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Severe railcar responses can result from crosslevel and vertical rail inputs. At low speeds rail joint excitation can coincide with the roll natural frequency of a vehicle. At high speeds, dynamic effects can cause high wheel loads and harsh ride for sensitive cargos. Computer simulation of these and other vertical dynamic effects cans assist in design selections of vehicle components and diagnosis of troublesome vehicle responses. Many dynamic models available today lack the complexity to analyze accurately some of the important dynamic effects. In this report a 28-degree-of-freedom railcar model has been developed to analyze the vertical dynamic responses of railcars subjected to random and deterministic track inputs. This model features carbody vertical bending and torsional modes, multiple component trucks and suspensions, and rail irregularity inputs at each of the eight wheels. Simulation results for a 100-ton vehicle operating on harmonic track inputs compare favorably with the AAR Flexible Carbody Model. Other simulations on random track evaluate the influence of auxiliary viscous stabilizers and increased payloads on railcar responses. These simulations demonstrate the effectiveness of the computer simulation as a design and analysis tool. / M.S.

The primary purpose of this study is to evaluate the use of Doppler Lidar sensors for assessing track weakening that would indicate early stages of track instability. Such track weakening could lead to gage widening or track buckling due to rail thermal expansion. A series of tests are performed at the Transportation Technology Center's High Tonnage Loop, where two sections of track are "doctored" to have weaker lateral strength, one on a tangent and another one in a curve. Multiple tests are performed at speeds ranging from 10 – 40 mph, during which the lateral and vertical deflections of the rail are measured under the weight of the passing wheels of a heavily-loaded gondola. The track weakness is created by removing the rail spikes from eight consecutive ties. The measurements from the soft sections are compared with a track section on a tangent that is determined to have nominally sufficient ("good") stiffness. The measurement system consists of four Doppler Lidar units, two oriented toward the rail gage face to measure lateral rail movement, and two directed to the top of the rail to measure vertical rail movement. The combination of the vertical and lateral measurements is used as an indicator of a lack of rail stability if larger-than-normal movement of the rail is detected in either direction. The data collected is analyzed through various methods designed to differentiate sections of track including Gaussian Mixture Model sorting algorithms, inspection via Short Time Fourier Transforms, Discrete Wavelet Transforms, and manual inspection. None of the methods can be done automatically; they each require a different amount of setup and pre-processing before the raw data can be made suitable for the analysis offered by each. The pre-processing can account for dropped data and can be used to identify some false positives such as switches or lubricators. The test results indicate that the system provides a distinctly different measurement in the sections that are doctored to have less track stability than the section with nominally sufficient stiffness. The detection of the loose track in the tangent sections, however, proves to be less reliable. For those, a mostly ad hoc approach is necessary to match the measured data with video images to pinpoint the exact location of the measurements. It is not clear to what extent such approaches would be feasible in practice. Further evaluations of the test data may be used to shed more light on practical analysis methods—possibly wavelets—that are more automated and less ad hoc. They can also provide alternative system setups or designs of experiments for future tests at TTC or on revenue service tracks. / Master of Science / The purpose of this study is to evaluate the effectiveness of a set of Doppler Lidar sensors for their ability to determine the locations of weaker sections of railroad track. These weaker sections could cause damage to the track or passing trains by deforming or buckling under load. A set of tests are performed at the Transportation Technology Center's High Tonnage Loop to evaluate these capabilities. The track had two sections, one of curved track the other of straight track, where the rail was purposefully weakened by removing retaining spikes from the railroad ties. The weakened sections were created by removing the vertical retaining spikes in eight consecutive ties. The tests were conducted at speeds of between 10 to 40 mph, and the sensors measured both the vertical and lateral movement of both rails. The results of these measurements were compared with the unaffected rail. The collected data is analyzed using various data processing techniques. These techniques included using a sorting algorithm to find sections of track with different characteristics as well as inspecting the time and frequency content of the data. None of these methods are automated, and each requires specific setup and adjustment to be effective. The data also needs to be prepared by correcting for any missing or incorrect data points. The tests indicate that the system is able to differentiate between the purposefully weakened track and the rest of the track, however the clearest results of this were for the weakened track in the curve. The straight track results were able to be found with the addition of aligning the video, Lidar, and GPS data sets. It is not clear whether the system could be improved to detect this type of weakness in straight track in practice. Additional testing and evaluation could serve to expand the range of data analysis methods used in differentiating the track conditions and could serve to automate the process. Additionally, alternative test setups could provide further information as to the capabilities of the sensors to detect different types of weakened track.

