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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Avaliação da tenacidade da solda de um aço baixa liga C-Mn obtido pelo processo FHPP (Friction Hydro Pillar Processing)

Freitas, Bruna Brito January 2015 (has links)
Os processos de soldagem por atrito apresentam diversas vantagens na união de materiais metálicos. O Friction Hydro Pillar Processing (FHPP) é um processo recente utilizado para fabricação e reparo de estruturas, que surge como uma alternativa à soldagem convencional. As interfaces das soldas FHPP são geralmente as partes mais suscetíveis à falha, devido à concentração de defeitos e microestrutura heterogênea. Por ser uma técnica recente e pouco difundida é importante avaliar as juntas soldadas por esse processo. Diante desse contexto, este trabalho teve como objetivo analisar os resultados macro e microestruturais de um aço C-Mn submetido ao processo FHPP, utilizando-se diferentes parâmetros, e relacioná-los com o perfil de microdureza. Além disso, avaliar a tenacidade ao impacto nas regiões de interface da solda e no material base. Para isso, foram realizados estudos metalográficos e perfis de microdureza Vickers em diferentes regiões das soldas. Complementarmente foram ensaiadas as interfaces das soldas que obtiveram os melhores resultados, através do ensaio Charpy, para avaliação de tenacidade ao impacto. Durante a soldagem foram utilizadas diferentes forças axiais e de recalque, obtendo como resultados variações, principalmente, nas interfaces soldadas. As alterações visualizadas nas interfaces, geraram uma tenacidade ao impacto menor do que a do material base. Esse fato pode ser atribuído, principalmente, porque o material base apresentou uma microestrutura predominantemente ferrítica, enquanto as interfaces soldadas apresentaram microestruturas heterogêneas, com presença de ferrita acicular, ferrita de Widmanstätten, martensita revenida e bainita. / Friction welding processes offer several advantages to join metallic materials. Friction Hydro Pillar Processing (FHPP) is a recent process used to manufacture and repair of underwater structure, emerging as an alternative for the conventional welding. FHPP welding interface are generally most susceptible to failure due to its heterogeneous microstructure and defects concentration. As FHPP is a quite recent little known technic, evaluate joints welded by this process is important. In this context, this study objective is to analyze macro and microstructural results of a C-Mn steel welded under different FHPP process parameters, and relate this results to a microhardness profile. Besides that, evaluate welding interface and base material impact toughness. To do that, metallographic analysis and microhardness profiles were done in different regions of the welded joint. In addition welded interfaces with the best results were Charpy tested for impact toughness evaluation. Different axial and forging forces were used, achieving macro and microstructural variations mainly in welded interface as a result. These variations caused interface to have lower impact toughness than base material. It can be explained by the base material mainly ferritic structure, whilst welded interface showed heterogeneous microstructures with acicular ferrite, Widmantätten ferrite, tempered martensite and bainite.
92

Avaliação da tenacidade à fratura em juntas soldadas por fricção com pino consumível

Chludzinski, Mariane January 2013 (has links)
O processo de soldagem por fricção com pino consumível possui como campo de aplicação a área de reparo e manutenção de estruturas. Por ser uma técnica desenvolvida recentemente, o conhecimento relativo à sua aplicação ainda não está completamente fundamentado. Dessa forma é necessário que se entenda o comportamento das juntas soldadas para determinar a viabilidade de sua utilização. Atualmente uma das ferramentas existentes para isso é o emprego dos conceitos de mecânica da fratura, que possibilitam a determinação de valores quantitativos de tenacidade. A partir disso objetiva-se identificar qual é a resposta frente à tenacidade à fratura que diferentes materiais desempenham quando soldados por fricção com pino consumível. No presente trabalho foi utilizada cpmo parâmetro de análise a medição de tenacidade à fratura pelo método de CTOD (Crack Tip Opening Displacement) em juntas soldadas com diferentes materiais de pino consumível e metal base. Essas medições concentraram-se nos materiais originais do pino, do metal de base e na região adjacente à interface lateral das juntas. Os materiais estudados foram o aço BS EN10025, os inoxidáveis austeníticos AISI 316L e ASTM F138, e o duplex UNS S31803. Adicionalmente foram realizadas análises fractográfica, macro e microestrutural, bem como ensaios de microdureza visando o entendimento do comportamento das juntas soldadas. Os resultados de CTOD indicaram que as microestruturas originadas com a soldagem, bem como a presença de inclusões de MnS, influenciam significativamente a tenacidade. / The Friction Hydro Pillar Processing has as a field of application in the area of repair and maintenance of structures. However as it is a technique developed recently, knowledge on its application is not fully established. Thus, it is necessary to understand the behavior of the joints in order to determine the feasibility of use. Nowadays one of the existing tools for this is the use of the concepts of fracture mechanics that allow the determination of quantitative values of toughness. From that this work aims to analyse fracture toughness in different materials welded by Friction Hydro Pillar Process. The analysis of fracture toughness was performed by the method CTOD (Crack Tip Opening Displacement) in samples welded with different materials of stud and base material. These measurements were concentrated in the original materials of and the interface zone of the welds. The materials investigated were BS EN10025, austenitic stainless steels AISI 316L and ASTM F138, the duplex stainless steel UNS S31803. Additionally were performed macro and microstructural characterization and microhardness tests aimed to understanding the behavior of joints. The CTOD results indicated that the microstructures as well as the presence of MnS inclusions significantly influence the toughness.
93

