Association Of American Railroads Research Articles

Weld Fatigue Damage Assessment of Rail Track Maintenance Equipment: Regulatory Compliance and Practical Insights

<div>The use of appropriate loads and regulations is of great importance in weld fatigue assessment of rail on-track maintenance equipment and similar vehicles for optimized design. The regulations and available loads, however, are often generalized for several categories, which proves to be overly conservative for some specific categories of machines. EN (European Norm) and AAR (Association of American Railroads) regulations play a pivotal role in determining the applicable loads and acceptance criteria within this study. The availability of track-induced fatigue load data for the cumulative damage approach in track maintenance machines is often limited. Consequently, the FEA-based validation of rail track maintenance equipment often resorts to the infinite life approach rather than cumulative damage approach for track-induced travel loads, resulting in overly conservative designs. The work presented in this article evaluates and compares the weld fatigue damage of track maintenance equipment for EN loads using infinite life approach and AAR loads using cumulative damage approach and highlights the need of having distinct category for track maintenance machines in regulations based on its usage and application to have close representative loads for the endurance limit approach or suitable loads for the cumulative damage approach. Additionally, the study utilizes the BS7608 regulation to determine weld class and predict weld fatigue damage. Both nominal and hot-spot stress approaches are employed to thoroughly investigate and calculate fatigue damage, providing a comprehensive analysis of weld fatigue in rail maintenance equipment.</div>

The influence of AAR coupler features on estimation of in-train forces

Inadequate management of large in-train forces transferred through coupler systems of a railway train leads to running and structural failures of vehicles. Understanding these phenomena and their mitigation requires accurate estimation of relative motions and in-train forces between vehicle bodies. Previous numerical studies have ignored inertia of coupling elements and the impacts between couplers. Thus, existing models underestimate the additional dynamic variations in in-train forces. Detailed multi-body dynamic models of two AAR (Association of American Railroads) coupler systems used in passenger and freight trains are developed, incorporating coupler inertia and various slacks. Due to the modeling and simulation complexities involved in a full train model, with such details of coupler system, actual longitudinal train dynamics is not studied. A system comprising only two coupling units, inter-connecting two consecutive vehicles, is modeled. Considered system has been fixed at one end and an excitation force is applied at the other end, to mimic a relative force transmission through combined coupler system. Simulation results obtained from this representative system show that, noticeable influence in in-train forces are expected due to the combined effect of inertia of couplers and intermittent impacts between couplers in the slack regime. Maximum amplitude of longitudinal reaction force, transferred from draft gear housing to vehicle body, is expected to be significantly higher than that predicted using existing models of coupler system. It is also observed that the couplers and knuckles are subjected to significant longitudinal and lateral contact forces, due to the intermittent impacts between couplers. Thus, accurate estimation of draft gear reaction force and impact forces between couplers are essential to design vehicle and coupler components, respectively.

Intermodal transportation in the context of the COVID-19 pandemic and digitalization

The paper deals with topical issues of organizing intermodal transportation in the context of the restrictions and difficulties that have arisen as a result of the COVID-19 pandemic, taking into account the increasingly active processes of digitalization of the logistics industry. The analysis of the main trends in the freight transportation market during the peak of the COVID-19 pandemic was made, as well as in 2020-2021. The main trends in the development of the market have been identified; both in the context of the current situation and taking into account the emerging trends. The priority types of transport are determined based on the analysis of data from the Association of American Railroads, JSC Russian Railways, the United Nations (railway transport, maritime transport, road transport - for the "last mile"), the relevance of which is obvious today. The relevance of the introduction of advanced digital and information technologies for all participants in the supply chain, both individually and globally, was also identified - the creation and implementation of digital logistics platforms.

Landsbergis, Johanning, Stillo Respond to Letter to the Editor.

Landsbergis, Johanning, Stillo Respond to Letter to the Editor.

Letter to the Editor: Landsbergis et al (2019) Titled "Work Exposures and Musculoskeletal Disorders Among Railroad Maintenance-of-Way Workers".

Letter to the Editor: Landsbergis et al (2019) Titled "Work Exposures and Musculoskeletal Disorders Among Railroad Maintenance-of-Way Workers".

