphic test devices (ATDs) instrumented to measure abdominal impact response and was shown to decrease injury risk compared to a baseline table design. Building on the knowledge gained in the development of the prototype table, the proposed standard requires force to the abdomen be limited while energy is absorbed by the table. Since manufacturers do not have access specialized ATDs, researchers proposed a two part testing requirement. The first part is a quasi-static test which measures the energy absorption capacity of the table with a maximum force level determined from testing with specialized abdominal ATDs. The second part is a sled test with a standard Hybrid III 50th percentile (HIII) ATD to assess compliance with occupant protection standards of compartmentalization and ATD injury assessment reference values (IARVs). This paper discusses the research performed to develop the performance requirement in the draft standard. Current injury measures, originally developed for the automotive industry, were examined to assess their applicability to workstation table impacts. Multiple Mathematical Dynamic Models (MADYMO) model simulations show the estimated injuries during a simulated sled test scenario. Several force-crush parameters were examined, including the initial stiffness of the force-crush curve, the plateau force and the target energy absorbed by the table, to determined the force-crush design characteristics of a table that are likely to reduce injury risk. The results of this study, combined with testing of the current prototype table described in a companion paper [1], led to a draft standard that will greatly improve the safety of workstation tables in passenger rail cars.

An Approach to Wind Blow-Over Risk Reduction at Norfolk Southern Rwy

A paper written for and presented at the ASME 2010 Joint Rail Conference explored the science and methodology that BNSF Railway has taken to avoid wind-caused derailments.1 This paper further develops this topic with the approach Norfolk Southern Corp (NS) has taken. The foundational fluid flow dynamics and vehicle dynamics modeling and analysis are reviewed. The modeling included doublestack platforms loaded with empty boxes, trailer-on-flatcar (“piggyback”) equipment, high-cube boxcars, hoppers/coal gondolas, and multilevel (“autorack”) flatcars. The implementation of the modeling is outlined as a description of NS’ Speed Restriction System (SRS). The SRS uses real-time weather data and a lookup table of vehicle responses to provide the traffic controller (dispatcher) with recommended train speeds. Thoughts and suggestions on further development of a blowover risk reduction system are presented.

A Rail Vehicle Clearance Calculation Program

This paper explains and illustrates a computer program for calculating clearances between a rail vehicle and wayside objects and between a vehicle on one track and a vehicle on an adjacent track. The program includes a graphic animation illustrating the geometrical proximity of the subject vehicle to successive wayside objects and to a vehicle in successive relative locations along an adjacent track. The situations of minimum clearance for given vehicle and track geometry inputs are highlighted in a report. The main program is accompanied by an auxiliary program that uses independent logic to calculate clearances for idealized situations and that generates input files representing those situations for the main program. This provides an efficient means for verifying basic aspects of the logic of the main program.

Exploration of Enhanced Heat Dissipation Design for Brake Disc of High Speed Train

The function of the brake disc is to provide the ultimate guarantee of the safety of high speed trains. A braking unit includes two discs and two brake shoes. Braking performance depends on the pressure of the brake shoe and the friction between the disc and the shoe. When a train is braked, the brake disc endures a thermal load, which may affect the mechanical properties of the disc. If the thermal load exceeds the strength limit of the material, it could impact the safe running of the train. Therefore, the thermal load should be reduced as much as possible. Now the frictional surface of disc is plane and heat congregates easily in the surface area. The purpose of this paper is to explore a design for enhanced heat dissipation. A gas channel was used on the frictional surface to achieve the effect of heat dissipation. This design was analyzed by means of tribology and heat transfer theory. The distribution of gas flow was also researched. The temperature and stress field of the disc were simulated and analyzed. By the analysis it can be seen that the gas channel on the frictional surface of disc has a remarkable effect on heat dissipation in the brake disc.