Analyse physique d'écoulements décollés fortement tridimensionnels par expérimentation. Structuration spatio-temporelle et sensibilité à une turbulence amont / Experimental and physical analysis of detached and massively three-dimensional flows. Spatio-temporal structuring and sensitivity to upstream turbulence

Affejee, Faisal 24 September 2015 (has links)
Ce travail a pour objectif l’étude du tourbillon conique engendré à partir d’une maquette générique représentant un montant de baie de véhicule automobile. Cette structure tourbillonnaire est responsable de fortes fluctuations sur les vitres latérales et génère du bruit dans l’habitacle. Ces véhicules étant soumis à des vents turbulents, la sensibilité de la dynamique de cette structure tourbillonnaire à une turbulence amont a été étudiée, en plaçant une grille à l’entrée de la veine d’essais de la soufflerie.Les propriétés spatiales et temporelles des champs de vitesse et de pression pariétale ont été étudiées en associant simultanément la mesure de la vitesse par Stéréo-PIV haute fréquence à la mesure de pression pariétale fluctuante par capteurs déportés. Nous avons montré qu’un niveau modéré de turbulence amont (intensité : 6%) se traduit par une modification très importante de la dynamique du tourbillon et de la pression pariétale fluctuante associée. Notre conjecture est qu’en l’absence de turbulence externe, la contribution principale au Cp’ est liée à l’empreinte du coeur tourbillonnaire et du décollement secondaire induit. Au contraire, en présence de turbulence amont, la forte augmentation du Cp’ semble associée à une réponse globale de la structure tourbillonnaire.L’étude de la dynamique spatio-temporelle à partir des corrélations pression-vitesse a permis de mettre en évidence le couplage fort existant entre la dynamique de la nappe cisaillée et celle du coeur de la structure tourbillonnaire. Il existe ainsi une modulation de la fréquence de battement de la structure pilotée par la géométrie de la maquette et par les caractéristiques de la turbulence amont (intensité et échelle intégrale). / This work aims to study conical vortices generated from a generic model representing the A-pillar of an automotive vehicle. This vortex structure is responsible of strong fluctuations on the side window and generates noise in the cabin. As these vehicles are subjected to the turbulent wind, the sensitivity of vortex structure dynamics to an upstream turbulence was studied by adding a grid at the test section entrance of the wind tunnel.The spatial and temporal properties of the velocity fields and the wall pressure were studied by simultaneously combining High Speed Stereo-PIV and wall fluctuating pressure measurements with distant sensors. It is shown that a moderate level of upstream turbulence (6% of intensity) results in a very significant change of the vortex dynamics and the associated wall fluctuating pressure. Our assumption is that in the absence of external turbulence, the main Cp’ contributionis linked to the footprint of the vortex core and of the induced secondary separation. On the contrary, in the presence of upstream turbulence, the strong increase of Cp’ seems to be associated with a global response of the vortex structure. The study of the spatio-temporal dynamics withpressure-velocity correlations allowed highlighting the strong coupling between the dynamics ofthe shear layer and of the core of the vortex structure. Thus, there is a modulation of the flapping frequency of the vortex controlled by the geometry of the model and by the characteristics ofthe upstream turbulence (intensity and integral length scale).
94

Dopady volby důchodového systému na jedince a na příjmy a výdaje ČR / The effects of choosing the pension system on the individual and on revenue and expenditure of the Czech Republic

