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Dissertations / Theses on the topic 'Bearings (Machinery) Design and construction'
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Stack, Jason R. "Fault signature detection for rolling element bearings in electric machines." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13276.
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Tekin, Koray Serdar. "Design And Construction Of Boundary Lubricated Bearing Test Rig And Wear Analysis In Earthmoving Machinery." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612751/index.pdf.
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Excavators which used as earthmoving machinery are exposed to heavy loads and operate long hours repeatedly. The forces that are transmitted trough pin bearings are observed to cause failure due to wear. Therefore, durability of bearings is crucial for excavators. The aim of this study is to perform wear analysis of excavator bearings running in boundary lubrication regime. A hydraulically powered test rig, which simulates the operating conditions of excavator bearings is designed and constructed. Wear is obtained applying both force and relative motion between pin and bearing on the test rig. Several tests are performed in this test bench. Force and material type are varied as the factors influencing wear. Results are compared and the effects of the factors on wear are determined.
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Lima, e. Silva Rafael Augusto de 1984. "Projeto mecânico de biela automotiva baseado em otimização estrutural." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265973.
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Orientador: Marco Lúcio BittencourtDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-24T09:08:40Z (GMT). No. of bitstreams: 1 LimaeSilva_RafaelAugustode_M.pdf: 10555723 bytes, checksum: 1d037ebafbabc24e214c06ad76c5f54a (MD5) Previous issue date: 2013
Resumo: O trabalho descreve o projeto mecânico convencional de uma biela automotiva de motor de combustão interna e apresenta uma metodologia alternativa baseada em métodos de otimização estrutural com o objetivo de reduzir a massa do componente. Para tal, é feita a descrição de todos os parâmetros de projeto assim como a definição de critérios de projeto. Em virtude da criticidade da aplicação selecionada, motor de ciclo Diesel utilizado em caminhões de trabalho pesado com picos de pressão de combustão de até 240 bar, a biela foi projetada sem bucha utilizando-se extensivamente os métodos numéricos. O Método dos Elementos Finitos foi aplicado para cálculo de tensões, deslocamentos, pressões de contato, flambagem, fadiga e para a síntese modal de componentes utilizados na análise dinâmica de multicorpos com mancais elasto-hidrodinâmicos. Dois modelos de fadiga dos materiais foram estudados: o modelo americano baseado no diagrama de Goodman e tensões principais e o modelo alemão baseado no diagrama de Haigh e efeito do gradiente de tensões multiaxiais; dos quais concluiu-se que o modelo americano é suficiente para o projeto da biela ao passo que o modelo alemão traz oportunidades adicionais de redução de massa. A otimização topológica, otimização de forma e análise de sensibilidade permitiram a obtenção de uma biela 210g (3\%) mais leve e com melhor desempenho dos mancais hidrodinâmicos. Finalmente, concluiu-se que o Método da Otimização Topológica apresenta oportunidades interessantes aos projetistas na fase de conceituação de produtos como alternativa aos desenhos convencionais, no entanto, demanda esforço adicional para o atendimento de todos os critérios de projeto do componente
Abstract: The present work consists of the conventional mechanical design description of an internal combustion engine connecting rod and also the proposal of an alternative methodology based on optimization methods with the objective of reducing the component mass. Therefore, it is performed a detailed view of all design parameters as well as the definition of design criteria. Because of the critical application selected, Diesel engine of heavy duty truck with combustion pressure reaching up to 240bar, the connecting rod was designed without bushing and with extensive use of numerical methods. The Finite Element Method was applied to assess stresses, displacements, contact pressures, buckling, fatigue and to perform the Component Modal Synthesis for multi-body dynamics simulation with elasto-hydrodynamic bearings. Two fatigue models were studied: the American model based on Goodman's diagram and principal stresses and the German model based on Haigh's diagram and multiaxial stress gradient effect; from which it was concluded that the American model is enough to design the connecting rod, while the German model presents additional weight reduction opportunities. The topology optimization, shape optimization and sensitivity analysis enabled a 210g (3\%) lighter connecting rod with improved bearings performance. Finally, it was concluded that the Topology Optimization Method presents good opportunities for the design engineers in the conceptual phases of product development with alternatives to the conventional designs. However, additional effort is necessary to fit the concept into all design criteria
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
4
Dawson, Benedict E. "Design and implementation of magnetic bearings and associated controllers." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360583.
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Strand, Henrik. "Design, testing and analysis of journal bearings for construction equipment." Doctoral thesis, Stockholm : Department of Machine Design, Royal Institute of Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-429.
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Rothwell, Benjamin Charles. "Design of robust PTFE faced bearings for performance and reliability in large rotating machinery." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/13348/.
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In this thesis a Finite Element Modelling (FEM) approach is proposed for modelling the visco-plastic creep effects that a PTFE-faced thrust bearing would undergo during normal operating conditions. A thermal elastic hydrodynamic lubrication (TEHL) model is developed, which uses the Reynolds equations for a fluid film, coupled with Hertzian contact theory and the energy equation to predict the pressure and film thickness on the PTFE face as well as the temperature and thickness of the fluid. These variables are then used with a Norton creep function to predict the secondary creep effects on the PTFE surface. This change in PTFE thickness due to visco-plastic effects are taken into account within the film thickness equations and the effects over a bearing’s operational life span studied. The Norton creep function is obtained from experimental creep results conducted on filled PTFE samples at the University of Leeds. This experimental method allowed for the displacement of the samples to be recorded over a 7 day test period at a representative range of pressure and temperature conditions and a Norton creep function to be obtained from the results. The Norton creep function was then included within the simulations to allow for the visco-plastic creep effects to be studied. Results obtained showed that whilst the secondary creep had a small effect on the pressure profile of the pad, the peak pressure was significantly affected during the duration of the pads operational life. It was concluded that this was due to the pad deformation changing, meaning a smaller peak pressure was observed, but the tilt angle did not change greatly, meaning the profile did not change. The pad and film thickness also changed as time passed, with the pad getting thinner in areas of high pressure and temperature, due to the secondary creep effects. It was also observed that the peak temperature of the pad also decreased as time passed, due to the film thickness increase in areas of high temperature.
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Tseng, Chaw-Wu. "Vibration of rotating-shaft design spindles with flexible bases /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/7129.
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Frew, David Anthony. "The design, development and vibration analysis of a high-speed aerostatic bearing." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/362.
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Mwenda, H. M. "Design, construction and evaluation of a nutation-spin rotary forging press." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371286.
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Mainland, Marlene Elise. "Analytical and experimental investigation of an efficient viscous pump." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15832.
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Neppalli, Srinivas. "Design, construction, inverse kinematics, and visualization of continuum robots." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-10312008-144310.
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Shartouny, Michael. "Design of assembly machine for fine-pitch surface mount components." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/18899.
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Wan, Iok-cheong, and 尹煜祥. "Investigate the dry and moist heat process for the design of industrial drying machinery for dye-houses." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47168936.
