The circular, single-stranded (ss) DNA genomes of plant viruses in the families Geminiviridae and Nanoviridae are replicated within the nucleus of a host cell by a mechanism called rolling circle replication (RCR). Although this process relies almost exclusively on the replication machinery of the host cell, initiation occurs via the interaction of the viral replication initiation protein (Rep) with regulatory DNA sequences within the viral genome. The use of a virus-based episomal amplification technology as a plant bioreactor platform exploits the process of Rep-mediated RCR for the high-level amplification of virus-based episomes in plants and subsequent expression of heterologous proteins; such an approach offers advantages over existing gene expression technologies. This PhD thesis describes research towards the development of a virus-based episomal amplification system for use in sugarcane. Such a crop is ideally suited for a plant bioreactor system due to the efficient high-level production of plant biomass and the existence of established production, harvesting and processing infrastructure. In order to rapidly assess the potential of a virus-based episomal amplification system in sugarcane, a transient assay system was established. Sugarcane callus was identified as the most suitable cell preparation; providing rapid cell regeneration, uniform experimental samples and upon isolation, total DNA suitable for Southern analysis. This assay system once established, proved effective in rapidly identifying virus-based episomes capable of undergoing RCR within sugarcane host cells. This transient assay system was then used to test the functionality of a virus-based episomal amplification system based on the ssDNA virus, Banana bunchy top virus (BBTV) in sugarcane. BBTV-based episomal amplification vectors were constructed with a reporter gene expression cassette flanked by two copies of the BBTV regulatory DNA sequences. The episomal amplification vectors were bombarded into sugarcane and banana host cells in various combinations and evidence of RCR was assessed through Southern blot analysis. RCR products were identified in banana host cells bombarded with the BBTV-based episomal amplification vectors in combination with vectors encoding BBTV Master-Rep (M Rep). RCR products were not identified within sugarcane cells bombarded with the same construct combinations. Integrated InPAct (In Plant Activation) episomal vectors based on BBTV were then employed to confirm the transient results, in addition, the functionality of an InPAct vector based on an alternate virus, Tobacco yellow dwarf virus (TYDV) was also assessed. InPAct vectors based on BBTV were constructed with an untranslatable expression cassette for integration within the sugarcane genome. Transient experiments were performed to assess the ability of BBTV M-Rep and TYDV Rep to initiate RCR of their respective InPAct vectors. Visual observation of GFP expression indicated that BBTV M-Rep was capable of initiating RCR of the BBTVbased InPAct vectors within banana host cells but no evidence was observed in sugarcane host cells. TYDV Rep was capable of initiating RCR of the TYDV-based InPAct vector within sugarcane host cells with a 100-fold increase in the number of fluorescent foci compared to cells bombarded with the TYDV InPAct vector alone. The BBTV-based InPAct vector was stably integrated within the sugarcane genome and the ability for BBTV M-Rep to initiate episome formation and RCR was assessed by Southern blot analysis. Evidence of BBTV M-Rep mediated RCR was not detected within the transgenic sugarcane bombarded with BBTV M-Rep. Transgenic sugarcane containing the TYDV-based InPAct vectors was assessed for the ability to be activated by TYDV Rep and undergo RCR. Southern blot analysis demonstrated that TYDV Rep was capable of recognising the integrated TYDVbased InPAct vector and RCR was detected within the transgenic sugarcane. The observation that episomal vectors based on TYDV were functional within sugarcane host cells and BBTV-based vectors were not, was unexpected. It had been hypothesised that an episomal vector based on a monocot-infecting virus would replicate in an alternate monocot host, while an episomal vector based on a dicot infecting virus would not. Virus replication is thought to be host-specific however most host range studies have been conducted with full length infectious clones and not deconstructed virus-based episomes. The implication that viral Reps may be functional in plant cells of non-host species was then investigated. The ability for viral Reps to recognise their cognate IR and initiate RCR of virus-based episomes in different host cells was assessed through cross-replication experiments. Four ssDNA plant viruses; BBTV, TYDV, Chloris striate mosaic virus (CSMV) and Tomato leaf curl virus - Australia (ToLCV-Au) were assessed via Southern blot analysis for their ability to initiate both autonomous replication of infectious clones and episomal amplification within three different plant hosts; tobacco, sugarcane and banana. Results from cross replication studies indicated a complex interaction between viral and host replication components. BBTV infectious clones and episomal vectors were restricted to replication within banana host cells providing a clear indication that episomal amplification vectors based on BBTV are restricted to Musa spp. BBTV M-Rep was unable to recognise the viral regulatory DNA sequences