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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Improved performance of railcar/rail truck interface components

Story, Brett Alan 15 May 2009 (has links)
The objective of this research is to improve the railcar/rail truck interface by developing a low maintenance bearing interface with a favorable friction coefficient. Friction and wear at the center bowl/center plate bearing interface cause high turning moments around curved track, wear of truck components, and increased detrimental dynamic effects. The recommended improvement of the rail truck interface is a set of two steel inserts, one concave and one convex, that can be retrofit to center bowls/center plates. The insert geometry addresses concerns about maintaining favorable pressure distribution on existing components, minimizing overall height increase to accommodate existing infrastructure, and retaining railcar stability. The stability of the railcar upon the design inserts has been ensured when the instantaneous center of rotation of the railcar body is above the railcar center of gravity. The damping ratio provided by the frictional moment within center bowl is 240 and eliminates the possibility of dynamic amplification. Using a 90 inch radius of curvature ensures stability and requires a 0.5 inch diameter reduction of the existing center plate for a gap of 1/16 inch. The increase in railcar height for the specific design is 0.71 inches which can be absorbed by either grinding of the center plate or new manufacturing dimensions. The design is feasible for small travel values corresponding to small vertical gaps at the side bearings. In addition to geometry alterations, the bearing surfaces are coated with a protective metallic layer. The literature suggests that optimum friction coefficients between bearing elements in the center bowl/center plate interface may reduce turning moments of the truck, wear of truck components, and detrimental dynamic effects such as hunting. Axial-torsional tests determined friction coefficient estimates and wear properties for a matrix of various metallic protective coatings and steel. Tungsten carbide-cobalt-chrome has a favorable coefficient of 0.3 under standard center bowl/center plate contact conditions.
2

IN SITU RAILWAY TRACK FAULT DETECTION USING RAILCAR VIBRATION

Pagnutti, Jeffrey L. 17 March 2014 (has links)
This thesis investigates the development of an automated fault detection system developed for a novel lightweight railway material haulage system; in particular, the study aims to detect railway track faults at the incipient stage to determine the feasibility of maintenance decision support, ultimately with the function of preventing catastrophic failure. The proposed approach is an extension of the current state of the art in fault detection of unsteady machinery. The most common railway track faults associated with train derailment were considered; namely, horizontal and transverse crack propagation, mechanical looseness, and railbed washout were the faults of interest. A series of field experiments were conducted to build a database of vibration, speed, and localization data in healthy and faulted states. These data were used to develop, investigate, and validate the effectiveness of various approaches for fault detection. A variety of feature sets and classification approaches were investigated to determine the best overall configuration for the fault detector. The feature sets were used to condense data segments and extract characteristics that were sensitive to damage, but insensitive to healthy variations due to unsteady operation. The pattern recognition classifiers were used to categorize new data members as belonging to the healthy class or faulted class. The fault detection results from the proposed approach were promising. The feasibility of an automated online fault detection system for the lightweight material haulage system examined in this study was confirmed. The conclusions of this research outline the major potential for an iv effective fault detection system and address future work for the practical implementation of this system.
3

Tactical Network Flow and Discrete Optimization Models and Algorithms for the Empty Railcar Transportation Problem

