Many phenomena determining the microstructure of a tool steel and consequently the properties of the material, are governed by multicomponent diffusion. The diffusion driven reactions that take place during, for example, tempering of a hot-work tool steel or when the microstructure develops during hot isostatic pressing of cold-work tool steel, are dependent on the types and amounts of alloying elements. In order for computational methods to be usable, these alloying effects need to be understood and incorporated in the models. In this work the influence of some typical tool steel alloying elements on the coarsening behavior of precipitates is investigated. Experimental coarsening studies are performed and the impact of the diffusion mobility descriptions and the thermodynamic descriptions are investigated by means of DICTRA coarsening calculations. The kinetic descriptions for diffusion in the body centered-cubic phase in the case of the chromium-iron-vanadium system and the chromium-iron-molybdenum system are improved by assessments of diffusion mobility parameters, and are shown to have a large impact on the calculated coarsening rate for vanadium-rich and molybdenum-rich precipitates. The effect of cobalt is examined by a coarsening experiment for vanandiumrich carbides and by a diffusion couple experiment for the investigation of the vanadium interdiffusion. The presence of cobalt is experimentally shown to have retarding effect on the coarsening rate of the carbides, but not on the vanadium diffusion. The coarsening rate of nitrogen-rich precipitates is compared to the coarsening rate of carbon-rich precipitates, and a lower coarsening rate for nitrides compared to carbides can be confirmed. Correlation between coarsening calculations and experiments is obtained suggesting that the thermodynamic description of the two systems is the underlaying reason for the different coarsening rates. Further, calculations utilizing the DICTRA software are combined with experimental investigations in order to study the possibility to apply computational methods for compound material development and explore application areas for high nitrogen alloyed tool steels produced by powder metallurgy. / <p>QC 20121011</p>

This thesis deals with the integral motor of tomorrow, and particularly with a variable speed, sensorless permanent magnet synchronous motor with an integrated converter. The rated power is 15 kW at 1500 r/min. The outer dimensions are approximately the same as for the equivalent standard induction motor. Control strategies for pumps and fans, i.e. suitable loads for variable speed motors, are briefly described. The huge energy savings that can be made by reducing the speed instead of throttling/choking the flow are pointed out. Compared to installing an induction motor with a separate converter, a PM integral motor will probably pay-off in less than a year. A totally analytical expression for calculating the airgap flux density of permanent magnet motors with buried magnets is derived. The analytical expression includes axial leakage, and iron saturation of the most narrow part of the magnetic circuit of the machine. A computer program for optimization of PM motors with buried magnets has been developed. It was used to design the manufactured prototype PM integral motor, and the parameters are investigated with analytical and/or FEM calculations. The optimization program is also used to suggest nearoptimum pole numbers for desired powers (4-37 kW) and speeds (750- 3000 r/min) of inverter-fed PM motors. Results show that compact buried PM motors should have relatively large airgaps and high NdFeB-magnet masses to improve the efficiency. Ferrite magnets are unsuitable. Measurements on the manufactured PM motor, the novel concept of stator integrated filter coils, and the complete PM integral motor are presented. Special attention was given to temperature and overall efficiency measurements. The rotor cage losses were investigated by time-stepping FEM. Four short circuit fault conditions were also examined in order to evaluate the risks of demagnetization of the buried magnets.

La contamination bactérienne et le développement de biofilms marins sont des problèmes récurrents, et terriblement coûteux sur les structures immergées des bâtiments de l'armée. L'emploi de composés bactéricides et nocifs pour l'écosystème est désormais interdit. Les travaux menés lors de cette thèse avaient donc pour objectif de mettre au point des traitements de surface originaux préventifs, permettant de limiter l'adhésion des bactéries marines et, le cas échéant, leur développement sur des matériaux à base de cuivre et de titane. Des surfaces de cuivre ont été fonctionnalisées par des espaceurs sur lesquels ont été greffées des molécules antibactériennes : un peptide, la Magainine I et une enzyme, le lysozyme HEWL. Une deuxième stratégie a consisté en le greffage d'espaceurs, puis des agents antibactériens, sur des surfaces microsctucturées à l'aide de photopolymères dérivés de poly(méthyl méthacrylate). Sur les surfaces de titane, la Magainine I et l'HEWL ont été greffés sur deux types d'espaceurs, un silane et un PEG diamine. Les traitements de surface, antibactériens, ont été optimisés grâce à des caractérisations à chaque étape par IR, XPS, AFM et mesures d'angle de contact. Afin de mettre en évidence les propriétés antibiofilms des surfaces fonctionnalisées, quatre tests ont été mis en place : un test d'adsorption de protéines, un test d'adhésion de bactéries, un test de viabilité des bactéries adhérées et enfin un test de croissance des bactéries après contact avec les surfaces fonctionnalisées. A titre d'exemples, le développement de bactéries sur les surfaces de titane a été réduit de 90% et l'adhésion de bactéries réduite de 80% sur les surfaces de cuivre