of the other three ssDNA viruses. TYDV infectious clones and episomal vectors were capable of replicating within all three host cells tested, indicating that TYDV is capable of undergoing RCR within a broad range of plant hosts. TYDV Rep was also capable of recognising the viral regulatory DNA sequences of both CSMV and BBTV given favourable conditions within specific plant hosts. Replication of the CSMV infectious clone was not detected in any of the three host cells, although fidelity of this clone requires further confirmation. CSMV episomal vectors were functional within banana host cells only, indicating that although closely related to TYDV, episomal amplification vectors based on CSMV have a restricted host range. CSMV Rep could not initiate RCR of episomal amplification vectors containing the viral regulatory DNA regions of the other three viruses in any of the plant host cells. ToLCV-Au infectious clones were capable of replicating within banana and tobacco host cells. Episomal amplification vectors based on ToLCV-Au extended the host range to sugarcane. ToLCV-Au Rep was unable to recognise the viral regulatory DNA sequences of the other three viruses in any of the plant host cells. The ability for a viral Rep to recognise its own cognate regulatory DNA sequences within alternate plant host cells is variable. Episomal amplification vectors based on TYDV and ToLCV-Au appear to be the most suitable for the further development of a virusbased bioreactor system in sugarcane. This study details the initial steps taken towards the development of a virus-based episomal amplification system in sugarcane. In doing so, fundamental knowledge into the mechanisms involved in Rep recognition of viral regulatory DNA sequences has been gathered. These research findings will provide a solid foundation for the further development of a sugarcane-based bioreactor.

APSDS is a layered elastic tool for aircraft pavement thickness determination developed and distributed by Mincad Systems and based on the sister software Circly. As aircraft pavement thickness determination remains an empirical science, mechanistic-empirical design tools such as APSDS require calibration to full scale pavement performance, via the S77-1 curve. APSDS provides the unique advantage over other tools that it models all the aircraft in all their wandering positions, negating the need for designers to use pass to cover ratios and acknowledging that different aircraft have their wheels located at difference distances from the aircraft centerline. APSDS requires a range of input parameters to be entered, including subgrade modulus, aircraft types, masses and passes and a pavement structure. A pavement thickness is then returned which has 50% design reliability. Greater levels of reliability are obtained by conservative selection of input values. Whilst most input parameters have a linear influence on pavement thickness, subgrade modulus changes have a greater influence at lower values and less influence at higher values. When selecting input values, designers should concentrate their efforts on subgrade modulus and aircraft mass as these have the greatest influence on the required pavement thickness. Presumptive or standard values are generally acceptable for the less influential parameters. S77-1 pavement thicknesses are of a standard composition with only the subbase thickness varying. Non-standard pavement structures are determined using the principle of material equivalence and the FAA provides range of material equivalence factors, of which the mid-range values are most commonly used. APSDS allows direct modelling of non-standard pavement structures. By comparing different APSDS pavements of equal structural capacity, implied material equivalences can be calculated. These APSDS implied material equivalences lie at the lower end of the ranges published by FAA. In order to obtain consistence between APSDS and the FAA guidance, the following material equivalence values are recommended: * Asphalt for Crushed Rock. 1.3. * Crushed Rock for Uncrushed Gravel. 1.2. * Asphalt for Uncrushed Gravel. 1.6. Proof rolling regimes remain an important part of the design and construction of flexible aircraft pavements. Historically, designers relied on Bousinesq's equation and the assumption of point loads on semi-finite homogenous materials to determine proof rolling regimes using stress as the indicator of damage. The ability of APSDS to generate stress, strain and deflection at any depth and any location across the pavement allows these historical assumptions to be tested. As the design of a proof rolling regime is one of comparing damage indicators modelled under aircraft loads to those under heavy roller loads, the historical simplifications are generally valid for practical design scenarios. Where project specific data is required, APSDS can readily calculate stresses induced by proof rollers and aircraft at any location and depth for comparison. APSDS is a leading tool for flexible aircraft pavement thickness determination due to its flexibility, transparency and being free from bias. However, the following possible areas for improvement are considered worthy of future research and development: * Improvements to the user interface. * Ability to model aircraft masses as frequency distributions. * Ability to copy stress with depth data to Excel(tm) spreadsheets. * Ability to perform parametric runs. * Inclusion of a reliability based design module.

