No description available.

No description available.

The wheel-rail contact is at the core of all research related to vehicletrackinteraction. This tiny interface governs the dynamic performanceof rail vehicles through the forces it transmits and, like any high stressconcentration zone, it is subjected to serious damage phenomena. Thus,a clear understanding of the rolling contact between wheel and rail is keyto realistic vehicle dynamics simulation and damage analysis. In a multi-body dynamics simulation, the demanding contact problemshould be evaluated at about every millisecond for several wheel-rail pairs.Hence, a rigorous treatment of the contact is highly time-consuming.Simplifying assumptions are therefore made to accelerate the simulationprocess. This gives rise to a trade-o between the accuracy and computationaleciency of the contact model in use. Conventionally, Hertz+FASTSIM is used for calculation of the contactforces thanks to its low computational cost. However, the elliptic patchand pressure distribution obtained by Hertz' theory is often not realisticin wheel-rail contact. Moreover, the use of parabolic traction bound inFASTSIM causes considerable error in the tangential stress estimation.This combination leads to inaccurate damage predictions. Fast non-elliptic contact models are proposed by others to tacklethis issue while avoiding the tedious numerical procedures. The studiesconducted in the present work show that the accuracy of these models iscase-dependent. To improve the accuracy of non-elliptic patch and pressure estimation,a new method is proposed. The method is implemented in an algorithmnamed ANALYN. Comparisons show improvements in patch and, particularly,pressure estimations using ANALYN. In addition, an alternative to the widely-used FASTSIM is developed, named FaStrip. Unlike FASTSIM, it employs an elliptic traction boundand is able to estimate the non-linear characteristic of tangential stressdistribution. Comparisons show more accurate estimation of tangentialstress and slip velocity distribution as well as creep forces with FaStrip. Ultimately, an ecient non-elliptic wheel-rail contact model consistingof ANALYN and FaStrip is proposed. The reasonable computationalcost of the model enables it to be used on-line in dynamics simulationand its accuracy can improve the damage predictions. / <p>QC 20160202</p>

Master of Landscape Architecture / Department of Landscape Architecture/Regional and Community Planning / Blake Belanger / Metropolitan Kansas City is a growing area, and the communities are considering new transportation options including a fixed guideway system. The addition of a fixed guideway system is often seen as controversial to people of the communities it affects, and many will not be in favor of it. Rail lines are great option for transportation because they are designed for the efficiency of getting people from place to place. However, they typically do not offer much of a visual experience to commuters. Making the transportation corridor more than just a transportation corridor through interactive, art installations will open people up to the idea of a fixed guideway system, provide trail users with destinations, and provide commuters with something interesting to look at creating a vibrant, visual experience. The RIC will become a place of destinations, recreation, vibrancy, sustainable features, and visual stimulants through the connection of the rail line, MetroGreen trails, installations, and the RIC communities. Locating literature related to the commuter rail, visual design, experience, aesthetics, and sustainability helped to determine how these elements fit into this project. Conducting precedent studies helped set guidelines for the design of installations. A process of using certain specifications in ArcGIS determined general suitability for installations resulting in twenty-eight identified sites. The development of a basic design framework through a set of matrices involving installation attributes and site conditions helped to determine site suitability for specific types of installations, which allowed me to develop a design specific to the site conditions taking the number of suitable sites down to twenty-one. Each site has a set of parameters specific to each installation. Some sites are fully designed and developed, while others are to be commissioned out to artists for design and development. This set of proposals presents a vision of the RIC as a place of destinations, recreation, vibrancy, sustainable features, and visual stimulants through the connection of the rail line, MetroGreen trails, installations, and the RIC communities. The transformation of the corridor through art installations enhances people’s experience of the corridor, promotes both the rail line and the MetroGreen trails, connects people to the corridor, and encourages sustainability.