<p>This thesis deals with the integral motor of tomorrow, and particularly with a variable speed, sensorless permanent magnet synchronous motor with an integrated converter. The rated power is 15 kW at 1500 r/min. The outer dimensions are approximately the same as for the equivalent standard induction motor.</p><p>Control strategies for pumps and fans, i.e. suitable loads for variable speed motors, are briefly described. The huge energy savings that can be made by reducing the speed instead of throttling/choking the flow are pointed out. Compared to installing an induction motor with a separate converter, a PM integral motor will probably pay-off in less than a year.</p><p>A <i>totally analytical</i> expression for calculating the airgap flux density of permanent magnet motors with buried magnets is derived. The analytical expression includes axial leakage, and iron saturation of the most narrow part of the magnetic circuit of the machine.</p><p>A computer program for optimization of PM motors with buried magnets has been developed. It was used to design the manufactured prototype PM integral motor, and the parameters are investigated with analytical and/or FEM calculations. The optimization program is also used to suggest nearoptimum pole numbers for desired powers (4-37 kW) and speeds (750- 3000 r/min) of inverter-fed PM motors. Results show that compact buried PM motors should have relatively large airgaps and high NdFeB-magnet masses to improve the efficiency. Ferrite magnets are unsuitable.</p><p>Measurements on the manufactured PM motor, the novel concept of stator integrated filter coils, and the complete PM integral motor are presented. Special attention was given to temperature and overall efficiency measurements.</p><p>The rotor cage losses were investigated by time-stepping FEM. Four short circuit fault conditions were also examined in order to evaluate the risks of demagnetization of the buried magnets. </p>

This thesis has been motivated by the growing needs for multi-degree of freedom (M-DOF) electromagnetic actuators capable of smooth and accurate multi-dimensional driving motions. Because high coercive rare-earth permanent-magnets (PMs) are widely available at low cost, their uses for developing compact, energy-efficient M-DOF actuators have been widely researched. To facilitate design analysis and optimization, this thesis research seeks to develop a general method based on distributed source models to characterize M-DOF PM-based actuators and optimize their designs to achieve high torque-to-weight performance with compact structures To achieve the above stated objective, a new method that is referred to here as distributed multi-level current (DMC) utilizes geometrically defined point sources has been developed to model electromagnetic components and phenomena, which include PMs, electromagnets (EMs), iron paths and induced eddy current. Unlike existing numerical methods (such as FEM, FDM, or MLM) which solve for the magnetic fields from Maxwell’s equations and boundary conditions, the DMC-based method develops closed-form solutions to the magnetic field and force problems on the basis of electromagnetic point currents in a multi-level structure while allowing trade-off between computational speed and accuracy. Since the multi-level currents can be directly defined at the geometrically decomposed volumes and surfaces of the components (such as electric conductors and magnetic materials) that make up of the electromagnetic system, the DMC model has been effectively incorporated in topology optimization to maximize the torque-to-weight ratio of an electromechanical actuator. To demonstrate the above advantages, the DMC optimization has been employed to optimize the several designs ranging from conventional single-axis actuators, 2-DOF linear-rotary motors to 3-DOF spherical motors. The DMC modeling method has been experimentally validated and compared against published data. While the DMC model offers an efficient means for the design analysis and optimization of electromechanical systems with improved computational accuracy and speed, it can be extended to a broad spectrum of emerging and creative applications involving electromagnetic systems.

