Finite element analyses (FEA) were conducted in this paper to understand the underlying mechanisms contributing to a commonly observed failure mode of cut spikes used with the elastic fastening systems for wood ties. This failure mode features fatigue cracking development in the internal cross-sectional spike surfaces located approximately 1.5 inches below the top surface of a tie. Previous computational studies applied elastic material properties with “perfect” material behaviors. The study presented in this paper adopted post-elastic failure models for both the steel spike and wood tie materials, which proved key to reconstructing the observed failure mode in modeling. The commercial FE software Abaqus was employed in this study. Continuum FE models were developed for a single cut spike embedded in a wood tie. The steel spike was modeled to yield plastically upon reaching a yield strength limit. A user material subroutine documented by Abaqus was adopted to simulate the 3D orthotropic failure of the wood tie. Both the elastic properties and strength limits of the wood material were orthotropic, with the properties in the transverse direction significantly lower than those in the fiber direction. Different combinations of vertical, lateral and longitudinal forces were applied in the analyses, deforming the spike in various bending modes. The forces were increased in magnitude until the steel reached its yield strength (i.e., developed permanent plastic deformations), and the yielding locations were recorded and compared with the observed failure mode. The FEA showed that damage initiated in the wood tie being pressed by the spike with sufficiently large forces and that wood damage preceded steel yielding. The farther the wood material deteriorated from the top down, the lower the steel yielding location was in the spike shaft. Longitudinal forces were reacted to in the weaker transverse direction of the wood tie and therefore resulted in lower damage initiation forces and lower steel yielding locations than lateral forces did. It was concluded that the orthotropic wood tie failure condition and a substantial presence of the longitudinal force were necessary conditions for the spike to initiate failure at about 1.5 inches below the top surface of a tie. This corroborated the findings in a derailment investigation involving the spike failure. The lateral force alone unlikely caused this failure mode, but the presence of a lateral force on the spike appeared to decrease the magnitude of the longitudinal force needed to initiate damage in the spike.

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.

Bearing degradation and defects can result in a premature failure. Water ingress into the bearing is a factor for premature degradation, as water may corrupt internal parts and degrade the bearing grease. This paper presents the investigation of the properties of grease degradation from bearings with water-related degradations. This research provides insight into the internal state of bearings that have been replaced due to grease degradation as a result of water ingress. Separately, the railroad industry has observed bearing roller “bluing” or “lube staining.” This discoloration may be a harmless surface effect, or it may be similar to heat bluing. Determining true metallurgical effects may lead to the understanding between these two different types of “bluing”. To study bearings with water-related lubrication degradation, grease samples were collected from two populations of bearing lubrication at bearing service locations. One population contains bearings identified with water-related damage, and a second population is a control set of bearings. Primary grease analysis was done per ASTM 7918, providing metrics of wear, contamination, consistency, and oxidative properties. Additional testing was performed where results indicated utility; including measurements of anti-oxidant remaining in grease and microscopic analysis of wear particles in the grease. “Bluing” or “lube stain” bearing components were examined through analysis of lubrication and metallurgical metrics. Collections of samples from bearing shops included representative small amounts of grease and “blued” steel parts from bearings exhibiting surface discoloration. A second sample set included steel parts and grease samples from a control set of bearings. A third set of rollers were heat blued in the lab. Lube stained rollers and control set rollers were tested for metallurgical changes. Analysis of the bearing steel consisted of hardness and micro-hardness testing of polished samples, examination to compare microstructural features, and residual stress tests. The tests conducted in the investigation of water-related bearing grease degradation indicate a difference between bearings with “Water-Etch” and “Non-Verified” degradation modes based on ferrous debris levels in the grease. This difference is due to wear of the bearing material deposited in the grease. The tests conducted in the investigation of lube stain in bearings show lube stain does not affect any tested metallurgical material properties, other than surface discoloration.

