VPT, Inc and the U.S. Dept. of Energy have sponsored the development of a high-speed 12 kW AC induction motor to drive automotive fuel cell air compressors. As one part of the development, thermal considerations and the cooling system are detailed in this paper. The motor and inverter are packaged in one unit with the heat sink in the middle. The heat sink is a cold chamber designed to absorb the maximum heat losses from the unit. Empirical data was used to validate the model of the cold chamber and finalize the design. A lumped capacitance finite-difference model was developed to simulate the entire motor inverter assembly. The individual components of the thermal model were tested and the data was used to calibrate and validate the thermal model. Using the model, the thermal overload conditions were investigated. The limiting factors are the stator copper winding temperatures, which can damage the plastic slot liners. The double current test was simulated and operating temperatures of the system remained within thermal limits for 4 minutes. As a conclusion from the model, the thermal resistances from the stator to the case or the heat sink need to be reduced. Integrating the motor casing and end plate to the heat sink, rather than building it in sections, would reduce the thermal contact resistances. Also the copper winding ends in the stator could be coated in material that would bond to the case, thus increasing heat transfer from the windings to the case. / Master of Science

D.L. A 1165-2006

Made available in DSpace on 2016-08-29T15:09:29Z (GMT). No. of bitstreams: 1 tese_2627_Dissertação Alexsander.pdf: 5180984 bytes, checksum: 966192c6ffb265a39e6fc19b1a7151a2 (MD5) Previous issue date: 2007-08-31 / Este trabalho apresenta uma metodologia para o estudo da dispersão de poluentes atmosféricos passivos e inertes em regiões de topografia complexa, onde modelos simplificados baseados uma abordagem gaussiana não são adequados. O campo de vento é obtido através de um modelo diagnóstico de análise objetiva, baseado na técnica variacional, a partir de medições de estações meteorológicas. As equações governantes são resolvidas numericamente através do método dos volumes finitos e o sistema de equações lineares resultante é resolvido através do método SOR com alternância no sentido de varredura. O campo de vento é validado a partir de um resultado numérico de simulação sobre uma montanha gaussiana isolada suave e através da reconstrução do campo de vento tridimensional sobre uma região de topografia complexa na Região da Grande Vitória ES, para testar sua capacidade em simular situações reais. Na primeira validação o modelo apresentou o mesmo comportamento qualitativo, apresentando pequenas diferenças quantitativas, que podem ser devido a parâmetros não fornecidos pelo trabalho de referência que aqui foram estimados, e por terem sido resolvidos por métodos numéricos diferentes. Na segunda validação os resultados foram compatíveis com os da literatura, entretanto o trabalho adverte sobre a qualidade das previsões onde não existem estações meteorológicas, devido à baixa espacidade da rede local.

Orientador: Fernando de Azevedo Silva / Banca: Gustavo Aristides Santana Martinez / Banca: João Alberto de Oliveira / Resumo: Estudo de falha por fratura em eixo da laminadora de aros Leifeld, fabricado em aço de baixa liga e alta resistência, ABNT 4340, forjado, temperado e revenido, com dureza de 39 HRc, abordando aspectos de modelagem pelo método de elementos finitos, utilizando o programa Ansys e critérios de fadiga utilizando o diagrama de Goodman modificado como ferramenta de definição do limite de tensão alternada para fadiga e propostas de mudanças geométricas no eixo a fim de minimizar as tensões sobre a aba da árvore bem como eliminar a possibilidade de fratura por fadiga da mesma. O estudo procura mostrar de forma clara a montagem de um modelo sólido através de um software comercial e a interação com a realidade vivida na manutenção de fábrica, sendo que o estudo surgiu devido a falhas freqüentes e prematuras de árvores em máquinas de repuxamento de aros, de procedência alemã, usada para a fabricação de aros para pneu com câmara utilizados em caminhões e ônibus, máquina esta de propriedade da empresa Maxion Sistemas Automotivos S/A. / Abstract: This is a fracture failure analysis of a Leifeld flow forming machine spindle, manufactured in a low alloy and high resistance, ABNT 4340 steel, forged, quenched and tempered with hardness of 39 HRc, approaching modeling aspects in finite elements method using the program Ansys and also approaching fatigue criteria using the diagram of Goodman modified as a tool for definition criterion of fatigue alternate stress limit and proposed of geometric changes in the spindle in order to minimize the tensions on the brim of it as well as to eliminate the fracture possibility for fatigue of the same. The study tries to show the assembly of a solid model in a clear way through a commercial software and the interaction with the reality lived in the factory maintenance, the study was proposed due the frequent and premature spindles failures in the flow forming machine, made in Germany, used for the production of rim for tire with tube used in trucks and buses, this machine is property of Maxion Sistemas Automotivos S/A company. / Mestre