Tempered Bainite and Martensite Embrittlement in Microalloyed Steel for Forged Railroad Wheel to Heavy Haul Application

Abstract This research shows two new microalloyed steels with niobium (Nb) for railroad wheels (Nb1 and Nb2) applied on heavy haul transportation (load over 30 tons/axle). The steels have mixed microstructure composed of pearlite and bainite (finished wheel rim section), and another one composed of martensite with bainite (black wheel section removed on machining) obtained by continuous cooling quenching heat treatment followed by tempering. The bainitic and martensitic microstructure are sensitive to the temper embrittlement phenomenon; therefore, knowing the embrittlement temperature range of these steels is mandatory in order to avoid such an event in the tempering process. Charpy specimens were extracted from the rim of railroad wheels, austenitized (860 oC), quenched in water for four minutes, and tempered at different temperatures to obtain the embrittlement curve. Three materials were compared: AAR (Association of American Railroads) Class C steel with pearlitic microstructure (not sensitive to embrittlement), Nb1, and Nb2 microalloyed steels with martensitic, bainitic, and pearlitic microstructures. The microalloyed steels have niobium (Nb), molybdenum (Mo), and silicon (Si) addition. The effect of Si content and the microstructure (analyzed by Scanning Electronic Microscope (SEM)), regarding the embrittlement phenomenon, was also studied. The microstructure of Nb2 steel was analyzed by with Transmission Electronic Microscope (TEM) for improving its characterization.

Recent studies on railway-track substructure at TTCI

Abstract Railway-track substructure is the foundation of the railway-track infrastructure and consists of four major components: ballast, sub-ballast, subgrade and drainage. Safety and performance of the track infrastructure, to a large degree, depends on the performance of the track substructure. Adequate support from the track substructure is the most critical element needed for good track performance. When properly constructed and maintained, the ballasted track is the most cost-effective track structure for railway operations, especially for heavy-haul freight operations. Good track-substructure support is characterized by good drainage and strong resistance of the ballast, sub-ballast and subgrade layers to excessive deformation and failures under repeated dynamic wheel loads. As the track substructure plays such important roles, research concerning track substructure has been broad and extensive around the world, with many universities and research institutes conducting various studies and investigations. This paper provides an overview of the recent research conducted at Transportation Technology Center, Inc. (TTCI), a subsidiary of the Association of American Railroads (AAR), in the following areas: ballast mud pumping and its effects on track performance, remediation of subgrade mud pumping, remediation of ballast pockets, ground-penetrating radar (GPR) for inspecting track substructure, and development of software tools with focus on track-substructure functions and management.

Effect of niobium and molybdenum addition on the wear resistance and the rolling contact fatigue of railway wheels

Brazilian heavy-haul railway companies have drawn extensive research in the last years for developing solutions that can make the operation in this area more efficient and safer, such as friction management, the use of new mechanical assemblies, and the use of new materials for wheels and rails. Another solution implemented is increasing the weight transported by train wagons; however, the more weight added, the more deterioration caused to wheels and rails, for example, promoting higher maintenance costs and risks to safety. Thus, the key to extending the life cycle of railroad wheels is to reduce the wear and rolling contact fatigue (RCF) in developing new materials and in manufacturing them. Niobium (Nb) and molybdenum (Mo) are usually added to increase the mechanical strength of pearlitic steels by decreasing the interlayer spacing. This way, comparative twin-disc test for wheel material under dry conditions was performed to verify the wear resistance of a commercial railway wheel (7C) and a newly developed class D railway wheel steel (7 M) with Nb and Mo addition. Following the specifications of the Association of American Railroads (AAR) standard, a twin-disc tribometer with automatic control of load and speed was used. The slip ratio was obtained from the difference between the axis rotation. 7 M steel was observed to present lower mass loss compared with 7C steel. The Magnetic Barkhausen noise analysis showed higher residual stress close to the surface for 7 M steel, which correlated with the work-hardened depth. Such results, therefore, indicate that 7 M steel presented better performance than 7C steel regarding the specific characteristics of the tests. To confirm the feasibility of the wheel material for use in service, further twin-disc tests are proposed for both wheel materials (7 M & 7C) against the same rail material.

Fatigue properties of AL/AL-MG alloy laminated materials for the applications to railway tank cars

In this study, Al/Al-Mg alloy laminated plates were developed, and such composite materials are applied in a 70 t tank car for transporting concentrated nitric acids. The fatigue tests of the base materials and the lap-welded joint of the Al/Al-Mg alloy laminated plate were conducted, and the stress-cycle (S-N) curve with a survival rate of 97.7% was obtained. The fatigue failure mode was analyzed, and its fracture mechanism of the laminated plates was determined. Furthmore, the mechanical behavior of Al/Al-Mg alloy laminated plate was investigated using the finite element analysis (FEA). Based on the load spectrum of 100 t tank car described in the Association of American Railroads (AAR) standard, in conjunction with the S-N curve of the base materials and the lap-welded joints, the fatigue life of the 70 t tank body was calculated based on the Miner’s linear accumulative damage theory. The results showed that the 70 t tank car constructed with such materials can meet the safety requirements of operating for 2.5 million km.