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Drying process needs lots of energy and usually prone to high equipment and operational cost. Research tasks have focused on improving the drying performance and reducing the energy consumption rate. Among a number of industries, textile manufacturing needs the process intensively. It is surprising that little research has concerned principle enhancement and drying process design. In the support by Fong’s National Engineering Company Limited, a series of research that targeting to the inadequacy of technology development for machinery and process design have been conducted. The redevelopment of machinery design has based upon a heat setting machine –ECO dryer. The machine was used as a working platform to supply all necessary testing information before and after the enhancement. The ductwork and air distribution system design have been revised to improve the unevenness drying problems appeared in the heat setting of fabrics. Two main research scopes have been performed that included the development of a new duct sizing approach –Uniform Jet Velocity (UJV) and redesigning the air chambers.
The proposed UJV approach is a new air duct design model developed from fluid dynamics principles. The air jet speed along each nozzle is maintained at a constant rate to provide a uniform jet impingement effect. A duct size algorithm was proposed to adjust the cross sectional area ratio between the main and branch streams for the target of producing a constant impingement velocity across the entire air duct. In the enhancement of the air distribution system design, Computational Fluid Dynamics (CFD) analytical approaches were used to model air flow patterns before and after the redesign of air chambers. The CFD analysis results told that a linear air distribution system with four sub-chamber design could produce the best air distribution pattern on the ECO dryer.
The request of an accurate drying cycle time predication is also large in textile industry. It is because the problems of under-and over-drying usually happen in the jet impingement process. The second essential objective in the research is to develop systematical approaches for a good qualifying of a drying cycle. Four analytical models have been studied that included First order kinetics, Diffusion, model based on solutions of diffusion equation and Wet surface. An equation for each of the models was developed to describe the characteristics of a porous type fabric drying process. In the study, the required modeling parameters were empirically determined, and the accuracy among the models has been compared. Findings from the research have proved that the model based on solutions of diffusion equation can be the best strategy in presenting a drying cycle under different machine settings.
The investigation has not ceased after the completion of the hot air jet impingement research. The study objectives have moved onto an alternative drying technology using steam as the drying medium. Due to many problems reported in the drying of yarn packages using electro-magnetic waves, moist heat drying technology is urgently needed. At the final part of the research, two CFD simulation models namely constant viscous resistance and increasing viscous resistance were studied. A preliminary result generated from ANSYS CFD analysis results was obtained that has opened up a new study area for further elaboration of a new drying technology, and hopefully can be practically applied to textile industry in the near future.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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Beargie, Aimee M. "Sliding mode control of a non-collocated flexible system." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/19306.
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Ulmer, Bernard C. Jr. "Fabrication and calibration of an open architecture diamond turning machine." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/17120.
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Lam, King-fung, and 林敬豐. "Experimental investigation for designing passive fences to orient parts by pushing." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841483.
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Sepehri, Nariman. "Dynamic simulation and control of teleoperated heavy-duty hydraulic manipulators." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30846.
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Some relevant aspects of dynamics and control of heavy-duty hydraulic machines in a teleoperated mode were investigated. These machines, such as excavators and forest
harvesters, are mostly used in primary industries. They have a manipulator-like structure with a nonlinear and coupled actuating system. The aim of the project is to investigate different approaches towards converting such machines, with minimum changes, into task-oriented human-supervisory control systems. This provides the opportunity
to use both human supervision and robotic power in hazardous environments and for tasks for which human decision is necessary.
A methodology was developed for fast and accurate simulations. Analytical, steady-state and numerical techniques were combined using Large-Scale Systems analysis. The inclusion of nonlinearities in the form of discontinuities (e.g., gear backlash and stick-slip friction) in the model was investigated. Numerical simplifications of the structural dynamics and alternative solutions for the hydraulic part were also studied.
The model describing the performance of the machine has been written in ACSL (Advanced Continuous Simulation Language) on a VAX computer system. A modified version of the program is at present running close to real-time on a single processor in conjunction with high speed graphics in a manner similar to a flight simulator used for human interface studies and training.
The model also evaluates the performance of the machine in a teleoperated mode and under different control strategies. As a result a velocity control algorithm has been developed which is applied in conjunction with the closed-loop components for teleoperation of heavy-duty hydraulic machines; it is basically a feedforward compensation
which uses the measured hydraulic line pressures along with fluid-flow equations as criteria
to control the joint velocities as well as to uncouple the interconnected actuating system. The control algorithm has been written in C language and is running on an IRONICS computer system, interfaced between the human operator and the machine. The simulation results are supported by the experimental evidence. The experiments were performed on a Caterpillar 215B excavator.
Improved operator safety, extension of human capability, job quality and productivity
increase are the advantages of a successful implementation of robotic technology to these industrial machines.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Huang, Ji Ming. "Design, modeling and control of a compliant parallel XY micro-motion stage with complete decoupling property." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2493609.
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Sari, Pelin. "Preliminary Design And Construction Of A Prototype Canola Seed Oil Extraction Machine." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607357/index.pdf.
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Growing energy demand in the world force people to investigate alternative energy sources. Unlike coal or other fossil fuels, renewable energy sources are promising for the future. Especially, seed oils are effectively used as energy sources such as fuel for diesel engines. The scope of this study is to develop an oil extraction machine specific to canola seed.
In this study, seed oil extraction methods have been investigated and various alternatives for the extraction machine have been considered. For continuous operation, oil extraction with a screw press is evaluated as the most appropriate solution. Four different prototypes have been designed and manufactured. According to the results of testing of prototypes, they have been modified and gradually improved to increase oil extraction efficiency. The working principle of the selected screw press based on the rotation of a tapered screw shaft mounted inside a grooved vessel. The screw shaft is a single square-threaded power screw having an increasing root diameter from inlet to exit while the outside diameter of the screw shaft is 66 mm. Seeds are taken into the system at the point where the depth of the screw thread is maximum. Then they are pushed forward by the threads on the rotating screw shaft and pass through inside the vessel. So, the fed seeds are compressed as they move to the other side of the vessel. Recovered oil escapes from high pressure zone and drains back. The oil is drained out from the oil drainage holes that are machined on high pressure zone of the vessel. Besides, the cake is extruded at the end of the vessel and the screw shaft. The cake thickness is adjustable by the axial movement of the screw shaft. By adjusting the cake thickness, different pressures can be obtained.
During the experiments, it is observed that four main features affect the oil recovery rate. These are the geometry of the grooves inside the vessel, the taper angle of the screw shaft, the operating temperature and the rotational speed. With the final prototype, an oil recovery efficiency of 62.5% has been achieved at 40 rpm with 15 kg/h seed capacity. Since the oil content of the seed is taken as 40%, oil recovery rate of the developed oil extraction machine is 3.75 kg/h. This efficiency is determined for a 0.8 mm cake thickness at 1.1 kW motor ower.
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Roberge, Martin. "Design and evaluation of performance of a crop processor for a pull-type forage harvester." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0020/NQ55375.pdf.
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Liu, Guang. "A photovoltaic-powered pumping system." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30592.