This paper examines alternative, improved materials for truck castings. The first part looks at steels that would not require post-weld heat treatment after repair welding. The second part investigates specific applications for temperatures below −50 °F. The rapid, dramatic temperature changes that occur during welding can form brittle phases or cracking in some steels. The weld has three areas of differing structure: the weld, the heat affected zone (HAZ), and the parent metal. The maximum hardness occurs in the HAZ and is the limiting factor in determining weldability. An ultraweldable steel is a steel that does not require post-weld heat treatment. Many steels were evaluated for their chemical composition and susceptibility to cracking; those that were likely to form brittle phases were eliminated from consideration. Four low alloy steels and one carbon steel were selected as being potentially ultraweldable. To evaluate the ultraweldability of these steels, groove welds and two types of spot welds were made on the five candidate alloys. The welds were then sectioned and prepared for microstructural and microhardness evaluation. Microhardness readings were taken across the weld, spanning the weld, HAZ, and base material. Three of the steels formed hard, brittle phases during most of the tests. This indicates these materials are not ultraweldable. Two of the low alloy steels did meet the requirements for ultraweldability. Future work in this area would include producing truck castings from these materials. At low temperatures, plain carbon steels, such as the types used in truck castings, can fracture in a brittle manner, with no visible deformation. The material property of deforming without fracture is toughness or ductility. Using materials that retain their toughness in low temperatures could prevent brittle failures of truck castings. Six grades of steel currently used in low temperature applications were selected for this research. Specimens from each of the six materials were evaluated for tensile properties at multiple temperatures. Charpy impact specimens were tested at temperatures ranging from −20 °F to −120 °F. The measured room temperature tensile properties of each of the six steels met or exceeded the requirements for Grade B+, the steel currently used for truck castings. Four of the steels showed impact energies far above that of the current Grade B+, but two of them gave consistently higher impact energies than all others. These would be the best candidates for future work in this area. Future work would involve producing full size truck castings from one or more of these alloys, then testing them for fatigue performance, preferably at low temperatures.

This paper presents the development and demonstration of an efficient reliability-based tool for the reinforced earth retaining wall design in heavy haul railway. Here, two major internal failure modes, rupture and pullout, are the focus in the demonstration. The First-Order Reliability Method (FORM) is adopted to estimate the probability of failure for each failure mode, and is implemented in a spreadsheet. The reliability analysis is conducted with the consideration of the effect of uncertainty in the reinforcement length, horizontal and vertical spacing between steel strips, tensile strength of steel strips as well as the material property of the backfills. Using this design tool, a few candidate designs can be easily obtained by meeting the acceptable probability of failure and the final design is determined based on cost. The results obtained using FORM are also verified by comparing with those from Monte Carlo simulation. This design tool is shown to be simple to use in the retaining wall design of the railway engineering.