Suharko, Arief Bimantoro 04 February 1998 (has links)
Prior to 1980, the practice in multilevel autorack management was to load the railcars at various origin points, ship them to the destination ramps, unload them, and then return each car to the loading point where it originated. Recognizing the inefficiency of such a practice with respect to the fleet size that had to be maintained, and the associated poor utilization due to the excessive empty miles logged, a consolidation of the railcars was initiated and completed by February 1982. Under this pooling program, a central management was established to control the repositioning of three types of empty railcars for eight principal automobile manufacturers. Today, the practice is to consolidate the fleets of all automobile manufacturers for each equipment type, and to solve the distribution problem of repositioning empty multilevel autoracks of each type from points at which they are unloaded to automobile assembly facilities where they need to be reloaded. Each such problem is referred to in the railroad industry as a repositioning scenario. In this dissertation, we present two tactical models to assist in the task of centrally managing the distribution of empty railcars on a day-to-day basis for each repositioning scenario. These models take into account various practical issues such as uncertainties, priorities with respect to time and demand locations, multiple objectives related to minimizing different types of latenesses in delivery, and blocking issues. It is also of great practical interest to the central management team to have the ability to conduct various sensitivity analyses in its operation. Accordingly, the system provides for the capability to investigate various what-if scenarios such as fixing decisions on running a specified block of cars (control orders) along certain routes as dictated by business needs, and handling changes in supplies, demands, priorities, and transit time characteristics. Moreover, the solution methodology provides a flexible decision-making capability by permitting a series of runs based on a sequential decision-fixing process in a real-time operational mode. A turn-around response of about five minutes per scenario (on a Pentium PC or equivalent) is desired in practice. This dissertation begins by developing several progressive formulations that incorporate many practical considerations in the empty railroad car distribution planning system. We investigate the performance of two principal models in this progression to gain more insights into the implementation aspects of our approach. The first model (TDSS1: Tactical Decision Support System-1) considers all the identified features of the problem except for blocking, and results in a network formulation of the problem. This model examines various practical issues such as time and demand location-based priorities as well as uncertainty in data within a multiple objective framework. In the second model (TDSS2: Tactical Decision Support System-2), we add a substantial degree of complexity by addressing blocking considerations. Enforcement of block formation renders the model as a network flow problem with side-constraints and discrete side-variables. We show how the resulting mixed-integer-programming formulation can be enhanced via some partial convex hull constructions using the Reformulation-Linearization Technique (RLT). This tightening of the underlying linear programming relaxation is shown to permit the solution of larger problem sizes, and enables the exact solution of certain scenarios having 5,000 - 8,000 arcs. However, in order to accommodate the strict run-time limit requirements imposed in practice for larger scenarios having about 150,000 arcs, various heuristics are developed to solve this problem. In using a combination of proposed strategies, 23 principal heuristics, plus other hybrid variants, are composed for testing. By examining the performance of various exact and heuristic procedures with respect to speed of operation and the quality of solutions produced on a test-bed of real problems, we prescribe recommendations for a production code to be used in practice. Besides providing a tool to aid in the decision-making process, a principal utility of the developed system is that it provides the opportunity to conduct various what-if analyses. The effects of many of the practical considerations that have been incorporated in TDSS2 can be studied via such sensitivity analyses. A special graphical user interface has been implemented that permits railcar distributors to investigate the effects of varying supplies, demands, and routes, retrieving railcars from storage, diverting en-route railcars, and exploring various customer or user-driven fixed dispositions. The user has the flexibility, therefore, to sequentially compose a decision to implement on a daily basis by using business judgment to make suggestions and studying the consequent response prompted by the model. This system is currently in use by the TTX company, Chicago, Illinois, in order to make distribution decisions for the railroad and automobile industries. The dissertation concludes by presenting a system flowchart for the overall implemented approach, a summary of our research and provides recommendations for future algorithmic enhancements based on Lagrangian relaxation techniques. NOTE: (03/2011) An updated copy of this ETD was added after there were patron reports of problems with the file. / Ph. D.
4

Estudo comparativo entre critérios de fadiga multiaxial aplicados ao contato roda-trilho : A comparative study of multiaxial fatigue criteria applied to the wheel-rail contact / A comparative study of multiaxial fatigue criteria applied to the wheel-rail contact

