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.

An important consideration when operating a fleet of passenger rail consists is the remaining service life of both the car structure and the trucks. Agencies may choose to undertake studies like this when considering a fleet wide capital improvement program, ranging from minor aesthetic upgrades to major system replacements and interior reconfigurations. With this in mind, the owner needs to determine the remaining fatigue life of the individual cars and trucks within the fleet. This paper describes the fitness-for-service (FFS) assessment performed on railcars and trucks and an example of the method applied in practice. To establish the current condition of the fleet, an initial structural and service history review was undertaken. In addition, nondestructive examinations (NDE) of a sample of cars and trucks were performed to investigate any regions that have experienced damage due to the years of service. After the baseline condition of the cars and trucks was determined, finite element analyses (FEA) were performed on both the cars and the trucks to assist in locating the potential fatigue critical regions. Strain gages and accelerometers were then installed on both the cars and trucks for field testing. Multiple runs of in-service testing were performed and a typical revenue service fatigue life of both the cars and trucks was calculated based on an S-N approach. Based on the calculated fatigue life and the current accumulated consist mileage, the remaining car and truck service lives were determined. For regions with known flaws more detailed fracture mechanics based crack growth analyses were developed to determine critical flaw sizes and their propagation times to critical from the known initial flaw sizes. Results of the FFS assessment provide information on the susceptible areas within the car structure and trucks. Depending on those results, decisions can be made on the required inspections, repairs, or decommissioning necessary to operate the fleet in the short term, while also providing valuable insight into long term fleet planning.

Concrete railroad ties have been used in increasing numbers in the U.S., particularly in high-speed rail, heavy-haul freight lines, and new track construction because of their reduced deflections, durability, and competitive cost. In-track assessment of concrete railroad ties can be a challenge, however because many exterior tie surfaces are covered by tie pads and rail or ballast. This damage may include concrete section wear from abrasion, cracking, or crumbling, or other types of defects. Damage internal to the concrete can also not be seen visually. The time and cost needed to inspect these tie surfaces means that it is not routinely performed. Non-destructive testing offers promise as a way to assess concrete tie integrity without having to remove ballast, however more information is needed to know how well non-destructive techniques work in detecting damage. Two of the most promising techniques for investigating the integrity of concrete non-destructively are ultrasonic pulse velocity and impact-echo. Ultrasonic pulse velocity (UPV) and Impact-echo (IE) were applied to investigate the uniformity of concrete railroad tie and its cavities, cracks and defects for concrete ties taken from track after service. This paper evaluated the variability of the test results in UPV and IE testing condition in which two concrete railroad ties with same manufacture and load history condition were tested in both methods. Two additional concrete ties with the same manufacture and load history as each other with visible longitudinal cracks were also examined to see how the damage affected the variability measured. For this purpose, wave pulse for every full length tie from full top, half top, longitude and two sides were measured using ultrasonic pulse (ASTM C597). Also, thickness of concrete ties on both sides, including rail seat location and the middle were assessed by standard tests method for measuring the p-wave speed and the thickness of concrete using the impact-echo method (ASTM C1383). Advice is given on how to interpret ultrasonic pulse velocity and impact-echo measurements and given the variability of the test method how to flag ties for potential deterioration given that most ties in service will not have initial measurements taken before damage for comparison.