The Federal Railroad Administration’s Office of Research and Development is conducting research into passenger locomotive fuel tank crashworthiness. A series of impact tests is being conducted to measure fuel tank deformation under two types of dynamic loading conditions — blunt and raking impacts. The results of this research program assist in development of appropriate standards for puncture resistance requirements to be applied to alternatively-designed fuel tanks, such as on diesel multiple unit (DMU) passenger rail equipment. This paper describes the results of the first blunt impact test performed on a DMU fuel tank. On June 28, 2016, FRA performed a dynamic impact test of a fuel tank from a DMU rail vehicle. The test was performed at the Transportation Technology Center (TTC) in Pueblo, Colorado. An impact vehicle weighing approximately 14,000 pounds and equipped with a 12-inch by 12-inch impactor head struck the bottom surface of a DMU fuel tank mounted vertically on an impact wall. The impact occurred on the bottom of the fuel tank at a location centered on two baffles within the fuel tank. The target impact speed was 11.5 mph, and the measured impact speed 11.1 mph. The test resulted in a maximum indentation of approximately 8 inches, the bottom of the tank bending away from the wall, and buckling of several internal baffles. Following the test, the tank was cut open to inspect the damage to the internal structure. This revealed that the buckling behavior of the baffles was isolated to the baffles immediately adjacent the impact location, each one buckling as the tank deformed inward. Prior to the test, finite element analysis (FEA) was used to predict the behavior of the tank during the test. The FE model of the tank required material properties to be defined in order to capture plastic deformation. The combination of metal plasticity, ductile failure, and element removal would permit the model to simulate puncture for this tank at sufficiently-high impact speeds. The pre-test FE model results compared very favorably with the test measurements, and both the pre-test model and the test resulted in similar modes of deformation to the DMU fuel tank. Following the test, material coupons were cut from undamaged areas of the fuel tank and subjected to tensile testing. The post-test FE model was updated with the material behaviors from the post-test material testing. This test is part of a research program investigating puncture resistance of passenger locomotive fuel tanks. The objective of this research program is to establish the baseline puncture resistance of current locomotive fuel tanks under dynamic impact conditions and to develop performance requirements for an appropriate level of puncture resistance in alternative fuel tank designs, such as DMU fuel tanks. Future tests are planned within this research program. The lessons learned during the series of tests support finite element (FE) modeling of impact conditions beyond what was tested. Additional tests investigating the puncture resistance of fuel tanks during sideswipe or raking collisions are also planned.

This paper presents the result of an evaluation program for the condition of the SEPTA Broad Street subway car shells and their capability to perform during an extended period of revenue service. SEPTA currently is evaluating various system upgrades to address equipment obsolescence and reliability, and wanted to verify that the current car shells are expected to be serviceable during this extended period. The evaluation focused on two aspects of the 1982-built car shells. First, what is the current and predicted condition of the shells and, second, how does the performance of the current car shell design compare to present day designs and requirements? Four sets of activities were done as part of this project. One-third of the fleet was randomly chosen for visual inspections. Service-induced cracks were identified at two locations: in ring welds below the doors, and on the side sill between the corner posts and the anti-climbers. The ring weld cracks have been identified on a small number of cars in the past, and SEPTA continues to monitor and reinforce these areas. The cracks between the corner posts and anticlimbers are also being monitored; to date, none of these cracks has progressed to the point that repair is required. In parallel with the visual inspections, the car shell camber and doorway dimensions were measured on approximately 10% of the fleet. All the measured vehicles had positive camber; doorway dimensions were uniform, except for scattered individual measurements that were car-specific. This part of the evaluation concluded that the car shells are not undergoing significant degradation or cracking. One car was instrumented with strain gauges in potential high-stress areas, and then operated at simulated full passenger-load weight over the Broad Street route. Cyclic strains imposed by simulated revenue service were measured and converted to stresses. This testing confirmed high stresses at the joint between the side sill and the body bolster. The lifetime limiting location on the car shells is in the ring welds below the doors, consistent with the results of the visual inspections. Using conservative assumptions of continuous full passenger loading and minimum material properties, the predicted lifetime to the initiation of visible cracks in this area is 7–14 years of service. This independent evaluation is consistent with the actual experience, and provided confidence in the analysis protocol. SEPTA is monitoring this location and repairing cracks as required. Evaluation of the car shell design with regard to performance in a collision revealed that, unlike most other cars of its era, the Broad Street car shell contains provisions to manage energy absorption during a low-speed collision. Records obtained from a car repair shop showed that, when a Broad Street car had a significant non-revenue end collision, these provisions worked as intended to localize the deformation. In similar collisions, the Broad Street car shell will not perform significantly different from cars built to current industry practices. Results from this study indicate that with continued attention to car shell condition, including regular inspections and limited repairs, the Broad Street car shells will continue to be safe and serviceable for an extended period.

