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- Integrated multi-functional morphing aircraft technologiesPublication . Santos, Pedro Daniel da Rocha; Gamboa, Pedro Vieira; Silva, José MiguelIn the past years, the development of morphing wing technologies has received a great deal of interest from the scientific community. These technologies potentially enable an increase in aircraft efficiency by changing the wing shape, thus allowing the aircraft to fly near its optimal performance point at different flight conditions. This thesis explores the development, analysis, building and integration of two new functional Variable-Span Wing (VSW) concepts to be applied in Remotely Piloted Aircraft Systems (RPAS). Additional studies are performed to synthesize the mass of such morphing concepts and to develop mass prediction models. The VSW concept is composed of one fixed rectangular inboard part, inboard fixed wing (IFW), and a moving rectangular outboard part: outboard moving wing (OMW). An aerodynamic shape optimization code is used to solve a drag minimization problem to determine the optimal values of wingspan for various speeds of the vehicle’s flight envelope. It was concluded that, at low speeds, the original wing has slightly better performance than the VSW and for speeds higher than 25 m/s the opposite occurs, due to the reduction in wing area and consequently the total wing drag. A structural Finite Element Model (FEM) of the VSW is developed, where the interface between wing parts is modelled. Deflections and stresses resulting from static aerodynamic loading conditions showed that the wing is suitable for flight. Flutter critical speed is studied. FEM is used to compute the VSW mode shapes and frequencies of free vibration, considering a rigid or the real flexible interface, showing that the effect of rigidity loss in the interface between the IFW and the OMW, has a negative impact on the critical flutter speed. A full-scale prototype is built using composite materials and an electro-mechanical actuation system is developed using a rack and pinion driven by two servomotors. Bench tests, performed to evaluate the wing and its actuation mechanism under load, showed that the system can perform the required extension/retraction cycles and is suitable to be installed on a RPAS airframe, which has been modified and instrumented to serve as test bed for evaluating the prototype in-flight. Two sets of flight tests are performed: aerodynamic and energy characterization. The former aims at determining the lift-to-drag ratio for different airspeeds and the latter to measure the propulsive and manoeuvring energy when performing a prescribed mission. In the aerodynamic testing, in-flight evaluation of the RPAS fitted with the VSW demonstrates full flight capability and shows improvements produced by the VSW over a conventional fixed wing for speeds above 19 m/s. At low speeds, the original wing has slightly better lift-to-drag ratio than the VSW. Contrarily, at 30 m/s, the VSW in minimum span configuration is 35% better than the original fixed wing. In the other performed test, it is concluded that the VSW fitted RPAS has less overall energy consumption despite the increased vehicle weight. The energy reduction occurs only in the high speed condition but it is so marked that it offsets the increase in energy during takeoff, climb and loiter phases. Following the work on the first VSW prototype, a new telescopic wing that allows the integration of other morphing strategies is developed, within the CHANGE EU project. The wing adopted span change, leading and trailing edge camber changes. A modular design philosophy, based on a wing-box like structure, is implemented, such that the individual systems can be separately developed and then integrated. The structure is sized for strength and stiffness using FEM, based on flight loads derived from the mission requirements. A partial span, fullsized cross-section prototype is built to validate the structural performance and the actuation mechanism capability and durability. The wing is built using composite materials and an electromechanical actuation system with an oil filled nylon rack and pinion is developed to actuate it. The structural static testing shows similar trends when compared with numerical predictions. The actuation mechanism is characterized in terms of actuation speed and specific energy consumption and it was concluded that it functioned within its designed specifications. A full-scale prototype is later built by the consortium and the leading and trailing edge concepts from the different partners integrated in a single wing. Wind tunnel tests confirmed that the wing can withstand the aerodynamic loading. Flight tests are performed by TEKEVER, showing that the modular concept works reliably. From the previous works, it is inferred that morphing concepts are promising and feasible methodologies but present an undesired mass increase due to their inherent complexity. On the other hand, mass prediction methods to aid the design of morphing wings at the conceptual design phase are rare. Therefore, a mass model of a