• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 53
  • 33
  • 9
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 138
  • 24
  • 23
  • 13
  • 13
  • 11
  • 10
  • 10
  • 9
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 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.
21

Minimising wheel wear by optimising the primary suspension stiffness and centre plate friction of self-steering bogies

Fergusson, Shelley Nadine 24 February 2010 (has links)
M.Ing. / This report documents the steps taken to gain insight into the dynamics of a HS MkVII self-steering three piece bogie. This was done by firstly studying the dynamics and stability of linear simplifications of the bogie and wagon and then by investigating the dynamics of the bogie by means of a non-linear model.With the necessary insight into the dynamics of the bogie, an optimised relationship between the primary suspension stiffness and the centre plate friction of a self-steering three-piece bogie was achieved. The optimised model’s wear is less than half that of the reference model and has a safe operating speed of 80km/h for an empty wagon and 140 km/h for a loaded wagon. It is recommended that the following be done before issuing a final technical recommendation; • A final optimisation of the lateral and longitudinal primary suspension stiffness arrangement; taking into consideration the physical vertical load bearing capacity of the rubber suspension elements. • A study in order to quantify the effects, on wear, of the increased misaligned position of the bogie on straight track following a curve. A verification of the ADAMS/Rail simulation results by conducting specific on-track tests. • A comprehensive cost-benefit analysis.
22

Experimental stress analysis of a steel light truck wheel.

Cosgriff, Kevin J, mikewood@deakin.edu.au January 1982 (has links)
The development of a new automotive wheel requires extensive testing and possible design changes. The wheel investigated had three major changes during development. These three designs were subjected to a stress analysis, by experimental methods, to allow a comparison to be made between each design. The experimental program tested the wheels under conditions designed to simulate the loading of the front wheels whilst cornering. A loading frame was built for this purpose and all testing was performed statically by multiple loading for different directions of bending moment. Brittle lacquer coatings were used on each wheel to highlight high strain areas and indicate optimum locations for the placement of strain gauges. The strain gauges were then used to evaluate the strains. Wheel stud loads were also monitored via strain gauges applied to two of the wheel studs. All data was stored on magnetic tapes and the stress analysis performed by means of a minicomputer. The results of the stress analysis showed quantitatively the improvement in design from the first to the third wheel design. The analysis of the stud loads and their variation during loading indicated the optimum wheel mounting face geometry to ensure nut loosening would not occur in service.
23

Precision control in compliant grinding via depth-of-cut manipulation

Hekman, Keith Alan 12 1900 (has links)
No description available.
24

Measuring systems for active steering of railway vehicles

Li, Hong January 2001 (has links)
This thesis studies measuring systems for active steering of railway vehicles. The aim of the study is to develop state estimation techniques to provide high integrity feedback variables for the active steering of railway vehicles. Practicality and provision of high-integrity data are two important aspects of the work. To avoid the use of expensive sensors and complex instrumentation, practical techniques for estimating vehicle variables are developed where only economical measurements are used and they can be easily implemented. The conventional solid-axle wheelset and wheelset with independently-rotating wheels are studied and their mathematical models are developed. The fundamental stability problem of these two models is analysed from a control engineering viewpoint for studies of actively-controlled wheelsets. The Kalman filters are then developed for these models to estimate all state variables, particularly variables of the wheelset relative to the track such as lateral displacement and yaw angle which are needed for active control. A number of sensing options are also identified, analysed for performance and assessed in a comparative sense. Fault detection and isolation schemes are then studied for the estimation techniques developed. Finally, some applications are considered. The techniques and analysis methods developed for the single wheel pair are extended and applied to a MKII coach and a two-axle railway vehicle. The estimation of cant deficiency for tilting trains is explored, and also the possibility of state estimation for a real profiled wheel.
25

An historical examination of water-powered mill sites and markets using geographic information system analysis : Augusta County, Virginia, 1880-1885 /

Miller, Matthew J., January 1994 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. One map in back pocket. Includes bibliographical references (leaves 73-75). Also available via the Internet.
26

The relationship between nutritional risk factors, nutritional risk indicators, and the severity of physical disability within older adult home delivered meal program participants

Fordyce, Janice L. Abood, Doris A. January 2005 (has links)
Thesis (M.S.)--Florida State University, 2005. / Advisor: Doris A. Abood, Florida State University, College of Human Sciences, Dept. of Nutrition, Food and Exercise Sciences. Title and description from dissertation home page (viewed Jan. 27, 2006). Document formatted into pages; contains x, 73 pages. Includes bibliographical references.
27