The main purpose of this ongoing study is to investigate the effect of heat generation within a railroad thermoplastic elastomer suspension element on the thermal behavior of the railroad bearing assembly. Specifically, the purpose of this project is to quantify the heat generated by cyclic loading of the elastomer suspension element as a function of load amplitude, loading frequency, and operating temperature. The contribution of the elastomer pad to the system energy balance is modeled using data from dynamic mechanical analysis (DMA) of the specific materials in use for that part. DMA is a technique that is commonly used to characterize material properties as a function of temperature, time, frequency, stress, atmosphere or a combination of these parameters. DMA tests were run on samples of pad material prepared by three different processes: injection molded coupons, transfer molded coupons, and parts machined from an actual pad. The results provided a full characterization of the elastic deformation (Energy Storage) and viscous dissipation (Energy Dissipation) behavior of the material as a function of loading frequency, and temperature. These results show that the commonly used thermoplastic elastomer does generate heat under cyclic loading, though the frequency which produces peak heat output is outside the range of common loading frequency in rail service. These results can be combined with a stress analysis and service load measurements to estimate internally generated heat and, thus, enable a refined model for the evolution of bearing temperature during operation.

Research to facilitate industry efforts to safely use natural gas as a locomotive fuel is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. This research is being conducted cooperatively with the Association of American Railroads (AAR). The research results are being shared with the AAR’s Natural Gas Fuel Tender Technical Advisory Group (NGFT TAG), which includes AAR, Member Railroads, and FRA, with support from ARA and Volpe Center. The NGFT TAG is developing industry requirements, including crashworthiness requirements, for revenue-service natural gas fuel tenders. Five accident scenarios have been drafted by the NGFT TAG: a train-to-train collision, a grade-crossing collision, rollover, shell impact, and head impact. Each scenario includes a description of the equipment, the impact conditions, and the prescribed outcome. Conceptually, these tender scenarios parallel the scenarios described in 49 CFR Part 229 Appendix E for locomotive crashworthiness. The focus of the NGFT TAG discussions has expanded to include alternative static requirements. Conceptually, the tender static requirements parallel the requirements for locomotive crashworthiness in AAR S-580. Requirements in S-580 for locomotive structure include static load capacities, material properties, and material thicknesses. For conventionally-designed locomotives, meeting the static requirements of S-580 is accepted as meeting the dynamic requirements of Appendix E. The tender static requirements under development are intended to provide the same level of crashworthiness as the previously proposed dynamic requirements. The primary advantage of static crashworthiness requirements is that compliance can be shown with classical closed-form engineering analyses. A disadvantage is that design features are presumed, such as the inclusion and location of collision posts in a conventional locomotive design. Design features are not presumed in dynamic crashworthiness requirements; however, compliance must be shown with a design-specific validated computer simulation model. So while dynamic requirements allow for a wide range of design approaches, showing compliance often requires extensive effort. This paper focuses on technical information to help support development of alternative static requirements for the train-to-train collision scenario. The goal of the static requirements is to provide the same level of crashworthiness as the dynamic requirements under discussion by the NGFT TAG. Tender features capable of providing the desired level of performance are proposed. These features have been selected such that a tender with these features would be crashworthy-compatible with a wide range of new and existing locomotive structural designs.

The primary purpose of this study is to use a nano-scale optical surface profilometer to assess the feasibility of such instruments in measuring localized friction coefficient on railways, beyond what can be commonly measured by tribometers used by the railroad industry. One of the important aspects of moving freight and passengers on railways is the ability to manage and control the friction between the rails and wheels. Creating a general friction model is a challenging task because friction is influenced by various factors such as surface metrology, properties of materials in contact, surface contamination, flash temperature, normal load, sliding velocity, surface deformation, inter-surface adhesion, etc. With an increase in the number of influencing factors, the complexity of the friction model also increases. Therefore, reliable prediction of the friction, both theoretically and empirically, is sensitive to how the model parameters are measured. In this study, the surface characteristics of four rail sections are measured at 20 microns over a rectangular area using a portable Nanovea JR25 optical surface profilometer and the results were studied using various statistical procedures and Fractal theory. Furthermore, a 2D rectangular area was measured in this study because 1D height profile doesn’t capture all the necessary statistical properties of the surface. For surface roughness characterization, the 3D parameters such as root-mean-square (RMS) height, skewness, kurtosis and other important parameters are obtained according to ISO 25178 standard. To verify the statistical results and fractal analysis, a British Pendulum Skid Resistance Tester is used to measure the average sliding coefficients of friction based on several experiments over a 5 cm contact length for the four rail sections selected for the tests. The results indicate that rail surfaces with lower fractal dimension number have a lower friction. The larger fractal dimension number appears to be directly proportional to larger microtexture features, which potentially increase friction.