Effect of wheel size and tread braking on subsurface crack initiation in heavy haul car wheels

Subsurface cracks initiating from internal defects are one of the main rolling contact fatigue damages that occur in heavy haul car wheels. Finite element analyses of the wheels are performed to assess the effects of the wheel size and tread braking on the subsurface crack initiations. Critical defect sizes for the subsurface crack initiations are calculated from the results of finite element analyses and fatigue tests of the wheel steel based on the multiaxial fatigue evaluation model. The critical defect sizes of 38 and 36 inch wheels are almost equivalent in service conditions in accordance with the AAR (the Association of American Railroads) standard. On the other hand, the 33-inch wheel has a larger critical defect size than the 38 and the 36-inch wheels. The 33-inch wheel has smaller stresses at the subsurface because it has a smaller wheel load than the other wheels. Stop braking with normal brake energy has fewer effects on the critical defect size. Therefore, the tread braking in this study is considered to have no negative effect on subsurface crack initiations.

2018 Railroad Tie Survey

This article reports results of a survey of railroad tie management conducted by the Association of American Railroads (AAR) reflecting 2017 practices. Similar surveys were previously conducted for 2013 and 2008 practices. North American railroads purchase approximately 23 million new wood crossties annually. Most ties are used to replace worn ties. Through this survey, the AAR seeks to provide clarity to its member railroads, the regulators, and other interested parties, regarding how the railroads’ tie purchase preferences and used tie management choices have been changing in response to changing technologies and regulations. Technology changes include use of borate preservatives to dual-treat wood ties to provide longer service life in high decay environments, non-wood ties made of concrete or plastic, and energy conversion methods for used ties such as gasification and torrefaction. Passage of the EPA Non-Hazardous Secondary Materials (NHSM) rule in 2011, including updates in 2013, 2016, and 2018, is reducing the potential for recycling used ties as fuel. However, the EPA is also promoting use of biological materials, such as wood, to produce energy without increasing carbon dioxide (CO2) levels in the atmosphere, thus reducing human caused climate change. Purchase and tie management trends are indicated by the survey results. Approximately 95% of all ties purchased are preservative-treated wood. Due to demonstrated longer service life in high decay zones for wood ties that are dual treated with borate and either creosote or copper naphthenate, the fraction of concrete and plastic tie purchases has decreased while the faction of dual treated wood tie purchases has increased. Recycling used ties for energy remains the most common practice, at 66% of ties, but has declined from 81% in 2013. Reuse of ties for other treated wood uses, such as landscape and agricultural type purposes, remains common at approximately 18%. Landfill disposal remains uncommon, but seems to be increasing at 6% of removed ties. The shift away from recycling for energy is thought to result from the both impact of the EPA NHSM rule and the low cost of natural gas. The smaller market tie users, mainly the short line railroads in contrast to the Class 1 railroads, manage far fewer ties per company, but purchase and manage approximately 31% of all ties. The short lines recycle to landscape and agricultural uses at about half the rate of the Class 1s and dispose in landfills at a much higher rate of 76% versus 1.2% for the Class 1s. This difference is thought to result from the economics and availability of local versus distant management options.

Development of Niobium Microalloyed Steel for Railway Wheel with Pearlitic Bainitic Microstructure

Heavy haul transportation (load over 30 tons/axle), as well as the axle load, has been more and more used in Brazil and worldwide. The stress generated in the wheel-rail contact with loads up to 30 tons/axle is around 760 MPa, which causes premature wear and cracks of conventional wheels (AAR (Association of American Railroads) class C). Microalloyed wheels are fundamental on heavy haul transport, whose main function is to combine high hardness, ductility, and yield strength of the material in order to prevent shelling. The main purpose of this research is to develop a new microalloyed wheel steel with niobium addition that meets all the requirements of the AAR class D material with mixed microstructure composed of pearlite and bainite. The 0.71C/0.020Nb steel developed in this study (Nb material) for railroad achieved the standards required for AAR class D in all mechanical properties, with fracture toughness higher than the usual vanadium microalloyed steel used in comparison. The Continuous Cooling Transformation (CCT) diagram showed the presence of bainite even at very low cooling rate, in the range between 0.3 - 2 °C/s. These cooling rates to form bainite are much lower than those observed in other steels with similar composition.

Research on Standard and Automatic Judgment of Press-fit Curve of Locomotive Wheel-set Based on AAR Standard

In the production of the Association of American Railroads (AAR) locomotive wheel-set, the press-fit curve is the most important basis for the reliability of wheel-set assembly. In the past, Most of production enterprises mainly use artificial detection methods to determine the quality of assembly. There are cases of miscarriage of justice appear. For this reason, the research on the standard is carried out. And the automatic judgment of press-fit curve is analysed and designed, so as to provide guidance for the locomotive wheel-set production based on AAR standard.

