Use of On-Board Hand Brake Monitoring to Prevent Freight Car Wheel Damage and Improve Maintenance and Safety

This paper discusses the benefits of using on-board hand brake sensors to determine whether a freight car hand brake is applied or released in service. Unreleased hand brakes are a significant source of wheel tread damage, which can lead to wheel removals, and in extreme cases can cause damage and derailments. Also, hand brake-related accidents are a significant cause of North American railroad accidents. Wheel tread damage and wayside wheel impact load detectors (WILD) are reviewed, along with AAR why made codes for wheel removals. Wheel failures and other wheel impact associated damage are discussed, along with operational considerations for hand brakes. Further, on-board sensors in general, and hand brake sensors in particular, are described in detail and service data from monitored cars is presented. Additionally, possible safety and operational improvements related to use of hand brake sensors are discussed, along with comments on the use of sensors to assist with proactive maintenance of freight cars.

Stress and Fatigue Analysis of a Fiberglass 3rd Rail Support Bracket

For mass transit rail systems employing a 3rd rail to provide the electric traction power, the 3rd rail support bracket must have the capability to withstand the dynamically applied service loads while also providing the necessary electric arc resistance. To meet the arc resistance requirement, fiberglass brackets have been steadily replacing metallic type brackets in fire retardation critical locations; therefore it was necessary to validate their structural performance when used in general service. To this end, a general stress analysis was performed on a representative support bracket to investigate potential stress profiles experienced under various static loading conditions. Historically, metallic brackets have not been susceptible to fatigue failures in service. In order to determine fatigue life characteristics of fiberglass brackets, service strains were collected and analyzed to compare the behavior of the fiberglass and metallic brackets and evaluate whether the service life of the new material is sufficient. Furthermore, the fatigue life of a support bracket is highly dependent on the operational conditions. Thus, a service fatigue life analysis was performed to determine the bracket’s response to the variation of operating environment parameters such as the 3rd rail material and track location. From the analyses performed, it was concluded that the current design was not sufficient in replacing the metallic brackets. A possible redesign was then analyzed and it can be shown that a fiberglass material is suitable for the service application if the proper bracket design is incorporated.

Assessment of Fire Hazards and Mitigation Methods in Locomotive Fuel Tanks

Diesel fuel carriage in locomotives, while safe in normal operational conditions, presents a potential hazard in the event of serious accident or derailment. Development of an effective mitigation method against this hazard requires an understanding of operational conditions that lead to fuel spill and fire. This paper describes a study of fire hazard stemming from rail accidents and potential approaches to mitigation. Data for the study was obtained from a large sample of National Transportation Safety Board (NTSB) investigation reports for accidents involving both freight and passenger locomotive accidents over a 10-year period. Approximately 25% of the events reviewed resulted in fuel release. In addition, of the events that resulted in fuel loss, a large majority (almost 70%) resulted in fire. Most cases with major fires led to loss of life and/or property, including destruction of multiple locomotives. Typical road locomotives carry 3,000–4,500 gallons of diesel fuel during normal operation. As the locomotive consumes fuel, large volumes are available for vapor generation within the tank. In a post-collision scenario, the vapor that vents to the atmosphere at temperatures close to flash point of the fuel presents a significant fire hazard. Further, flammable mists can be generated by the sprays that develop due to fuel leaks from the post-impact movement of a train. Previous laboratory tests on a scaled tank demonstrated that fire in a fuel-rich vapor can flash back inside the tank causing an explosion or a large fire. This paper also assesses potential technologies to prevent or mitigate fire hazards in locomotive fuel tanks. These include fuel tank leak prevention or reduction of outflow from breached fuel tanks, monitoring vapor concentration within fuel tanks, and limiting vapor concentrations inside tank to maintain levels below the Lower Explosive Limit (LEL). Potential benefits of the latter method include minimization of pollution from escaping vapor as well as partial recovery of reusable fuel from vapor.