Heavy haul railway operations permit the transport of huge volumes at lower cost than other modes of transport. The low cost can only be sustained if the maintenance costs associated with such railway operations are minimised. The maintenance costs are mainly driven by wheel and rail damage in the form of wear and rolling contact fatigue (RCF). Low wear rates in the wheel-rail interface have resulted in an increase in the prevalence of rail RCF, thereby increasing rail maintenance costs. The aim of this study is to develop an approach to reduce rail RCF on South Africa’s iron ore export line by managing the worn wheel shape. This approach is developed by evaluating wheel and rail profile shapes that contribute the most to RCF initiation, studying the influence of suspension stiffness and rail profile changes as well as a redesign of the wheel profile. The influence of wheel and rail profile shape features on the initiation of rolling contact fatigue (RCF) cracks was evaluated based on the results of multibody vehicle dynamics simulations. The damage index and surface fatigue index were used as two damage parameters to assess the influence of the different features. The damage parameters showed good agreement to one another and to in-field observations. The wheel and rail profile shape features showed a correlation to the predicted RCF damage. The RCF damage proved to be most sensitive to the position of hollow wear and thus bogie tracking. RCF initiation and crack growth can be reduced by eliminating unwanted shape features through maintenance and design and by improving bogie tracking. Two potential mitigation measures had been adapted from those published in literature to reduce RCF. The mitigation measures involved changes in suspension stiffness to spread wheel wear across the tread and the use of gauge corner relief rail profiles. These mitigation measures were evaluated by means of multibody dynamics and wear maintenance costs. These mitigation measures, however, did not prove to be successful in reducing RCF initiation while maintaining a low wheel wear rate. The current operating conditions on South Africa’s iron ore line, although still not optimal overall, were found to be better in terms of their wear and RCF performance than the two proposed RCF mitigation measures. Based on the finding of the study on two RCF mitigation measures it was recommended that a conformal wheel profile be developed to spread the wheel wear across the tread to reduce the occurrence and propagation of RCF cracks, while still maintaining low wheel wear rates. A comparative study of this new wheel profile design and the current wheel profile design was therefore performed using multibody dynamics simulation together with numerical wheel wear and RCF predictions. The advantages of the conformal wheel profile design were illustrated by evaluating the worn shape and resulting kinematic behaviour of the conformal design. The conformal design had a steadier equivalent conicity progression and a smaller conicity range compared with the current wheel profile design over the wheel’s wear life. The combination of a conformal wheel profile design with 2 mm hollow wear and inadequate adherence to grinding tolerances often result in two-point contact, thereby increasing the probability of RCF initiation. The conformal wheel profile design was shown to have many wear and RCF benefits compared with the current wheel profile design. However, implementation of such a conformal wheel profile must be accompanied by improved rail grinding practices to ensure rail profile compliance. Based on these findings an approach is proposed where the conformal wheel profile design together with improved compliance of the in-service rail profiles to the target rail profile are implemented. This has the potential to reduce RCF initiation on South Africa’s iron ore export line. / Thesis (PhD)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / PhD / Unrestricted

In this dissertation, we have developed computer vision methods for measurement of rail gauge, and reliable identification and localization of structural defects in railroad tracks. The rail gauge is the distance between the innermost sides of the two parallel steel rails. We have developed two methods for evaluation of rail gauge. These methods were designed for different hardware setups: the first method works with two pairs of unaligned video cameras while the second method works with depth maps generated by paired laser range scanners. We have also developed a method for detection of rail defects such as damaged or missed rail fasteners, tie clips, and bolts, based on correlation and MACH filters. Lastly, to make our algorithms perform in real-time, we have developed the GPU based library for parallel computation of the above algorithms. Rail gauge is the most important measurement for track maintenance, because deviations in gauge indicate where potential defects may exist. We have developed a vision-based method for rail gauge estimation from a pair of industrial laser range scanners. In this approach, we start with building a 3D panorama of the rail out of a stack of input scans. After the panorama is built, we apply FIR circular filtering and Gaussian smoothing to the panorama buffer to suppress the noise component. In the next step we attempt to segment the rail heads in the panorama buffer. We employ the method which detects railroad crossings or forks in the panorama buffer. If they are not present, we find the rail edge using robust line fit. If they are present we use an alternative way: we predict the rail edge positions using Kalman filter. In the next step, common to both fork/crossings conditions, we find the adjusted positions of rail edges using additional clustering in the vicinity of the edge. We approximate rail head surface by the third degree polynomial and then fit two plane surfaces to find the exact position of the rail edge. Lastly, using rail edge information, we calculate the rail gauge and smooth it with 1D Gaussian filter. We have also developed a vision-based method to estimate the rail gauge from a pair of unaligned high shutter speed calibrated cameras. In this approach, the first step is to accurately detect the rail in each of the two non-overlapping synchronous images from the two cameras installed on the data collection cart by building an edge map, and fitting lines into the edge map using the Hough transform, and detecting persistent edge lines using a history buffer. After railroad track parts are detected, we segment rails out to find rail edges and calculate the rail gauge. We have demonstrated how to apply Computer Vision methods (the correlation filters and MACH filters in particular) to find different types of railroad elements with fixed or similar appearance, like railroad clips, bolts, and rail plates, in real-time. Template-based approaches for object detection (correlation filters) directly compare gray scale image data to a predefined model or template. The drawback of the correlation filters has always been that they are neither scale nor rotation invariant, thus many different filters are needed if either scale or rotation change. The application of many filters cannot be done in real-time. We have succeeded to overcome this difficulty by using the parallel computation technology which is widely available in the GPUs of most advanced graphics cards. We have developed a library, MinGPU, which facilitates the use of GPUs for Computer Vision, and have also developed a MinGPU-based library of several Computer Vision methods, which includes, among others, an implementation of correlation filters on the GPU. We have achieved a true positive rate of 0.98 for fastener detection using implementation of MACH filters on GPU. Besides correlation filters, MinGPU include implementations of Lucas-Kanade Optical Flow, image homographies, edge detectors and discrete filters, image pyramids, morphology operations, and some graphics primitives. We have shown that MinGPU implementation of homographies speeds up execution time approximately 600 times versus C implementation and 8000 times versus Matlab implementation. MinGPU is built upon a reusable core and thus is an easily expandable library. With the help of MinGPU, we have succeeded to make our algorithms work in real-time.