The role of microstructure and its stability in performance of wheels in heavy haul service

Thermal or thermo-mechanical loading is one of the major causes of wheel surface damage in Australian heavy haul operations. In addition, multi-wear wheels appear to be particularly sensitive to thermo-mechanical damage during their first service life. Such damage can incur heavy machining penalties or even premature scrapping of wheels. The combination of high contact stresses as well as substantial thermal loading (such as during prolonged periods of tread braking) can lead to severe plastic deformation, thermal fatigue and microstructural deterioration. For some high-strength wheel grades, the increased sensitivity to thermo-mechanical damage observed during the first service period may be attributed to the presence of a near-surface region in which the microstructure is more sensitive to these loading conditions than the underlying material. The standards applicable to wheels used in Australian heavy haul operations are based on the Association of American Railroads (AAR) specification M-107/M-208, which does not include any requirements for microstructure. The implementation of acceptance criteria for the microstructure, in particular that in the near-surface region of the wheel, may be necessary when new wheels are purchased. The stability of wheel microstructures during thermo-mechanical loading and the effects of alloying elements commonly used in wheel manufacturing are reviewed. A brief guide to improving thermal/mechanical stability of the microstructure is also provided.

Environmental Reviews and Case Studies: Setting Policy and Precedence: CREATE in Motion

The Chicago Region Environmental and Transportation Efficiency (CREATE) Program is a nationally prominent rail-infrastructure program. It is managed by the unique partnership of the United States Department of Transportation (DOT), the State of Illinois, the City of Chicago, Metra, Amtrak, Association of American Railroads, and six of the nation’s Class I freight railroads. The CREATE 75 th Street Corridor Improvement Project (CIP) received a National Environmental Policy Act (NEPA) Environmental Impact Statement (EIS) Record of Decision in September 2014. As a result of 75 th Street CIP and other completed preliminary engineering and project environmental reviews within the 70 rail-improvements program, CREATE has set a national-policy example with regard to mitigation under the environmental justice Executive Order (EO) 12898. This article provides some background on the CREATE Program and examines the development of the CREATE Environmental Justice Policy. It describes the impetus for creating the policy, namely noise impacts on low-income and minority populations resulting from the 75 th Street CIP and other CREATE Program rail projects. This article also discusses the extensive coordination among Federal and State agencies, among the public and private CREATE partners, and among Community Advisory Groups and residents, all of which led to the specific mitigations addressed in the CREATE environmental justice policy. The result of these encompassing efforts, led by Federal Highway Administration and the Illinois Department of Transportation’s Division of Public and Intermodal Transportation, is a precedent-setting framework for analyzing and, when necessary, mitigating the potential environmental justice impacts of the CREATE Program rail projects. The CREATE Environmental Justice Policy is precedent setting in a few ways: (a) it establishes policy where none currently exists and where existing highway-oriented policies do not seem appropriate or applicable; (b) it provides greater specificity with regard to what mitigation measures are “practicable” to address predicted noise impacts of CREATE Program rail projects on low-income and minority populations; (c) it clarifies the lead agencies’ intent to maintain the transportation linkage and focus when developing and evaluating practicable mitigation measures for other (i.e., non-noise) impacts; and (d) it helps assure the equity of the transportation investment by better balancing the distribution of burdens and benefits at the project level. This article identifies the steps, when considering disproportionately high and adverse impacts to low-income and/or minority populations, on how to evaluate other practicable mitigation measures with merit under EO 12898. This article also describes the lessons learned and the dialogue necessary to receive broad support from the CREATE partners for both needed rail improvements and additional mitigations to provide offsetting benefits and opportunities to enhance Chicago-area communities, neighborhoods, and residents’ quality of life. Environmental Practice 17: 256–269 (2015)

Lac‐Mégantic accident: What we learned

A tragic train derailment in Lac‐Megantic, a small Quebec community caused 47 fatalities, the destruction of part of the town and huge cleaning costs. The Transportation Safety Board of Canada (TSB) has conducted an in‐depth investigation of the causes of Lac‐Mégantic accident and has formulated recommendations. The catastrophic consequences of the Lac‐Mégantic accident and the known increase over the last several years in rail transportation of Class 3 hazardous materials has made it clear, the need to review the existing regulations and industry practices to such transportation. Canada Transport Safety Board, U.S. National Transportation Safety Board, Transport Canada, U.S. Pipeline and Hazardous Material Safety Administration, and U.S. Federal Railroad Administration are working closely to upgrade rail transport regulations to prevent similar incidents from occurring. The tragedy in Lac‐Mégantic was not caused by one single person, action, or organization. Many factors played a role, and addressing the safety issues will take a concerted effort from regulators, railways, the Association of American Railroads, shippers, tank car manufacturers, and refiners in Canada and the United States. © 2014 American Institute of Chemical Engineers Process Saf Prog 34: 2–15, 2015

