Analyses of Full-Scale Tank Car Shell Impact Tests

This paper describes analyses of a railroad tank car impacted at its side by a ram car with a rigid punch. This generalized collision, referred to as a shell impact, is examined using nonlinear (i.e., elastic-plastic) finite element analysis (FEA) and three-dimensional (3-D) collision dynamics modeling. Moreover, the analysis results are compared to full-scale test data to validate the models. Commercial software packages are used to carry out the nonlinear FEA (ABAQUS and LS-DYNA) and the 3-D collision dynamics analysis (ADAMS). Model results from the two finite element codes are compared to verify the analysis methodology. Results from static, nonlinear FEA are compared to closed-form solutions based on rigid-plastic collapse for additional verification of the analysis. Results from dynamic, nonlinear FEA are compared to data obtained from full-scale tests to validate the analysis. The collision dynamics model is calibrated using test data. While the nonlinear FEA requires high computational times, the collision dynamics model calculates gross behavior of the colliding cars in times that are several orders of magnitude less than the FEA models.

Improved Tank Car Safety Research

Three recent accidents involving the release of hazardous material have focused attention on the structural integrity of railroad tank cars: (1) Minot, ND, on January 18, 2002; (2) Macdona, TX, on June 28, 2004; and (3) Graniteville, SC, on January 6, 2005. Each of these accidents resulted in fatalities. Research is being conducted to develop strategies for improving railroad tank cars so they can maintain tank integrity in severe accidents. A collaborative effort called the Next Generation Rail Tank Car (NGRTC) Project intends to use these research results to help develop improved tank car designs. Dow Chemical Company, Union Pacific Railroad, and Union Tank Car Company are the industry sponsors of the NGRTC Project. The Federal Railroad Administration (FRA) and Transport Canada participate in the NGRTC project through Memoranda of Cooperation. FRA and the Pipeline and Hazardous Materials Safety Administration intend to use these research results to support rulemaking. The approach taken in performing this research is to define the collision conditions of concern, to evaluate the behavior of current design equipment in these scenarios, and to develop alternative strategies for increasing the maximum impact speed for which tank integrity is maintained. The accident scenarios have been developed from a review of accidents and are intended to bound the range of main-line accidents that can lead to a release of hazardous material from a tank car. The accident scenarios and collision modes have been used to define car-to-car impact scenarios. These car-to-car impact scenarios define the conditions under which the commodity must be contained. The impact scenarios are being used to evaluate the integrity of current design and improved design tank cars. Full-scale impact tests are also being conducted, to help validate modeling of the baseline equipment. The models have been refined based on the test results. The models are now being applied to develop the improved equipment designs. This paper describes the overall research framework and provides an overview of the research done to date, as well as the planned efforts.

A Novel Method for Estimating the Neutral Temperature of Continuously Welded Rail

Traditionally, railroad track is installed so that rails that are welded together into strings longer than 400 feet experience no longitudinal thermal force at rail temperatures of 90 to 115 degrees °F. This rail temperature at which the thermal force is zero is commonly referred to as the rail’s neutral temperature. Rail at temperatures higher than the neutral temperature are in a state of compression, and in cooler temperatures are in tension. Except for the textbook case of a perfectly straight rail, these longitudinal forces must be reacted along the length of the rail via friction and the rail fasteners. A new device is designed to exploit changes in vibration of the rails within these fastenings and yield a non-destructive estimate of the installed neutral temperature. This paper will report on various on-track tests conducted at the Transportation Technology Center, Inc. (TTCI) in Pueblo, CO. This behavior was first noted empirically, without a background engineering mechanics outline. Similarly, this paper will follow the same evolution. After presentation of test data, engineering explanations will follow using theory and mechanical modeling.

Recent Research to Improve Wheel and Axle Composition, Properties and Designs

This paper describes research efforts by a North American railroad wheel and axle manufacturer to improve steel chemistry, cleanliness, and properties for improved component service performance. The authors describe extensive work to improve steel cleanliness in the melting process. Also they review attempts to correlate ultrasonic testing data with microcleanliness test results, and detail subsequent work to determine steel cleanliness using the Advanced Steel Cleanliness Assessment Technique (ASCAT), which is being developed by a university and a supplier. Emphasis is placed on determining the type, number and size of discontinuities within the steel. Additionally, efforts to improve mechanical properties of microalloyed axles are reviewed along with microstructural details relevant to the work. The role of vanadium, molybdenum, aluminum, and other elements, on axle structure and properties is discussed. A new axle design, with significantly larger body diameter, is described and finite element analysis (FEA) results for the design are presented.

Onboard Locomotive Exhaust Emissions Measurement

Limiting harmful locomotive exhaust emissions is important to the Nation’s health and safety. The Environmental Protection Agency (EPA) has comprehensive gaseous exhaust emissions (or referred to as emissions hereto) testing requirements in place. All current tests are conducted on stationary locomotives. This paper discusses the development of an efficient stationary emissions measurement system that is compact, portable, easy to use, and applicable to onboard locomotives for in-use, over-the-road testing. More efficient locomotive emissions testing and better understanding of in-use emissions would be beneficial to all stakeholders. Sharma & Associates, Inc., (SA) adapted an off-the-shelf, portable, on-road, heavy-duty diesel truck emissions analyzer for locomotive use. This process included development of the necessary peripheral equipment and a computer program to take the raw emissions and report them as brake-specific emissions rates and duty cycle emissions. This paper describes the use of this system on a stationary locomotive. The system is currently being fitted and tested for over-the-road use. The measurement of particulate matter and smoke opacity were out of scope of the phase of the project that this paper is based on and not addressed hereto.