The experimental alloy powders of 1% Mg treated Al-8Fe-1.8V-8Si were obtained by air atomization. The screen analysis of powders was made by sieves with meshes ranging from +90&micro / m, +63&micro / m, +53&micro / m, +45&micro / m, +38&micro / m to -38&micro / m. Unreinforced and TiC particulate reinforced specimens were produced by hot dynamic consolidation which is known as hot swaging. Powders were canned into pure aluminium tubes of about 10cm length and 2.2cm diameter. Single action and double action cold pressing were applied to some of the specimens before hot dynamic compaction and some specimens of canned loose powder were also processed. The diameters of the hot compacts were decreased in a two step process by swaging machine (rotary dynamic compaction). During the first step, after canning, compacts had been held at 480&deg / C for 1 hour and swaged, thus the diameter decreased from 2.2 cm to 1.97cm. Secondly, the compacts were reheated to 480&ordm / C and held for 1 hour and further swaged to obtain a diameter decrease from 1.97cm to 1.54cm. Generally, the microstructures of the hot dynamic compacted specimens were homogeneous except the specimens produced by using -63 &micro / m +53 &micro / m powder size fraction. By SEM study, a vanadium free cross like AlFeSi phase was observed near the outer regions of the specimen. No considerable coarsening of the dispersoids was observed after hot dynamic compaction of +63 &micro / m size powder. For -90&micro / m +63&micro / m size powders, maximum flexural strength values obtained by three point bending test increased by addition of 10% TiC to from 152 MPa to 285 MPa at double pressed condition and from 76MPa to 190MPa at loose powder canning condition. By hardness tests, it was observed that hardness values were inversely proportional to powder size and increased from 107 BHN to 147 BHN for corresponding powder size range of +90&micro / m to -38&micro / m. Porosity values obtained by Archimedes principle for single pressing varied between 0.03 % and 1.10% for corresponding size range of +38&micro / m to +90&micro / m. No considerable porosity was detected for double pressing. Porosity values of canned loose powder were between 3% and 10% for the range of +38 &micro / m- +45 &micro / m. By X-Ray analysis, it was revealed that Mg2Si reaction did not form after artificial aging of specimens up to 8 hours at 190&deg / C. Also, x-ray analysis of individual powders and specimens obtained by hot dynamic compaction of the same powder showed that / after hot dynamic compaction, the alloy powders were stable and no new phase formation was detected for +63&micro / m size. DSC examination of the specimens produced from +90&micro / m, +63&micro / m, +53&micro / m, -38&micro / m powder confirmed the microstructure stability up to the melting temperature. Melting temperature was detected to be in the range of 560&deg / C-575&deg / C by DSC.

The wind power research at the division of Electricity at Uppsala University is aimed towards increased understanding of vertical axis wind turbines. The considered type of wind turbine is an H-rotor with a directly driven synchronous generator operating at variable speed. The experimental work presented in this thesis comprises investigation of three vertical axis wind turbines of different design and size. The electrical, control and measurement systems for the first 12 kW wind turbine have been designed and implemented. The second was a 10 kW wind turbine adapted to a telecom application. Both the 12 kW and the 10 kW were operated against dump loads. The third turbine was a 200 kW grid-connected wind turbine, where control and measurement systems have been implemented. Experimental results have shown that an all-electric control, substituting mechanical systems such as blade-pitch, is possible for this type of turbine. By controlling the rectified generator voltage, the rotational speed of the turbine is also controlled. An electrical start-up system has been built and verified. The power coefficient has been measured and the stall behaviour of this type of turbine has been examined. An optimum tip speed ratio control has been implemented and tested, with promising results. Use of the turbine to estimate the wind speed has been demonstrated. This has been used to get a faster regulation of the turbine compared to if an anemometer had been used.

L'objectif de ces travaux est d'étudier les effets d'une irradiation ultrasonore haute fréquence (500 kHz) sur la synthèse électrochimique de polymères conducteurs en milieu aqueux. Les ultrasons favorisent la réaction de polymérisation électrochimique en augmentant le transport des espèces électroactives vers l'électrode. Ils engendrent des films plus compacts, présentant une topographie plus fine et plus homogène. Les effets chimiques engendrés par la propagation de l'onde acoustique permettent un meilleur taux de dopage des films. Néanmoins, leur conductivité électrique se trouve légèrement diminuée, dû à une dégradation des chaînes polymères par l'activité cavitationelle. La possibilité de contrôler les propriétés de morphologie fut mise à profit dans différentes applications comme celles des capteurs pH potentiométriques ou des revêtements anti-corrosion. Pour de telles applications, utilisant ces films en tant que couche fonctionnelle, les surfaces obtenues en présence d'irradiation ultrasonore mènent à de meilleurs résultats. Une technique de masquage sélectif à base d'ultrasons focalisés a également été développée afin d'élaborer un substrat biphasique laissant présager d'intéressantes applications biologiques