The Federal Railroad Administration’s Office of Research and Development is conducting research into passenger locomotive fuel tank crashworthiness. A series of impact tests is being conducted to measure fuel tank deformation under two types of dynamic loading conditions — blunt and raking impacts. This program is intended to result in a better understanding of design features that improve the puncture resistance of passenger locomotive fuel tanks. One reason for performing this program is to aid in development of appropriate standards for puncture resistance to be applied to alternatively-designed fuel tanks, such as on diesel multiple unit (DMU) passenger rail equipment. This paper describes the results of the third blunt impact test of retired F-40 locomotive fuel tanks. The test setup was designed for the Transportation Technology Center (TTC) in Pueblo, Colorado, to impart blunt impacts to the bottom of each fuel tank specimen. The specimens tested to date are from FRA-owned retired F-40 passenger locomotives. To conduct the test, each tank was emptied of fluid and mounted on a crash wall with the bottom surface exposed. A rail cart modified with a “rigid” indenter measuring 12 inches by 12 inches, was released to impact the bottom of fuel tank at a target impact speed. The first two tests, conducted on October 8 and 9, 2013, were designed to impact the center of two different tank designs. Tests were conducted at impact speeds of 4.5 and 6.2 mph and caused maximum residual dents of 5 inches and 1.5 inches, respectively. On August 20, 2014 the test of fuel tank 234 was conducted to impact the tank off-center between two baffles. Force-deformation measurements were collected for each tank during the three tests. The series of tests provide information regarding the influence of tank design on puncture resistance. In the test of tank 234, the target impact speed was 12.5 mph, and the actual impact occurred at 11.2 mph. The test resulted in a residual dent depth of approximately 9 inches, and buckling of several internal baffles. The impact did not result in puncture of the tank. Following the test, the tank was cut open to permit examination of the baffles. This examination revealed a different baffle geometry than was modeled based on pre-test measurements. Finite element analysis (FEA) was used to predict the behavior of the tank during the test. The FE model of the tank required several material properties to be defined in order to capture puncture behavior. The combination of metal plasticity, ductile failure, and element removal would permit the model to simulate puncture for this tank. Following the test, the tank was cut open, revealing a different baffle arrangement than had been initially thought. The post-test FE model was then updated to include the actual baffle arrangement of tank 234. With the actual baffle arrangement included in the model, the FE results are in fairly good agreement with the test. Additional changes to the ductile failure criterion were also made in the post-test model. The objective of this research program is to establish the baseline puncture resistance of current passenger locomotive fuel tanks under dynamic impact conditions and to develop performance requirements to ensure an appropriate level of puncture resistance in alternative fuel tank designs, such as DMU fuel tanks.