The Process of Spalling in Railroad Wheels

Although the term “Spalling” means different things to different disciplines and product types, for railroad wheels the term is used for the process by which tread cracks form as a result of a sliding event. The process includes rapid heating and austenitizing of the tread surface during a slide followed by rapid cooling and transformation to untempered martensite. Preexisting cracks in the area of a slide can grow from shallow and harmless cracks into cracks of greater significance due to high thermal and transformation stresses. Case crushing of the tread caused by high loads can also develop into spalls. Lastly, rolling contacts can cause fatigue cracks to form at the edges of a martensite patch in the heat affected zone. A complex combination of lower material strength and higher residual and applied stresses and the limiting hardenability of carbon steel produce conditions ideal for the formation of fatigue cracks. This investigation uses finite element analyses and laboratory tests to characterize the process of spalling.

Wheel Rim Axial Residual Stress and a Proposed Mechanism for Vertical Split Rim Formation

Railroad wheels are manufactured with beneficial residual compressive hoop stresses, which are imparted by rim quenching and tempering. Hoop and radial residual stresses for wheels have been studied in detail by various organizations over the years and are relatively well characterized. However axial residual stresses, in the orientation across the rim width from back rim face to front rim face, have not been extensively investigated. This paper describes a failure mode known as a vertical split rim (VSR) and describes efforts to measure the axial residual stresses in, 1) new wheels, 2) service worn wheels and 3) wheels that have failed from VSRs. Initial axial residual stress measurement efforts, using core drilling and x-ray diffraction from the tread surface, are briefly reviewed. Further more extensive work using x-ray diffraction to measure axial residual stress on radial wheel slices is described and data are presented, focusing on differences between the three wheel types. The concept of Axial Stress Amplification (ASA) is outlined, and the relationship of axial residual stress to VSRs is discussed. A proposed mechanism for VSR formation is described. Future work, with a goal of reducing or eliminating VSRs in service, is considered.

Preliminary Finite Element Analysis of Locomotive Crashworthy Components

The Office of Research and Development of the Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. A research program is being conducted that aims to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler. Preliminary designs for these components have been developed. This paper provides details on the finite element models of the crashworthy components and how the component designs behave in the finite element analyses. The component designs will be evaluated to determine if the requirements have been met, such as the energy absorption capability, deformation modes, and force/crush characteristics.

Occupied Volume Integrity Testing: Elastic Test Results and Analyses

The Office of Research and Development of the Federal Railroad Administration (FRA) and the Volpe Center have been conducting research into developing an alternative method of demonstrating the occupied volume integrity (OVI) of passenger rail equipment through a combination of testing and analysis. This research has been performed as a part of FRA Office of Research and Development’s Railroad Safety Research and Development program, which provides technical data to support safety rulemaking and enforcement programs of the FRA Office of Railroad Safety. Previous works have been published on a series of full-scale, quasi-static tests intended to examine the load path through the occupant volume of conventional passenger cars retrofitted with crash energy management (CEM) systems. This paper reports on the most recent testing and analysis results. Before performing any tests of proposed alternative loading techniques, an elastic test of the passenger car under study was conducted. The elastic test served both to aid in validating the finite element (FE) model and to verify the suitability of the test car to further loading. In January, 2011, an 800,000 pound conventional buff strength test was performed on Budd Pioneer 244. This test featured arrays of vertical, lateral, and longitudinal displacement transducers to better distinguish between the deformation modes and rigid body motions of the passenger car. Pre-test car repairs included straightening a dent in one side sill and installing patches over cracks found in the side sills. Additionally, lateral restraints were added to the test frame due to concerns in previous tests associated with lateral shift in the frame. As a part of this testing program, a future test of a passenger car is planned to examine an alternative load path through the occupied volume. In the case of Pioneer 244, this load path places load on the floor and roof energy absorber support structures. Loading the occupant volume in this manner more closely simulates the loading the car would experience during a collision. FE analysis was used in conjunction with full-scale testing in this research effort. An FE model of the Pioneer car was constructed and the 800-kip test was analyzed. The 800-kip test results were then compared to the analysis results and the model was adjusted post-test so that satisfactory agreement was reached between the test and the model. In particular, the boundary conditions at the loading and reaction locations required careful attention to appropriately simulate the support conditions in the test. Because the 800-kip load was applied at the line of draft, this test results in significant bending as well as axial load on the car. To ensure that both the axial and bending behaviors are captured in the model, the key results that were compared between test and model are the longitudinal force-displacement behavior and the vertical deflections at various points along the car. The post-test model exhibited good agreement with the compared test results. The validated model will be used to examine the behavior of the occupant volume when loaded along the alternative load path.