När en konstruktion byggs på det viset att dess bottenplatta hamnar under grundvattenytan, skapas ett grundvattentryck upp mot bottenplattan och konstruktionen, som kan åstadkomma stora problem. Grundvattnet, som tryckts undan av konstruktionen, vill nå upp till sin ursprungliga nivå och därmed trycka med sig konstruktionen upp. Detta fenomen kallas hydraulisk bottenupptryckning. Fenomenet kan motverkas på olika sätt, där rapporten beaktar två olika sätt att motverka hydraulisk bottenupptryckning på: genom en bottenplatta som är tyngre än grundvattentrycket eller förankra bottenplattan mot ett fast underlag. Genom att uppmärksamma och sammanställa projekt (huvudsakligen konstruerade av Tyréns) som tagit hänsyn till ovan nämnda fenomen vid dimensioneringen av bottenplattan, har en rapport skapats. Denna rapport ska finnas för att åstadkomma kunskapsåterföring av de problem som uppstått i projekten och deras lösningar. Utöver att skapa en rapport där de berörda projekten sammanställs ska en bottenplatta optimeras, huvudsakligen med hänseende till bottenplattans tjocklek och dess bärförmåga mot genomstansning för olika förankringstyper. Optimeringen ska ske i enlighet med, huvudsakligen Eurokod 2 kapitlen 6.4 och 7.3. Det har bestämts att tre tjocklekar på bottenplattan ska beaktas, och dessa är 400, 550 och 800 mm. Genom diskussioner med våra handledare, sakkunnig personal på Tyréns och representanter inom branschen, valdes ett antal förankringstyper som skulle jämföras. För att kunna jämföra kombinationerna av de olika tjocklekarna på bottenplattan och de olika förankringstyperna, har Tyréns projekt Biomedicum med dess förutsättningar, utnyttjats som referensobjekt. Att ta fram de inre krafterna i bottenplattan via handberäkningar är mycket komplicerat och tidskrävande för att rymmas inom ramen för denna studie. Därför används programmet FEM Plate (Strusoft) för att ta fram dessa krafter. De inre krafter som tas fram från FEM Plate utnyttjas sedan för att med hjälp av handberäkningar, i enlighet Eurokod 2, dimensionera Biomedicums bottenplatta enligt de moment som krävs. Jämförelsen av de olika kombinationerna visar på att bottenplattan 400 mm med förankringstypen stålkärna av diameter 80 mm från Inexa Profil är den optimala lösningen för Biomedicums bottenplatta. Denna förankringstyp (för bottenplattan 400 mm) är den enda som får en tillräcklig bärförmåga mot genomstansning av bottenplattan, endast med åtgärden skjuvarmering runtomkring förankringen. En föreslagen lösning på hur förankringstypen bör monteras i bottenplattan har tagits fram. Diskussioner med sakkunnig personal från Minova (tillverkare av MAI-förankringen) har lett till övertygelsen om att föreslagen lösning fungerar utan några kapacitetsförsämringar på förankringen. En modellering av bottenplattan 400 mm med föreslagen lösning på MAIförankringen och efterföljande handberäkningar, visar att lösningen optimerar bottenplattan än mer. föreslagen lösning på monteringen i bottenplattan bör dessutom kunna tillämpas på de andra förankringstyperna, men har endast beaktats för MAI-förankringen. Eftersom fokus endast är på att den optimala bottenplattan är 400 mm och ingen hänsyn tas till kostnaderna, är föreslagen lösning på MAI-staget den optimala lösningen. Det är den enda förankringen som har en tillräcklig bärförmåga mot genomstansning för bottenplattan 400 mm, utan några som helst extra åtgärder. En bottenplatta med vot under förankringen bör undvikas, eftersom förtjockningen av bottenplattan under förankringen kräver mycket extra tid i utförande. Därför rekommenderas det att en jämntjock bottenplatta dimensioneras med eventuell skjuvarmering, om bottenplattans bärförmåga mot genomstansning inte är tillräcklig utan skjuvarmering. Den optimering som tagits fram är en generalisering av Biomedicums bottenplatta. Detta leder till att de modeller och beräkningar som gjorts, enkelt kan implementeras på andra bottenplattor med samma problem genom att justera indata.

