Abdullatif K. Zaouk

Long-Haul Whole-Body Vibration Assessment of Locomotive Cabs

Locomotives produce vibrations and mechanical shocks from irregularities in the track, structural dynamics, the engines, the trucks, and train slack movement (Mansfield, 2005). The different directions of the irregularities give rise to car-body vibrations in multiple axes including the following:• longitudinal, or along the length of the train (x);• lateral, or the side-to-side direction of the train (y);• vertical (z).The structural dynamics of rail vehicles give rise to several resonances in the 0.5–20Hz frequency range (Andersson, et al., 2005). Resonances are frequencies in the locomotive that cause larger amplitude oscillations. At these frequencies, even small-amplitude input vibration can produce large output oscillations. Further exacerbating the vibration environment, coupling of the axes of movement occurs: Motions in one direction contribute to motion in a different direction. The magnitude of vertical vibration in rail vehicles is reportedly well below many other types of vehicles (Dupuis & Zerlett, 1986; Griffin, 1990; Johanning, 1998). However, a lack of data from long-haul freight operations prevents an adequate characterization of the vibration environment of locomotive cabs.The authors describe results from 2 long-haul whole-body vibration (WBV) studies collected on a 2009 GE ES44C4 locomotive and a 2008 EMD SD70ACe. These WBV studies sponsored by the Federal Railroad Administration (FRA) examined WBV and shock in locomotives over 123 hours and 2274 track miles. The researchers recorded vibration data using 2 triaxial accelerometers on the engineers’ seat: a seat pad accelerometer placed on the seat cushion and a frame accelerometer attached to the seat frame at the base. The research team collected and analyzed vibrations in accordance with ISO 2631-1 and ISO 2631-5. ISO 2631-1 defines methods for the measurement of periodic, random and transient WBV. The focus of ISO 2631-5 is to evaluate the exposure of a seated person to multiple mechanical shocks from seat pad measurements.Exposure to excessive vibration is associated with an increased occupational risk of fatigue-related musculoskeletal injury and disruption of the vestibular system. While this is not an established causal relationship, it is possible that vibration approaching the ISO 2631-1 health caution guidance zones may lead to an increased occupational risk.The results from these rides show that the frequency-weighted ISO 2631 metrics are below the established health guidance caution zones of the WBV ISO 2631 standards. The goals of these studies are to:• collect data in accordance with international standards so results can be compared with similar findings in the literature for shorter duration rides as well as vibration studies in other transportation modes,• to characterize vibration and shock in a representative sample of locomotive operations to be able to generalize the results across the industry, and• collect benchmark data for future locomotive cab ride-quality standards.Copyright

Next Generation Locomotive Cab

This paper discusses the development of a user-centered control stand for the Federal Railroad Administration’s (FRA) Next Generation Locomotive Cab (NGLC) demonstration program. A “modified” Association of American Railroads (AAR) 105 side-mounted control stand was used as a starting point to facilitate bidirectional locomotive operation. Researchers applied a variety of qualitative human factor methods, including literature review, naturalistic observation, computer modeling, and heuristic evaluation, to design the improved control stand. The final design included a decluttered side control stand, a short desktop with three-panel front touchscreen displays that can accommodate and integrate current and future locomotive train technologies, and an overhead ceiling panel that replaces, in part, controls and displays traditionally located behind the engineer on the back wall. A mockup of the revised control stand design was fabricated as part of this program to demonstrate the human factors and ergonomic improvements. Researchers conducted structured interviews with locomotive engineers to validate the user-centered design approach. The engineers engaged in interactive scenarios that assessed the functionality of the workspace. The usability results provided the opportunity to improve upon the initial NGLC user-centered design. Changes included minor relocation of controls because they were in the reach path of other controls. Certain frequently accessed controls required relocation to more accessible locations. The LCD displays were redesigned with respect to information groupings and visibility issues. Feedback revealed that the transition from mechanical operations to electronic operations will result in the loss of auditory cues inherent in mechanical operations. The researchers suggest simulating auditory cues to promote personnel transition from mechanical to electronic operations. The results of this usability assessment identify the opportunity for future R&D cab integration efforts and demonstrate the importance of user-centered design and usability assessment in these efforts.Copyright

Feasibility of a Variable-Directivity Locomotive Horn

It is estimated that up to 9.3 million persons may be impacted by locomotive horn noise and up to 4.6 million of those may be severely impacted.1 In 2009, there were over 1,900 incidents, over 700 injuries and over 240 fatalities at highway-rail grade crossings.2 The National Academy of Engineering Committee on Technology for a Quieter America has indicated that the public would benefit if train warning horns were more directional and has recommended that research and development be undertaken to better understand the effects on safety and benefits to the public.3 A directive train horn has the potential to focus audible warning signals to desired locations including pedestrians and motorists at highway-rail grade crossings while minimizing noise to the surrounding community and employees in the locomotive cab.As a part of an ongoing Federal Railroad Administration (FRA)-sponsored research and development effort, the authors have examined the feasibility of and recommended an acoustical specification for an optimized train horn that would improve the detectability of the warning signal for motorists at critical positions along the crossing road while reducing the area of environmental noise impact. The detectability, noise impact area and occupational noise exposure have been compared for the optimized horn and several typical standard horns.Near the beginning of most sounding events (1/4-mile from the grade crossing) the optimized horn reduces noise exposure because a narrow beam of sound can be generated and focused at the grade-crossing. As the train approaches the crossing, the beam width must become wider. It is found that detectability could be improved and noise impact area reduced by up to 57%, but the optimized horn must have a directivity pattern and amplitude that dynamically changes as a function of train position relative to the crossing.Current acoustic source technologies which generate directive sound were examined including “acoustic hailing devices” (AHDs) which are recent technological advancements typically used for naval communications. Capable of focusing high amplitudes of sound within a narrow beam and dynamically changing the directivity pattern through electronic beam steering, AHDs have been identified as a feasible means of meeting the required specifications. A critical design issue for the optimized horn is controlling the directivity pattern at low frequencies. Development and testing of a prototype is in progress and actual improvements to detectability and reductions in noise impact will be analyzed. The paper briefly discusses the feasibility of the optimized horn and general information on cost and implementation.Copyright