Freight Car Electrically Driven Set and Release Hand Brake (EDHB)

For years, American freight railroads have attempted to eliminate freight train crew injuries when applying and releasing freight car hand brakes. Currently, a person has to crank a handle or turn a wheel while in ergonomically awkward positions to apply a hand brake. If the operator slips or the brake’s mechanisms slip, injuries occur. Also, there are inherent safety issues with the climbing of ladders or steps to operate the brake and the need for going in-between cars to access the brakes. Additionally, today’s hand brakes are applied manually to varying degrees because there is no indicator to tell the crew that the hand brake is fully applied. Many times the hand brake is over applied and becomes damaged. Moreover, a hand brake that is not released upon train movement leads to wheel flats that damage the car, lading, and the track. Wheel set replacement is one of the most costly remediation activities on the railroad and damaged track adversely affects equipment and operations. With the objective of reducing or completely eliminating the issues mentioned above, the Federal Railroad Administration (FRA) has sponsored the development of an ‘Electrically Driven Set & Release Hand Brake’ (EDHB). Under this effort, Sharma & Associates, Inc. (SA) has conducted research into related concepts/products conceptualized and evaluated different arrangements selected a promising concept and developed a prototype. Functional laboratory demonstration tests have been conducted on the prototype. Future plans include working with the industry in developing and implementing performance and testing specifications for the EDHB, and validating the design through lab and field-testing.

Energy Harvesting Systems to Power Onboard Railroad Equipment

A practical and innovative solution to answer the need for power in freight cars is presented. The lack of available electric power in the vast majority of freight cars limits the use of electronic devices such as measuring (sensor) systems, GPS tracking devices or active RFID tags. An energy harvesting system has been developed to keep a battery charged and electric equipment running. The basic idea is to generate power using the relative motion of the car suspension as an input, scavenging energy that is normally wasted as heat in the damping system. Based on a promising first generation unit used as a proof of concept, the current prototype is designed to fit inside a typical suspension spring (D5) and so, can easily be implemented in virtually any rail car. During laboratory tests, the system is capable of efficiently generating up to 80W of power, on quasi-continuous basis, with a sinusoidal input of 3/8 inch at 2Hz. Durability tests have also been conducted to ensure that the system can withstand the harsh railroad environment. Additionally, actual suspension displacement measurements have been used to replicate real conditions and forge a more precise idea of the behavior that can be expected once implemented in a rail car. With encouraging laboratory tests, the next steps are to further validate the system and to confirm the obtained results with field testing.

Implementation of Wireless Temperature Sensors for Continuous Condition Monitoring of Railroad Bearings

At present there are no existing bearing health monitoring systems capable of continuous monitoring and tracking of railroad bearings on freight cars. Current wayside equipment is used to garner intermittent bearing cup temperatures, which at times could be every 65 km (∼40 mi) or more. Such devices are not designed to provide continuous condition monitoring which would enable users to assess the rate of bearing health degradation and predict when a bearing will require service. To this end, IONX, LLC, a subsidiary of Amsted Rail, Inc., has developed low power Wireless Sensor Nodes (WSNs) which can be retrofitted to existing bearing adapters. The WSNs provide continuous monitoring of bearing temperatures as well as the current ambient temperature. Since the nodes are affixed to the bearing adapter surface, a correlation is necessary to estimate the bearing cup temperature using the measured adapter surface temperature. This paper describes research conducted at The University of Texas-Pan American (UTPA) to devise a reliable mathematical model to correlate both temperatures. Additionally, these wireless nodes are currently in use on ten railroad cars that are part of an Australian fleet. The nodes have been collecting data since March 2010. The acquired data was used to devise and test a series of metrics that can automatically detect distressed bearings and predict time to maintenance. The development of bearing health monitoring metrics and their use to assess bearings in the Australian fleet is also discussed in this paper.