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This thesis studies the optimal design for a photovoltaic-powered medium-head (30 meters) water pumping system, with the emphasis on improving the efficiency and reducing the maintenance requirements of the electrical subsystem. The reduction of maintenance requirements is realized by replacing the conventional brush-type permanent magnet dc motor with a brushless dc (BLDC) motor. Different BLDC motor control techniques such as position-sensorless operation, sinusoidal and trapezoidal excitations are investigated. The improvement in efficiency is achieved by maximizing the output power from the photovoltaic array and by minimizing the losses in various parts of the electrical sub-system. A microprocessor-based double-loop maximum power tracking scheme is developed for maximization of the photovoltaic array output power. Over 99% utilization factor is achieved for a typical clear day regardless of the season of the year. The system losses are minimized mainly by performing loss analysis and selecting most suitable switching topologies and switching components. Experimental results show that the combined converter-motor efficiency is comparable to those of high-efficiency brush-type dc motor systems.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Gogas, Kyriakos. "Design of a robust speed and position sensorless decoupled P-Q controlled doubly-fed induction generator for variable-speed wind energy applications." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99762.
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Wind energy is a relatively young but rapidly expanding industry. In order for wind generation to be cost effective, it must produce energy at a minimum cost per dollar of investment. Performance characteristics such as power output versus wind speed must be optimized in order to compete with other energy sources. Also, if the utility uses wind power for a part of its generation, the output power of these turbines must have the same high quality and reliability when it enters the utility grid. The ability to vary operating speed is important in wind generation because it allows for an optimization of the transfer of power from the wind to the turbine shaft. Doubly-fed induction generators (DFIG) are an interesting solution for variable-speed systems with limited variable speed range, and are typically used in wind energy conversion systems.The objectives of this thesis are to implement a decoupled P-Q control of a DFIG that does not rely on mechanical sensors and to design a speed and position sensorless algorithm that is robust to variations of the values of the machine parameters. The sensorless DFIG control algorithm presented in this thesis is based on a modified phasedlock loop with an improved positioning algorithm. With the measured stator voltages, stator and rotor currents, the speed and position of the DFIG are estimated. The speed is estimated independent of machine parameters, which results in a significant improvement in speed control robustness to parameter variations. In addition, the algorithm avoids using differentiation, which significantly improves its immunity to noise and does not require the measurement of the rotor voltages. Also, it is shown that the positioning algorithm has an improved operation in generator mode. Although the accuracy of the positioning algorithm is depended on machine parameters; it is shown with the designed controller that the P-Q decoupled control is robust to changes of machine parameters. Theoretical and simulation results are validated on an experimental setup.
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Luong, David, and Ibrahim Salloum. "Investigation of electromagnetic compatibility (EMC) of low-voltage (<60V) DC electric motors in construction machinery application." Thesis, Linköpings universitet, Fysik och elektroteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-162160.
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The brushed DC motor is a source of electromagnetic emission that may cause interference. The main issues with brushed DC motor are arcing, which occurs between the brushes and commutator, and inrush current. It is possible to decrease the electromagnetic emissions by addressing the source (brushed dc motor) and the installation. The source may be addressed by using filters in the form of X2Y-capacitors on the terminals or ferrites on the cables. The installation does not produce any emission, but it is possible to lower its contribution. This is done by altering the installation like changing the placement of cables and provide good coupling. An effective way of decreasing inrush currents is by using negative-thermal-coefficient (NTC) thermistors. Another measure to improve the EMC properties of the brushed DC motor is to design the motor so that it can trap EM emissions. Some of these parameters are motor house material, end-cap material, vent holes or slots on motor housing, placement of power terminals, crimping tabs and motor enclosure.
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Unal, Sadullah Utku. "Design, Construction And Preliminary Testin Of An Aeroservoelastic Test Apparatus To Be Used In Ankara Wind Tunnel." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607034/index.pdf.
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In this thesis, an aeroservoelastic test appratus is designed to investigate the flutter phenomena in a low speed wind tunnel environment. Flutter is an aeroelastic instability that may occur at control surfaces of aircrafts and missiles. Aerodynamic, elastic, and inertial forces are involved in flutter. A mathematical model using aeroelastic equations of motion is derived to investigate flutter and is used as a basis to design the test setup. Simulations using this mathematical model are performed and critical flutter velocities and frequencies are found. Stiffness characteristics of the test setup are determined using the results of these simulations. The test setup is a two degrees of freedom system, with motions in pitch and plunge, and is controlled by a servomotor in the pitch degree of freedom. A NACA 0012 airfoil is used as a control surface in the test setup. Using this setup, the flutter phenomena is generated in Ankara Wind Tunnel (AWT) and experiments are conducted to validate the results of the theoretical aeroelastic mathematical model calculations.
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Arnold, David Patrick. "Magnetic Machines for Microengine Power Generation." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4854.
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This dissertation presents an investigation of miniaturized magnetic induction and permanent magnet (PM) machines, intended for use in a microengine. Similar to a macroscale turbogenerator, a microengine comprises a small, gas-fueled turbine engine for converting chemical fuel energy into mechanical power and an integrated electrical generator for converting mechanical power to electrical power. The microengine system is proposed as a revolutionary, high power-density source for portable electronics.
In this research, miniaturized magnetic induction machines and PM machines were designed, fabricated, and characterized. Both types of machines used axially directed magnetic fields and were nominally 10 mm in diameter and 1.5-2.3 mm in thickness. Innovative microfabrication techniques were developed to demonstrate the feasibility of integrating magnetic machines within a bulk-micromachined, silicon-based microengine system.
Two-phase, eight-pole induction machines were constructed within silicon substrates using Cu coils in a laminated, slotted ferromagnetic NiFe or CoFeNi stator core. Silicon etching, wafer bonding, and electrodeposition were used to form all of the magnetic machine components. The induction machines were characterized in motoring mode using tethered rotors and demonstrated motoring torques of up to 2.5 uN-m.
Also, three-phase, eight-pole, surface wound PM machines were built using a hybrid microfabrication/assembly approach. The stators were fabricated by electroplating Cu coils on ferromagnetic NiFeMo (Moly Permalloy) substrates. The rotors were formed by assembling a magnetically patterned SmCo PM with a FeCoV (Hiperco 50) back iron. The PM machines were tested as generators with free-spinning rotors, powered by an air-driven spindle, and demonstrated 2.6 W of mechanical-to-electrical power conversion with continuous DC power generation of 1.1 W at 120 krpm rotor speed.
The primary contributions of this work are (1) the demonstration of microfabricated magnetic machines integrated within bulk-micromachined silicon and (2) the demonstration of multi-watt power conversion from a microfabricated PM generator. These achievements represent progress in the ongoing development of silicon-based microengines, but in addition, the fabrication technologies and device structures may find application in other microsystems.
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Van, der Linde Jaco. "Discrete element modeling of a vibratory subsoiler." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/721.
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Bruneau, Phillippe Roger Paul, and Backstrom T. W. Von. "The design of a single rotor axial flow fan for a cooling tower application." Thesis, Stellenbosch : University of Stellenbosch, 1994. http://hdl.handle.net/10019.1/15528.