Rotational Energy Harvesting Systems for Unpowered Freight Rail Cars

Commonly, freight cars have no available source of electric power, thus preventing the use of any electronic devices that could improve convenience, performance, and efficiency of railroad operations. The devices introduced in this paper are motion-based electromagnetic energy harvesting systems. Similar in size and shape to a conventional damper or shock absorber, the systems are to be placed in the coil spring of the suspension to convert part of the energy usually wasted as heat into useful electric energy. This paper will present the design, development and testing of such devices. Tests of prototype devices on a shock dynamometer show that more than 20 Watts RMS of power can be produced with motions that can be encountered in train suspensions. The devices presented, although primarily developed for railroad applications, are not limited to use in freight cars and could be similarly applied in various vehicles with suspension like tractor-trailers, buses or automobiles.

Track Health Monitoring Using Wavelets

This paper presents a defect detection algorithm for rail health monitoring that could potentially be used with limited bogie. Current wheel and track monitoring requires expensive track instrumentation and/or time consuming operation of railway monitoring vehicles. The proposed health monitoring algorithm can potentially be used with a portable data acquisition system that can be relocated from train to train to monitor and diagnose the conditions of the track as a train is driven during typical day-to-day operation. The algorithm processes the data using wavelets and is able to locate defects and provide information that may help to distinguish between various types of rail defects. In recent years, wavelets have been used extensively in signal processing because of their ability to analyze a signal simultaneously in the time and frequency domains. The Fourier transform has been used traditionally in signal processing to locate dominant frequencies in a signal, but it is unable to provide time localization of those frequencies. Unlike the Fourier transform, the wavelet transform uses a set of basis functions with finite energy, which is advantageous for detecting the irregular events that may show up in a transient signal. The wavelets used in the proposed signal processing routine were chosen for optimal signal decomposition through consideration of the signals that are likely to be generated from common rail and wheel defects, including rail cracks, squats, corrugation, and, wheel out-of-rounds. A sample accelerometer signal was generated from information found in existing literature and was then processed using the proposed defect detection algorithm. Results show the potential of this algorithm to locate and diagnose defects from limited bogie vertical acceleration data. This study is intended to present a proof-of-concept for the proposed defect detection algorithm, providing a basis for which a more comprehensive defect detection and diagnosis algorithm can be developed.

Evaluation of Testing Methods to Develop Test Requirements for a Workstation Table Safety Standard

Investigations of passenger train accidents have revealed serious safety hazards associated with the thin, rigid tops of workstation tables, which are common fixtures aboard rail cars. Thoracic and abdominal injuries caused by occupant impact with workstation tables have been cited as the likely cause of two fatalities during a 2002 accident in Placentia, CA [1]. Additionally, workstation tables have been cited as the cause of injury in reports on accidents in Intercession City, FL [2], and Burbank, CA [3]. Currently there are no regulations or safety standards governing the crashworthiness of tables in passenger trains beyond attachment strength requirements. However, research sponsored by the Federal Railroad Administration (FRA) and in collaboration with the American Public Transportation Association (APTA) Passenger Rail Equipment Safety Standards (PRESS) Construction & Structural working group is underway to develop a mandatory industry safety standard for tables to ensure that they will be designed to provide a minimum level of safety during a train accident. FRA’s Equipment Safety Research Program has already developed and tested a prototype table design to demonstrate the improved occupant protection provided by an energy-absorbing table. The prototype table design was tested using a THOR [4] and an H3RS [5], which are advanced anthropomorphic test devices (ATDs), onboard a 35 mph full-scale train-to-train impact test of rail cars modified to incorporate crash energy management (CEM) [6]. Test results demonstrated that the Injury Assessment Reference Values (IARVs) measured by the instrumented ATDs were within human tolerance levels established by the National Highway Traffic Safety Administration (NHTSA) for automotive crashworthiness for the head, neck, chest, abdomen, and femur. Having demonstrated the effectiveness of an energy-absorbing table, the next step is developing a performance-based safety standard for tables that ensures a minimum level of crashworthiness. The safety standard would employ the use of an 8G dynamic sled test with instrumented ATDs to evaluate occupant injury and structural integrity of the table, similar to the seat test requirements in APTA-SS-C&S-016-99 [7], which is the industry safety standard for passenger seats in rail cars. Normally, advanced ATDs like the THOR would be required to measure abdominal and thoracic loads caused by the table impact during the sled test. However, use of these experimental ATDs for table qualification testing is not feasible due to their limited availability. Therefore, alternative test methods must be developed to evaluate the crashworthiness of workstation tables. This paper evaluates several potential methods to measure table crashworthiness, including quasi-static crush testing, pendulum impact testing, drop tower testing, and sled testing with standard Hybrid III 50th percentile ATDs. The pros and cons of these tests are also described. After evaluating the various testing methods, test conditions for two separate tests are proposed for an industry table standard. A companion paper [8] describes analysis results used to establish performance requirements proposed for evaluating table crashworthiness for the safety standard, in accordance with the test conditions proposed in this paper.