Assessment of a Diesel Vapor Reclamation System for Use in Diesel Electric Locomotives

Diesel fuel used in locomotives generally does not pose a fire hazard. However, diesel vapor generated within tank vapor space attains flammability condition as the fuel temperature gets closer to the fuel-flash point, which may cause a fire hazard in the event of a tank breach due to collision or derailment of the locomotive. As a part of an ongoing Federal Railroad Administration (FRA) sponsored research effort, a proof-of-concept laboratory scale demonstration has shown that it is possible to circulate the mixture of diesel vapor and air through a small vapor condenser unit to reclaim the fuel vapor. The recovered fuel is shown to possess almost similar specific heat value and hydrocarbon constituents as that of neat diesel fuel and hence reusable. Furthermore, the vapor reclamation process enables mitigation of fire hazard and reduction of diesel vapor escape to the environment. In order to assess the real potential of diesel vapor reclamation on a running locomotive, real-time fuel temperature data was collected during a medium-haul run of a BNSF Railway freight locomotive.This paper presents the real-time fuel temperature data collected on a BNSF Railway instrumented locomotive tank as well as results of computational fluid dynamics (CFD) analyses performed for the full-scale locomotive tank. In continuation of the research and development effort, the design of a scaled up diesel vapor reclamation system is presented. The scope of its integration with a railroad freight locomotive is summarized and subsequent steps for its performance evaluation on a running locomotive are discussed.© 2012 ASME

Improving Crashworthiness of Railroad Rolling Stocks with New Generation Shock Energy Absorbers

This paper describes the results of quasi-static and dynamic tests of a new shock energy absorber (SEA) capable of high energy absorption while limiting peak dynamic force magnitude in the event of an impact or collision. The SEA utilizes the unique reversible phase transition behavior of Ultra High Molecular Weight Poly-Ethylene (UHMWPE) material under pressure. A prototype drop hammer test confirmed the device’s high energy absorption as well as high damping capabilities at a relatively high deformation rate. The results of the test were used to calibrate a finite element (FE) model that enabled scalability of the SEA for practical applications. Preliminary design and FE simulations were made under a Federal Railroad Administration (FRA) sponsored program toward using a set of SEA as a part of a crash energy management (CEM) system to improve locomotive crashworthiness. The main objective of the program was to prevent locomotive override in the event of an inline collision with a hopper car consist at a closing speed of 30 mph. The FE model, without CEM, was validated to a previously performed full-scale locomotive crashworthiness test at Transportation Technology Center, Inc. (TTCI), Pueblo. The FE simulation results with added CEM system showed successful prevention of locomotive override up to 32.1 mph collision speed. Further scope of using suitably tailored SEA units as buffers to the ends of passenger coaches and tank cars with the objective of enhancing their crashworthiness is discussed.Copyright

Whole-Body Vibration in Locomotive Cabs

Locomotives produce vibrations and mechanical shocks from irregularities in the track, structural dynamics, the engines, the trucks, and train slack movement (Mansfield, 2005). The different directions of the irregularities give rise to car-body vibrations in multiple axes including the following: • Longitudinal, or along the length of the train (x); • Lateral, or the side-to-side direction of the train (y); • Vertical (z). Some reports suggest that acceleration at the seat pan is greater than that at the floor, indicating that the seat may amplify the vibration (Johanning, et al., 2006; Mansfield, 2005; Oborne & Clarke, 1974; Transport, 1980). The magnitude of vertical vibration in rail vehicles is reportedly well below many other types of vehicles (Dupuis & Zerlett, 1986; Griffin, 1990; Johanning, 1998). However, some research reports that rail vehicles experience far more lateral vibratory motion than cars and trucks (Lundstrom & Lindberg, 1983). Many factors influence the impact of shock felt by the engineer including train speed, consist, engineer control skills, anticipation of the shock, motion amplitude, shock duration, and body posture. Shock events and vibration affect ride quality; however, shocks are less controllable by locomotive design. Common sources of mechanical shock are coupling and slack run-ins and run-outs (Multer, et al., 1998). While there are investigations of whole-body vibration (WBV) in locomotive cabs reported in the literature, there have been no studies to date that have examined long-haul continuous vibrations (> 16 hr). The authors describe a long-haul WBV study collected on a 2007 GE ES44DC locomotive. It is the first in a series of studies sponsored by the Federal Railroad Administration (FRA) to examine WBV and shock in locomotive cabs. The researchers recorded vibration data using 2 triaxial accelerometers on the engineers’ seat: a seat pad accelerometer placed on the seat cushion and a frame accelerometer attached to the seat frame at the base. Data collection occurred over 550 track miles for 16hr 44min. ISO 2631-1 defines methods for the measurement of periodic, random and transient WBV. The focus of ISO 2631-5 is to evaluate the exposure of a seated person to multiple mechanical shocks from seat pad measurements. The research team collected and analyzed vibrations in accordance with ISO 2631-1 and ISO 2631-5. The results from the study as well as future planned long-haul studies will provide a benchmark set of WBV metrics that define the vibration environment of present-day locomotive operations.Copyright

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.Copyright