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Thesis (MEng (Mechanical Engineering))--University of Stellenbosch, 1994.213 leaves printed on single pages, preliminary pages i-xix and numbered pages 1-116. Includes bibliography, list of tables, list of figures and nomenclature.
Digitized at 600 dpi grayscale to pdf format (OCR), using a Bizhub 250 Konica Minolta Scanner.
ENGLISH ABSTRACT: A design methodology for low pressure rise, rotor only, ducted axial flow fans is formulated, implemented and validated using the operating point specifications of a 1/6th scale model fan as a reference. Two experimental fans are designed by means of the design procedure and tested in accordance with British Standards 848, Type A. The design procedure makes use of the simple radial equilibrium equations, embodied in a suite of computer programs. The experimental fans have the same hub-tip ratio and vortex distribution, but differ in the profile section used. The first design utilises the well known Clark-Y aerofoil profile whilst the second takes advantage of the high lift characteristics of the more modern NASA LS series. The characteristics of the two designs are measured over the entire operating envelope and compared to the reference fan from which the utility and accuracy of the design procedure is assessed. The performance of the experimental fans compares well with both the reference fan as well as the design intent.
AFRIKAANSE OPSOMMING: 'n Ontwerpmetode vir lae drukstyging, enkel rotor aksiaal waaiers is geformuleer, toegepas en bevestig deur gebruik te maak van die ontwerppunt spesifikasies van 'n 1/6 skaal verwysingswaaier. Twee eksperimentele waaiers is ontwerp deur middel van die ontwerpmetode en getoets volgens die BS 848, Type A kode. Die ontwerpmetode maak gebruik van die eenvoudig radiale ewewigsvergelykings en 'n stel rekenaarprogramme. Die twee eksperimentele waaiers het dieselfde naaf-huls verhouding en werwel verdeling, maar verskil daarin dat verskillende vleuelprofiele gebruik is vir elkeen van die twee waaiers. Die eerste ontwerp maak gebruik van die bekende Clark-Y profiel terwyl die tweede die moderne NASA LS profiel gebruik. Die karakteristieke van die twee eksperimentele waaiers is gemeet oor die hele werkbereik en vergelyk met die verwysings waaier waardeur die geldigheid en akkuraatheid van die ontwerpmetode bepaal is. Die werkverigting van die eksperimentele waaiers vergelyk goed met die verwysingswaaier en bevredig die ontwerpsdoelwitte.
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Zhang, Qiang Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "A study of high performance twist drill design and the associated predictive force models." Awarded by:University of New South Wales. Mechanical and Manufacturing Engineering, 2007. http://handle.unsw.edu.au/1959.4/31220.
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This thesis presents a detailed analysis of the plane rake faced drill design, its grinding method and grinding wheel geometry. A fundamental geometrical analysis has then been carried out on the major cutting edges of the modified drills according to the national and international standards. It has been shown that this new drill design results in a significant increase in the normal rake angle at lips as well as point relieving at the chisel edge region. Geometrical models for the various drill point features have been established which uniquely define the drill point features of the modified drill design. A comprehensive experimental investigation has been carried out to study the drilling performance of the modified drills, when drilling a high tensile steel, ASSAB 4340, with TiN coated high speed steel drills over a wide range of drilling conditions. Comparing to the drilling performance with conventional twist drills under the corresponding conditions, it has been found that the modified drills can reduce the thrust force by as much as 46.9% with the average of 23.8%; the reduction of drilling torque is also significant at an average of 13.2% and the maximum of 24.9%. Similarly, the new drill design shows great superiorities over the conventional drills in terms of drill-life. In the drill-life tests, a few conventional drills were broken, but all plane rake faced drills performed very well. In order to estimate the cutting performance in process planning on a mathematical and quantitative basis when drilling with the modified drills, predictive cutting force models have been developed based on the unified-generalized mechanics of cutting approach. The models have been assessed qualitatively and quantitatively and showed good agreements with the experimental thrust, torque and power. Empirical-type force equations have also been developed to provide simple alternatives for practical applications.
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Doan, Donald Scott. "Using Motor Electrical Signature Analysis to Determine the Mechanical Condition of Vane-Axial Fans." Thesis, University of North Texas, 2002. https://digital.library.unt.edu/ark:/67531/metadc3256/.
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The purpose of this research was a proof of concept using a fan motor stator as transducer to monitor motor rotor and attached axial fan for mechanical motion. The proof was to determine whether bearing faults and fan imbalances could be detected in vane-axial fans using Motor Electrical Signature Analysis (MESA). The data was statistically analyzed to determine if the MESA systems could distinguish between baseline conditions and discrete fault frequencies for the three test conditions: bearing inner race defect, bearing outer race defect, and fan imbalance. The statistical conclusions for these proofs of concept were that MESA could identify all three faulted conditions.
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Fourie, Marna. "A subcritical and transcritical carbon dioxide refrigeration system utilizing multiple expansion devices." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86380.
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Thesis (MScEng)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Carbon dioxide is a natural gas that has been used as a refrigerant as far back as the 1850s. It was then primarily used because it was easily obtainable and non-toxic. Due to the high operating pressure and relatively low critical temperature (and high critical pressure) of CO2, it was gradually phased out and replaced with hydrochlorofluorocarbons and chlorofluorocarbons. With the discovery of the greenhouse effect, greenhouse gasses and ozone depleting gasses, the Montreal Protocol and the Kyoto Protocol were placed into effect. These two protocols call for the reduction in use of certain greenhouse gasses and the complete exclusion of others. The focus turned to natural gasses that are more environmentally friendly and easier to come by. Carbon dioxide is one such gas. However, CO2 has a low critical temperature and high pressure, 33.98 °C and 73.77 bar respectively. CO2 refrigeration systems are more effective, have a greater coefficient of performance and have a greater operating temperature difference (over the gas-cooler) when used under transcritical conditions. It is preferred to have transcritical CO2 refriger-ation systems. The drawback of such a system is the extreme operating conditions. A special system must be designed, built and commissioned at the University of Stellenbosch. The system will demand the use or manufacture of unique, special-ised components. Most of the components utilised are extremely expensive and/or difficult to come by, or designed and manufactured specifically for this system. The CO2 system at the University of Stellenbosch is exceptional and stands out from conventional systems in that: - it can operate under both the subcritical and transcritical conditions; - it has multiple expansion units, which can be alternated, giving a total of four different operating configurations; - the system can run with fully automated controllers or as a static system; - the internal heat exchanger can be included or excluded from the system; - all the heat exchangers can run in counter flow or parallel flow; and - The system has multiple testing points, for both temperature and pressure, to give the operator accurate measurements to be used in comparison with design software, etc. Three simulation programs are given that describe the physical system. The first simulation program is a steady-state simulator used to aid in the design of the heat exchangers and the capillary tube. The second simulator is a steady-state program that determines the mass flow rate in the capillary tube. The third simulation is a transient program, programmed to determine the steady-state conditions of a sys-tem, given set initial conditions and a transient start-up.