On open-deck railroad bridges, the crossties (sleepers) are directly supported by the bridge superstructure and anchored with deck tie fasteners such as hook bolts. These fasteners provide lateral resistance for the bridge ties. Currently there are no provisions to assist in the calculation of lateral resistance provided by railroad ties on open-deck bridges, and as a result there are no specific requirements for the spacing of deck tie fasteners. This has led to different design practices specific to each railroad, and inconsistent fastener spacing in existing railroad bridges. A research plan was conducted to experimentally quantify the lateral resistance of timber crossties on open-deck plate girder bridges using different wood species and types of fasteners. Experimental tests were conducted on five different species of timber crossties (beech, sycamore, southern pine, Douglas-fir, and oak) with three different types of fasteners (square body hooks bolt, forged hook bolts, and Quick-Set Anchors). A structural test setup simulated one half of an open-deck bridge with a smooth-top steel plate girder, and hydraulic actuators to apply both vertical and horizontal load to a railroad tie specimen. The three main contributions to lateral resistance on open-deck bridges were identified as friction resistance between tie and girder due to vertical load from a truck axle, resistance from the fastener, and resistance from dapped ties bearing against the girder flange. Initial testing isolated each component of lateral resistance to determine the friction coefficient between tie and girder as well as resistance from just the fastener itself. Additional testing combined both vertical load and fastener to determine whether or not the overall resistance is simply the sum of the friction and fastener resistance. Results indicated that friction resistance varies based on the magnitude of vertical axle load, species of wood, and creosote retention in the tie, while fastener resistance varies based on type of fastener and lateral displacement of the tie. An approximation of the lateral resistance as a function of lateral displacement was established depending on the vertical load, type of hook bolt, and coefficient of friction between tie and girder. The approximation was used in a structural analysis, which modelled a section of railroad track as a beam supported by non-linear springs spaced at discrete distance. Based on anticipated lateral loads, the analysis was used to determine a preliminary chart for a safe and economical fastener spacing for a railroad track based on type of hook bolt, creosote retention, tie species, and curvature of bridge. / Master of Science / On open-deck railroad bridges, the crossties are directly supported by the steel bridge girders and connected to the girders with fasteners as hook bolts. These fasteners provide lateral resistance for the bridge ties. Currently there are no provisions to assist in the calculation of lateral resistance provided by railroad ties on open-deck bridges, and as a result there are no specific requirements for the spacing of deck tie fasteners. This has led to different design practices specific to each railroad, and inconsistent fastener spacing in existing railroad bridges. A research plan was conducted to experimentally quantify the lateral resistance of timber crossties on open-deck plate girder bridges using different wood species and types of fasteners. Experimental tests were conducted on five different species of timber crossties (beech, sycamore, southern pine, Douglas-fir, and oak) with three different types of fasteners (square body hooks bolt, forged hook bolts, and Quick-Set Anchors). A structural test setup simulated one half of an open-deck bridge with a smooth-top steel plate girder, and hydraulic actuators to apply both vertical and horizontal load to a railroad tie specimen. The three main contributions to lateral resistance on open-deck bridges were identified as friction resistance between tie and girder due to vertical load from a truck axle, resistance from the fastener, and resistance from dapped ties bearing against the girder flange. Initial testing isolated each component of lateral resistance to determine the friction coefficient between tie and girder as well as resistance from just the fastener itself. Additional testing combined both vertical load and fastener to determine whether or not the overall resistance is simply the sum of the friction and fastener resistance. Results indicated that friction resistance varies based on the magnitude of vertical axle load, species of wood, and creosote retention in the tie, while fastener resistance varies based on type of fastener and lateral displacement of the tie. An approximation of the lateral resistance as a function of lateral displacement was established depending on the vertical load, type of hook bolt, and coefficient of friction between tie and girder. The approximation was used in a structural analysis, and the analysis was used to determine a preliminary chart for a safe and economical fastener spacing for a railroad track based on type of hook bolt, creosote retention, tie species, and curvature of bridge.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The vibrations and noise “pollution” that rail vehicles produce have become of particular concern in recent years. More pressure is being placed on operators of trains and trams (especially those operating in urban environments) to reduce their impact on neighbouring infrastructure. This project investigated the infrastructure available for vibration and noise mitigation and generated material models for some of the materials used in these types of rail infrastructure. The most common type of rail infrastructure used in South Africa is ballasted sleepers. Rail pads are sometimes used to reduce the transmitted vibration of these sleepers; this study focused on the materials used in the manufacture of these pads. Since most of these materials can be described as resilient/viscoelastic, the study of literature regarding these materials is essential within the scope of this project. Models found in literature were adapted by the addition of a non-linear stiffness element to account for the material behaviour at higher preloads. Three commercially available materials were tested and optimisation algorithms applied to determine their material coefficients (damping and stiffness), focusing on the preload and frequency dependency of these coefficients. / AFRIKAANSE OPSOMMING: Die vibrasie en geraas “besoedeling” wat spoor voertuie genereer het in die in die afgelope paar jare van kritieke belang geword. Meer druk word op operateurs van treine en trems geplaas (veral die operateurs met operasies in stedelike gebiede) om hulle impak op aangrensende infrastruktuur te verminder. Hierdie projek is dus daarop gemik om te bepaal watter infrastuktuur beskikbaar is vir die vermindering van vibrasie en geraas asook die ontwikkeling van materiaal modellle vir sommige van die materiale wat gebruik word in hierdie tipes van spoor infrastruktuur. Die mees algemene spoor infrastruktuur wat gebruik word in Suid-Afrika is dwarslêers met ballas. Spoor blokke word soms gebruik om die oordrag van vibrasies te verminder vir hierdie dwarslêers en daarom het hierdie studie fokus geplaas op die materiale wat gebruik word in die vervaardiging van hierdie blokke. Aangesien die meeste van hierdie materiale beskryf kan word as veerkragtig/visco, is 'n literatuurstudie oor hierdie materiale noodsaaklik binne die bestek van hierdie projek. Modelle wat gevind is in die literatuur is aangepas deur 'n nie-lineêre styfheids element by te voeg wat voorsiening maak vir die materiale se gedrag by hoër voorspannings. Drie algemene kommersieël beskikbare materiale is getoets en optimeringsprossesse is toegepas om hulle materiaal koëffisiënte (demping en styfheid) te bepaal met die klem geplaas op die voorspanning en frekwensie afhanklikheid van hierdie koëffisiënte.