Les structures en béton armé sont amenées à répondre à différentes exigences pouvant dépasser la simple résistance mécanique. Pendant le processus de fissuration, les contraintes dans le béton armé sont progressivement redistribuées entre l’acier et le béton via l’interface entre ces deux matériaux. Cette redistribution de contraintes a un impact direct sur l’état de fissuration final et doit donc être prise en compte dans la modélisation. Il existe différents modèles numériques capables de représenter les effets de la liaison acier-béton. Cependant, leur usage est, pour l’instant, incompatible avec les applications concernant les structures de grandes dimensions (difficultés de maillage, coût de calcul…). Dans ce cadre d’application, l’hypothèse de liaison parfaite entre l’acier et le béton (déplacement identique) est donc toujours utilisée. On se propose ici de développer un nouveau modèle éléments finis de liaison acier-béton qui soit à la fois représentatif des phénomènes physiques se produisant à l’interface entre les deux matériaux et compatible avec les contraintes de modélisation des structures de grandes dimensions. Ce travail de thèse se découpe en trois grandes parties : - le développement d’un modèle élément fini de liaison acier-béton adapté aux contraintes de modélisation des structures de grandes dimensions. Ce modèle numérique permet ainsi de tenir compte des interactions mécaniques entre le béton et les armatures d’acier représentées à l’aide d’éléments barres. - la caractérisation du comportement de la liaison acier-béton. Un modèle de loi d’adhérence (évolution de la contrainte d’adhérence en fonction du glissement) basé sur des observations expérimentales (campagne expérimentale de pull-out menée au cours de la thèse et données bibliographiques) est proposé. Il permet en particulier de différencier le cas d’une rupture par arrachement, d’une rupture par éclatement en tenant compte des caractéristiques matériaux et géométriques de la structure. - l’application du modèle proposé à un élément structurel (poutre). Un essai de poutre en flexion quatre points visant à caractériser l’évolution de la fissuration (évolution de l’ouverture de fissure mesurée à l’aide de la technique de corrélation d’images notamment) a ainsi été proposé. Ces résultats ont ensuite été comparés à ceux de simulations numériques tenant compte de la liaison acier-béton d’une part ou de l’hypothèse de liaison parfaite d’autre part. Les deux modélisations donnent une bonne approximation du comportement extérieur de la structure (comportement global et ouvertures de fissure des surfaces extérieures de la poutre). Le modèle de liaison acier-béton apporte cependant une meilleure caractérisation de la phase de fissuration active (apparition des fissures) et modifie plus particulièrement le comportement local de la structure à proximité directe des armatures (limitant le développement de l’endommagement du béton le long des renforts). / Reinforced concrete structures may have to fulfill functions that go beyond their simple mechanical resistance. During the cracking process, stresses are progressively transferred from steel to concrete through the steel-concrete interface. This stress transfer has a direct impact on the crack properties. Taking into account these effects seems thus essential to predict correctly the cracking of reinforced concrete structures. Different models exist to represent the steel-concrete bond behavior. However, these models are rarely compatible with large scale simulations (meshing difficulties, heavy computational cost…). To overcome these difficulties, a perfect relation between steel and concrete (same displacements) is generally considered for structural applications. In this contribution, a new finite element approach is proposed to represent the steel-concrete bond effects in a context adapted for large scale simulations. This thesis is divided in three parts: - the development of a finite element steel-concrete bond model adapted for large scale structural applications . This model takes into account mechanical interactions between concrete and steel reinforcement represented by truss elements. - the characterization of the steel-concrete bond behavior. A model for the bond stress-slip law based on experimental observations (experimental campaign on pull-out test carried out during the thesis and data of literature) is proposed. This model differentiates the case of a pull-out failure and of splitting failure and takes into account the material properties and the geometric characteristics of the structure. - an application of the proposed model on a structural element (beam). A four point bending beam is experimentally tested. This test aims to characterize the crack evolution (in particular the crack opening using the image correlation technique). Experimental results are then compared with numerical simulations taking into account the bond–slip effect between steel and concrete or considering the perfect relation hypothesis. The two simulations give a good approximation of the external behavior of the structure (global behavior and crack opening on the external face of the beam). Nevertheless, the bond model improves the cracking description during the active cracking phase (beginning of crack apparition) and influences the local behavior of the structure especially near the steel bars (avoiding the propagation of the damage of concrete along the steel reinforcement).