AFRIKAANSE OPSOMMING: Koolstofdioksied is 'n natuurlike gas wat gebruik word as 'n verkoelingsmiddel so ver terug as die 1850's. Dit is toe hoofsaaklik gebruik omdat dit maklik verkrygbaar en nie giftig is nie. As gevolg van die hoë werksdruk en relatief lae kritiese temperatuur (en hoë kritiese druk) van CO2, is dit geleidelik uitgefaseer en vervang met hidrochloorfluoorkoolstof en chloorfluoorkoolstowwe. Met die ontdekking van die kweekhuiseffek, kweekhuisgasse en osoon-afbrekende gasse, is die Montreal-protokol en die Kyoto-protokol in werking gestel. Hierdie twee protokolle vereis die afname in die gebruik van sekere kweekhuisgasse en die algehele uitsluiting van ander. Die fokus het verskuif na natuurlike gasse wat omgewingsvriendeliker en makliker is om te bekom. Koolstofdioksied is so 'n gas. Maar CO2 het 'n lae kritiese temperatuur en hoë kritiese druk, 33.98 °C en 73.77 bar onderskeidelik. CO2 verkoelingstelsels is meer effektief, het 'n groter koëffisiënt van werksverrigting en het 'n groter bedryfstemperatuur-verskil (oor die gas-verkoeler) wanneer dit gebruik word onder transkritiese toestande. Dit is dus verkieslik om transkritiese CO2 verkoelingstelsels te hê. Die nadeel van so 'n stelsel is die relatief uiterste bedryfstoestande. 'n Spesiale stelsel moet ontwerp word, dikwels met die gebruik of vervaardiging van unieke, hoogs gespesialiseerde komponente. So 'n stelsel is ontwerp vir die Universiteit van Stellenbosch. Die meeste van die komponente wat gebruik is, is baie duur en/of moeilik om te bekom, of is spesifiek ontwerp en vervaardig vir hierdie stelsel. Die CO2-stelsel by die Universiteit van Stellenbosch is uitsonderlik en staan uit bo konvensionele stelsels deurdat: - dit kan funksioneer onder beide subkritiese en transkritiese toestande; - dit verskeie gasuitsettings-eenhede het, wat afgewissel kan word, wat 'n totaal van vier verskillende bedryfskonfigurasies gee; - die stelsel bedryf kan word met volle outomatiese beheerders of as 'n statiese stelsel; - die interne hitte-uitruiler óf in-, óf uitgesluit kan word van die stelsel; - al die hitte-uitruilers bedryf kan word in kontra-vloei of parallelle vloei; en - die stelsel verskeie toetspunte het, vir beide temperatuur en druk, wat die operateur akkurate metings gee om te vergelyk met die ontwerp sagteware, ens., wat gebruik word. Drie gegewe simulasieprogramme beskryf die fisiese stelsel. In een simulasie word 'n bestendige toestand-simulator gebruik om te help met die ontwerp van die hitteruilers en die kapillêre buis. Die tweede simulasie program is 'n bestendige toestands-program wat die algehele vloeitempo in die kapillêre buis bepaal. Die laaste simulasie is 'n vlugtige program, geprogrammeer om die tydelike toestande van 'n stelsel te bepaal, gegewe vasgestelde aanvanklike toestande en 'n kortstondige aanskakeling.
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Abu, Hanieh Ahmed. "Active isolation and damping of vibrations via stewart platform." Doctoral thesis, Universite Libre de Bruxelles, 2003. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211336.
Full textAbstract:
In this work, we investigate the active vibration isolation and damping of sensitive equipment. Several single-axis isolation techniques are analyzed and tested. A comparison between the sky-hook damper, integral force feedback, inertial velocity feedback and LagLead control techniques is conducted using several practical examples.The study of single-axis systems has been developed and used to build a six-axis isolator. A six degrees of freedom active isolator based on Stewart platform has been designed manufactured and tested for the purpose of active vibration isolation of sensitive payloads in space applications. This six-axis hexapod is designed according to the cubic configuration; it consists of two triangular parallel plates connected to each other by six active legs orthogonal to each other; each leg consists of a voice coil actuator, a force sensor and two flexible joints. Two different control techniques have been tested to control this isolator :integral force feedback and Lag-Lead compensator, the two techniques are based on force feedback and are applied in a decentralized manner. A micro-gravity parabolic flight test has been clone to test the isolator in micro-gravity environment.
ln the context of this research, another hexapod has been produced ;a generic active damping and precision painting interface based on Stewart platform. This hexapod consists of two parallel plates connected to each other by six active legs configured according to the cubic architecture. Each leg consists of an amplified piezoelectric actuator, a force sensor and two flexible joints. This Stewart platform is addressed to space applications where it aims at controlling the vibrations of space structures while connecting them rigidly. The control technique used here is the decentralized integral force feedback.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished
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Bočková, Andrea. "Stavebně technologický projekt přípravy a realizace administrativní budovy firmy TREFAL, spol. s r.o." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-409917.
Full textAbstract:
The aim of this thesis is the development project of the firm TREFAL, Spol. s.r.o. The object SOO2 - Administrative building - that is a constituent of the area of TREFAL, Spol. s.r.o. is discussed topic of this thesis. The main focus is the construction development of the monolithic supporting construction objects. The thesis further depicts and investigates accompanying and overall technical report, an implementation study of the main technological stages, situational designs, a solution of the broader traffic relations including a proposal for the supplementation of the construction development, BOZP plan, budget and timeline, a proposal for the new local communication and following textual and design documentation according to the thesis assignments.
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Topinka, Jiří. "Dalniční most u Soběslavi - příprava, realizace a řízení stavby." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227312.
Full textAbstract:
Master´s thesis processes Construction technology project and implementation of bridge at Soběslav on the route D3, section D3 Tábor – Veselí nad Lužnicí, concretely SO 7-216 Bridge over the route III/15527, Černovický stream and biocorridor km 94,100. This is a permanent road bridge about 25 fields with the continuous construction of precast prestressed concrete beams longitudinally coupled concrete slab.
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Yau, Henry. "Frequency Response Based Repetitive Control for Periodic Coefficient Systems Motivated by Cam Followers." Thesis, 2017. https://doi.org/10.7916/D8Q244W2.
Full textAbstract:
Cam follower systems are generally designed to operate at a fixed speed or a range of fixed speeds. However manufacturing defects, wear, or a change of design goals may require altering the camshaft speed to produce a follower trajectory which is not possible using a fixed speed. The follower trajectory may also be optimized for some performance criteria such as minimizing vibration and wear. Like most real world systems, the differential equations governing a cam follower system are nonlinear.
A common approach for controlling a nonlinear system is to first linearize the system about a nominal operating point, then apply linear control laws. In many cases, such as the cam follower system, one can create a trajectory and numerically solve the nonlinear system for the inputs required to follow it.
Linearizing about this solution creates a linear time varying system whose states are deviations from the desired solution. The speed trajectory in the cam follower system is periodic, which results in a linear system with periodic coefficients.