MotivePower Incorporated (MPI) a Wabtec company and CTLGroup have completed stress testing of a new two-axle passenger locomotive truck (bogie) frame for use in North America. Testing was performed in accordance with International Union of Railways (UIC) Code 615-4 – Bogie Frame Structural Strength Tests [1]. Static testing was performed to simulate exceptional, main in-service and particular in-service loads. A three-phase dynamic fatigue test of 10 million cycles was also performed. Factors for quasi-static, dynamic and track twist (warp) loads were increased from those recommended by the UIC Code for normal operating conditions on European railways to represent North American track conditions. Significant engineering thought was invested in fixture design, with each load application and reaction point receiving careful consideration. Static testing required ten different servo-controlled loading systems to simulate independent or superimposed vertical, lateral and/or longitudinal forces. The applied loads represented tractive effort, braking effort, curving, vehicle lateral dynamics, vehicle vertical dynamics and track twist. Fatigue testing required four different servo-controlled loading systems utilizing synchronized force functions to simulate alternating quasi-static and dynamic load sequences. The apparatus also included provisions for measuring vertical reactions at each primary spring pocket. Vertical reaction loads were measured by instrumented pedestals using a full Wheatstone bridge configuration to cancel out longitudinal and lateral load effects. Prior to testing, the prototype truck frame was instrumented with 133 strain gages installed at selected points of interest. Stress values discerned from the measured strains conformed to the allowable stress criteria and compared well with those predicted by finite element analysis. Measured force reactions also showed strong correlation with predicted values. No indications of cracks were discovered during periodic non-destructive inspections. In conclusion, the UIC Code 615-4 test protocol was utilized to successfully demonstrate the strength and durability of a new two-axle passenger locomotive truck frame.

Nonlinear guided wave propagation is a field that has received considerable attention in the last few decades mainly because the use of nonlinear features of elastic waves appears very promising for Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM) of several structures. Recent findings show that the characteristics of nonlinear wave propagation significantly enhance both sensitivity and efficiency compared to more traditional NDE/SHM approaches. Nonlinear features (in particular higher harmonics generation) may be very efficient indicators of some structural states that are difficult or even impossible to be detected by other means. The complex mathematical framework governing these phenomena is the main obstacle to the widespread diffusion of these techniques; in the past investigations pertaining to higher harmonic generation have been limited in applicability to structures with simple geometries where an analytical solution for the waveguide modes was available. In the present paper the classical Semi-Analytical Finite Element (SAFE) formulation (necessary to analyze complex geometries) is extended to the nonlinear regime and is implemented into a commercial code, exploiting all its capabilities. The resulting tool is able to efficiently study the nonlinear elastic wave propagation and the internal resonance conditions in a broad spectrum of structural systems. After a brief description of the theoretical background and the proposed algorithm, a railroad track is considered as case-study. The nonlinear analysis reveals optimal combinations of primary and secondary modes and also pinpoint “false positives” where internal resonance does not occur. It is emphasized how the knowledge of these ideal combinations of modes is pivotal for the application of any NDE/SHM technique relying on nonlinear features of elastic wave propagation; in light of this fact the formulation proposed in the present work appears very promising.

A rulemaking issued by the Department of Transportation (DOT) revises Hazardous Materials Regulations (HMR) to replace the hydrostatic pressure test with appropriate nondestructive evaluation (NDE) methods. The rule change is contained in Federal Register 49 Code of Federal Regulations (CFR) Part 180.509, “Requirements for inspection and test of specification tank cars,” paragraph (e) “Structural integrity inspection tests” [1]. The CFR authorizes liquid penetrant (PT), magnetic particle (MT), radiography (RT), ultrasonic (UT), and optically aided visual testing (VT) as allowable NDE methods for structural integrity inspections and tests. Other NDE methods may be allowed under special exemption issued by the Federal Railroad Administration (FRA) Office of Safety. Also included under the requirements of 49 CFR Part 179.7 is the need to qualify not only NDE personnel, but the procedures used to perform NDE reliably. In order to be effective, federal regulations require that the NDE methods have a proven sensitivity and reliability for finding the type and size of flaws likely to cause a tank car failure. In the early 1970s, an internationally accepted quantitative approach that assesses the probability of detection (POD) was developed for the National Aeronautics and Space Association (NASA) and was published in NASA CR-2369, February 1974 [2]. Transportation Technology Center, Inc. (TTCI), under contract with the FRA, and along with industry participation, uses the NASA approach to determine the POD for various NDE methods used in the inspection of railroad tank car circumferential butt welds (girth seam welds), fillet welds, and leak test samples. The emergence of a damage tolerance approach to determine inspection intervals for an engineered structure — in this case a railroad tank car — requires the quantification of the detectable flaw size for the NDE methods used during inspection. Damage tolerance techniques have initiated an evolution in NDE understanding, methods, and requirements. National Transportation Safety Board safety recommendations R-92-21 through R-92-24 address the suggested process of performing reliable inspection of railroad tank cars based on a damage tolerance approach [3]. NDE quantification using the POD approach is a key measure of NDE effectiveness and is integral to damage tolerance requirements. TTCI, working with the FRA, Railroad Tank Car Industry and D&W Enterprises (A NDE consulting company providing expertise in the area of NDE POD), has developed baseline POD curves for the allowed NDE methods. Initial evaluations were performed on the inspection of tank car circumferential butt welds. Subsequent efforts focused on butt welds, longitudinal fillet welds and leak test samples requiring inspection under the CFR. This paper reports quantitative results obtained during this research effort that address system safety and risk analysis during handling and transportation of railroad tank cars carrying hazardous materials.