Organisationer med komplexa projekt som sträcker sig över ett flertal år finner svårigheter att förhålla sig till projektens fördefinierade parametrar tid, kostnad och omfattning. Skenande kostnader och förseningar är vanligt förekommande i dessa typer av projekt, då projekten omfattar ett samspel av ett flertal aktiviteter och där projektets omfattning ofta förändras. Det finns metoder som verksamheter kan tillämpa för att kontrollera ovannämnda parametrar och i ett tidigt skede kunna identifiera när någon av parametrar tenderar att överskridas. En metod som styrker prestationsmätningar är Earned Value Mangament, EVM. Syftet med studien var att identifiera vart organisationer brister gentemot branschstandarden inom EVM, ANSI/EIA-748. Standarden innehåller viktiga steg för att kunna utföra en korrekt prestationsmätning tillsammans med teorin från Earned Value Management. Resultat studien presentera indikerar på att organisationer måste skapa tydliga riktlinjer hur ANSI/EIA-748 skall tillämpas. Till exempel att alla bryter ner arbetet och fördelar sina budgetar på samma sätt. Studiens resultat antyder också att Rolling Wave är ett lämpligt verktyg för komplexa och långa projekt. Av den anledningen att projektledare inte planerar för mycket i onödan eftersom projektets omfattning ständigt förändras.

The formation of microstructural alterations in bearing steels under rolling contact fatigue (RCF) is systematically studied. A literature review summarizes current understanding in this field, leading to the key to the formation of these microstructural features being carbon redistribution as a consequence of cyclic rolling contact. In this context, a novel theory is postulated to describe the migration of carbon caused by gliding dislocations. The theory combines the Cottrell atmosphere theory with the Orowan equation and is capable of quantifying the dislocation-assisted carbon flux. Based on the proposed theory, models are suggested for different types of microstructural alterations formed in rolling contact fatigued bearings – dark etching regions (DERs), white etching bands (WEBs) and white etching areas (WEAs). Very good agreement is obtained between the predications made by the models and the experimental data from both this research and the literature. Moreover, the models consider the effects of contact pressure, temperature, rotational speed and number of cycles, and thus can be applied for universal RCF testing conditions. The reproduced microstructural features are also characterized using advanced characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT), with the observation validating the postulated formation mechanisms. It is demonstrated that DERs, WEBs and WEAs follow the same principle during formation – strain induced carbon redistribution. This is the first time that these microstructural alterations are quantitatively described using a unified theory. The achievements obtained from this research can be far reaching. It not only leads to great progress in understanding the phenomenology of RCF in bearing steels, but also can be further extended to other scenarios with similar phenomena such as severe plastic deformation and hydrogen embrittlement.