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The focus of this thesis is on the optimal design and evaluation of FI-PM machines to be used with a MG transmission drive-train for EV application. The machines presented are optimised using a gradient-based optimisation algorithm of the VisualDoc software together with FE software and Python scripts. Each machine is optimised for its own objective function. The focus is to reduce expensive rare earth material. High torque ripple issues of the optimised machines are solved by implementing a relatively new topology where the rotor poles/barriers are made asymmetric. The asymmetric rotor topology implemented is effective and can be used as an alternative for rotor stack skewing. PM demagnetisation and rotor deformation studies are conducted on the optimum designed machines to ensure that no PM demagnetisation on the surface of the PMs and critical rotor deformation occur. The FE performance results of the optimum designed machines are shown and discussed. One of the optimum designed FI-PM machines is manufactured and tested in the laboratory. The FE and measured results of the machine are compared and shows good correlation. The saliency performance of the optimum designed machines are evaluated as it determines its position sensorless control capability. It is shown that the saliency ratios increase linearly with load, making it favourable for position sensorless control. It is also shown that the asymmetric rotor topologies introduced a larger mutual inductance compared to their symmetric counterparts, thus higher cross-coupling is present in these rotors and therefore a higher saliency shift, which is undesirable. Two case studies are performed in order to improve saliency performance. The objective of the first case study is to improve the saliency shift by reducing the flux leakage paths in the rotor. The objective of the second case study is to optimise a FI-PM machine in order to improve the saliency ratio and -shift. The results of the two case studies are compared with the saliency performance of the other machines. / AFRIKAANSE OPSOMMING: Die fokus van hierdie tesis is op die optimale ontwerp en evaluering van veld versterking permanente magneet masjiene vir veelvoudige-rat elektriese voertuig toepassings. Die masjiene teenwoordig is geoptimeer met behulp van ’n helling-gebaseerde optimering algoritme. Elke masjien is geoptimeer vir sy eie doel funksie. Die fokus is om duur seldsame permanent magneet materiaal te verminder. Hoë wringkrag-rimpeleffek van die optimale masjiene word opgelos deur die implementering van ’n relatief nuwe topologie waar die rotor pole/vloedbarrière asimmetries gemaak word. Die asimmetriese rotor topologie wat geimplementeer is, is effektief en kan dus as ’n alternatief vir die rotor stapel skeef metode gebruik word. Permanent magneet demagnetisering en rotor vervorming studies is ook uitgevoer op die optimum ontwerpte masjiene om te verseker dat geen demagnetisering plaasvind nie en ook geen kritiese rotor vervorming nie. Die eindige-element resultate van die optimum ontwerpte masjiene word getoon en bespreek. Een van die optimum ontwerpte veld versterking permanente magneet masjiene is vervaardig en getoets in die laboratorium . Die eindige-element en gemete resultate van die masjien word vergelyk en toon goeie korrelasie. Die speek prestasie van die optimum ontwerpte masjiene word geëvalueer aangesien dit die sensorlose posisie beheer vermoë bepaal. Daar word getoon dat die speek koëffisiënt verhoog lineêr met vrag wat dit gunstig maak vir posisie sensorlose beheer . Daar word ook gewys dat die asimmetriese rotor topologie ’n groter wedersydse induktansie het in vergelyking met hul simmetriese eweknieë, dus is daar hoër kruis-koppeling teenwoordig in die rotors en dus ’n ho¨er speek skuif, wat ongewens is. Twee gevallestudies om speek prestasie te verbeter is uitgevoer. Die doel van die eerste gevallestudie is om die speek skuif te verbeter deur die vermindering van die vloed lekkasie paaie in die rotor. Die doel van die tweede gevallestudie is om ’n veld versterking permanente magneet masjiene te optimeer ten einde die speek koëffisiënt en - skuif te verbeter. Die resultate van die twee gevallestudies word vergelyk met die speek prestasie van die ander masjiene.