Transportation Technology Center, Inc. (TTCI) has investigated various nondestructive inspection (NDI) methods to determine if they are capable of reliably inspecting side frames, bolsters, knuckles, and couplers. The NDI methods used for this investigation include dry and wet (fluorescent) magnetic particle, liquid penetrant, alcohol wipe, visual, ultrasonic (pulse-echo and phased array), and radiography. Inspection results from all methods were used to determine which methods produced repeatable results. From the initial inspection analysis, TTCI engineers determined that the magnetic particle inspection method is the most capable for detecting defects in railroad castings. Further investigation of the magnetic particle technique was completed to develop reliable inspection methods for use on bolsters, side frames, knuckles, and couplers. Each of the inspection techniques have been used for inspections in the field. Using the results of the field tests, procedures were developed by TTCI and submitted to the Association of American Railroads’ (AAR) Coupling Systems and Truck Castings Committee for review and implementation. The inspection procedures can be used by manufacturers, railroads, and car repair shops. Limitations of the inspection procedures include the amount of time necessary to perform the inspection and the reliability of detecting certain types of defects below the surface of the casting. Although these limitations exist, the procedures developed by TTCI are expected to improve the quality of in-service castings and reduce the number of train partings and derailments due to broken or cracked components.

Magnetic particle inspection (MPI) is a nondestructive testing method used to test ferromagnetic components for surface and subsurface defects. The method, in use since the 1940’s is an efficient means of inspection. MPI as with all other inspection methods must be performed in accordance with specific steps to be effective. This paper provides an overview of the method and describes the test sequence to ensure proper inspection of components. The discussion will focus on inspection of freight car loose axles and wheel sets although the points brought forth apply to any part tested using MPI.

The Washington Metropolitan Area Transit Authority (WMATA) contracted with Booz Allen Hamilton to conduct a non-destructive structural assessment of the 2000 and 3000 series rapid transit rail cars. The main goals of the assessment were to identify any significant changes that have occurred to key elements of the car body structure since their date of manufacture and to confirm that no significant and obvious structural deterioration or damage exists. The methodology behind selecting a small representative sample of cars is discussed as an introduction to this work. The paper then discusses the process by which several critical areas were selected for non-destructive inspection. One of the biggest challenges in successfully completing this project was not interfering with WMATA’s fleet operating requirements. The use of WMATA facilities had to be coordinated to create minimum interference with WMATA’s daily maintenance activities. Also, the inspection work had to be planned in such a way as to minimize the amount of vehicle component disassembly in order to return the vehicle to revenue service as soon as possible. The inspections produced valuable results regarding the construction and condition of these cars. The structural welds of the car appear to have performed satisfactorily through the operational life of the cars to date without any significant deterioration. Some corrosion was noted in the door opening areas of the cars, particularly at the door thresholds. The findings of this report will be used to target specific areas of the car during the upcoming mid-life rehabilitation project.