Fumes, Fabiano Gonzaga, 1986- 24 August 2018 (has links)
Orientador: Auteliano Antunes dos Santos Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T19:33:54Z (GMT). No. of bitstreams: 1 Fumes_FabianoGonzaga_M.pdf: 12049048 bytes, checksum: df4dc1dd45d74bbdc31c6a5893edd4fe (MD5) Previous issue date: 2014 / Resumo: Este trabalho apresenta a comparação entre os diversos critérios de fadiga multiaxial de alto ciclo aplicados ao problema de contato roda-trilho. Para isto, é utilizado um modelo elastoplástico tridimensional de elementos finitos capaz de permitir o cálculo tanto das tensões geradas pelo rolamento de uma roda livre de tensões residuais de fabricação como de uma roda que contenha as tensões residuais provenientes do processo de tratamento térmico, obtidas através de uma simulação térmico-estrutural. Estes dois cenários são avaliados segundo critérios de fadiga multiaxial baseados tanto em planos críticos, como Dang Van, Matake e McDiarmid, quanto nos baseados em invariantes do tensor de tensões, como Sines, Crossland e Kakuno Kawada. Pela natureza da fadiga de contato, que não possui condição de vida infinita, é estimado para cada critério um número de ciclos para o aparecimento das trincas. Como resultado, observa-se que para alguns critérios como Dang Van, Sines e Kakuno-Kawada, a vida em fadiga é beneficiada pelo processo de tratamento térmico, enquanto para os demais, as tensões residuais de fabricação provocam uma redução no número de ciclos para o aparecimento das trincas / Abstract: This work presents a comparison of different high cycle multiaxial fatigue criteria, applied to wheel- rail contact. For this, it is used a three-dimensional elastoplastic finite element model able to calculate stresses generated by the rolling of a wheel free of residual stresses from manufacturing process and also by a wheel containing the residual stresses from heat treatment process, generated by a thermal-structural simulation. These two scenarios are evaluated according to multiaxial fatigue criteria based on critical planes, as Dang Van, Matake and McDiarmid, and also based on the invariants of the stress tensor, as Sines, Crossland and Kakuno Kawada. Due to the nature of rolling contact fatigue, which has no condition of infinite life, a number of cycles for crack appearance are estimated for each criterion. It can be notice that for some criteria, such as Dang Van, Sines and Kakuno-Kawada, fatigue life is benefited by the heat treatment process, while for others the residual stresses from manufacturing promote a reduction in the number of cycles / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica
5

Pohonný a brzdový systém motorového vozu železnice pro muzeum průmyslových železnic / The propulsion and braking system of a motor vehicle for a railroad museum of industrial railways

Gerec, Matúš January 2017 (has links)
This thesis deals with the design of the propulsion and braking system for narrow gauge railcar. It contains the design of hydrostatic drive system with closed-loop hydraulic circuit. Then thesis describes the concept of propulsion system placement in the frame of the railcar and design of the braking system.
6

MODELAGEM E IMPLEMENTAÇÃO DE UM SISTEMA MULTIAGENTE PARA SELEÇÃO DE FALHAS E TOMADA DE DECISÃO EM VIRADORES DE VAGÕES. / MODELING AND IMPLEMENTING A MULTIAGENT SYSTEM FOR FAULT SELECTION AND DECISION MAKING IN WAGON VIRATORS.

FARIAS, Osevaldo da Silva 09 February 2009 (has links)
Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-08-16T14:43:36Z No. of bitstreams: 1 Osevaldo.pdf: 5559401 bytes, checksum: 1ce073c772c3403a0b7875f9f9a13ed9 (MD5) / Made available in DSpace on 2017-08-16T14:43:36Z (GMT). No. of bitstreams: 1 Osevaldo.pdf: 5559401 bytes, checksum: 1ce073c772c3403a0b7875f9f9a13ed9 (MD5) Previous issue date: 2009-02-09 / FAPEMA, CAPES / This work leads to the modeling and implementation of a multi-agent application of faults selection and decision making for VALE’s rotary railcar dumpers. The work explore development approaches and knowledge-based achtectures aiming to SADDEM build, a multi-agent system applyed to decision making in ore unload cells. The particularities of cognitives agents structures are based on Jess inference engine in order to link decisions and maintain plans recommendations made by the system. The ontology is developed throught elicitation of information and knowledge during interviews and VV311-K01 car positioner set operating activities. The artifacts produced during the development clycle phases employs PASSI methodology technics, Artificial Intelligence and support engineering to software development using JADE framework. The real time module is linked to the software of supervision and monitoring of the unloading cell productions of VALE. / Este trabalho apresenta a modelagem e implementação de um aplicação multiagente para a seleção de falhas e tomada de decisão em viradores de vagões da VALE. A proposta investiga abordagens de desenvolvimento e arquiteturas baseadas no conhecimento para criação do SADDEM, um sistema multiagente aplicado ao apoio a decisão em células de descarga de minério. As particularidades das estruturas cognitivas de agentes são baseadas no mecanismo inferência Jess, objetivando encadear decisões e recomendações de planos de manutenção feitas pelo sistema. A ontologia do sistema é elaborada por meio das informações e conhecimento eliciados durante entrevista e atividades operacionais referentes ao conjunto carro posicionador observadas no equipamento virador de vagões VV311- K01. Os artefatos produzidos durante as fases do ciclo de desenvolvimento têm a aplicação das técnicas da metodologia PASSI, Inteligência Artificial e das engenharias de apoio ao desenvolvimento de software com uso do framework JADE. O módulo de tempo real do sistema está vinculado ao software de supervisão e monitoramento das células de produção do setor de descarga de minério da VALE.
7