This paper presents a study of the fatigue life (i.e. number of stress cycles before failure) of Class K cast iron conventional and modified railroad bearing adapters for onboard monitoring applications under different operational conditions based on experimentally validated Finite Element Analysis (FEA) stress results. Currently, freight railcars rely heavily on wayside hot-box detectors (HBDs) at strategic intervals to record bearing cup temperatures as the train passes at specified velocities. Hence, most temperature measurements are limited to certain physical railroad locations. This limitation gave way for an optimized sensor that could potentially deliver significant insight on continuous bearing temperature conditions. Bearing adapter modifications (i.e. cut-outs) were required to house the developed temperature sensor which will be used for onboard monitoring applications. Therefore, it is necessary to determine the reliability of the modified railroad bearing adapter. Previous work done at the University Transportation Center for Railway Safety (UTCRS) led to the development of finite element model with experimentally validated boundary conditions which was utilized to obtain stress distribution maps of conventional and modified railroad bearing adapters under different service conditions. These maps were useful for identifying areas of interest for an eventual inspection of railroad bearing adapters in the field. Upon further examination of the previously acquired results, it was determined that one possible mode of adapter failure would be by fatigue due to the cyclic loading and the range of stresses in the railroad bearing adapters. In this study, the authors experimentally validate the FEA stress results and investigate the fatigue life of the adapters under different extreme case scenarios for the bearing adapters including the effect of a railroad flat wheel. In this case, the flat wheel translates into a periodic impact load on the bearing adapter. The Stress-Life approach is used to calculate the life of the railroad bearing adapters made out of cast iron and subjected to cyclic loading. From the known material properties of the adapter (cast iron), the operational life is estimated with a mathematical relationship. The Goodman correction factor is used in these life prediction calculations in order to take into account the mean stresses experienced by these adapters. The work shows that the adapters have infinite life in all studied cases.

The KENTRACK program is a finite element based railway trackbed structural design program that can be utilized to analyze trackbeds having various combinations of all-granular and asphalt-bound layered support. It is applicable for calculating compressive stresses at the top of subgrade, indicative of potential long-term trackbed settlement failure. Furthermore, for trackbeds containing an asphalt layer, it is applicable for calculating tensile strains at the bottom of the asphalt layer, indicative of potential fatigue cracking. The program was recently expanded to include both English and international units. A procedure has been incorporated to provide a path to save results in a text formation in post-Windows XP operating systems. More importantly, properties of performance graded (PG) asphalt binders and the Witczak E* predictive model have been incorporated in the 4.0 Version of the program. Component layers of typical trackbed support systems are analyzed while evaluating the significance of layer thicknesses and material properties on design and predicted performance. The effect of various material parameters and loading magnitudes on trackbed design and evaluation, as determined and predicted by the computer program, are presented. Variances in subgrade modulus and axle loads and the incorporation of a layer of asphalt within the track structure have significant effects on subgrade vertical compressive stresses and predicted trackbed service lives. The parameter assessments are presented and evaluated using sensitivity analysis.