Projeto de experimentos em rodas ferroviárias fundidas em aço, com o uso da técnica de Taguchi

Ribeiro, Carlos Barbosa [UNESP] 18 September 2008 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-09-18Bitstream added on 2014-06-13T20:00:01Z : No. of bitstreams: 1 ribeiro_cb_me_guara.pdf: 645547 bytes, checksum: 8c2576a34583837cd05d929fb4a16856 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Aplicou-se experimentos em rodas ferroviárias tipo D-38 (38 polegadas de diâmetro), fundidas em aço, obtidas pelo processo de pressão controlada. Estudou-se a influência de 15 fatores (variáveis de entrada), com o objetivo de minimizar ou eliminar a descontinuidade interna denominada “microrechupe”, a qual apresentou-se como variável de saída constante em todas as rodas experimentadas, na região do aro das rodas (região de contato com os trilhos da ferrovia). As descontinuidades internas foram detectadas por ensaio ultrassônico, através do método indireto de avaliação, com o auxílio do diagrama AVG, e uso de transdutor normal. Em função da quantidade e tamanhos diferenciados das descontinuidades internas detectadas em todas as rodas experimentadas, foi criado um método específico para mensurá-las, estabelecendo desta forma, respostas diferenciadas que possibilitaram a análise da influência dos fatores (variáveis de entrada). Para estudo e análise da influência das variáveis de entrada e suas respectivas interações, foi utilizado o método de Taguchi, com um Arranjo Ortogonal L-16. Os fatores (variáveis de entrada) operaram em dois níveis com uma razão sinal / ruído para a função “maior é melhor”, sendo utilizada a análise de variância ANOVA para testar a significância dos efeitos. Os resultados demonstraram que as variáveis “posição relativa da roda na corrida de vazamento” e “tempo de cura dos massalotes radiais” tiveram maior significância para a redução da descontinuidade microrechupe (output). / It was applied experiments in railroad wheels, casting in steel, D-38 type (38- inches- diameter), produced by controlled pressure process. It was studied influence of the 15 factors (entrance variables) with objective to minimize or to eliminate a internal discontinuity, called microshrinkage, which was presented as constant output in all tried wheels, inside the rim wheels (region of contact with railroad tracks). The internal discontinuities had been detected by ultrasonic test, through the indirect method of evaluation, with aiding of AVG diagram, with the use of normal transducer. In function of the amount and different sizes of the internal discontinuities detected in all the tried wheels, a new method was created to measure them, establishing different answers, in such a way that make possible the factors influence analysis. For study and analysis of the factors and its interactions, the Taguchi approach was used, with L-16 Ortogonal Array. The process factors had operated in two levels with a signal-to-noise ratio called “bigger is better” function and it was used variance analysis by ANOVA to determine the main significance of the effects. The results had demonstrated that, the factors “relative position of the wheel in the production line” and “cure time of radial risers” had greater significance for the reduction of the discontinuity microshrinkage (output)
28

Towards quantum information processing with Cr3+ based heterometallic clusters

Albring, Morten January 2014 (has links)
An investigation of the electronic structure of some transition metal clusters comprising anti-ferromagnetically coupled, heterometallic arrays of eight metal ions that are wheel-shaped, is reported. The compounds were synthesized and provided by Dr. Grigore Timco of The University of Manchester and are formulated by their metal content as Cr7M, where M = a divalent 3d metal. Two families of wheels are the subject of this research, defined ‘green’ and ‘purple’ from their physical appearance. Within each family, the compounds are all isostructural. From simulation using a single Hamiltonian for Cr7M-purple compounds, where M = Zn, Mn, or Ni, it is shown that with only two exchange parameters, one JCr-Cr and one JCr-M, data from bulk magnetization, neutron scattering, Electron Paramagnetic Resonance (EPR) spectroscopy at multiple frequencies and specific heat measurements can be modelled and that there is transferability of parameters. Preliminary attempts to measure electron spin relaxation times for two of the purple wheels have shown values of T1 and T2 that are comparable with those of the more extensively studied green wheels and hence further studies in this area are warranted. Variable temperature Q- and W-band EPR spectra for a series of nine heterodimers comprising one green and one purple wheel, M=Zn, Mn or Ni in each case, are reported. For Cr7Zn-purple there is no magnetic exchange detected, whereas weak and quantifiable exchange is required to interpret the spectra from the other six dimers. EPR studies of three trimers of the form purple-green-purple are reported and the presence of magnetic exchange is identified by comparison with the spectra of the component single and double wheel compounds, although this is not quantified because of the numerical size of the simulations that are required. The process of comparing simulated to experimental spectra is a complex problem and one which is central to the work reported in this thesis. The problem of fitting has been investigated and two novel solutions, one based upon pixel mapping and the other based on wavelet transformation are proposed.
29