No description available.

No description available.

Ce travail réalisé dans le cadre d'une collaboration industrielle avec la société ALSTOM Transport porte sur l'étude de la dégradation des voies ferrées urbaines. Les composantes de voie retenus pour cette étude sont le rail et la dalle de voie en béton. Concernant le rail, différents problèmes sont abordés : contact roue – rail, usure du rail, usure ondulatoire du rail, et fatigue de contact de roulement (RCF) du rail. Un outil numérique avec des interfaces graphiques, nommé CONUS, est développé pour le problème de contact roue – rail et le problème d'usure du rail. Des théories classiques (Hertz, Kalker, Archard, etc.) sont implantées dans cet outil. La méthode stationnaire est implantée dans un code de calcul par éléments finis pour étudier l'état asymptotique de l'acier du rail sous le chargement répété des trains. Ceci nous permet de prédire les régimes de RCF du rail. La mécanique de l'endommagement est utilisée pour prédire la fatigue du matériau béton. Le formalisme de Marigo couplé avec le modèle d'endommagement de Mazars permet de modéliser la dégradation progressive de la rigidité du matériau sous chargement cyclique. Une campagne d'essais de fatigue du béton en flexion a été réalisée. Elle a pour but de valider le modèle théorique et d'identifier les paramètres du matériau. Le dimensionnement d'une dalle de voie en béton a fait l'objet d'une application de cette méthode. Le modèle de réseau de poutres (lattice model) a été utilisé pour étudier la propagation des fissures dans les structures en béton. Ce modèle a été implanté dans le logiciel de calcul par éléments finis, CESAR-LCPC. Les résultats numériques (propagation de fissures) obtenus pour les structures simples sous chargement statique sont en tout point comparables avec les résultats d'essais expérimentaux. Ce modèle a ensuite été utilisé pour étudier la fissuration sous chargement de fatigue. Pour cela un modèle d'endommagement simple modélisant la dégradation des éléments «poutres» s'est avéré suffisant pour décrire la cinématique de propagation des fissures / This work is part of the collaboration between the laboratory Navier (UMR ENPC /IFSTTAR/ CNRS) and ALSTOM Transport company (TGS/Trackway). It focuses on the study of the degradation of urban railways. The components of track considered in this study are the rail and the concrete slab. Regarding the rail, different problems are discussed : wheel – rail contact, rail wear, rail corrugation and rolling contact fatigue (RCF). A numerical tool with graphical interfaces, called CONUS, is developed to predict the behaviour of the wheel - rail contact, the rail wear, and the rail corrugation problems. Classical theories (Hertz, Kalker, Archard, etc...) are implemented in this tool. The stationary method is implemented in a finite element software to study the asymptotic state of the rail steel under repeated loading of trains.The damage mechanics is used to predict the fatigue life of concrete. Marigo's formalism coupled with Mazars' damage model is used to predict the gradual degradation of material stiffness under cyclic loading. A campaign of fatigue tests for concrete in bending was conducted. It aims at validating the theoretical model and identifying material parameters. We applied this method in order to design the concrete slabs of urban railway. The lattice model was used to study the crack propagation in concrete structures. This model was implemented in the finite element software, CESAR-LCPC. The numerical results obtained for simple structures under static loading are consistent with the results of laboratory experiments. This model was then used to study the crack propagation under fatigue loading. For that purpose, a simple damage model of degradation of the "beams" elements describes the kinematics of crack propagation with a satisfying accuracy

Master’s thesis deals with design of rail-to-rail second generation current conveyor in CMOS technology. Describes principles of function of different generations of current conveyors, as well as the basic principle of design of second generation current conveyor based on operational amplifier. Addresses circuit topology of input rail-to-rail stage and class AB output stage. The objective of this thesis is to design, characterize performance and create layout of second generation current conveyor with input common mode voltage rail-to-rail capability in ONSemi I3T25 technology.