Redl, Jan January 2012 (has links)
This thesis deals with current pension reform and particularly with the new second pillar of the pension system. The current status of the pension system and negative demographic prognoses, which advocate the necessity of change, are described. Further, with a help of a study written by Ondrej Schneider and Jiri Satava (both Idea Cerge -- EI), the thesis analyses the benefits and ill effects of the second pillar of the system for an individual taking part in it. Various assumptions in the study were critically evaluated, especially the rate of profit. The prediction of the number of persons who will participate in the second pillar was accepted. On the basis of this number, the impact on revenues and expenditures of the pension system up to 2050 was modelled, assuming a certain demographic structure of population. Decreasing revenue is participated on revenues caused by opt-out. Expenditure is influenced by pension reduction and by increasing number of pension applicants. The cost of pension corporation which will take part in the second pillar was investigated too.
95

Analýza mandatorních výdajů se zaměřením na důchodovou reformu / Analysis of mandatory spending focusing on pension reform

Čichovská, Tereza January 2012 (has links)
The thesis is focus on problems of increasing ratio of mandatory spending and total spending of state budget when I apply my mind to statutory mandatory spending which contains social transfers (especially benefits of pension insurance). I apply my mind to development of mandatory spending, retirement system and prepared retirement reform in individual parts of the thesis. Within retirement reform I am concerned with approved changes, basic parameters of retirement reform and I characterize newly established second pillar of retirement system. I focus on II. pillar in detail and I analyze how many people (especially employees) are going to probably join the II. pillar. When I practice the analysis I respect basic facts and conditons of joining the II. pillar and I take into account various recommendations of that. In closing I also calculate which impact the joining the II. pillar have on revenue part of state budget.
96

Sloupový jeřáb mobilní s nosností 600kg / Pillar jib crane with a load capacity 600 kg

Wojnar, Tomasz January 2017 (has links)
The diploma thesis deals with the design of a mobile crane for working in a manufacturing environment. The crane has load capacity 600 kg, length of radius 3 m and load-lifting height 3m. It is equipped with the electric chain hoist with electric trolley, rotation by held by hand of burden. The diploma thesis contains crane design and control and design calculations of important components. Technical drawings are also part of the thesis.
97

Předčasný důchod a předdůchod, jejich dopad na příjmy v důchodovém věku / Early Retirement and Pre-retairment, their Impact on Retirement Income

Stejskalová, Zuzana January 2014 (has links)
The thesis is focused on the part of the pension reform, the issue pre-retairments as alternatives to early retirement. The thesis also includes assessing the impact of these two options to employees and employers.
98

Zhodnocení rizik vybraných způsobů spoření na penzi / Risk Assessment of Selected Methods of Retirement Saving

Vojáčková, Šárka January 2014 (has links)
The Master Thesis „Risk Assessment of Selected Methods of Retirement Saving“ deals with retirement savings risk assessment in three selected alternatives. The theoretical part focuses on the collection and processing of data: II. pillar, Unit Linked Insurance and separate investments. Companies representing all the different alternatives are selected and described. In the second part of the Master thesis are calculated models of alternatives. The risk analysis for all considering saving options is carried out by Ripran Method.
99

Sustainable Investing : On the relation between sustainability rating and greenhouse gas emissions

Grundström, Gustav, Miedel, Isabelle January 2021 (has links)
Sustainability and finance should go hand in hand. A financial system that supports sustainablegrowth is necessary for the transition to a carbon-free society. Environmental, Social andGovernance (ESG) is a sustainability performance measurement used worldwide. Previousresearch within the ESG area has mainly focused on ESG score and financial performance.Environmental performance gets more attention from investors, and the Nordic countries areall in the top five when it comes to sustainability ranking. This research examines the relationbetween sustainability ratings (E score and ESG score) in the Nordic countries as well as if therelation differs between different rating agencies. To study the relationships, a regressionanalysis was performed, and we could not draw any concrete conclusions whether low CO2emissions are associated with a higher E- or ESG score in the Nordic countries. The resultindicates that a high E- or ESG score does not seem to be associated with lower CO2 emissions.A significant result was found on the fact that the E- and ESG scores relation to CO2 aredifferent between rating agencies. However, full access to one of the rating agencies has notbeen granted, which entails some limitations and further research on the questions isrecommended.
100

Nosná konstrukce autosalonu / The Steel Structure of the Car Schowroom

Pelechová, Denisa January 2012 (has links)
The master’s thesis treat of design and appreciation load-bearing steel structure of Motor Show. The object is situated on the lokality Brno. Structure is composed of rolling sections and tubes. Overall height of the structure is 17,395 meters and overall lenght is 32,60 meters. Cross link iscomposed of arched girders panel that are supported on fixed pillars. Theoutside links are composed of panel columns. Load is composed of self weight, additonal imposed load, payload and climate load caused by wind and snow that is reached for given locality.Static rewiew comes out from previous load and it has been accomplished by Scia Engineer 2008 and hand computation.

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