Flexible Wheel/Rail Contact Model for Railway Vehicle Dynamics Without Pre-Calculation

An advanced method using progressive concept of geometrical correspondence is applied to create a new wheel/rail contact model based on virtual penetration theory. The geometry and contact mechanism are solved simultaneously because of the independency in a defined correspondence. The model takes the penetrated profiles of wheel and rail and also associated creeps as inputs, and produces driving contact forces as output. The advantage of this model is that it doesn’t require pretabulation of rigid contact situation. The method allows calculating flexible, non-elliptical, multiple contact patches during integration of the model. Consequently the rails with substructures can vibrate separately from the vehicle in a flexible wheel/rail contact model. The simulation results indicate that this method can be used in various rail vehicle dynamic problems.

Dynamic Behavior of Different Wheel Profiles and Their Sensitivities to Track Characteristics

Wheel/rail interaction and the relevant phenomena have been of much concern to many railways and researchers during last two or three decades. On going research is being conducted for optimizing interaction between wheel and track. Safety, comfort and economical aspects in rail transportation systems are the very most common research interests in rail transportation systems. The attempts made to increase both the speed and axle load of new railroad vehicles have been the main incentives of the current progressive research in rail industries. Several strategies have been implemented and are still in use by railroad agencies to control the wear of wheels and rails and to enhance safety and ride comfort. Optimizing contact characteristics of wheel and rail using the most compatible wheel and rail profiles is an important issue concerning dynamic interaction of wheel and rail. In this paper, the effect of S1002, IR1002 and P8 wheel profiles on the interaction of wheel and rail for similar track conditions are considered.

Analysis of Impact Energy to Fracture Unnotched Charpy Specimens Made From Railroad Tank Car Steel

This paper describes a nonlinear finite element analysis (FEA) framework that examines the impact energy to fracture unnotched Charpy specimens by an oversized, nonstandard pendulum impactor called the Bulk Fracture Charpy Machine (BFCM). The specimens are made from railroad tank car steel, have different thicknesses and interact with impact tups with different sharpness. The FEA employs a Ramberg-Osgood equation for plastic deformations. Progressive damage and failure modeling is applied to predict initiation and evolution of fracture and ultimate material failure. Two types of fracture initiation criterion, i.e., the constant equivalent strain criterion and the stress triaxiality dependent equivalent strain criterion, are compared in material modeling. The impact energy needed to fracture a BFCM specimen is calculated from the FEA. Comparisons with the test data show that the FEA results obtained using the stress triaxiality dependent fracture criterion are in excellent agreement with the BFCM test data.

An Innovative Quasi-Continuous Power Transmission System

Conventional stepped power transmission systems exhibit abundant energy dissipation, complicated handling and costly maintenance. On the other hand, continuously-variable power transmissions (CVTs), which are recently considered to be used in the industry, despite their high capabilities, face a number of drawbacks including limited torque transmission capacity, high-precision manufacturing and installation requirements, low cost effectiveness and relatively modest power transmission efficiencies. Therefore, innovative power transmission systems that intend to resolve or lessen one or more of these disadvantages are critical in power transmission from pinion to wheel in electric traction motors of both diesel and electric locomotives; especially when active and advanced control of traction effort and adhesion is of high importance and are going to be welcomed by rail industries. In this research, an innovative quasi-continuous power transmission (QCPT) system is introduced. In this system, a fully-automatic gear box including six pairs of engaging gears is considered where only one pair of gears is engaged in any operating moment. The main components of the QCPT are the input and output shafts each having six engaging gears, speed regulating sensor, electrical module and intelligent pins. The governing parameter in this design is output shaft rotating speed or output torque of the system. When high output torque is needed, the system automatically transfers power to lower gears, and in the need of high output speed, higher gears are assigned. The proposed system is simple and cost-effective, while having high reliability and efficiency.

A Methodology for the Modeling of Rail Vehicles From Time Series Measurements Using Time-Delay Neural Networks

The main goal of this research is to develop and demonstrate a general, efficient, mathematically and theoretically based methodology to model nonlinear forced vibrating mechanical systems from time series measurements. A system identification modeling methodology for forced dynamical systems is presented based on dynamic system theory and nonlinear time series analysis that employs phase space reconstruction (delay vector embedding) for modeling of dynamical systems from time series data using time-delay neural networks (TDNN). The first part of this work details the modeling methodology including background on dynamic systems, phase space reconstruction, and neural networks. In the second part of this work the methodology is evaluated based on its ability to model selected analytical lumped parameter forced vibrating dynamic systems including an example of a linear system predicting lumped mass displacement using a displacement forcing. function The work discusses the application to nonlinear systems, multi degree-of-freedom systems, and multi-input systems. The methodology is further evaluated on its ability to model an analytical passenger rail vehicle predicting vertical wheel/rail force using vertical rail profile as input. Studying the neural modeling methodology using an analytical systems shows the clearest observations from results which provide prospective users of this tool an understanding of the expectations and limitations of the modeling methodology.