Made available in DSpace on 2016-06-02T19:55:20Z (GMT). No. of bitstreams: 1 TeseRLB.pdf: 1678742 bytes, checksum: 886848bd535c0fd818fc2937a34451b0 (MD5) Previous issue date: 2005-05-05 / Universidade Federal de Sao Carlos / In the present work, breathable particulate matter (PM10) concentration was measured in their fine (PM2.5-10) and ultra-fine (MP2.5) fractions, in the municipal district of São Carlos. The samplings were carried out from 2001 to 2004 for PM10 (complemented with data from 1997 to 2001 taken from the research group databank) and for the period of 1 year (2001-2002) for PM2.5. PM10 was sampled with a high volumes sampler, while PM2.5 and PM2.5-10 were sampled with a dichotomous sampler. In order rationalize the seasonal variation MP, the year was separated in two different periods, the so-called dry period characterized by colder months and smaller incidence of rains and the rainy period, characterized by hotter months and by larger incidence of rains. After the collection, XRF analysis were carried out to quantify the chemical elements with mass molar superior to 12 a.m.u.. Also, DIC/DOC (dissolved organic and inorganic carbon) analysis were performed. The results showed 14 chemical elements, on average, both in fne and ultrafine fractions. The chemical elements that appear in larger concentrations in the PM are organic carbon, inorganic carbon, Al, Si, Ca, Ti, K, S and Fe. Two receptor models, the principal factors analysis (PFA) and chemical mass balance (CMB) were used to quantify the probable pollution sources for responsible for the sampled PM in the receptor site. PFA suggests that 3 main sources are responsible for the PM in the ultrafine fraction, both in the dry as well as in the rainy season. As for the fine fraction, the PFA suggests that 4 main sources are responsible for the pollution in the receptor site. The CMB analysis indicates that, for the ultrafine fraction the main source is the gas/particle conversion from sulfur, both in the dry and rainy periods. For the dry period, the biomass burning becomes significant as a pollution source. In the fine fraction of MP, the main sources identified were soil resuspension and vehicular emission. / xix No presente trabalho mediu-se a concentração de Material Particulado (MP) respirável (MP10), em suas frações fina (MP2,5-10) e super fina (MP2,5) no município de São Carlos. As amostragens foram realizadas de 1997 a 2004 para o MP respirável sendo que para o período de 1997 a 2000 foram utilizados dados disponíveis no banco de dados do Grupo de Controle ambiental e pelo período de 1 ano (2001-2002) para o MP2,5. O MP respirável foi amostrado com amostrador de grandes volumes, enquanto o MP2,5 e MP2,5-10 foi amostrado com amostrador dicotômico. Para facilitar o estudo da variação sazonal do MP dividiu-se o ano em dois períodos distintos, o chamado período seco (caracterizado por meses mais frios e menor incidência de chuvas) e o período chuvoso (caracterizado por meses mais quentes e de maior incidência de chuvas). Após a coleta, foram realizadas análise de XRF (Fluorescência de Raios X) para quantificar os elementos químicos com número atômico superiores a 12 u.m.a., e análise de carbono orgânico e inorgânico por DIC/DOC (carbono inorgânico e orgânico dissolvidos). Foram observados em média 14 elementos químicos, tanto para a fração fina como super fina. Os elementos químicos que aparecem em maiores concentrações no MP são carbono orgânico, carbono inorgânico, Al, Si, Ca, Ti, K, S e Fe. Foram utilizados modelos receptores análise de fatores principais (AFP) e balanço químico de massas (BQM) para quantificar as prováveis fontes poluidoras responsáveis pela carga de MP amostrada no receptor. A AFP sugere que há 3 fontes principais responsáveis pela carga de MP super fino no receptor tanto para o período seco como para o período chuvoso. Para o MP fino a AFP sugere que existam 4 fontes principais responsáveis pela poluição no sítio receptor. O BQM indica que para a fração super fina a principal fonte é a conversão gás / partícula de enxofre, tanto para o período seco como para o período chuvoso. Para o período seco a queima de biomassa passa a ter importância significativa como fonte poluidora. Na fração fina do MP as principais fontes identificadas foram ressuspensão do solo e emissão veicular.