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A computational approach to the prediction of wheel wear profilesWang, Bor-Tsuen 01 August 2012 (has links)
Wheel wear profiles are interesting for both economic and performance reasons. A good wheel profile design should be able to resist wear and to allow stable vehicle running. The ability to resist wear reduces the wheel reprofiling and replacement cost. The ability to allow stable vehicle running is important for safety and ride quality. In this work, a wear model based upon the work done in the wheel/rail contact patch is used to predict wheel wear profiles. The effects of train dynamic response, random rail alignment and the non-linearity of wheel/rail contact geometry are included The distribution of contact patch work is obtained by discretized method and applied to the wheel wear problem. Using the contact patch work wear model, consecutive wheel wear profiles for tread contact and slight flange contact are predicted. These analytical wear profiles match well with experimental results and other analytical approaches. / Master of Science
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Prediction of wheel wear profiles by analytical methodsDávila, Carlos G. January 1986 (has links)
A method is presented for the prediction of the wear history of a train wheel by a numerical simulation. The method consists of three fundamental steps. First, the wheel/rail contact geometry is characterized. Contact points, Herzian contact patch area and creep coefficients are determined as functions of the wheelset lateral position. Second, a time history of the wheelset positions and velocities is determined from a simulation of the vehicle response to a specified track input. Finally, a wear algorithm dependent on the geometry and the dynamics is used to compute the amounts of material to be removed at the discrete points describing the wheel profile. The process is repeated recurrently to simulate the gradual wearing of the wheel.
The method has been tested with several different wear models and it has been found that worn profiles are relatively insensitive to the selection of wear model. A parametric study on the effect of creep coefficient and payload on wear rate has been used to differentiate the wear models.
Results include predictions of AAR and CN worn wheel profiles. The predictions show that the CN profile wears parallel to the new profile. This trend has been observed in practice. / M.S.
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Desenvolvimento do aço microligado para rodas ferroviárias / Development of microalloyed steel for railway wheelsVillas Bôas, Renato Lyra 07 January 2010 (has links)
Orientador: Paulo Roberto Mei / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T10:24:52Z (GMT). No. of bitstreams: 1
VillasBoas_RenatoLyra_M.pdf: 13424471 bytes, checksum: c7a6d60275922ab9255b8f8e74fd29e1 (MD5)
Previous issue date: 2010 / Resumo: Neste trabalho foi desenvolvido um aço microligado com 0,7% de carbono para fabricação de rodas ferroviárias. Tomou-se como base um aço classe C da norma AAR M-107 e adicionou-se nióbio e molibdênio. A pesquisa foi realizada em duas etapas distintas. A primeira etapa estudou-se o efeito da adição de nióbio e molibdênio no aço com 0,7% de carbono antes e após a deformação por laminação, simulando o forjamento real das rodas ferroviárias produzidas na MWL Brasil. Com os dados disponíveis passou-se à segunda etapa da pesquisa onde foram fabricadas e ensaiadas rodas ferroviárias na MWL Brasil usando um aço com composição química semelhante à utilizada na primeira etapa para observar o efeito do nióbio e molibdênio nas mesmas. Os aços foram austenitizados a 1250 °C para solubilização do nióbio na austenita e deformados a partir de 1200 °C. Na primeira etapa o aço foi laminado em 4 passes sofrendo uma deformação total na espessura de 67% e resfriado ao ar. Na segunda etapa, o aço foi forjado pelo processo de fabricação usado pela MWL Brasil. Após o tratamento térmico, foram realizados ensaios de dureza da perlita, tração, impacto, tenacidade à fratura, além de microscopia ótica e medida do tamanho de grão austenítico. Observou-se aumento no limite de escoamento (8,5%), ductilidade (15%), energia de impacto (29%), tenacidade à fratura (33%) e temperabilidade pela microadição de nióbio e molibdênio, mostrando que esses elementos podem melhorar o desempenho das rodas ferroviárias atualmente produzidas. / Abstract: In this work it was developed a microalloyed steel with 0.7% carbon to manufacture railway wheels. It was taken as basis a steel class C of standard AAR M-107 and added niobium and molybdenum. The research was conducted in two stages. The first step was studied the effect of the addition of niobium and molybdenum on 0.7% C steel before and after deformation by rolling, simulating the actual forging of railroad wheels process in MWL Brasil. With the available data