La thèse s'inscrit dans la perspective de l'explosion du trafic de données générée par l'augmentation du nombre d'utilisateurs ainsi que la croissance du débit qui doivent être prises en compte dans la définition des futures générations de communications radiocellulaires. Une solution est la technologie «large-scale MIMO » (systèmes MIMO de grande dimension) qui pose plusieurs défis. La conception des nouveaux algorithmes de détection de faible complexité est indispensable vu que les algorithmes classiques ne sont plus adaptés à cette configuration à cause de leurs mauvaises performances de détection ou de leur complexité trop élevée fonction du nombre d'antennes. Une première contribution de la thèse est un algorithme basé sur la technique de l'acquisition comprimée en exploitant les propriétés des signaux à alphabet fini. Appliqué à des systèmes MIMO de grande dimension, déterminés et sous-déterminés, cet algorithme réalise des performances (qualité de détection, complexité) prometteuses et supérieures comparé aux algorithmes de l'état de l'art. Une étude théorique approfondie a été menée pour déterminer les conditions optimales de fonctionnement et la distribution statistique des sorties. Une seconde contribution est l'intégration de l'algorithme original dans un récepteur itératif en différenciant les cas codé (code correcteur d'erreurs présent) et non codé. Un autre défi pour tenir les promesses des systèmes large scale MIMO (efficacité spectrale élevée) est l'estimation de canal. Une troisième contribution de la thèse est la proposition d'algorithmes d'estimation semi-aveugles qui fonctionnent avec une taille minimale des séquences d'apprentissage (égale au nombre d'utilisateurs) et atteignent des performances très proches de la borne théorique. / The thesis is part of the prospect of the explosion of data traffic generated by the increase of the number of users as well as the growth of the bit rate which must be taken into account in the definition of future generations of radio-cellular communications. A solution is the large-scale MIMO technology (MIMO systems oflarge size) which poses several challenges. The design of the new low complexity detection algorithms is indispensable since the conventional algorithms are no longer adapted to this configuration because of their poor detection performance or their too high complexity depending on the number of antennas. A first contribution of the thesis is an algorithm based on the technique of compressed sensing by exploiting the propertiesof the signals with finite alphabet. Applied to large-scale, determined and under-determined MIMO systems, this algorithm achieves promising and superior performance (quality ofdetection, complexity) compared to state-ofthe-art algorithms. A thorough theoretical study was conducted to determine the optimal operating conditions and the statistical distribution of outputs. A second contribution is the integration of the original algorithm into an iterative receiver by differentiating the coded and uncoded cases. Another challenge to keeping the promise of large- scale MIMO systems (high spectral efficiency) is channel estimation. A third contribution of the thesis is the proposal of semi-blind channel estimation algorithms that work with a minimum size of pilot sequences (equal to the number of users) and reach performances very close to the theoretical bound.

Most of existing North American bridge infrastructure is reported to be deficient. Present infrastructure management mainly relies on qualitative evaluation, where bridge safety and serviceability are judged through routine visual inspection. With the successive increase in the number of severely deficient bridges and the limited available resources, it is crucial to develop a performance-based quantitative assessment evaluation approach that enables an accurate estimation of aging bridges ultimate and seismic capacities and ensures their serviceability. Reinforcement corrosion is the main cause of most of North American concrete infrastructure deterioration. Experimental investigations prove that reinforcement corrosion results in reduction of the steel reinforcement cross sectional area, localized (or global in very extreme cases) loss of bond action, concrete spalling, loss of core concrete confinement, and structural collapse. Field observations show that damage due to reinforcement corrosion in reinforced concrete (RC) bridge columns is localized in highly affected zones by splash of deicing water. In this thesis, an innovative performance-based semi-quantitative assessment framework is developed using newly developed simplified nonlinear static and dynamic finite element analysis approaches. The framework integrates the bridge’s available design and after-construction information with enhanced inspection and additional material testing as sources for accurate input data. In order to evaluate the structural performance and the capacity of the corrosion-damaged bridge columns, four nonlinear static and dynamic analysis approaches have been developed: (i) simplified nonlinear sectional analysis (NLSA) approach that presents the basis of the analysis approaches to estimate the ultimate and seismic capacities, and serviceability of bridge columns; (ii) simplified nonlinear finite element analysis (NLFEA) approach, which enables estimating the ultimate structural capacity of corrosion-damaged RC columns; (iii) simplified hybrid linear/nonlinear dynamic finite element analysis (SHDFEA) approach to evaluate the serviceability of the bridge; and, (iv) simplified non-linear seismic analysis (SNLSA) approach to evaluate the seismic capacity of the bridge columns. The four analysis approaches are verified by comprehensive comparisons with available test experimental and analytical results. The proposed semi-quantitative assessment framework suggests three thresholds for each performance measure of the evaluation limit states to be decided by the bridge management system team. Case studies are presented to show the integrity and the consistency of using the proposed assessment framework. The proposed assessment framework together with the analysis approaches provide bridge owners, practicing engineers, and management teams with simplified and accurate evaluation tools, which lead to reduce the maintenance/rehabilitation cost and provide better safety, and reduce the variation in the data collected using only traditional inspection methods.

Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-12Bitstream added on 2014-06-13T19:07:18Z : No. of bitstreams: 1 monteiro_fl_me_guara.pdf: 2693716 bytes, checksum: 79334c2a393c7aaa40e71c0ef9ab7905 (MD5) / Universidade Estadual Paulista (UNESP) / Estudo de falha por fratura em eixo da laminadora de aros Leifeld, fabricado em aço de baixa liga e alta resistência, ABNT 4340, forjado, temperado e revenido, com dureza de 39 HRc, abordando aspectos de modelagem pelo método de elementos finitos, utilizando o programa Ansys e critérios de fadiga utilizando o diagrama de Goodman modificado como ferramenta de definição do limite de tensão alternada para fadiga e propostas de mudanças geométricas no eixo a fim de minimizar as tensões sobre a aba da árvore bem como eliminar a possibilidade de fratura por fadiga da mesma. O estudo procura mostrar de forma clara a montagem de um modelo sólido através de um software comercial e a interação com a realidade vivida na manutenção de fábrica, sendo que o estudo surgiu devido a falhas freqüentes e prematuras de árvores em máquinas de repuxamento de aros, de procedência alemã, usada para a fabricação de aros para pneu com câmara utilizados em caminhões e ônibus, máquina esta de propriedade da empresa Maxion Sistemas Automotivos S/A. / This is a fracture failure analysis of a Leifeld flow forming machine spindle, manufactured in a low alloy and high resistance, ABNT 4340 steel, forged, quenched and tempered with hardness of 39 HRc, approaching modeling aspects in finite elements method using the program Ansys and also approaching fatigue criteria using the diagram of Goodman modified as a tool for definition criterion of fatigue alternate stress limit and proposed of geometric changes in the spindle in order to minimize the tensions on the brim of it as well as to eliminate the fracture possibility for fatigue of the same. The study tries to show the assembly of a solid model in a clear way through a commercial software and the interaction with the reality lived in the factory maintenance, the study was proposed due the frequent and premature spindles failures in the flow forming machine, made in Germany, used for the production of rim for tire with tube used in trucks and buses, this machine is property of Maxion Sistemas Automotivos S/A company.

Most of existing North American bridge infrastructure is reported to be deficient. Present infrastructure management mainly relies on qualitative evaluation, where bridge safety and serviceability are judged through routine visual inspection. With the successive increase in the number of severely deficient bridges and the limited available resources, it is crucial to develop a performance-based quantitative assessment evaluation approach that enables an accurate estimation of aging bridges ultimate and seismic capacities and ensures their serviceability. Reinforcement corrosion is the main cause of most of North American concrete infrastructure deterioration. Experimental investigations prove that reinforcement corrosion results in reduction of the steel reinforcement cross sectional area, localized (or global in very extreme cases) loss of bond action, concrete spalling, loss of core concrete confinement, and structural collapse. Field observations show that damage due to reinforcement corrosion in reinforced concrete (RC) bridge columns is localized in highly affected zones by splash of deicing water. In this thesis, an innovative performance-based semi-quantitative assessment framework is developed using newly developed simplified nonlinear static and dynamic finite element analysis approaches. The framework integrates the bridge’s available design and after-construction information with enhanced inspection and additional material testing as sources for accurate input data. In order to evaluate the structural performance and the capacity of the corrosion-damaged bridge columns, four nonlinear static and dynamic analysis approaches have been developed: (i) simplified nonlinear sectional analysis (NLSA) approach that presents the basis of the analysis approaches to estimate the ultimate and seismic capacities, and serviceability of bridge columns; (ii) simplified nonlinear finite element analysis (NLFEA) approach, which enables estimating the ultimate structural capacity of corrosion-damaged RC columns; (iii) simplified hybrid linear/nonlinear dynamic finite element analysis (SHDFEA) approach to evaluate the serviceability of the bridge; and, (iv) simplified non-linear seismic analysis (SNLSA) approach to evaluate the seismic capacity of the bridge columns. The four analysis approaches are verified by comprehensive comparisons with available test experimental and analytical results. The proposed semi-quantitative assessment framework suggests three thresholds for each performance measure of the evaluation limit states to be decided by the bridge management system team. Case studies are presented to show the integrity and the consistency of using the proposed assessment framework. The proposed assessment framework together with the analysis approaches provide bridge owners, practicing engineers, and management teams with simplified and accurate evaluation tools, which lead to reduce the maintenance/rehabilitation cost and provide better safety, and reduce the variation in the data collected using only traditional inspection methods.