VSW with a trailing edge device is proposed. The structural mass prediction is based on a parametric study. A minimum mass optimization problem with stiffness and strength constraints is implemented and solved, being the design variables structural thicknesses and widths, using a parametric FEM of the wing. The study is done for a conventional fixed wing and the VSW, which are then combined to ascertain the VSW mass increment, i.e., the mass penalization of the adopted morphing concept. Polynomials are found to produce good approximations of the wing mass. Additionally, the effects of various VSW design parameters in the structural mass are discussed. On one hand, it was found that the span and chord have the highest impact in the wing mass. On the other hand, the VSW to fixed wing ratio proved that the influence of span variation ratio in the wing mass is not trivial. It is found that the mass increase does not grow proportionally with span variation ratio increase and that for each combination of span and chord, exists a span variation ratio that minimizes the mass penalty. Using the VSW to fixed wing ratio function, the mass model is derived. To ascertain its accuracy, a case study is performed, which demonstrated prediction errors below 10%. Although the mass model results are encouraging, more case studies are necessary to prove its applicability over a wide range of VSWs. The work performed successfully demonstrated that VSW concepts can achieve considerable geometry changes which, in turn, translate into considerable aerodynamic gains, despite the increased weight. They influence all aspects of the wing design, from the structural side to the actuation mechanisms. The parametric study summarizes the mass penalties of such concepts, being successful at demonstrating that the mass penalty is not straightforward and that a careful selection of span, chord and variable-span ratio can minimize the mass increase.
- Design and Thermal Conductivity Characterization of a Functionally Gradient Ceramic Based on CaZrO3 – MgO CompositionPublication . Babo, Débora Rafaela Telha de; Nunes-Pereira, J.; Pereira Silva, A; Pena, Pilar; Baudin, CarmenSpace exploration involves the use of state-of-the-art technologies such as satellite production, propulsion systems, avionics, aerodynamics, research and development of materials, etc. In the particular case of human spaceflight, the insulation system of the spacecraft is also required in order to ensure crew safety in re-entry of the atmosphere and, if possible, the spacecraft re-use. In the case, where the structure is exposed to high temperature gradients, among other systems a thermal barrier must be used for the structure in order to protect it from critical damage. Based on this concept, in this work it was developed and characterized a design of a functional gradient ceramic coating. Recently, several studies have proposed the stoichiometric composition of calcium zirconate (CaZrO3) as a viable alternative for harsh environments subjected to high temperatures, corrosion and wear, and the mechanical properties of this compound can be improved through a solid solution ion order to obtain a CaZrO3-MgO multiphase ceramic composites. In this work, a functional gradient material was produced with successive layers with variation in its molar composition (1:3, 1:1 and 2:3 of CaZrO3:MgO) and its thermal conductivity characterized.
- Análise térmica de edifício multifamiliar da década de 60 em PortugalPublication . Marcelino, Inês Isabel Gonçalves; Lanzinha, JoãoNa atualidade dá-se cada vez maior atenção à necessidade de tornar os edifícios existentes mais sustentáveis tentando limitar os consumos exagerados de energia que resultam da resposta às crescentes exigências de conforto dos ocupantes. A reabilitação dos edifícios existentes deverá estar diretamente ligada ao conceito de eficiência energética com a redução dos consumos de energia, aplicando técnicas de análise e de reabilitação térmica de carácter passivo e promovendo a implementação de sistemas técnicos de apoio com base em energias renováveis. O parque edificado europeu apresenta um alto consumo de energia no setor doméstico, porque os edifícios mais antigos tendem a consumir mais energia devido ao tipo de construção praticada na época. Como exemplo, cerca de 40% dos edifícios na Europa anteriores a 1960 não respeitam qualquer requisito de eficiência energética. No intervalo entre 1960 e 1990, construíram-se em Portugal paredes exteriores simples e paredes duplas de alvenaria de tijolo sem isolamento térmico sendo muito importante empreender medidas para a sua reabilitação. No caso dos edifícios construídos depois de 1990 verifica-se que a implementação de regulamentação específica melhorou o seu desempenho energético. Neste trabalho apresenta-se um caso de estudo que corresponde à análise térmica de um edifício multifamiliar da década de 60. Recorreu-se a um conjunto de termogramas efetuados em dois períodos do dia na estação de aquecimento, a medições em contínuo de temperatura e humidade relativa e à análise térmica dos diferentes alojamentos com base na regulamentação atual.
