Thermal Analysis of Railroad Bearings: Effect of Wheel Heating

Catastrophic bearing failure is a major concern for the railroad industry because it can lead to costly train stoppages and even derailments. Excessive heat buildup within the bearing is one of the main factors that can warn of impending failure. A question is often raised regarding the transfer of heat from a wheel during braking and whether this can lead to false setouts. Therefore, this work was motivated by the need to understand and quantify the heat transfer paths to the tapered roller bearing within the railroad wheel assembly when wheel heating occurs. A series of experiments and finite element (FE) analyses were conducted in order to identify the different heat transfer mechanisms, with emphasis on radiation. The experimental setup consisted of a train axle with two wheels and bearings pressed onto their respective journals. One of the wheels was heated using an electric tape placed around the outside of the rim. A total of 32 thermocouples scattered throughout the heated wheel, the axle, and the bearing circumference measured the temperature distribution within the assembly. In order to quantify the heat radiated to the bearing, a second set of experiments was developed; these included, in addition to the axle and the wheel pair, a parabolic reflector that blocked body-to-body radiation to the bearing. The appropriate boundary conditions including ambient temperature, emissivity, and convection coefficient estimates were measured or calculated from the aforementioned experiments. The FE thermal analysis of the wheel assembly was performed using the ALGOR™ software. Experimental temperature data along the radius of the heated wheel, the bearing circumference, and at selected locations on the axle were compared to the results of the FE model to verify its accuracy. The results indicate that the effect of thermal radiation from a hot wheel on the cup temperature of the adjacent bearing is minimal when the wheel tread temperature is at 135°C (275°F), and does not exceed 17°C (31°F) when the wheel tread is at 315°C (600°F).

Evolutions in Railway Signaling: A “New Age” of Control?

The development of railroad signaling systems evolved with the need to provide interlocking between points and signals, and block working to keep trains a safe distance apart. Accordingly, the archetypal behavior of train control is summed up as providing (1) safe and efficient train movement by (2) the management of train routing and separation. This has been rudimentary since the advent of railway signaling and propagated in even the most contemporary of technologies today.

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

Energy Savings With Reversible Thyristor Controlled Rectifier

The paper deals with energy savings in Traction Systems available with Thyristor Controlled Rectifiers (TCR) and Reversible TCR (RTCR). TCR provides active voltage control, RTCR in addition has power recuperation into AC line. The energy balance of the TCR and diode rectifier systems are calculated, including losses in the rails, car’s power train and friction losses. The TCR advantages over diode rectifiers: better voltage regulation and fault current limiting allow us to reduce the number of substations and increase their service life. Major energy savings are through recuperation back to AC line using RTCR, with additional savings through increased DC bus voltage. The estimated energy savings depending on the system parameters, train speed profile, etc. can be as high as 50%.

Mechanical Properties of Tank Car Steels Retired From the Fleet

As a consequence of recent accidents involving the release of hazardous materials (hazmat), the structural integrity and crashworthiness of railroad tank cars have come under scrutiny. Particular attention has been given to the older portion of the fleet that was built prior to steel normalization requirements instituted in 1989. This paper describes a laboratory testing program to examine the mechanical properties of steel samples obtained from tank cars that were retired from the fleet. The test program consisted of two parts: (1) material characterization comprised of chemical, tensile and Charpy V-notch (CVN) impact energy and (2) high-rate fracture toughness testing. In total, steel samples from 34 tank cars were received and tested. These 34 tank cars yielded 61 different pre-1989 TC128-B conditions (40 shell and 21 head samples), three tank cars yielded seven different post-1989 TC128-B conditions (four shell and three head samples), and six tank cars yielded other material (A212, A515, and A285 steel) conditions (six shell and five head samples). The vast majority of the TC128-B samples extracted from retired tank cars met current TC128-B material specifications. Elemental composition requirements were satisfied in 97 percent of the population whereas the required tensile properties were satisfied in 82 percent of the population. Interpretation of the high-rate fracture toughness tests required dividing the pre-1989 fleet into quartiles that depended on year of manufacture or age, and testing three tank cars per quartile. Considering the high-rate fracture toughness results at 0°F for the pre-1989 fleet, 100 percent of the oldest two quartiles, 58 percent of the second youngest quartile, and 83 percent of the youngest quartile exhibited adequate or better fracture toughness (defined as toughness greater than 50 ksi√in). High-rate fracture toughness at –50°F was adequate for 83 percent of two quartiles (the youngest and second oldest), but the other two quartiles exhibited lower toughness with only 33 (2nd youngest) to 50 percent (oldest) exhibiting adequate properties.