The Federal Railroad Administration’s Office of Research and Development is conducting research into fuel tank crashworthiness. A series of impact tests are planned to measure fuel tank deformation under two types of dynamic loading conditions — blunt and raking impacts. This paper describes the results of the first set of blunt impact tests for two retired EMD F-40 locomotive fuel tanks, Tank 232 and Tank 202. On October 8, 2013 and October 9, 2013, the FRA performed impact tests on two conventional passenger locomotive fuel tanks at the Transportation Technology Center (TTC) in Pueblo, Colorado. Each fuel tank was emptied of fluid and mounted on a crash wall with the bottom surface exposed. A rail cart modified with a “rigid” indenter was released to impact the center of the bottom of each fuel tank at about 6 mph. A center-impact on Tank 232 was chosen to impact between two baffles. A center-impact on Tank 202 was chosen to impact on a baffle. In the first test, Tank 232 was impacted by the indenter at 4.5 mph. The maximum residual indentation on the bottom of the tank measured approximately 5 inches. The tank deformed across the middle longitudinal span of the tank forming a diamond-shaped indention. In the second test, Tank 202 was impacted by the indenter at 6.2 mph. The maximum residual indentation on the bottom of the tank measured approximately 1.5 inches. The bottom of the tank deformed with an “X” shape spanning out from the location of square indenter at the center of the tank. Post-test autopsies revealed the deformation of the interior structures, i.e. baffles and attachments. There was no damage to the baffles in Tank 232. Deformation to the interior structure of Tank 202 was limited to the baffle directly beneath the impact location, which folded in the area near the impact location. Material coupons were cut and tensile testing performed to determine the properties of the materials used in each tank. Prior to the test, computer models were developed from measurements taken on the test articles. Material properties were estimated based on Brinell hardness measurements. Computer analyses were conducted to determine the conditions for the test, i.e. instrumentation, location of impact, target impact speeds and to predict the deformation behavior of the tank. Post-test, the resulting stress-strain relationships for the bottom sheets and baffles of both tanks were used to update the finite element models of the two tanks. The models were also updated to reflect the actual geometry of the tanks as confirmed by measurements of the tank interiors. The results of the finite element (FE) models run at the test conditions with the updated tank details are compared with the results from the test itself. Specifically, the deformation progression and the residual dent depth are compared between the tests and the models. In accidents, fuel tanks are subjected to dynamic loading, often including a blunt or raking impact from various components of the rolling stock or trackbed. Current design practice requires that fuel tanks have minimum properties adequate to sustain a prescribed set of static load conditions. Current research is intended to increase understanding of the impact response of fuel tanks under dynamic loading.

Insulated rail joints (IJs) are critical components of railroad track infrastructure. It is essential for IJs to maintain railroad track’s structural continuity while having an important role in track circuit design and implementation. The structural integrity and performance of IJs have been recognized as a key interest area by the railroads as a result of increasing average axle loads and train traffic. While there are many different designs offered by various manufacturers around the globe, the main approach utilized by heavy haul railroads in the US, Canada and many other countries has been to use adhesively bonded insulated joint bars between two rails. This approach offers the benefit of a composite assembly where the continuous bond between rails and bars offer a geometrically uninterrupted transfer of loads between rails and bars. The main components of a bonded IJ are joint bars, insulation material, adhesive, endpost, and bolts or other fasteners. This paper summarizes recent design improvements on these components. The main focus areas of the research are bar design, bar material selection, insulator and adhesive selection and using a novel endpost design for load transfer between two rails. Track support conditions’ impact on IJ performance has also been considered as a factor influencing IJ performance in track and incorporated in the study. The impact of insulation material selection on IJ performance is discussed. Finite element analysis was used extensively in the study where the analysis results were supported by laboratory and field testing. The results of the study indicate dynamic stresses in bonded IJs can be reduced nearly 40% in joint bars by a combination of design improvements on IJ components. Improved bar material properties are expected to lead to considerably reduced risk of bar fatigue failures in track.

Currently, there are divergent design and performance demands on railway infrastructure components due to increasing freight axle loads and cumulative gross tonnages, as well as increased investment in high-speed passenger rail development in North America. The divergence in loading and performance demands on shared infrastructure arises from the fact that while high-speed passenger trains exert lower loads at relatively high speeds, freight trains exert high loads at relatively low speeds. Improvements in infrastructure component designs are needed to achieve increased durability and tighter geometric tolerances. According to a rail industry survey administered by University of Illinois at Urbana-Champaign (UIUC) in 2008, Rail Seat Deterioration (RSD) is the principal performance problem limiting the service life of concrete crossties in North America. Rail infrastructure researchers and industry experts agree that abrasive wear may occur due to relative motion between the rail pad and concrete crosstie rail seat, potentially resulting in RSD. The complex tribological process of abrasion is further complicated and expected to be accelerated by the presence of abrasive fines and moisture, creating 3-body wear condition. Lack of understanding of the abrasion mechanism has resulted in a sub-optimal and iterative design of ties, causing reduced service life. This paper summarizes our efforts in understanding the effect of changing the mix design of concrete on the abrasion resistance of the rail seat which will eventually help us in modeling abrasive wear in RSD by constructing a mathematical relationship between the rail seat wear rate and input parameters including concrete mix design, mechanical/tribological properties of materials involved, normal load applied, presence of moisture, and abrasive fines. To simulate abrasive wear in RSD, a simple experiment is being carried out using a rotating wheel (lapping machine) capable of abrading concrete samples as a part of UIUC’s Small-Scale Abrasion Resistance Test (SSART). The objective of this research is to develop wear performance curves (e.g. wear depth versus load/time/cycles) for lab specimens developed from concrete crosstie mix designs that are currently being used in the industry, as well as for the evaluation of new mix designs. These data will help the rail industry in mechanistically designing concrete crossties by improving the understanding of materials used for concrete crosstie mix designs, with the objective of decreasing life cycle costs for the crosstie and fastening system. Preliminary SSART results are in agreement with relevant literature documenting the relationships between concrete mix designs and curing conditions and the resulting rate of abrasion.