Active RFID for Enhanced Railway Operations

RFID tags have been used by railways for many years, RFID has proven its worth in inventory management, yet this technology is underutilized for enhancing railway operations and health monitoring due to limitations of passive RFID technology. Active RFID provides enhanced capabilities with potential to improve railway operations. Active technology differs from passive RFID by incorporating an onboard power source enabling longer ranges, changeable data fields, and the ability to transmit independently of the reader. This paper compares the advantages and disadvantages of active compared to passive RFID in terms of power requirements, transmission range, and dynamic data. A survey of existing products and vendors is presented. The existing active RFID standards are reviewed and elements of the data tag protocols are detailed as well as protocols for mitigating collisions of data packets. Finally, specific railway applications utilizing active RFID are discussed.

Criteria and Procedures for Assessing Occupied Volume Integrity

With the potential for tremendous growth in the passenger rail industry, providing for the safety of the train-riding public and the crews who transport them becomes an ever-greater priority. To provide for safety while making best use of its resources and to facilitate passenger rail industry growth, the Federal Railroad Administration (FRA), in consultation with the rail industry, has developed alternative Criteria and Procedures for assessing the crashworthiness and occupant protection measures of rail passenger equipment. These Criteria and Procedures are intended to be applicable to a wide range of equipment designs, particularly equipment designs not complying with current U.S. standards and regulations. Because the latest technology in rail equipment crashworthiness has been used to develop the Criteria and Procedures, aspects of the resulting Criteria and Procedures are fundamentally different from their corresponding regulations. While technical results from sophisticated analyses and tests have been necessary, judgment was also needed to develop the Criteria and Procedures. This judgment was provided by the Engineering Task Force (ETF), and ultimately accepted by FRA. The ETF is a government/industry working group, organized under the auspices of the Railroad Safety Advisory Committee (RSAC). The Criteria and Procedures are intended to provide an engineering-based methodology for comparing the crashworthiness of alternatively-designed equipment with that of compliant designs. One particularly important aspect of passenger car crashworthiness is occupied volume integrity (OVI). It is essential that all passenger vehicles meet some base minimum level of OVI. A primary goal of crashworthiness is to maintain a volume for occupants to ride out a collision. In the U.S., this base level has been demonstrated through a vehicle’s ability to react a quasi-static load of 800,000 pounds along its line of draft without experiencing permanent deformation. This car-level requirement has existed, in some form, since the early 20th century. However, alternatively-designed vehicles may not be able to demonstrate the ability to support this load, but may still prove to be equivalently crashworthy. Based on analyses performed on conventional and alternatively-designed passenger equipment, three options have been developed to demonstrate the OVI of alternatively-designed equipment. These options consist of three load magnitudes placed along the collision load path with a corresponding pass/fail criterion for each load. OVI may be demonstrated by sustaining an 800,000 pound load with no permanent deformation, a 1,000,000 pound load with limited permanent deformation, or a 1,200,000 pound load without exceeding the crippling load of the occupied volume. This paper discusses the pass/fail criteria associated with each option, the analysis and test procedures used in applying each option, and the technical basis used in developing the Criteria and Procedures for OVI evaluation. By applying such techniques, the results of evaluations of alternatively-designed equipment can be compared with the Criteria values for compliant designs. In this manner, the crashworthiness performance of alternatively-designed equipment can be assessed relative to the performance of compliant designs. A companion paper to this one discusses the development of the train-level Criteria and Procedures.