Environmental and Track Factors That Contribute to Abrasion Damage

Sites with known occurrences of mud pumping or other track concerns were investigated to determine the prevalence of concrete bottom tie abrasion and environmental and track conditions that could contribute to its occurrence. Field investigations showed that it occurs in diverse geographic locations around the U.S. and is a source of continued maintenance concern for railroads. Water appeared to be a significant factor involved in concrete bottom tie abrasion. Ballast fouling, center-binding cracking, rail surface profile variations, and large track movement during loading was seen in locations with concrete bottom tie abrasion. Bumps or track stiffness changes were often found at locations of abrasion damage. Specifically, some locations with known stiff track conditions exhibited significant abrasion damage.

Simulation Methodology for Occupant Safety Assessment of Indian Railway Passenger Coach

This work intends to lay the groundwork for Computer Aided Engineering (CAE)-based occupant safety of a typical tier-III Indian Railway (IR) passenger coach in a collision accident. Our previous work presented in International Crashworthiness Conference 2010 under the title “Simulation of Crash Behaviour of a Common Indian Railway Passenger Coach” provided crashworthiness assessment of a typical tier-III passenger coach structure for representative head-on collision scenarios namely, against an identical passenger coach and against a stationary locomotive. These scenarios were envisioned to be part of a bigger accident scenario e.g - head-on collision between two trains moving towards each other. Analysis of involved chain of events for entire rolling stock and resulting internal collisions between individual passenger cars was out of scope of this work and necessary inputs were obtained from available literature on the same. This work used a full scale Finite Element (FE) simulation model and commercial explicit solver LS-Dyna. FE model was validated using International Railway Union (UIC) code OR566 specified proof loads for design. Simulation methodology used for dynamic impact was validated by component level crushing experiments using a drop tower facility. Material modelling incorporated strain rate effect on yield strength which is essential for obtaining accurate structural deformations under dynamic impact loading. Contacts were modelled using the penalty method option provided by the solver. This model was simulated for collisions at 30, 40 and 56 km/h against a stationary rigid barrier. Collision speeds were chosen to simulate impact energies involved in collision scenarios as mentioned above. The structure was found to exhibit global bending deformation and jackknifing with pivot position at the door section. In this paper, we present an extension of this work — coupled occupant safety simulation and injury assessment. It was accomplished by recording head, neck, chest and knee responses of a Hybrid-III 50th percentile male Anthropomorphic Test Device (ATD) FE model, seated in passenger position on lower berth of the first cabin of a passenger car. Interiors were modelled to represent the actual structure. Dummy model was adapted to passenger cabin’s excessive mobility conditions and responses were revalidated against Federal Motor Vehicle Safety Standards (FMVSS) limits. Injury interpretation was based on Abbreviated Injury Scale (AIS), automotive injury criteria and injury risk curves for Head Injury Criterion (HIC), thoracic spine acceleration, neck bending moment in flexion and extension and knee force. This study provides with estimates of injury and fatality based on computer simulation of accident scenarios. However, attempts of correlating to any available injury and fatality statistics were out of scope of this study.

Philosophy and Evolution of Wayside Signals

This paper begins with examining the fundamental nature of wayside signals and considers the first know signaling practices used to communicate the condition of the track ahead to the train engineer. The principle of wayside signals is to keep trains separated and to provide knowledge of the conditions ahead; speed and routing information. Most railways have gone through many different evolutions of signals and practices some driven by railway mergers which drove the operating rules. This consistently required changes within the training of locomotive engineers assigned operate trains within their territory. This paper will focus on a few transitions between signal types, the specific makeups and effectiveness of wayside signals since the beginning of railway signals in the early 1830s. Starting with the term “High Ball” not related to a popular drink known today, but a raising of a large ball into the air that could be seen from afar instructing a train his status to train operating schedule. Later, signals were developed to provide the train engineer the status of the track ahead by dividing the track into short sections. This allowed the track section to be labeled as “occupied” a train present or “un-occupied”, train not present within the track section. Wayside signals continued to be advanced such that today’s standards, aspects (mimicking the wayside signals) are displayed within the operating cab providing the indication directly to the engineer. As we continue forward, wayside signals have been reduced and in the future, they may be only in a museum next to the cassette player.