Modellierung, Simulation und Bewertung parallel-hybrider Antriebskonfigurationen für dieselhydraulische Triebwagen im Nah- und Regionalverkehr

Kache, Martin 09 October 2014 (has links) (PDF)
Ausgangspunkt der Untersuchung ist die Frage, ob Hybridkonzepte auf hydrostatischer Grundlage eine realistische Alternative zu elektrohybriden Antriebskonfigurationen für Dieseltriebwagen sein können. Die Untersuchung dieser Fragestellung erfolgt mit Hilfe von Simulationsmodellen, die auf der 1-d-Simulationsumgebung Imagine.Lab AMESim beruhen. Zunächst wird die fahrdynamische und antriebstechnische Modellierung eines dieselhydraulischen Regionaltriebwagens unter Berücksichtigung einer energiesparenden Fahrweise dargestellt. Ausgehend von Massenbilanzen werden untereinander vergleichbare Hybridkonfigurationen auf hydrostatischer (Gasdruckspeicher), elektrostatischer (Doppelschichtkondensatoren) und elektrochemischer (Li-Ionen-Speicher) Basis entwickelt. Die Modellierung der hydraulischen und elektrischen Antriebsstränge wird eingehend diskutiert. Die abgeleiteten Hybridkonfigurationen werden anschließend bezüglich spezieller Fahrspiele und Betriebskonzepte detailliert untersucht, um auf dieser Grundlage günstige Parametrierungen der Systeme ableiten und die günstigste Betriebsstrategie identifizieren zu können. Anschließend wird eine umfangreiche Analyse des Verhaltens der verschiedenen Hybridkonfigurationen auf ausgewählten realen Nahverkehrsstrecken vorgenommen. Im Rahmen der durchgeführten Simulationen wird schließlich das Kraftstoffeinsparpotential in Abhängigkeit von Streckenprofil, Hybridkonfiguration und Zugart ermittelt und verglichen.
8

Resource Allocation on Networks: Nested Event Tree Optimization, Network Interdiction, and Game Theoretic Methods