RF Coupling Simulation Model Development for Optimal Placement of Antennas Supporting Wireless Communications Systems

The locomotive cab’s limited rooftop area requires that the transmitting and receiving antennas for communications be placed in close proximity to one another. Currently, no means exist to aid the railroad radio frequency (RF) engineer in placing these antennas so that mutual communications interference is minimized. The goal of this paper is to describe a method that can be used to determine optimal antenna placement in a time- and cost-effective manner. The method described below utilizes various forms of the Friis transmission equation in Monte Carlo simulations.

A New Security and Safety Solution for Public Guided Transport

Railway and Public Guided Transit Properties often employ large numbers of video cameras to supervise critical areas and facilitate incident management. Capabilities of Central Control Staff is, however, limited to check the increasing number of CCTV images and so far automated image processing solutions had been insufficiently reliable. TelSys GmbH (a railway telematics company in Dresden, Germany) had therefore developed over the last seven years together with the University of Technology in Dresden and some public transport providers (subway of Berlin, subway of Prague) a robust solution to supervise automatically critical areas like tunnel entrances, station tracks or station platform edges. Also qualifications with German Railways and in Finland had been performed. The automatic image processing software reliably differentiates between trains (“permitted” objects) and objects that move from the platform into the tracks or move too close to otherwise prohibited areas. Object sizes, alarm times, reliability and safety requirements had been taken from the VDV 399 standard of the German Public Transport Operators Association. After years of reliability and safety research and demonstration the system is now in regular operation (stopping automatically incoming driverless trains if an object is detected in the track) and can be considered as the first safe video image processing system according to railway standards. Experiences, system architecture and principles as well as further development plans and planned demonstration installation in North America are discussed.

A Train Operations and Energy Simulator Model of the Steered Frame Truck

A Train Operation and Energy Simulator (TOES™) model was created in order to investigate the potential benefits of replacing three-piece trucks with the “Steered Frame Truck” currently under development. Loaded coal trains were simulated with three-piece trucks and with Steered Frame Trucks. Both trains were modeled traveling on Norfolk Southern’s Pocahontas division from MP V435 to V399. The consist and direction of travel are based on actual trains in service. It was found that the model predicts several benefits for replacing three-piece trucks with Steered Frame Trucks. These resulted from the Steered Frame Truck having a greatly reduced rolling resistance while traveling around a curve. The benefits were found to include: a significant reduction in fuel consumption, a reduction in in-train forces, and a small increase in average velocity. One drawback was also predicted: that the reduced rolling resistance would necessitate the increased use of air brakes while traveling down-hill. Although Steered Frame Trucks should produce a considerable reduction in lateral forces, modeling such a reduction was beyond the scope of this work. Similarly, modeling other potential benefits not directly derived from the Steered Frame Truck’s reduced rolling resistance was not considered here.

Complex Bogie Modeling Incorporating Advanced Friction Wedge Components

This research focuses on the dynamic behavior of the three-piece bogie that supports the freight train car bodies. While the system is relatively simple, in that there are very few parts involved, the behavior of the bogie is somewhat more complex. Our research focuses primarily on the behavior of the friction wedges under different operating conditions that are seen under normal operation. The Railway Technologies Laboratory (RTL) at Virginia Tech has been developing a model to better capture the dynamic behavior of friction wedges using 3-D modeling software. In previous years, a quarter-truck model, and half-truck variably damped model have been developed using MathWorks MATLAB®. This year, research has focused on the development of a half-truck variably damped model with a new (curved surface) friction wedge, and a half-truck constantly damped model, both using the MATLAB® based software program. Currently a full-truck variably damped model has been created using LMS Virtual.Lab. This software allows for a model that is more easily created and modified, as well as allowing for a much shorter simulation time, which became a necessity as more contact points, and more complex inputs were needed to increase the accuracy of the simulation results. The new model consists of seven rigid bodies: the bolster, two sideframes, and four wedges. We have also implemented full spring nests on each sideframe, where in previous models equivalent spring forces were used. The model allows six degrees-of-freedom for the wedges and bolster: lateral, longitudinal, and vertical translations, as well as pitch, roll, and yaw. The sideframes are constrained to two degrees-of-freedom: vertical and longitudinal translations. The inputs to the model are vertical and longitudinal translations or forces on the sideframes, which can be set completely independent of each other. The model simulation results have been compared with results from NUCARS®, an industrially-used train modeling software developed by the Transportation Technology Center, Inc. (TTCI), a wholly owned subsidiary of the Association of American Railroads (AAR), for similar inputs, as well as experimental data from warping tests performed at TTCI.