Manage Successful Brownfield Applications

This paper provides a unique perspective on successful brownfield railroad applications. It presents realistic challenges and solutions when applying a turnkey solution with a replacement or an overlay system. Brownfield commissioning takes place when an existing infrastructure is to upgrade to a new system with a different technology than the incumbent one. As signaling systems are getting more and more complex, it is extremely important to maintain robustness in the system design as well as project execution, such as logistics, documentation, and issue reporting. Many transportation authorities are moving from their current train control signaling system to a new system to combat obsolescence issues, to gain better system capacity, and to lower operation and maintenance costs. This paper discusses brownfield commissioning in general, and also presents specific cases in migration from a track circuit interlocking system to a Communications Based Train Control (CBTC) system. These two systems have distinct characteristics that provide opportunities of coexistence, but also introduce difficulties in mixed-mode operations.

Rail Defect Detection Using Fiber Optic Sensors and Wavelet Algorithms

Early detection of rail defects can avoid derailments and costly damage to the train and railway infrastructure. Small breaks, cracks or corrugations on the rail can quickly propagate after only a few train cars have passed over it, creating a potential derailment. The current technology makes use of a dedicated instrumented car or a separate railway monitoring vehicle to detect large breaks. These cars are usually equipped with accelerometers mounted on the axle or side frame. The simple detection algorithms use acceleration thresholds which are set at high values to eliminate false positives. As a result, rail surface defects that produce low amplitude acceleration signatures may not be detected, and special track components that produce high amplitude acceleration signatures may be flagged as defects. This paper presents the results of a feasibility study conducted to develop new and more advanced sensory systems as well as signal processing algorithms capable of detecting various rail surface irregularities. A dynamic wheel-rail interaction model was used to simulate train dynamics as a result of rail defects and to assess the potential of this new technology on rail defect detection. In a future paper, we will present experimental data in support of the proposed model and simulations.

Investigating the Rolling Contact Fatigue in Rails Using Finite Element Method and Cohesive Zone Approach

A micromechanical-based 2D framework is presented to study the rolling contact fatigue (RCF) in rail steels using finite element method. In this framework, the contact patch of rail and wheel is studied by explicitly modeling the grains and grain boundaries, to investigate the potential origin of RCF at the microstructural level. The framework incorporates Voronoi tessellation algorithm to create the microstructure geometry of rail material, and uses cohesive zone approach to simulate the behavior of grain boundaries. To study the fatigue damage caused by cyclic moving of wheels on rail, Abaqus subroutines are employed to degrade the material by increasing the number of cycles, and Jiang-Sehitoglu fatigue damage law is employed as evolution law. By applying Hertzian moving cyclic load, instead of wheel load, the effect of traction ratio and temperature change on RCF initiation and growth are studied. By considering different traction ratios (0.0 to 0.5), it is shown that increasing traction ratio significantly increases the fatigue damage. Also by increasing traction ratio, crack initiation migrates from the rail subsurface to surface. The results also show that there are no significant changes in the growth of RCF at higher temperatures, but at lower temperatures there is a measurable increase in RCF growth. This finding correlates with anecdotal information available in the rail industry about the seasonality of RCF, in which some railroads report noticing more RCF damage during the colder months.

Evaluation of Substation Capacity Using Headway Shift and Perturbation Parameters

The variations in the operation timetable or schedule of an electrified transit rail system can lead to substantial fluctuations in power demands of its traction power network. This paper studies the correlation between the maximum power demands and timetable perturbations for electrified transit rail systems. Specifically, the operation schedule uncertainties are quantified as two parameters: headway shift and headway perturbation. A computation algorithm is introduced to illustrate how to use these two parameters to obtain the worst case scenario to obtain maximum power demand of traction power substations. Also a special type of catenary-free light rail system is used as an example to illustrate the algorithm and numerical results.

Relationships Between Wheel/Rail Surface Impact Loadings and Correspondingly Transmitted Tie/Ballast Impact Pressures for Revenue Train Operations