ROCHA FILHO, F. A. M. Estudo da perda de ductilidade a quente e resistência à corrosão de vergalhões laminados com e sem a utilização da etapa de reaquecimento. 2017. 97 f. Dissertação (Mestrado em Engenharia e Ciência de Materiais)-Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Pós-Graduação Ciência de Materiais (materiais@metalmat.ufc.br) on 2017-10-02T16:47:29Z No. of bitstreams: 1 2017_dis_famrochafilho.pdf: 4083178 bytes, checksum: da1e3baa97d72a6d875bf5f3a505a3bf (MD5) / Rejected by Marlene Sousa (mmarlene@ufc.br), reason: Prezado Alberto: Existe uma orientação para que normalizemos as dissertações e teses da UFC, em suas paginas pré-textuais e lista de referencias, pelas regras da ABNT. Por esse motivo, sugerimos consultar o modelo de template, para ajudá-lo nesta tarefa, disponível em: http://www.biblioteca.ufc.br/educacao-de-usuarios/templates/ Vamos agora as correções sempre de acordo com o template: 1. Na capa falta a informação do nome do Departamento entre o centro e o programa. 2. Na folha de aprovação, mesmo não sendo obrigatório, sugerimos colocar a data da defesa 3. Na folha de agradecimentos deixe parágrafos ao iniciar os agradecimentos 4.Nas listas de figuras e tabelas observe o alinhamento da margem de modo que quando aumentar o número de dígitos das figuras elas fiquem no mesmo alinhamento de quando tinham um dígito. Ex Figura 1 e 10. Na LISTAS DE FIGURAS e LISTA DE TABELAS, Quando o título da figura ou da tabela não couber na mesma linha, sua continuação deve ficar na mesma margem da primeira letra da linha de cima e não voltar para a margem do F de Figura ou do T de Tabela. 5. Nas listas de Abreviaturas e símbolos observe no template como deve ser o alinhamento. 6. O sumário não deve ter recuo da margem para não caracterizar capítulos. Pois estes não são usados em dissertações e teses. Observe o alinhamento da margem. Não use REFERENCIAS BIBLIOGRÁFICAS mas sim, REFERÊNCIAS. 7. Na lista de REFERÊNCIAS a palavra deve ser centralizada na folha Quando vc estiver referenciando artigos de revistas o que deve ficar em negrito não é o título do artigo e sim o nome da revista. Corrigir em toda a lista. Ao realizar essas alterações enviaremos o nada consta pro seu e-mail e para o do secretário Att. Marlene Rocha mmarlene@ufc.br 3366-9620 on 2017-10-06T18:17:27Z (GMT) / Submitted by Pós-Graduação Ciência de Materiais (materiais@metalmat.ufc.br) on 2017-10-30T11:36:03Z No. of bitstreams: 1 2017_dis_famrochafilho.pdf: 4081151 bytes, checksum: c897beceaac55281ae4207765bcca1e8 (MD5) / Approved for entry into archive by Marlene Sousa (mmarlene@ufc.br) on 2017-10-30T14:40:18Z (GMT) No. of bitstreams: 1 2017_dis_famrochafilho.pdf: 4081151 bytes, checksum: c897beceaac55281ae4207765bcca1e8 (MD5) / Made available in DSpace on 2017-10-30T14:40:18Z (GMT). No. of bitstreams: 1 2017_dis_famrochafilho.pdf: 4081151 bytes, checksum: c897beceaac55281ae4207765bcca1e8 (MD5) Previous issue date: 2017-08-09 / Hot rolling is one of the main forming processes where the semi-finished product obtained in the steel plant, is deformed plastically by compression forces applied between rotating cylinders. During rolling process the hot shortness phenomenon may occur and this may cause of split ends of bar during the sequence of cross section reduction passes. This split ends of bar can be severe and cause disruptions in the production process. The hot shortness may be associated with several factors, such as: the chemical composition of steel; the defects present in the semi-finished product, in the case of billet, produced in the process of continuous casting; the steel temperature during the process; and the conditions of rolling process, where it is worth mentioning the deformation rates, reductions, cylinder diameters, type of rolling stand and pass design. In the process under study, hot shortness generally occurs associated with the production of low carbon steel bars which are rolled from billets with as cast structure, which do not go through the reheating process in natural gas furnaces. Since there is great difficulty in inspecting semi-finished products directly from the continuous casting process, and there are limitations related to modification of rolling process conditions, the objective is to evaluate the influence of billet temperature along its section and the microstructure formed prior to the rolling process, mainly related to grain size and the presence of sulphides. These factors were associated with the hot shotness phenomenon of the steel, through a comparative examination between steels rolled directly from continuous casting and steels that pass through the reheating furnace before being rolled. It was possible to observe that the directly rolled billets had a smaller grain size prior to rolling and higher temperature loss throughout the process, which factors associated with a low Mn / S ratio and high reductions and deformation rates favored the hot shortness of bar during the rolling process. Both production routes provide small microstructural differences in the final product, which did not cause significant differences in the properties