Análise do desempenho de diferentes fluidos de corte aplicados na técnica de MQL na retificação cilíndrica de mergulho do aço AISI 4340 com rebolo de CBN /

Saes, Saulo Aguiar. January 2019 (has links)
Orientador: Eduardo Carlos Bianchi / Banca: Hamilton José de Mello / Banca: Carlos Elias da Silva Junior / Resumo: Com o desenvolvimento da indústria metal-mecânica e a crescente demanda por formas mais ecológicas de utilização e manutenção dos recursos naturais, tem-se a meta de utilizar e gerar menos resíduos que sejam nocivos ao meio-ambiente, bem como aos seres humanos. Isso se aplica aos processos de usinagem, nos quais se procuram por fontes alternativas de lubrificação, as quais reduzam os malefícios gerados ao ecossistema. Seguindo essa vertente tem-se a técnica de mínima quantidade de lubrificação - MQL, a qual preza por uma maior eficiência do processo ao utilizar menos fluido se comparada com o uso de líquidos refrigerantes em abundância. Porém, a utilização de MQL demanda certos cuidados no que se refere à limpeza da zona de corte, e às trocas de calor do sistema ferramenta-peça. Portanto, o presente trabalho analisou o comportamento da técnica de MQL associada à limpeza, onde foram utilizados três tipos de fluidos: Rocol Biocut 9000 fluido próprio para a aplicação na técnica de MQL, Quimatic Tapmatic ME-2: fluido sintético, normalmente utilizado na refrigeração convencional, mas que tende a ter resultados bons na utilização em MQL e um terceiro fluido VCI Aqua 180: fluido com propriedades anticorrosivas e com inibidor de empastamento. Todos os fluidos foram diluídos nas proporções 1:5 ou seja uma parte de óleo e cinco partes de água (83% de diluição em agua), 1:10 ou seja uma parte de óleo e dez partes de água (90,90% de diluição em agua) além do óleo puro. Dessa forma, foram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: With the development of the metal-mechanic industry and the growing demand for more ecological ways of using and maintaining natural resources, the goal is to use and generate less waste that is harmful to the environment as well as to humans. This applies to machining processes in which alternative sources of lubrication are sought, which reduce the damage to the ecosystem. Following this strand is the technique of minimum amount of lubrication - MQL, which values a greater efficiency of the process when using less fluid when compared with the use of abundant soft liquids. However, the use of MQL requires certain care regarding the cleaning of the cutting zone, and the heat exchanges of the tool-part system. Therefore, the present work analyzed the behavior of the MQL technique associated to cleaning, where three types of fluids were used: Rocol Biocut 9000 suitable for the application in the MQL technique, Quimatic Tapmatic ME-2: synthetic fluid, normally used in refrigeration conventional but which tends to have good results in the use in MQL and a third VCI Aqua 180 fluid: fluid with anticorrosive properties and with impasto inhibitor. All the fluids were diluted 1: 5 in either one part oil and five parts water (83% dilution in water), 1:10 or one part oil and ten parts water (90.90% dilution in water) plus pure oil. In this way, process output variables were analyzed, such as roughness, circularity deviation, G ratio (volume of removed material / volume of worn grinding ... (Complete abstract click electronic access below) / Mestre
30

Durability design with reliability methods: a case study of automotive wheel assemblies

Ridder, Richard L. 29 September 2009 (has links)
The incorporation of reliability theory into a fatigue analysis program is studied. A thorough background in probabilistic methods and metal fatigue is presented, allowing a full understanding of these processes. An automotive wheel assembly is then introduced as an example of the applications of this durability/reliability design package. A detailed step-by-step procedure is utilized to develop the basic information needed to analyze the wheel assembly: material properties, geometry, and loading; the relationship between applied load and stress; and the degree of variation in specific material properties, wheel thickness, and service loading. An in depth documentation of the effect of these “real world” variations on wheel reliability is then presented in graphical form. Several different approaches in altering the design variables are used in order to thoroughly illustrate the resulting component reliability. Such information is particularly relevant where product quality and warranty formulation are concerned. / Master of Science

Page generated in 0.0727 seconds