Introduction of Heavy Axle Loads

The Association of American Railroads (AAR) initiated the Heavy Axle Load (HAL) Research Program in 1988 in order to “provide guidance to the North American railroad industry about whether to increase axle loads and to determine the most economic payload consistent with safety” (Kalay and Martland 2001). The research demonstrated the technical feasibility and economic desirability of increasing axle loads and the ability of technology to mitigate the adverse effects of heavier loads. In 1991, the industry decided to accept cars with 286,000 lb. gross vehicle weight (286k GVW) in interchange service. Since then, more than 90% of all bulk equipment acquired has been rated for 286k GVW. By 2010, nearly 100% of coal traffic and 30% of general freight moved in 286k loads. Technological improvements resulting from the HAL research program have been critical in enabling the industry to reduce costs of 286k operations. Stronger materials, better designs, and improved maintenance techniques reduced life cycle costs for rail and other track components. Bridge costs did not increase as much as expected, because of technological developments and better understanding of their ability to withstand HAL loads. Net benefits of HAL operations to railroads, suppliers, and their customers were approximately $6 billion between 1994 and 2010. Annual net benefits exceeded $600 million in 2010. Benefits included reductions in equipment expense, more efficient operations, and increases in line capacity. Given the technological advances in railroad engineering over the past 20 years, further increases in GVW or loading density should now be considered. OVERVIEW OF THE HAL RESEARCH PROGRAMThis paper has two major objectives. First, it estimates the net benefits achieved by increasing the maximum GVW to 286k, taking into account impacts on operations and infrastructure. Second,

Effects of wheel/rail contact patterns and vehicle parameters on lateral stability

In North American freight service, lateral instability (vehicle hunting) is normally associated with light vehicles and high-speed operations. However, recent research conducted by Transportation Technology Center, Inc. (TTCI), under the Association of American Railroads’ Strategic Research Initiatives Program, has shown that some new designs of heavy axle load freight cars are now susceptible to hunting when fully loaded at normal freight train operating speeds. Undesirable wheel/rail (W/R) contact conditions interacting with the car body dimensions and inertial parameters, combined with the characteristics of the suspensions, contribute to hunting. A summary of the investigation is presented here, which includes results of the vehicle tests, wheel and rail profile measurements and analyses, and NUCARS®1 computer simulations. The effects of the vehicle suspension parameters and car body inertial parameters, combined with undesirable W/R contact patterns, are shown to have a significant influence on the vehicle's lateral stability performance, with potential consequences for damage to both vehicles and track, and increased potential for derailment.

Properties and microstructure of high performance wheels

The methodology followed by Transportation Technology Center, Inc., to develop a pearlitic high performance wheel steel (identified as SRI) is described in the first part of this paper. Ideally, this steel will be proposed as high performance wheel steel to the Association of American Railroads (AAR). If successful, the SRI steel will be identified as AAR Class D steel. The second part of the paper provides the results of the mechanical testing of seven high performance wheels (six pearlitic and one bainitic) manufactured by different companies and are compared to the SRI steel. Some of these high performance wheel steels had been tested in heavy haul lines, but had not been tested in the USA heavy haul environment. The results in this paper indicate that the mechanical properties of the SRI steel are superior to those of AAR Class C steel. Vacuum degassing can significantly improve fatigue resistance and is recommended for the SRI steel. The experimental SRI wheels were forged in Brasil at the MWL Brasil facilities. The cleanliness and mechanical properties of the SRI wheel steels compared to the other high performance wheel steels show that among the pearlitic steels, the SRI steel has the highest cleanliness and mechanical properties.

Development and Evaluation of Advanced Wheel Steels to Prevent Wheel Failures in the North American Heavy Haul Operating Environment

This paper presents the results of metallurgical analysis and mechanical and residual stress tests for high performance wheels that are currently under test under 35-metric ton (39 ton) load axles. For this test, eight high performance wheels were tested from various suppliers including an experimental wheel developed by the Transportation Technology Center, Inc. (TTCI) under the Association of American Railroads' Strategic Research Initiatives Programme. All high performance wheels are currently under an accelerated heavy haul test at the TTCI.