of corrosion resistance and mechanical properties of rebar. / A laminação a quente é um dos principais processos de conformação onde o produto semi-acabado obtido na aciaria, é deformado plasticamente através de esforços de compressão aplicados entre cilindros rotativos. Durante o processo de laminação pode ocorrer o fenômeno da perda de ductilidade a quente e este pode causar a separação entre as extremidades da barra durante a sequência de passes de redução da seção transversal do laminado. Essa separação da barra pode ser severa e causar interrupções no processo produtivo. A perda de ductilidade pode estar associada a diversos fatores entre eles estão: a composição química do aço; os defeitos presentes no semi-acabado, no caso tarugo, produzido no processo de lingotamento contínuo; a temperatura do aço durante o processo; e as condições do processo de laminação, onde merece destaque as taxas de deformação, as reduções, diâmetros dos cilindros, tipo de cadeira de laminação e projeto de passes. No processo em estudo, a perda de ductilidade a quente geralmente ocorre associada à produção de barras de aço baixo carbono que são laminadas a partir de tarugos com estrutura bruta de fusão, não passando pelo processo de reaquecimento em fornos a gás natural. Visto que há grande dificuldade de inspeção nos produtos semi-acabados vindos diretamente do processo de lingotamento contínuo, e que há limitações quanto à modificação nas condições do processo de laminação, tem-se como objetivo avaliar a influência da temperatura do tarugo ao longo de sua seção e da microestrutura formada prévia ao processo de laminação, relacionada principalmente com o tamanho de grão e a presença de sulfetos. Esses fatores foram associados com fenômeno de perda de ductilidade a quente do aço, através de um exame comparativo entre os aços laminados diretamente a partir do lingotamento contínuo e os aços que passam pelo forno de reaquecimento antes de serem laminados. Foi possível observar que os tarugos laminados diretamente possuíam menor tamanho de grão prévio a laminação e maior perda de temperatura ao longo do processo, fatores esses que associados a uma baixa relação Mn/S e elevadas reduções e taxas de deformação, favoreceram a perda ductilidade a quente da barra durante o processo de laminação. Ambas as rotas de produção proporcionam pequenas diferenças microestruturais no produto final, que não causaram diferenças significativas nas propriedades de resistência à corrosão e nas propriedades mecânicas dos vergalhões.

L'objectif initial de la thèse était de proposer une nouvelle modélisation simplifiée du laminage permettant un calcul rapide, si possible en temps réel, afin que le modèle soit éventuellement intégré à un outil de pilotage des machines de production. Ce modèle ne doit pas négliger les déformations élastiques afin de pouvoir être éventuellement appliqué à l'étude de phénomènes associés à la variation de largeur de la bande ou à des phénomènes de planéité. Il doit par ailleurs être assez ouvert pour que l'on puisse y intégrer éventuellement une description de la microstructure du matériau polycristallin et prendre en compte la déformation des cylindres de laminage. Pour atteindre cet objectif, nous avons proposé de tenter de construire un modèle simplifié semi-analytique du laminage. Dans ce type de modèle, le gradient de la transformation globale peut alors être décomposé multiplicativement en un produit d'une première transformation locale « plastique » , qui transforme le voisinage local initial de dans la configuration relâchée, par une seconde transformation locale « élastique » qui transforme la configuration relâchée dans la configuration actuelle . Cette décomposition est à la base de l'analyse thermodynamique de l'évolution mécanique lorsque le matériau subit de grandes transformations élastoplastiques, laquelle analyse fournit les concepts d'efforts intérieurs et de variables d'état nécessaires à l'écriture de ce comportement. Nous avons montré deux approches permettant le calcul analytique de ces champs lorsque l'histoire de est connue au voisinage d'une particule .Nous avons ensuite proposé l'étude d'une classe particulière d'évolutions élastoplastiques que nous avons appelées « simples radiales » et nous avons montré que les évolutions obéissaient à un principe de minimum énergétique. Nous avons enfin conjecturé que ce principe pouvait être étendu en régime permanant pour permettre de construire une modélisation simplifiée des processus de laminage / The initial aim of the thesis was to propose a new simplified model for rolling allowing a rapid calculation, if possible, in real time, so that the model would eventually integrate into a management tool production machines. This model should not neglect the elastic deformations in order to be applied to the study of phenomena associated with the change in bandwidth or flatness phenomena. It must also be open enough that we can integrate the description of microstructure of polycrystalline material and possibly take into account the deformation of rolling rolls. To achieve this goal, we proposed to