Lunday, Brian Joseph 08 April 2010 (has links)
This dissertation addresses five fundamental resource allocation problems on networks, all of which have applications to support Homeland Security or industry challenges. In the first application, we model and solve the strategic problem of minimizing the expected loss inflicted by a hostile terrorist organization. An appropriate allocation of certain capability-related, intent-related, vulnerability-related, and consequence-related resources is used to reduce the probabilities of success in the respective attack-related actions, and to ameliorate losses in case of a successful attack. Given the disparate nature of prioritizing capital and material investments by federal, state, local, and private agencies to combat terrorism, our model and accompanying solution procedure represent an innovative, comprehensive, and quantitative approach to coordinate resource allocations from various agencies across the breadth of domains that deal with preventing attacks and mitigating their consequences. Adopting a nested event tree optimization framework, we present a novel formulation for the problem as a specially structured nonconvex factorable program, and develop two branch-and-bound schemes based respectively on utilizing a convex nonlinear relaxation and a linear outer-approximation, both of which are proven to converge to a global optimal solution. We also investigate a fundamental special-case variant for each of these schemes, and design an alternative direct mixed-integer programming model representation for this scenario. Several range reduction, partitioning, and branching strategies are proposed, and extensive computational results are presented to study the efficacy of different compositions of these algorithmic ingredients, including comparisons with the commercial software BARON. The developed set of algorithmic implementation strategies and enhancements are shown to outperform BARON over a set of simulated test instances, where the best proposed methodology produces an average optimality gap of 0.35% (compared to 4.29% for BARON) and reduces the required computational effort by a factor of 33. A sensitivity analysis is also conducted to explore the effect of certain key model parameters, whereupon we demonstrate that the prescribed algorithm can attain significantly tighter optimality gaps with only a near-linear corresponding increase in computational effort. In addition to enabling effective comprehensive resource allocations, this research permits coordinating agencies to conduct quantitative what-if studies on the impact of alternative resourcing priorities. The second application is motivated by the author's experience with the U.S. Army during a tour in Iraq, during which combined operations involving U.S. Army, Iraqi Army, and Iraqi Police forces sought to interdict the transport of selected materials used for the manufacture of specialized types of Improvised Explosive Devices, as well as to interdict the distribution of assembled devices to operatives in the field. In this application, we model and solve the problem of minimizing the maximum flow through a network from a given source node to a terminus node, integrating different forms of superadditive synergy with respect to the effect of resources applied to the arcs in the network. Herein, the superadditive synergy reflects the additional effectiveness of forces conducting combined operations, vis-à-vis unilateral efforts. We examine linear, concave, and general nonconcave superadditive synergistic relationships between resources, and accordingly develop and test effective solution procedures for the underlying nonlinear programs. For the linear case, we formulate an alternative model representation via Fourier-Motzkin elimination that reduces average computational effort by over 40% on a set of randomly generated test instances. This test is followed by extensive analyses of instance parameters to determine their effect on the levels of synergy attained using different specified metrics. For the case of concave synergy relationships, which yields a convex program, we design an inner-linearization procedure that attains solutions on average within 3% of optimality with a reduction in computational effort by a factor of 18 in comparison with the commercial codes SBB and BARON for small- and medium-sized problems; and outperforms these softwares on large-sized problems, where both solvers failed to attain an optimal solution (and often failed to detect a feasible solution) within 1800 CPU seconds. Examining a general nonlinear synergy relationship, we develop solution methods based on outer-linearizations, inner-linearizations, and mixed-integer approximations, and compare these against the commercial software BARON. Considering increased granularities for the outer-linearization and mixed-integer approximations, as well as different implementation variants for both these approaches, we conduct extensive computational experiments to reveal that, whereas both these techniques perform comparably with respect to BARON on small-sized problems, they significantly improve upon the performance for medium- and large-sized problems. Our superlative procedure reduces the computational effort by a factor of 461 for the subset of test problems for which the commercial global optimization software BARON could identify a feasible solution, while also achieving solutions of objective value 0.20% better than BARON. The third application is likewise motivated by the author's military experience in Iraq, both from several instances involving coalition forces attempting to interdict the transport of a kidnapping victim by a sectarian militia as well as, from the opposite perspective, instances involving coalition forces transporting detainees between interment facilities. For this application, we examine the network interdiction problem of minimizing the maximum probability of evasion by an entity traversing a network from a given source to a designated terminus, while incorporating novel forms of superadditive synergy between resources applied to arcs in the network. Our formulations examine either linear or concave (nonlinear) synergy relationships. Conformant with military strategies that frequently involve a combination of overt and covert operations to achieve an operational objective, we also propose an alternative model for sequential overt and covert deployment of subsets of interdiction resources, and conduct theoretical as well as empirical comparative analyses between models for purely overt (with or without synergy) and composite overt-covert strategies to provide insights into absolute and relative threshold criteria for recommended resource utilization. In contrast to existing static models, in a fourth application, we present a novel dynamic network interdiction model that improves realism by accounting for interactions between an interdictor deploying resources on arcs in a digraph and an evader traversing the network from a designated source to a known terminus, wherein the agents may modify strategies in selected subsequent periods according to respective decision and implementation cycles. We further enhance the realism of our model by considering a multi-component objective function, wherein the interdictor seeks to minimize the maximum value of a regret function that consists of the evader's net flow from the source to the terminus; the interdictor's procurement, deployment, and redeployment costs; and penalties incurred by the evader for misperceptions as to the interdicted state of the network. For the resulting minimax model, we use duality to develop a reformulation that facilitates a direct solution procedure using the commercial software BARON, and examine certain related stability and convergence issues. We demonstrate cases for convergence to a stable equilibrium of strategies for problem structures having a unique solution to minimize the maximum evader flow, as well as convergence to a region of bounded oscillation for structures yielding alternative interdictor strategies that minimize the maximum evader flow. We also provide insights into the computational performance of BARON for these two problem structures, yielding useful guidelines for other research involving similar non-convex optimization problems. For the fifth application, we examine the problem of apportioning railcars to car manufacturers and railroads participating in a pooling agreement for shipping automobiles, given a dynamically determined total fleet size. This study is motivated by the existence of such a consortium of automobile manufacturers and railroads, for which the collaborative fleet sizing and efforts to equitably allocate railcars amongst the participants are currently orchestrated by the \textit{TTX Company} in Chicago, Illinois. In our study, we first demonstrate potential inequities in the industry standard resulting either from failing to address disconnected transportation network components separately, or from utilizing the current manufacturer allocation technique that is based on average nodal empty transit time estimates. We next propose and illustrate four alternative schemes to apportion railcars to manufacturers, respectively based on total transit time that accounts for queuing; two marginal cost-induced methods; and a Shapley value approach. We also provide a game-theoretic insight into the existing procedure for apportioning railcars to railroads, and develop an alternative railroad allocation scheme based on capital plus operating costs. Extensive computational results are presented for the ten combinations of current and proposed allocation techniques for automobile manufacturers and railroads, using realistic instances derived from representative data of the current business environment. We conclude with recommendations for adopting an appropriate apportionment methodology for implementation by the industry. / Ph. D.
9