A series of specially designed granular material pressure cells were precisely positioned directly below the rail at the tie/ballast interface to measure typical interfacial pressures exerted by revenue freight trains. These vertical pressures were compared to the recorded wheel/rail nominal and peak forces for the same trains traversing nearby mainline wheel impact load detectors (WILDs). The cells were imbedded within the bottom of new wood ties so that the surfaces of the pressure cells were even with the bottoms of the ties and the underlying ballast. The cells were inserted below consecutive rail seats of one rail to record pressures for a complete wheel rotation. The stability and tightness of the ballast support influenced the magnitudes and consistencies of the recorded ballast pressures. Considerable effort was required to provide consistent ballast conditions for the instrumented ties and adjacent undisturbed transition ties. Norfolk Southern (NS) crews surfaced and tamped through the test section and adjacent approach ties. This effort along with normal accruing train traffic subsequently resulted in reasonably consistent pressure measurements throughout the test section. The impact ratio (impact factor) and peak force values recorded by the WILDs compared favorably with the resulting magnitudes of the transferred pressures at the tie/ballast interface. High peak force and high impact ratio WILD readings indicate the presence of wheel imperfections that increase nominal forces at the rail/wheel interface. The resulting increased dynamic impact forces can contribute to higher degradation rates for the track component materials and more rapid degradation rates of the track geometry. The paper contains comparative WILD force measurements and tie/ballast interfacial pressure measurements for loaded and empty trains. Typical tie/ballast pressures for locomotives and loaded freight cars ranges from 20 to 30 psi (140 to 210 kPa) for smooth wheels producing negligible impacts. The effect of increased wheel/rail impacts and peak force values on the correspondingly transmitted pressures at the tie/ballast interface is significant, with increased pressures of several orders of magnitude compared to nominal impact forces from wheels.

Material Characteristics Evaluation of Existing Pre-Stressed Concrete Railroad Ties After Service Period

As an important element in track, pre-stressed concrete railroad ties in the high-speed rail industry must meet the safety and performance specifications of high-speed trains. Systematic destructive and non-destructive evaluation of existing concrete ties can lead to a better understanding of the effect of prestressed concrete tie material design on performance and failure within their service life. It has been evident that environmental and climate conditions also have a significant impact on concrete railroad ties, causing various forms of deterioration such as abrasion and freeze-thaw damage. Understanding of the material characteristics that cause failure in different types of existing concrete railroad ties taken from different places is the main focus of this paper. Observing the current status and damages of railroad ties taken from track might give a correlation between the material characteristic and type of distress and cracking seen. Although it has been seen by previous works that effective factors such as air void system and material composition directly affect the performance of concrete ties such as freeze-thaw, material evaluation of existing ties after service life has not been addressed in previous publications. In this research, the authors have investigated the material characteristic such as aggregate and air-void system of existing pre-stressed concrete railroad ties taken from track. However, compressive and splitting tensile strength and fractured surface of samples cored from the ties were acquired. In order to obtain the strength of concrete materials of existing ties, six samples were cored from six different types of ties taken from tracks across the U.S., according to ASTM C42-16, and tested using ASTM C39 and ASTM C496 methods. However, the concrete air-void system (ASTM C457) was measured on saw-cut samples extracted from the ties to evaluate the influence air content and distribution on mechanical properties of the ties. Regarding the history and service life condition of the ties, it seems that material properties of the ties effectively alter the performance of the ties. Aggregate sources used at each location may have different properties such as texture, angularity, and mineralogy, contributing either propagation or resistance in splitting cracking in concrete. Furthermore, the polished surface of samples extracted from the ties show the uniformity and air void system in some ties which demonstrate their superiority in terms of resistance to freeze-thaw damage. Considering the results of this research, comprehensive evaluation of material characteristics might give a better view of existing concrete railroad ties situation, providing a worthwhile background for future tie design considerations.

Lifetime Maximization by Optimizing the Computation/Communication Strategy for Railway Wireless Monitoring System

For the railway wireless monitoring system, energy efficiency is important for prolonging the system lifetime and ensuring the successful transmission of the inspection data. In general, decreasing the size of the data packet is conductive to declining the transmission energy consumption. Hence, the inspection data packets should be processed before being transmitted. However, the energy consumption of data processing may also be considerable, especially for the vision-based monitoring system. Therefore, we propose an optimization methodology to address the trade-off of the energy usage between data processing and transmission in railway wireless monitoring systems. In addition, the various data types and transmission distances of the sensors may cause the unbalanced energy consumption, and it will shorten the system lifetime due to the failure of some sensors. To address this challenge, in our proposed optimization framework, we adopt customized compression ratios for each sensor to balance its energy consumption. On this basis, the system lifetime can be extended by minimizing and balancing the energy consumption simultaneously. Finally, we use several generalized numerical examples to demonstrate the superiority and practicality of the proposed strategy. Compared to previous methods in the literature, our proposed approach can increase service lifetime of wireless monitoring systems using equal and less energy.