the second stage of the research was conducted, manufacturing and testing railway wheels in MWL Brasil, using a steel with similar chemical composition to that was used in the first step to observe the effect of niobium and molybdenum in them. The steels were austenitized at 1250 °C for niobium solubilization in austenite and deformed from 1200 °C. In the first stage, the steels were rolled at 4 passes undergoing a total deformation of 67% in thickness and aircooled. In the second step, the steels were forged by MWL Brasil manufacturing process. After heat treatment, tests on pearlite hardness, tensile, impact, fracture toughness were performed. Microstructure was observed by optical microscopy and the austenite grain size was measured. It was observed an increasing on the yield strength (8,5%), ductility (15%), impact energy (29%), fracture toughness (33%) and hardenability by niobium and molybdenum microalloying, showing that these elements can improve the performance of railway wheels nowadays produced by MWL Brasil. / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica
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Probabilistic modeling of microgrinding wheel topographyKunz, Jacob Andrew 20 September 2013 (has links)
This work addresses the advanced probabilistic modeling of the stochastic nature of
microgrinding in the machining of high-aspect ratio, ceramic micro-features. The
heightened sensitivity of such high-fidelity workpieces to excessive grit cutting force
drives a need for improved stochastic modeling. Statistical propagation is used to
generate a comprehensive analytic probabilistic model for static wheel topography.
Numerical simulation and measurement of microgrinding wheels show the model
accurately predicts the stochastic nature of the topography when exact wheel
specifications are known. Investigation into the statistical scale affects associated
microgrinding wheels shows that the decreasing number of abrasives in the wheel
increases the relative statistical variability in the wheel topography although variability in
the wheel concentration number dominates the source of variance. An in situ
microgrinding wheel measurement technique is developed to aid in the calibration of the
process model to improve on the inaccuracy caused by wheel specification error. A
probabilistic model is generated for straight traverse and infeed microgrinding dynamic
wheel topography. Infeed microgrinding was shown to provide a method of measuring
individual grit cutting forces with constant undeformed chip thickness within the grind
zone. Measurements of the dynamic wheel topography in infeed microgrinding verified
the accuracy of the probabilistic model.
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Desempenho da friabilidade de grãos de CBN na retificação do ferro fundido nodular perlítico FE 70002 /Lopes, José Claudio. January 2019 (has links)
Orientador: Eduardo Carlos Bianchi / Coorientador: Luiz Eduardo de Angelo Sanchez / Banca: Hamilton José de Mello / Banca: Alessandro Roger Rodrigues / Resumo: A aplicação de ferro fundido nodular perlítico na indústria vem se destacando devido a sua elevada resistência mecânica e possibilidade de fácil manufatura, uma vez que sua alta fluidez permite fundir peças com dimensões próximas à final. Entretanto, em componentes que exigem elevada precisão dimensional, como eixos virabrequins, pistões e bielas, por exemplo, é indispensável a utilização do processo de retificação. A indústria desenvolveu diversos tipos de grãos abrasivos de óxido de alumínio para essa aplicação. Todavia, o desenvolvimento de novos grãos abrasivos visa readequar o seguimento, de modo a aplicar no mercado uma nova classe de grãos abrasivos de nitreto de boro cúbico (CBN), suprindo uma lacuna existente no desenvolvimento industrial. Desta forma, foram desenvolvidos diversos tipos de grãos abrasivos de CBN com diferentes níveis de friabilidade, visando assim um melhor desempenho de acordo com determinado processo. Embora a retificação de ferro fundido nodular perlítico seja ampla na indústria, são escassos os estudos pertinentes ao assunto, sendo exíguo sua aplicação quando relacionado a friabilidade de grãos abrasivos. Portanto, vislumbrou-se o estudo do tema a partir da iniciativa da indústria, fabricante de rebolos de CBN, para o entendimento dos fenômenos relacionados ao processo, catalogando o funcionamento dos rebolos e estabelecendo relações em prol do seu desempenho durante o processo de retificação. Deste modo, a rugosidade média aritmética, desvios de... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The application of pearlitic ductile cast iron in the industrial sector has been outstanding due to its high mechanical resistance and possibility of easy manufacture, since its high fluidity allows melting pieces with dimensions close to the end. However, for components requiring high dimensional precision, such as crankshafts, pistons and connecting rods, for example, it is essential to use the grinding process. The industry has developed various types of aluminum oxide abrasive grains for this application. Thereby, the development of new abrasive grains aims at re-adjusting the follow-up, so that a new class of cubic boron nitride (CBN) abrasive grains is available on the market, supplying a gap in industrial development. Thus, different types of CBN abrasive grains with different levels of friability were developed, aiming at a better performance according to a certain process. Although the grinding of pearlitic ductile cast iron is ample in the industry, the pertinent studies are rare, and its application is scarce when related to the friability of abrasive grains. Therefore, the study of the theme was glimpsed from the initiative of the industry, manufacturer of CBN grinding wheels, to understand the phenomena related to the process, cataloging the grinding of the grinding wheels and establishing relationships in favor of its performance during the grinding process. In this way, the average surface roughness, roundness deviation, diametrical wear wheel, G-ratio, electri... (Complete abstract click electronic access below) / Mestre
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Narrating lives and raising consciousness through dance : the performance of (dis)ability at Dancing Wheels /Quinlan, Margaret M. January 2009 (has links)
Thesis (Ph.D.)--Ohio University, June, 2009. / Release of full electronic text on OhioLINK has been delayed until June 1, 2012. Includes bibliographical references (leaves 371-443)
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Narrating lives and raising consciousness through dance the performance of (dis)ability at Dancing Wheels /Quinlan, Margaret M. January 2009 (has links)
Thesis (Ph.D.)--Ohio University, June, 2009. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until June 1, 2012. Includes bibliographical references (leaves 371-443)
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DYNAMIC TERRAMECHANIC MODEL FOR LIGHTWEIGHT WHEELED MOBILE ROBOTSIrani, Rishad 08 August 2011 (has links)
This doctoral thesis extends analytical terramechanic modelling for small
lightweight mobile robots operating on sandy soil. Previous terramechanic
models were designed to capture and predict the mean values of the forces
and sinkage that a wheel may experience. However, these models do not
capture the fluctuations in the forces and sinkage that were observed in
experimental data.
The model developed through the course of this research enhances existing
terramechanic models by proposing and validating a new pressure-sinkage
relationship. The resulting two-dimensional model was validated with a
unique high fidelity single-wheel testbed (SWTB) which was installed on a
Blohm Planomat 408 computer-numerically controlled creepfeed grinding
machine. The new SWTB translates the terrain in the horizontal direction
while the drivetrain and wheel support systems are constrained in the
horizontal direction but allowed to freely move in the vertical direction.
The design of the SWTB allowed for a counterbalance to be installed and, as
a result, low normal loads could be examined. The design also took advantage
of the grinding machine's high load capacity and precise velocity control.
Experiments were carried out with the new SWTB and predictable repeating
ridges were found in the track of a smooth rigid wheel operating in sandy
soil. To ensure that these ridges were not an artifact of the new SWTB a
mobile robot was used to validate the SWTB findings, which it did. The new
SWTB is a viable method for investigating fundamental terramechanic issues.
A series of experiments at different slip ratios and normal loads were
carried out on the SWTB to validate the new pressure-sinkage relationship
which explicitly captures and predicts the oscillations about the mean
values for the forces and sinkage values for both a smooth wheel and a wheel
with grousers. The new pressure-sinkage relationship adds two new
dimensionless empirical factors to the well known pressure-sinkage
relationship for a rigid wheel. The first new factor accounts for changes in
the local density of the terrain around the wheel and the second factor
accounts for the effects grousers have on the forces and sinkage.
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Medicine wheels and the media : seeking journalistic balance from a native perspective /Forbes, David January 1900 (has links)
Thesis (M.J.) - Carleton University, 2002. / Includes bibliographical references (p. 190-203). Also available in electronic format on the Internet.
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Roman and Islamic water-lifting wheelsSchiøler, Thorkild. January 1973 (has links)
Thesis--Copenhagen. / Summary in Danish. Includes bibliographical references and index.
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