Repetitive control creates control systems that aim to converge to zero tracking error following a periodic command, or aim to completely cancel the effects of a periodic disturbance. Using the inverse of the steady state frequency response as a compensator has been shown to be very effective for linear time invariant systems. That idea is applied here to linear time periodic systems. The periodic state matrices lend themselves well to frequency domain representations, which can be used to construct a matrix form of the steady state frequency response.
The first law studied in this work analyzes a moving window implementation which monitors the output errors and previous commands to create an update to the change in the command for the current time step using the inverse of the steady state frequency response matrix. Asymptotic convergence conditions for zero tracking error are derived.
When the number of samples in one period is not an integer number, the moving window method is not feasible without interpolation. Therefore a second method based on the projection algorithm from adaptive control is developed and analyzed.
In linear constant coefficient systems, one generally needs to incorporate a frequency cutoff filter to robustify to high frequency model error. The additional intricacies of designing a cutoff filter for periodic systems is considered, aiming to handle the fact that for periodic coefficient systems, addressing error components below the intended cutoff can excite harmonics above the cutoff.
The control laws developed in this work are applicable to any nonlinear system which may be linearized about a periodic trajectory.
Development of these control laws is motivated by improving the performance of a cam follower system. Additional improvements in cam follower behavior can be done through parameter optimization. This includes optimizing a nonlinear follower spring such that it provides just sufficient force to maintain contact while reducing the load on the cam.
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Pretorius, Jan Harm Christiaan. "Drie-dimensionele magnetiese laer vir rotors met hoë rotasiesnelhede." Thesis, 2014. http://hdl.handle.net/10210/10647.
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Lawrence, Tom Marquis. "Characterization and Measurement of Hybrid Gas Journal Bearings." 2012. http://hdl.handle.net/1805/2926.
Full textAbstract:
Indiana University-Purdue University Indianapolis (IUPUI)This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to “basics” to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner’s permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow “compensation” should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an “apples-to-apples” comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is developed to study in unprecedented detail the aerostatic component of the hybrid bearings. It is used to definitively compare the feedhole bearings to the porous liner bearings. The hydrostatic bearing efficiency (HBE) is defined and it is determined that the maximum achievable hydrostatic bearing efficiency (MAHBE) is determined solely by the bearing’s mass addition configuration. The MAHBE of the porous liner bearings is determined to be over 5 times that of the feedhole bearings. The method also presents a means to tune the Kmeas to the clearance to achieve the MAHBE as well as giving a complete mapping of the hitherto misunderstood complex shapes of aerostatic load versus radial deflection curves. This method also rediscovers the obscure phenomenon of static instability which is called in this thesis the “near surface effect” and appears to be the first work to present a practical method to predict the range of static instability and quantify its resultant stiffness fall-off. It determines that porous liner type bearings are not subject to the phenomenon which appears for feedhole type bearings when the clearance exceeds a critical value relative to its mass-addition compensation. The standing pressure waves of hydrostatic and hybrid bearings with the 2 configurations of external pressurization as well as a geometrically identical hydrodynamic bearing are studied in detail under the methodology of the “CFD microscope”. This method is used to characterize and identify the development, growth, and movement of the pressure wave extrema with increased hydrodynamic action (either increasing speed or increasing eccentricity). This method is also used to determine the “cause” of the “near surface effect”. A gedanken experiment is performed based on these results which indicates that a bearing with a “stronger aerostatic strength” component should be more stable than one with a low aerostatic strength component. Numerical instability “speed limits” are found that are also related to the hydrostatic strength of the bearing. The local conditions in the standing waves are characterized in terms of their local Mach number, Knudsen number, Reynolds number, and Taylor Number. It is concluded that low eccentricity bearing whirl can be attributed to the off load-line orientation of the bearing load force caused by the overlay of the hydrodynamic bearing standing wave onto the hydrostatic bearing wave of the hybrid bearing, whereas it is hypothesized that aperiodic and random self-excited vibration which occurs at high eccentricity, as reported in the literature, is probably due to shock waves, turbulence, near surface effect, and slip at local areas of the standing wave.
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Ridgway, Ian G. "Prototype combine for grain harvesting based on internal pneumatic transfer / by Ian Gilbert Ridgway." 2002. http://hdl.handle.net/2440/22428.
Full textAbstract:
"July 2002"Bibliography: leaves 82-83.
xv, 192 leaves : ill., plates ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
The aim of this project was to build a combine harvester with a reduced number of components, a maximum of five moving parts, which could reap most if not all crops from ground level upwards and be self-cleaning.
Thesis (M.App.Sc.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002
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Ramatsetse, Boitumelo. "Development of a reconfigurable vibrating screen." 2014. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001520.
Full textAbstract:
M. Tech. Industrial EngineeringThe ability to respond to changes and uncertainty in production demands currently constitutes a crisis in small and medium scale mining industries in South Africa. The case study of various mining and mineral processing site visits which was carried out revealed that the existing conventional screening methods are not scalable or able to be integrated and have limited processing capacity, which constitutes a high production cost on a long-term basis. In view of this, the Reconfigurable Vibrating Screen machine was designed and manufactured with the intension of eliminating these challenges faced by small and medium scale mining industries. The newly developed vibrating screen utilizes the concept of re-configurability, making it simple to attain full capacity processing production on the same machine. The design of a reconfigurable vibrating screen is based on the idea of enhancing the processing capacity by adjustable width and length of the screen structure with regard to the desired processing output.
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Styger, Gary. "An investigation of the effect of the manufacturing process on the performance of conveyor pulleys." Thesis, 2012. http://hdl.handle.net/10210/5390.
Full textAbstract:
M.Phil.Pulleys are critical items in belt conveyors. Their primary role is to drive large mining conveyor systems, facilitating the transportation of ore over extensive distances, both in South Africa and abroad. The effect of the manufacturing process (with specific emphasis on the induced residual stresses) on the fatigue performance of conveyor pulleys is herein investigated and reported. A pre-selected pulley was chosen based on size, suitable for experimental work as well as practical specifications. The static and fatigue performance of the pulley were investigated both with the current design criteria as well as Finite Element Analysis, with comparisons drawn. The material data for the Finite Element Models was obtained experimentally with tensile tests of the SANS 1431 350 WA plate. The magnitude of the residual stresses were obtained experimentally by using the incremental hole-drilling technique for non-uniform residual stresses. The method was verified by comparison with the Finite Element Analysis results for the non-linear material analysis of the roll-bending of the shell. The fatigue analysis revealed that the stress ranges of interest for the pulley were below the non-propagating stress range, and hence theoretically infinite fatigue life would be possible under constant amplitude conditions. The operational fatigue life required for the pulley would be possible, when considering the latest S-N curve for "very high cycle fatigue". The stress intensity factors for the weld details were also below the threshold value and hence crack growth should not occur, upon crack initiation. A new design criteria was proposed for the fatigue analysis considering either fatigue assessment standards or fracture mechanics for the assessment of the butt-welds. This investigation showed that the manufacturing-induced residual stresses may play a significant role in the fatigue life of a pulley. The fatigue strength of a machined stressrelieved joint is higher if the stress range is partly compressive. The fatigue strength of a machined as-welded joint is higher than estimated by the fatigue classifications. This is due to residual stress relaxation that occurs at the weld toe because of yielding and hence a subsequent reduction and redistribution of the residual stresses. This reduction in the mean stress level, with a stress range that is partly compressive, would mean an increase in the fatigue strength of the joint. This would in conclusion result in similar fatigue strengths for a stress-relieved and an aswelded joint. This would additionally depend on the extent of the reduction of the residual stress in the as-welded joint. Recommendations were suggested for further experimental and numerical work for both the T-bottom and Turbine-type pulleys.