Modellierung, Simulation und Bewertung parallel-hybrider Antriebskonfigurationen für dieselhydraulische Triebwagen im Nah- und Regionalverkehr

Kache, Martin 03 June 2014 (has links)
Ausgangspunkt der Untersuchung ist die Frage, ob Hybridkonzepte auf hydrostatischer Grundlage eine realistische Alternative zu elektrohybriden Antriebskonfigurationen für Dieseltriebwagen sein können. Die Untersuchung dieser Fragestellung erfolgt mit Hilfe von Simulationsmodellen, die auf der 1-d-Simulationsumgebung Imagine.Lab AMESim beruhen. Zunächst wird die fahrdynamische und antriebstechnische Modellierung eines dieselhydraulischen Regionaltriebwagens unter Berücksichtigung einer energiesparenden Fahrweise dargestellt. Ausgehend von Massenbilanzen werden untereinander vergleichbare Hybridkonfigurationen auf hydrostatischer (Gasdruckspeicher), elektrostatischer (Doppelschichtkondensatoren) und elektrochemischer (Li-Ionen-Speicher) Basis entwickelt. Die Modellierung der hydraulischen und elektrischen Antriebsstränge wird eingehend diskutiert. Die abgeleiteten Hybridkonfigurationen werden anschließend bezüglich spezieller Fahrspiele und Betriebskonzepte detailliert untersucht, um auf dieser Grundlage günstige Parametrierungen der Systeme ableiten und die günstigste Betriebsstrategie identifizieren zu können. Anschließend wird eine umfangreiche Analyse des Verhaltens der verschiedenen Hybridkonfigurationen auf ausgewählten realen Nahverkehrsstrecken vorgenommen. Im Rahmen der durchgeführten Simulationen wird schließlich das Kraftstoffeinsparpotential in Abhängigkeit von Streckenprofil, Hybridkonfiguration und Zugart ermittelt und verglichen.

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