Onboard Detection of Rail Friction Conditions

A sensor system is proposed that measures sound and vibration close to the interface, mounted to the locomotive while the train is in motion. Through the use of navigation technology, measurement ‘snapshots’ are tagged with time, location and speed information. The data is subsequently analyzed in both the time and frequency domains, coupled to the location where the measurement was taken on the track.

Seasonal Effect on the Optimization of Rail Defect Inspection Frequency

Broken rails are the most common cause of severe freight-train derailments on American railroads. Reducing the occurrence of broken-rail-caused derailments is an important safety objective for the railroad industry. The current practice is to periodically inspect rails using non-destructive technologies such as ultrasonic inspection. Determining the optimal rail defect inspection frequency is a critical decision in railway infrastructure management. There is a seasonal variation in the occurrence of broken rails that result in train derailments. This paper quantifies the effect of this seasonal variation on the risk-based optimization of rail inspection frequency. This research can be incorporated into a larger framework of broken rail risk management to improve railroad transportation safety.

Determining Transfer Length in Pre-Tensioned Concrete Railroad Ties: Is a New Evaluation Method Needed?

The transfer length is perhaps the most significant KEY indicator of the bond quality between reinforcing wire/strand and concrete, and its measurement in pre-tensioned concrete railroad ties can enable concrete tie producers to identify problem ties before they are put into service. The 95% AMS method is the traditional method used to determine the transfer length from measurements of surface strain. The method generally presumes the underlying existence of a bilinear strain profile. During recent field trips to six concrete railroad tie plants, we conducted hundreds of transfer length measurements on concrete railroad cross-ties using a newly developed automated Laser Speckle Imaging device. It has been observed that many of the strain profiles depart significantly from this underlying bilinear profile, and bring to question the general validity and applicability of the 95% AMS (95% Average Maximum Strain) method. This paper discusses the difficulties with accurate determination of transfer length in various practical situations using the traditional 95% AMS method. Deviations of the strain profiles from the simple bilinear shape are shown to be partially due to the non-prismatic shape of typical concrete railroad ties. In addition, computational evidence suggests that the underlying strain distribution may be exponential in nature, with an asymptotic approach to the fully-developed compressive strain, potentially superimposed on the non-prismatic problem identified above. These departures are discussed along with proposed solutions to the basic problem of accurate transfer length assessment.

Modern Uncertainty Quantification Methods in Railroad Vehicle Dynamics

This paper describes the results of the application of Uncertainty Quantification methods to a simple railroad vehicle dynamical example. Uncertainty Quantification methods take the probability distribution of the system parameters that stems from the parameter tolerances into account in the result. In this paper the methods are applied to a low-dimensional vehicle dynamical model composed by a two-axle truck that is connected to a car body by a lateral spring, a lateral damper and a torsional spring, all with linear characteristics. Their characteristics are not deterministically defined, but they are defined by probability distributions. The model — but with deterministically defined parameters — was studied in [1] and [2], and this article will focus on the calculation of the critical speed of the model, when the distribution of the parameters is taken into account. Results of the application of the traditional Monte Carlo sampling method will be compared with the results of the application of advanced Uncertainty Quantification methods [3]. The computational performance and fast convergence that result from the application of advanced Uncertainty Quantification methods is highlighted. Generalized Polynomial Chaos will be presented in the Collocation form with emphasis on the pros and cons of each of those approaches.

Cost Benefit Analysis of Alternative Fuel and Motive Power

A research initiative by the Federal Railroad Administration (FRA) and Transportation Technology Center, Inc. (TTCI) was developed to better understand the potential cost and benefits of using alternative fuels for United States freight and passenger locomotive operations. The framework for a decision model was developed to evaluate the feasibility of these newly emerging technologies. Because these alternatives (fuels and engine designs) are at early stages of development, the objective is to identify the most feasible alternatives and support their future development. Energy security policies developed by the US Department of Energy (DOE) and emission standards set forth by US Environmental Protection Agency (EPA) are driving most of the technology initiatives related to alternative fuels in the US. Identifying alternatives that may provide benefits in the areas of emissions and energy security in relation to their potential cost, safety, and operating efficiencies are the main analysis objectives of this study. Some of the alternative energy sources being studied, and that may be in limited use are biomass, natural gas and coal. These energy sources have the potential to replace diesel fuel and provide power for locomotive operations. However, most are considered experimental by the railway industry. In most cases engine modifications or complete motive power design changes are required. As a result, the use of alternative fuels or locomotives that are different from current diesel engine designs represent only a small percent of the total railroad fleet. The main drivers for the decision model identified in this research effort are Cost, Energy, Security, Emissions, Safety and Efficiency. Under each decision driver there are multiple criteria that may be used for comparison between proposed alternatives. The goal of the decision model is to understand if the criteria under the decision drivers are independently a cost or benefit to industry stakeholders as compared to a baseline case.