Thesis (Master of Engineering in Mechanical Engineering)--Cape Peninsula University of Technology, 2018. / South Africa’s railway system is the most highly developed in Africa. There are different kinds of transport systems in South Africa but rail transport is considered as one of an important element of the country’s transport infrastructure. In South Africa, over 2.4 million passengers make use of rail transport to get them to their destinations. However, evidence shows that train accidents have become a common occurrence across the country. Train-related accidents such as collision, derailments, platform change incidents and commuter accidents, cost South Africa over R400 million per year. The analysis of derailments indicates that the most significant single contributor to derailments is rail breaks. This contrasts considerably with prescribed relevant local and international benchmarks, which show a much lower percentage of derailments due to rail break. The frequency of derailments due to rail breaks in South Africa seems to be higher in the northern than the southern region. Furthermore, the proportion of rail breaks that result in derailment is considerably higher than the set benchmarks and therefore, if there is a rail break, then the probability of this translating into a derailment is astonishingly high. Equally, the high incidence of derailments due to rail breaks is affected by the train length and axle load and further exacerbated by the absence of track circuitry. Since derailments are a direct function of the incidence of rail breaks, focus is required to characterize the factors causing defects on rail lines. This study investigated steel rail material by characterising the piece of the damaged rail with the aim to gain a better understanding of the wear mechanism. Chemical composition analysis of steel rail sample was conducted with the use of a Scanning Electron microscopy. Hardness of steel rail was measured with a Vickers hardness tester. An Optical Microscopy was used to examine the microstructure features of the worn rail samples. This study discovered that the worn out rail, which was produced from high carbon steel with pearlite and ferrite microstructure, undergoes decarburization and a plastic deformation process. The decarburization process happens when the rail track is heated to 700 oC and above when the carbon atoms at the surface interact with the atmospheric gases and are removed from the steel as a gaseous phase. Plastic deformation is created when the iron atoms are heated above the elastic point resulting in the permanent movement of iron atoms.

Thesis (Ph.D.)--Ohio University, August, 2009. / Release of full electronic text on OhioLINK has been delayed until September 1, 2014. Includes bibliographical references (leaves 200-205)

Thesis (Ph.D.)--Ohio University, August, 2009. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until September 1, 2014. Includes bibliographical references (leaves 200-205)

Thesis (M. Arch.)--University of Hong Kong, 2001. / Includes bibliographical references.

Thesis (M. Arch.)--University of Hong Kong, 1996. / Includes bibliographical references.