build a simplified semi-analytical model of rolling. In this type of model, the gradient of global transformation can be multiplicatively decomposed of the first local transformation "plastic" which transforms the initial local neighborhood of in the relaxed configuration, and the second local transformation "elastic" which transforms the relaxed configuration in the current configuration. This decomposition is the basis of thermodynamic analysis of the mechanical evolution when the material undergoes large elastoplastic transformations, which provides the concepts of internal forces and necessary variable state to write this behavior. We showed two approaches to the analytical calculation of the mechanical fields when the history of was known in the neighborhood of particle .We then proposed to study a particular class of elastoplastic evolution that we called "simple radial" and we showed that the evolutions followed the principle of minimum energy. Finally, we conjectured that this principle can be extended in steady state, which allowed to build a simplified model of the rolling process

Orientador: José Luiz Gasche / Banca: André Luiz Seixlack / Banca: Paulo Eduardo Lopes Barbieri / Resumo: Devido à solubilidade mútua entre o fluido refrigerante e o fluido lubrificante usados em sistemas de refrigeração por compressão de vapor, eles formam uma mistura homogênea que influencia tanto os processos de transferência de calor no evaporador e no condensador, como os processos de lubrificação e de selagem de vazamentos no interior do compressor. O vazamento de refrigerante através da folga radial de compressores rotativos de pistão rolante é de particular importância para o bom desempenho do compressor, uma vez que ele influencia significativamente a eficiência volumétrica do compressor, chegando a somar cerca de 30% das perdas totais de refrigerante. No presente trabalho foram desenvolvidos modelos de escoamento de misturas óleo-refrigerante através desta folga, incluindo a mudança de fase do refrigerante devida à variação da sua solubilidade no lubrificante. A solução da equação da energia constitui uma evolução do processo de modelagem deste escoamento em relação aos modelos até então desenvolvidos. Quatro modelos diferentes foram usados para simular o escoamento: modelo de escoamento bifásico homogêneo isotérmico, modelo de escoamento bifásico isotérmico com formação de espuma, modelo de escoamento bifásico homogêneo não-isotérmico e modelo de escoamento bifásico homogêneo não-isotérmico com termo de força inercial. O estudo foi realizado para três misturas óleo-refrigerante: óleo éster Freol a10 e refrigerante R134a, óleo éster EMKARATE RL10H e refrigerante R134a e óleo mineral SUNISO 1 GS e refrigerante R12. Para todos os modelos e misturas, realizou-se um estudo paramétrico envolvendo as principais variáveis do problema: pressão de entrada, temperatura de entrada, vazão de mistura e valor da folga mínima... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Due to the mutual solubility between the refrigerant and lubricant of refrigeration systems using mechanical compression of vapor, they form a homogeneous mixture which influences the heat transfer processes in the evaporator and condenser as well as the compressor lubrication and refrigerant leakage. The refrigerant leakage through the radial clearance of rolling piston compressors plays an important role to the volumetric efficiency in this type of compressor, in which it represents about 30% of the total refrigerant loss. In the present work several models to predict the lubricant-refrigerant mixture flow through this clearance, including the refrigerant phase change due to the reduction of the refrigerant solubility in the lubricant, are developed. Four different models were developed to simulate the flow: isothermal homogeneous two-phase flow, isothermal two-phase flow with foam formation, non-isothermal homogeneous two-phase flow and non-isothermal homogeneous two-phase flow containing inertial force. The simulations were performed for three mixtures: ester oil Freol a10-refrigerant R134a, ester oil EMKARATE RL10H-refrigerant R134a, and mineral oil SUNISO 1 GS-refrigerant R12. The influences of the inlet pressure, inlet temperature, mixture mass flow rate, and minimal clearance were analyzed for all mixtures. The results showed that it is important to consider the foam formation, the inertial force, and the solution of the energy equation in the flow modeling. Concerning the volumetric efficiency of the compressor the ester oil Freol a10-R134a was the best mixture because it produced the lowest refrigerant leakage. / Mestre

Made available in DSpace on 2014-10-09T12:38:47Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:11Z (GMT). No. of bitstreams: 1 02807.pdf: 9990488 bytes, checksum: c598e49555ce62b0c216c8ed607963b6 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