Track substructure design is an often overlooked step in the design of railroad track. The lack of consideration for the substructure when designing track results in greater maintenance demands due to inadequate track substructure performance. Railway track is a stable structure with a progressive failure process that allows track engineers to manage the degradation of the track through maintenance. However, increasing demands for track availability from high traffic volumes require that track maintenance be minimized while ensuring safety. Additionally, developing high speed rail and intercity passenger rail on existing corridors necessitates higher levels of substructure performance due to tighter track roughness tolerances. Reduction in maintenance needs can be achieved by ensuring that new construction and rehabilitation projects be designed to provide a stable track structure throughout the design life. Lack of readily available data for substructure materials is a drawback to the use of track design methods. This paper provides a summary of several available substructure track design methods along with the required data for design. The track design data is related to track measurements that could be used to determine much of the information necessary for design of track rehabilitation. Track load-deflection data could be used to develop much of the needed design data while ground penetrating radar could support delineation of similar track segments. Benefits of track structure design include knowledge of expected life, reduced maintenance, material properties for quality control, and development of material properties that could permit application of performance based contract specifications.

A cause of failure within end-of-car (EOC) arrangements for cushioned cars with F-shank couplers is that of the yoke bolt failing in shear. This mode of EOC failure is of particular concern due to the concealed nature of the bolt not easily allowing for early detection of the onset of failure. To this end, a finite element analysis (FEA) was performed on a 7/8” bolt and F-bracket assembly to determine the stress state developed within the bolt in an effort to understand the potential cause or causes for the bolt failure. Several parameters, including bolt strength, bolt preload (initial torque), and external loading were varied to determine their effects on bolt performance. The subsequent results indicate that both inherent strength and initial preload have a significant effect on whether a bolt can effectively withstand the various external loading conditions encountered in the field. In addition, it is also apparent that some of the simulation loading scenarios analyzed contain the potential to initiate bolt shearing during operation. From these results, some failure mechanism theories are proposed to describe the type of failure encountered by each bolt grade, either ductile or brittle depending on the inherent material properties.

This study investigates the effects of the material properties and the fatigue behaviors in the SM490A material weld specimens, which are made by same method of railway vehicle structure, due to the heat-treatment and the grinding. In the fatigue behavior, the heat treatment affects the fatigue life. The S-N curves of both base metal specimens and butt weld specimens are reversed at some cycle by with or without heat treatment. The grindings on the beads make the fatigue limit decrease in the all specimens. But the reinforcement removed, the fatigue limit increases at the high cycle. Also, this study investigates the fatigue life estimation by examining butt weld bead profiles. The butt weld beads, which are welded by semi-robot method, have non-uniform bead profiles described by angle θ, radius ρ and height h. The stress concentration factors K t , are changed by each different θ, ρ and h. In combination among θ, ρ and h, as θ becomes lower and ρ and h become higher, K t increases. And the fatigue life for the AAY specimens can be estimated very closely using only butt weld bead profiles.