Transfer Bond Test Used to Predict Transfer Length of Concrete Railroad Ties

A study was conducted at Kansas State University to determine the correlation between tensioned-wire pullout tests and the corresponding transfer lengths in prestressed concrete railroad ties. Five different 5.32-mm-diameter pre-stressing wires were selected to be used on this project based on previous testing conducted at Kansas State University (KSU). The wires were tested to simulate the transfer-length bond. The transfer-length bond test involved tensioning each of the wires to 75% of their ultimate capacity, casting concrete around each wire and then de-tensioning the wire when the concrete had reached 4,500 psi. End-slip and force measurements were recorded on both sides of the specimen as the wire was de-tensioned. Transfer bond data was used to investigate the transfer length that each wire type would expect to see in a concrete railroad tie. Prisms with each wire type were cast and the transfer length was measured for each type of wire. Prism measurements were used along with the transfer bond data to correlate a relation between the transfer bond test and the transfer lengths of the prisms.

High Performance Coupling Systems

The freight railway industry relies on the interchangeability of coupling system parts (i.e., couplers, locks, throwers, pins, knuckles). Variability in the dimensions of the components affects the ability to change parts efficiently and the performance of the components. Because of the complex shapes and dimensions involved, it has been difficult to identify the component causing most of the problems for a combination of coupling system parts. Transportation Technology Center Inc. (TTCI) has developed a digital E-type coupler gage that can be combined with 3-dimensional scanning technologies to help railroads and manufacturers find areas that may be causing fitment problems. Physical gages are also being developed for use in production and field environments. The digital and physical gages can be used for fitment quality checks by the railroads and manufacturers. The digital gage requires a laser scanning of the coupler in question to be completed. A 3-dimensional scan of a coupler can be overlaid with the digital gage to find the dimensions causing a problem. Though it is currently a destructive method, further development of scanning technology could make the process more efficient and nondestructive. Using a combination of the digital and physical gages with the proper procedure may reduce the number of problems with properly fitting components and premature failure of couplers in service.

Improved Quality Truck Castings

Component failure in bolsters and side frames remains a problem for both railroads and suppliers, causing expensive repairs and even derailments. To understand and combat this problem, an evaluation of the steel was required. Bolsters were obtained from several suppliers to evaluate the current state of Association of American Railroads (AAR) M-201 standard for Grade B+ cast steel. Charpy impact and tensile test samples were machined from critical areas of these castings and tested at an independent laboratory. Distinct differences were found in processes and in mechanical properties between some suppliers. Supplier names are not identified in this paper. Based on the chemical and mechanical testing results and data analysis, changes to AAR M-201 Grade B+ requirements have been proposed. Additional bolsters have been obtained for further testing. These bolsters will incorporate the proposed changes to the standard and the same mechanical testing will be performed on them to determine the effectiveness of the proposed changes. Full scale static or fatigue testing will be conducted on additional bolsters. A survey of scrapped bolsters and side frames from several railcar producers and reclaim operations was conducted to determine the leading causes of failures of components removed from service. These results form the basis for a database that can be used to identify failure trends.

Analyses for Lateral Deflection of Railroad Track Under Quasi-Static Loading

This paper describes analyses to examine the lateral deflection of railroad track subjected to quasi-static loading. Rails are assumed to behave as beams in bending. Movement of the track in the lateral plane is constrained by idealized resistance characteristics, while movement in the vertical plane is resisted by a continuous, linear and elastic foundation. These analyses are based on solving the ordinary differential equations for beam deflections. In certain cases, convenient mathematical expressions may be used to represent idealized lateral resistance characteristics and derive closed-form equations to relate lateral force as a function of track lateral deflection. However, in general, the idealized lateral resistance characteristic may be nonlinear, in which case numerical methods are required to examine the lateral load versus track lateral deflection behavior. In these general cases, a Fourier series technique is used to solve the governing equations numerically. The analysis of track lateral deflection subjected to quasi-static loads may be applied to examine track shift. For example, lateral resistance of track may be measured using Track Lateral Pull Tests (TLPT). The Fourier method is also used to examine the relationship between lateral and vertical wheel loads and track lateral shift.

Evaluation of LIDAR Track Measurement Systems in Car Body and Truck-Mounted Configurations

This study presents track alignment and curvature measurement results from a Doppler LIDAR (light detection and ranging) speed measurement system, a non-contact speed and distance measurement system comparable to encoders found on research geometry cars. The system has multiple mounting capabilities with the primary implementations being body-mounted and truck-mounted. Track speed is measured using the individual rails as reference targets, producing two speed signals. Curvature data is obtained from the measured speed differential as the train navigates tangent and curved track. The different dynamic behaviors of the truck and car body influence the motion of the LIDAR system, and thus the results vary depending on the mounting configuration. The curvature, speed, and distance data obtained from the LIDAR system has been compared with results from a geometry car and manual track measurements. The results indicate the LIDAR system has strong potential in serving as a highly precise, non-contact speed, distance, and curvature measurement device suitable for implementation in rail geometry applications.