In this thesis, the behavior of pearlitic steel was characterized under controlled wear conditions in the laboratory and service conditions in two ore mining stages, comminution and transportation. The thesis consists in three experimental chapters, divided according to the tribosystems analyzed. On all the chapters Electro Microscopy techniques for the microstructural analysis were employed. Scanning Electron Microscopy (SEM), Focused Ion Beam (FIB-SEM), Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM) were used. The first experimental chapter shows the analysis of the pearlite under abrasive wear with loose abrasive particles in multi-events conditions. The sample was taken from Semi-Autogenous Grinding mills (SAG) and experimental simulation was carried out in laboratory using the Dry Sand Rubber Wheel Abrasion Test (DSRW). The results show a polycrystalline layer formation in both cases, characterized by ultra-fine grains of ferrite in the layer closer to the surface. It was also concluded that the DSRW can simulate the wear produced on field (superficial and microstructural features) in conditions of higher normal load than recommended by the ASTM Standard G65. The second experimental chapter explores the characterization of the microstructure after the indenter pass in scratch test using two conditions of normal load applied and five sequences of scratch. The microstructural analysis shows the formation of two subsuperficial layers identified by the level of the microstructural alterations. In the subsuperficial layer (close to the surface), the formation of new ultra-fine grains of ferrite was observed. A second layer was observed deeper in the sample and denominated as layer of the microstructure transition, characterized by the combination of deformed (reduction of the interlamellar spacing) and pearlite colonies not affected plastically by the mechanical loading. On this layer, the crystallographic texture in RD // in samples tested at 4 N (normal load) and one-pass scratch was determined. Later, on this chapter, the microstructure in a ground rail (industrial procedure characterized as a multi-event scratch test) was analyzed. Two grinding conditions were used for the analysis with variation of the grinding linear speed and load on the grinding stones (discs). The combination of low grinding speed and high load promotes a higher deformed layer formation beneath the patch zone and low randomized orientation of the pearlite colonies. Finally, in the third experimental chapter, the pearlitic characterization was concluded with the study of samples of railway wheel and rail under wear in service and Rolling Contact Fatigue (RCF) in laboratory. The laboratorial simulation was carried out using the twin-disc rolling contact tribometer with a variation of number of cycles. The characterization of railway wheel shows that the WEL is characterized by levels of breaking and aligned cementite and zones with dissolution of the carbon atom in the ferrite to form the supersaturated carbon ferrite. The polycrystalline ferrite formation (ultra-fine grains) in the sub-superficial layer and it was identified a preferential orientation of RD // in the layer of microstructural transition. The results of the laboratory test show surface crack nucleation and propagation at low angle in the more severe deformed layer. The microstructure of the layer consists in polycrystalline ferrite and the cementite dissolution. / Nesta tese foi caracterizado o comportamento do aço perlítico em condições controladas de desgaste em laboratório e em serviço em dois estágios do processo de mineração de minério, cominução e transporte ferroviário. A tese consiste em três capítulos experimentais divididos segundo o tribosistema analisado. Em todos os capítulos do trabalho foi utilizada a técnica de microscopia eletrônica para análise microestrutural. Foi utilizado Microscopia eletrônica de varredura (MEV), Focused Ion Beam (FIB-SEM), Electron Backscatter Diffraction (EBSD) e Microscopia eletrônica de transmissão (MET). O primeiro capítulo experimental mostra a análise da perlita in condições de desgaste abrasivo com partículas soltas em eventos múltiplos. As amostras foram tiradas de um moinho semi-autógeno (SAG) e realizada uma simulação experimental do desgaste em condições controladas usando o tribômetro de roda de borracha (RWAT). Os resultados mostraram a formação de camada branca em ambas as condições de análise, consistindo em uma camada poli cristalina caracterizada pela formação de grãos ultrafinos na camada mais próxima da superfície de desgaste. Também foi concluído que a roda de borracha pode simular o desgaste produzido nos moinhos SAG tanto nas características superficiais quanto microestruturais em condições de maior severidade as comumente utilizadas na norma ASTM G65 (procedimento B). O Segundo capítulo experimental explora a caracterização da microestrutura depois da passagem do endentador no ensaio de riscamento (scratch test) utilizando duas condições de carga normal aplicada e 5 sequências de riscamento. A análise microestrutural mostrou a formação de duas camadas subsuperficiais identificadas pelo nível de alteração microestrutural. Na camada mais próxima da superfície de desgaste foi observada a formação de grãos ultrafinos de ferrita. A segunda camada identificada