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Kim, Daejong. "Design and fabrication of sub-millimeter scale gas bearings with tungsten-containing diamond like carbon coatings." Thesis, 2004. http://hdl.handle.net/2152/2039.
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Salim, Mohamed Ali 1968. "Finite element based rotor design optimization for the brushless doubly-fed machine." Thesis, 1993. http://hdl.handle.net/1957/37050.
Full textAbstract:
Brushless Doubly-Fed Machines have potential benefits in variable speed
generation and adjustable speed drive applications by combining a robust machine
structure with a reduced power converter rating. While recent work has demonstrated
feasibility, steady-state performance has not been optimized. The nature of doubly-fed
operation causes rotor currents of varying, relatively high frequency. Moreover, the rotor
structure deviates from conventional squirrel cages. Consequently, induction machine
rotor bar geometries need to be carefully examined and refined for applicability in the
doubly-fed system.
The present thesis uses finite element analysis to investigate alternative rotor bar
design. Two-dimensional finite element analysis is used to investigate basic rotor bar
characteristics. Interface with a detailed simulation program enables investigation of
assembled rotors, otherwise a three-dimensional analysis problem.
Rotor bar geometries for a high speed alternator are investigated. Bar shapes are
kept simple to allow manufacturing of the rotor in the absence of the-casting equipment.
Rotor prototypes are constructed using custom, laser-cut laminations and experimental
results for the alternator verify improved line-to-shaft efficiencies over conventional rotor
geometries as well as off-the-shelf alternators.Graduation date: 1994
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Sithole, Phila Elvis. "Two-dimensional CCD position sensor system for active magnetic bearings." 2007. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001047.
Full textAbstract:
M. Tech. Digital Technology.This dissertation reports on an optical-based two-dimensional position sensor for use in Active Magnetic Bearings (AMB) to measure the position of the levitated rotor. The motivation for the deployment of optical technology is the well-known advantage of high precision contactless displacement measurement. The radial and axial edges of the rotor are illuminated by red and green laser beams respectively. The position of the rotor is determined from its image projected on a Charge Coupled Device (CCD) sensor. The measuring principle is demonstrated as a position sampler in the closed loop control of an active magnetic bearing model. The image representing the position is processed with a real-time algorithm on a Field Programmable Logic Gate Array. The principle of operation of a CCD as a position sensor is analysed in order to establish how the image captured by the CCD can be processed to determine the position of the rotor. A simple AMB is modelled in which the sensor acts as a feedback position device. The main objective of the model is to evaluate the accuracy of the system. The purpose of the overall sensing technique to be used is to achieve highly accurate and precise measurements with CCD-based optical metrology.
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"Design and experimental study on miniature vapor compression refrigeration systems." 2012. http://library.cuhk.edu.hk/record=b5549443.
Full textAbstract:
近年來微型製冷系統有許多應用。例如，電子器件的冷却是研製更快速、更小型和更可靠的芯片的重要課題, 隨著電子芯片功耗的增加，散熱量不断增長，傳統的被動式散熱方法已經過時，新的主動式散熱方法成爲必須。又例如微型個人冷卻系統可用於救火等各種惡劣環境。与其它製冷方法相比，蒸氣壓縮製冷技術是最有潜力的方法。本文闡述了两种微型蒸氣壓縮製冷系統的研製工作：一是電子冷却系统，一是個人热舒适系统。研究主要包括以下幾個方面：
1) 微型蒸氣壓縮製冷系統的熱力學分析。對系統在不同工作條件下（包括壓縮機效率、環境溫度等）的性能進行了分析。对換熱器的設計也作了详述。
2) 微型蒸氣壓縮製冷系統的熵分析。通過分析發現，壓縮機和系統漏熱造成的熵是產生系統不可逆性的主要因素,因此高效的壓縮機和降低系統漏熱是提高微型蒸氣壓縮製冷系統性能的關鍵所在。
3) 實驗系统的詳細介紹。一共做了两套微型蒸氣壓縮製冷系統，一为電子冷卻系統和一为個人冷卻系統。爲了縮小微型蒸氣壓縮製冷系統的尺寸，系統的元件必須小型化。系統的壓縮機是在市場上直接购買的，但是換熱器包括冷板蒸發器、管翅式蒸發器和微通道冷凝器都是特別設計和製造的。實驗裝置建成可以方便的改變工作條件，諸如壓縮機轉速、製冷劑充灌量、毛細管長度、換熱器面積等。
4) 對電子冷卻系統和個人冷卻系統分別進行了實驗。對於電子散熱系統來，當發熱管的功率為200瓦時，冷板溫度可以控制在大約60攝氏度。系統的熱力學完善度在0.23到0.31，而壓縮機的效率介乎40%至65%。對個人冷卻系統來，系統製冷量可達321瓦，其性能係數達到4.59。系統的熱力學完善度為0.21 ~ 0.27。 兩种系統的熱力學完善度都與當前家用製冷系统的熱力學完善度相似。相信不久的将来会有不少应用。
Micro refrigeration systems are being increasingly used nowadays. One example is electronic cooling. With the rapid advancement of chips, traditional passive heat dissipation techniques are becoming obsolete and hence, new active cooling techniques become necessary. The other example is the personal thermal comfort system demanded by people working in the hazardous environment, such as fire fighting. Among various cooling methods, Vapor Compression Refrigeration (VCR) is the most promising method. According literatures, however, few miniature refrigeration systems are available.
This thesis presents two Miniature Vapor Compression Refrigeration (MVCR) systems, one for electronics cooling and the other for personal thermal comfort. In particularly, following aspects are focused:
1) Thermodynamic analysis. The thermodynamic models of the systems are developed and the performances are studied under various working conditions including compressor efficiencies, ambient temperature and so on.
2) Entropy analysis. It is found that entropy of the compressor and the heat leakage play crucial roles. High efficient compressor and the heat leakage minimization are very important.
3) Prototype building. Two prototypes are built: one for electronics cooling and the other for personal thermal comfort. The miniature compressors are purchased from market. The heat exchangers, including the cold pate, tube-fin evaporator and micro channel condenser, are custom designed and made.
4) Experiment testing. The two prototypes are tested under various working conditions such as compressor speed, refrigerant charge and capillary tube length. For the electronics cooling system, the cold plate temperature could be maintained at about 60 ºC under the 200 W heater power input. The second-law efficiency of the system varies from 0.23 to 0.31; and the compressor efficiency is between 40% ~ 65%. For the personal thermal comfort system, its capacity could reach 321 W with 100 g refrigerant charge, 1200 mm capillary tube length, and the compressor speed of 4503 rpm. The COP is 4.59 and the second-law efficiency is between 0.21 ~ 0.27. The performances of the two systems are comparable to that of the current domestic refrigeration systems. Therefore, it is expected that they will find some practical applications in the near future.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Wu, Zhihui.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 99-110).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.