mais profundamente na amostra, denominada como camada de transição, é caracterizada pela combinação de colônias deformadas (redução do espaçamento interlamelar) e camadas não afetadas pelos esforços produzidos no contato. Nesta camada foi determinada a texturização em direção RD // nas amostras testadas a 4 N (carga normal aplicada) e uma passada. Posteriormente à análise de riscamento foi caracterizada a microestrutura de uma amostra tirada de um trilho esmerilhado (processo industrial que pode ser considerado como aplicação do ensaio de riscamento). Foram consideradas duas condições de esmerilhamento com variação de velocidade de esmerilhamento (deslocamento linear do veículo esmerilhador) e potência dos motores dos rebolos usada no procedimento. A combinação de baixa velocidade de esmerilhamento e alta potência nos motores controladores dos rebolos promoveu uma grande deformação nas camadas subsuperficiais na região de contato e uma baixa aleatoriedade das orientações cristalográficas das colônias de perlita. Finalmente, no capítulo três, a caracterização da microestrutura perlitica foi finalizada com o estudo de amostras de roda e trilho em condições de desgaste em campo e de Rolling Contact Fatigue (RCF) em ensaios de laboratório. A simulação experimental foi realizada utilizando o tribômetro twin-disc rolling (configuração disco-disco) com variação do número de ciclos. A caracterização da roda ferroviária mostrou a formação da camada branca caracterizada por níveis de cementita fraturada e alinhada em direção do movimento de rolamento/deslizamento com áreas de dissolução do átomo de carbono na ferrita formando uma ferrita supersaturada. Foi identificado a formação de policristais de ferrita (grãos ultrafinos) na camada mais superficial e uma orientação preferencial RD // na camada de transição. Os resultados dos ensaios de laboratório mostraram a nucleação de trincas superficiais se propagando a baixo ângulo na camada branca. A transformação microestrutural dessa camada após ensaios de laboratório consiste em policristais de ferrita e dissolução da cementita.

É cada vez maior a demanda pela eficiência dos sistemas ferroviários. A confiabilidade do material rodante é um dos fatores de desempenho mais importantes para a eficiência global dos trens de passageiros. Para que índices satisfatórios de confiabilidade, disponibilidade, mantenabilidade e segurança (CDMS) sejam alcançados, deve-se considerar esses fatores desde a elaboração da especificação técnica do material rodante até a operação da frota, incluindo projeto, fabricação, testes, comissionamento e garantia. No presente trabalho foram pesquisados os principais requisitos, normas e boas práticas empregadas na indústria ferroviária mundial para o gerenciamento da confiabilidade em projetos de material rodante, levando-se em conta os aspectos práticos e científicos. Para isso, foram inicialmente apresentadas algumas especificidades do setor ferroviário assim como alguns dos principais tipos de veículos ferroviários e seus sistemas, para que se tenha uma visão geral do contexto em que o trabalho está inserido. Em relação ao gerenciamento de CDMS propriamente dito, são mencionadas as principais tarefas a serem realizadas, de acordo com as referências consultadas. Foi dada uma atenção especial às especificações técnicas de CDMS, levando-se em conta a classificação das falhas e a determinação de parâmetros contratuais. Também foram abordados os aspectos teóricos e práticos das principais ferramentas e métodos de análise de CDMS empregados, tais como alocação de metas, predição de confiabilidade, diagrama de blocos, FMECA, FTA, monitoramento da confiabilidade em campo, etc. / Demand for efficiency in railway systems is increasing through the years. Rolling stock reliability is one of the most important performance factors for the global efficiency of passenger trains. To attain satisfactory reliability, availability, maintainability and safety (RAMS) figures, these factors must be considered from the elaboration of rolling stock technical specifications up to the operation of the fleet, including design, manufacturing, tests, commissioning and warranty. In the present work a research on main requirements, standards and good practices applied in worldwide railway industry for managing reliability in rolling stock designs was carried out, taking into account practical and scientific aspects. Some specificities of railway industry as well as some of the main railway vehicles types and related systems were presented, so that one can have an overview of the context where this work is inserted. Related to RAMS management, the main tasks to be done are presented, according to the references. Special attention was paid to RAMS technical specifications, considering failure classifications and determination of contractual parameters. The theoretical and practical aspects of the main tools and analysis methods of RAMS applied to the rolling stock design, such as apportionment of targets, reliability predictions, reliability block diagrams, FMECA, FTA, monitoring of field reliability, etc., were also covered.