Abstract --- p.I
Acknowledgement --- p.IV
List of Tables --- p.VIII
List of Figures --- p.IX
Nomenclature --- p.XII
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Backgound --- p.1
Chapter 1.2 --- Thesis Outline --- p.5
Chapter Chapter 2 --- Literature Review --- p.6
Chapter 2.1 --- History of Refrigeration --- p.6
Chapter 2.2 --- Availabe Refrigeration Methods --- p.7
Chapter 2.2.1 --- Heat pipe and vapor chamber --- p.9
Chapter 2.2.2 --- Thermoelectric cooler --- p.10
Chapter 2.2.3 --- Stirling refrigerator --- p.10
Chapter 2.2.4 --- Pulse tube refrigerator --- p.11
Chapter 2.2.5 --- Absorption refrigerator --- p.12
Chapter 2.3 --- Vapor Compression Refrigeration System --- p.14
Chapter 2.3.1 --- Development of the miniature refrigeration system --- p.15
Chapter 2.3.2 --- Development of the miniature compressors --- p.20
Chapter 2.3.3 --- Development of the micro heat exchangers --- p.24
Chapter 2.3.4 --- Applications --- p.28
Chapter Chapter 3 --- System Analsysis and Components Design --- p.29
Chapter 3.1 --- A Brief Review of a Typical VCR System --- p.29
Chapter 3.1.1 --- Refrigerant comparison --- p.33
Chapter 3.1.2 --- Effect of the compressor efficiency --- p.34
Chapter 3.1.3 --- Effect of the ambient temperature --- p.35
Chapter 3.1.4 --- Effect of the evaporator temperature --- p.36
Chapter 3.2 --- Analysis on Entropy Generation of a MVCR System --- p.37
Chapter 3.2.1 --- Derivation of coefficient of performance --- p.38
Chapter 3.2.2 --- Entropy generation calculation for a MVCR system --- p.39
Chapter 3.3 --- System Design --- p.46
Chapter 3.3.1 --- System Configuration --- p.46
Chapter 3.3.2 --- Heat Exchanger Design --- p.47
Chapter 3.3.2.1 --- Condenser design --- p.48
Chapter 3.3.2.2 --- Cold plate design --- p.50
Chapter 3.3.2.3 --- Tube-fin evaporator design --- p.51
Chapter Chapter 4 --- The MVCR System for Electronics Cooling --- p.55
Chapter 4.1 --- Experimental Setup --- p.55
Chapter 4.1.1 --- Components --- p.55
Chapter 4.1.2 --- Instrumentation --- p.61
Chapter 4.1.3 --- Testing plans --- p.63
Chapter 4.1.4 --- Data reduction --- p.64
Chapter 4.1.5 --- Uncertainty analysis --- p.67
Chapter 4.2 --- Results and Discussion --- p.68
Chapter 4.2.1 --- Effect of the compressor speed --- p.68
Chapter 4.2.2 --- Effect of the refrigerant charge --- p.70
Chapter 4.2.3 --- Effect of the capillary tube length --- p.71
Chapter 4.2.4 --- Cold plate temperature comparison --- p.72
Chapter 4.2.5 --- Location of the Cartridge heater --- p.76
Chapter 4.2.6 --- System efficiency --- p.78
Chapter 4.2.7 --- Thermal resistance --- p.81
Chapter 4.3 --- Summary --- p.83
Chapter Chapter 5 --- The MVCR System for Personal Cooling --- p.85
Chapter 5.1 --- Experimental Setup --- p.85
Chapter 5.2 --- Results and Discussions --- p.87
Chapter 5.2.1 --- Effect of the compressor speed --- p.87
Chapter 5.2.2 --- Effect of the refrigerant charge --- p.88
Chapter 5.2.3 --- Effect of the capillary tube length --- p.89
Chapter 5.2.4 --- Effect of the evaporator area --- p.90
Chapter 5.2.5 --- Effect of the evaporator fan speed --- p.91
Chapter 5.2.6 --- System efficiency --- p.92
Chapter 5.3 --- Summary --- p.94
Chapter Chapter 6 --- Conclusions and Future Work --- p.96
Chapter 6.1 --- Conclusions --- p.96
Chapter 6.2 --- Future Work --- p.98
Bibliography --- p.99
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Hunt, Clive Wilfred. "A computer simulation for the design of percussive hydraulic drills." Thesis, 2013. http://hdl.handle.net/10539/13124.
Full text
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Grobler, Steven Robert. "The dual ema-fem approach to dynamic analysis." Thesis, 1990. https://hdl.handle.net/10539/28733.
Full textAbstract:
A dissertation submitted to the Faculty of Engineering, University
of the Witwatersrand, Johannesburg, in fulfillment of
the requirements for the degree of Master of Science in EngineeringIt has been said that experimental modal analysis (EMA) "grew to prominence because the engineering community was incapable of properly analyzing the dynamics of commercially significant structures" [24]. The advent of powerful theoretical methods, such as the Finite Element Method (FEM) has not, however, resulted in the demise of EMA. In fact both FEM and EMA have undergone rapid growth and the merging of the two into an effective design and diagnostic tool has had a major impact on the engineering community's approach to dynamics related problems. In this study, the term dual has no mathematical connotations and is used to describe the complementary use of the techniques of EMA and FEM. The mining industry, worldwide, has experienced dynamics related problems in the operation of conveyances in vertical shafts. A study undertaken in South Africa investigated the behaviour of shaft steelwork and skips, resulting in a set of design guidelines for future shaft steelwork designs. This work only investigated the dynamic behaviour of skips. In this project, the ABAQUS and MODEL SOLUTION FEM codes were used to construct models of a. mine cage. An impact modal test was carried ant on the cage, using a GenRad 2515 CAT system, An impact hammer, suitable for exciting large structures, and a strain gauge force transducer were designed and built for the purpose of the test. The natural frequencies and mode shapes obtained from both FEM and EMA are compared by means of the modal assurance criterion (MAC). The test data is used to tune the model to produce accurate results. The model Could then be used (with minimal further test work) for predicting the response of the structure to dynamic loading or the effects of structural modifications.
Andrew Chakane 2020
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Motaung, Mokete Isaac. "Modelling and control of an electric wheelchair virtual reality platform." 2014. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001341.
Full textAbstract:
M. Tech. Electrical Engineering.Discusses how to develop the kinematic and dynamic model and the controller for the 2-DOf motion platform used in an augmented reality environment for wheelchair driving. This comes as a motivation to help to train disabled and elderly people to drive wheelchairs.. With accurate inverse dynamic model, it is possible to achieve high performance control algorithms of robots and direct dynamic model is required for their simulation. The other part of this research was to model and control the roller for the feedback of the wheelchair wheels.