- Fabrication Of Adhesively-Bonded CFRP T-Joints For Stiffener Pull-Off TestsPublication . Cardoso, João; Nunes-Pereira, J.; Silva, AbilioAdhesively bonded joints have been increasingly applied in primary aerostructures, mainly due to their numerous advantages over riveted or fastened joints. More specifically, bonded T-joints made from carbon fibre reinforced plastics (CFRP) are commonly found as stiffening members (stiffeners, or stringers) on wing panels and fuselage sections. However, aluminium stiffeners can yet be considered a safer and more conservative solution, since composite T-joints face delamination problems that typically initiate at the central noodle of the stiffener - the part where the three arms of the stiffener come together. In order to better comprehend the failure mechanisms and sequence of these joints, Stiffener-Pull- Off Tests (SPOT) were experimentally conducted on a two CFRP adherends (SEAL® Texipreg HS 160 REM) - skin and stiffener - adhesively bonded with a structural film adhesive (EA451 U150). These specimens were fabricated following a novel fabrication plan, which left open the possibility of re-engineering the noodle region with the scope of increasing the through-thickness strength of the bonded joint. This can be achieved by eliminating the problem of the twisted fibres at the noodle that occur during the cure stage when no filler material is used.
- Mechanical Properties of Fused Filament Fabrication MaterialsPublication . Santos, João; Silva, Jorge; Gamboa, Pedro; Neves, JoãoThe last decades have witnessed a significant development and increased usage of additive manufacturing (AM) technologies. Among these technologies, the fused filament fabrication (FFF) is being characterized by a massive worldwide spreading, from specialized companies with high-quality equipment to the hobbyist with home-made 3D printers. Thus, and aiming to help the user achieving the best results, it is essential to continuously perform studies and analyses concerning the mechanical properties resulting from different feedstock materials and printing settings. This study covers the execution and the subsequent comparative analysis of the results of flexural and tensile tests on three different types of FFF materials: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and CarbonFilTM. It also comprehends a parallel study of the infill setting, more specifically the testing of specimens with a 50% infill reduction. All tests were executed according to the corresponding American Society for Testing and Materials (ASTM) standards. This work aims to clarify the properties of three different materials and the effect of the internal material reduction on the mechanical properties of 3D printed objects.
- Essays on globe energy consumption and economic growth nexusPublication . Marques, Luís Miguel Soares Santos; Fuinhas, José Alberto Serra Ferreira Rodrigues; Marques, António Manuel CardosoThe way that economic growth and energy consumption interact with each other has been a rising interest in the last few decades. The continuous globe economic growth and the shift in large energy demand to emerging economics such as India and China raise new challenges requiring study. Regarding this, the literature is scarce and the study of energy-growth nexus at higher macroeconomic levels has been overlooked. The worldwide changes occurring in energy markets are expected to raise interest in globe nexus. In order to evaluate the interactions between globe economic growth and energy consumption, bivariate and multivariate models were developed. The aim of this research in not only to examine both short- and long-run nexus behaviours, but also to identify how the energy policies that some countries can follow, or how the development of globalization can have an impact on a globe scale. Following this path, different variables were introduced as explanatory of globe economic growth and energy consumption. By developing four essays, the thesis seeks to raise awareness of the importance of understanding the impact of economic policy decisions at the globe level. The first two essays focus on studying the energy-growth nexus at the globe level and by dividing the globe into four regions, without interference from any other variables. The third and fourth essays introduce the concept of study of the globe augmented energy-growth nexus. Additionally, in the third essay, China’s economic growth and energy consumption were introduced as possible explanatory variables of economic growth and energy consumption through different globe regions. The fourth essay, examines the impact of different globalization dimensions on globe energy-growth nexus. The followed econometric approaches considered the data requirements as well as the predictable presence of structural breaks. Moreover, the aim to examine both the short- and the long-run relationships influenced the methodology choice. For those reasons, autoregressive models such as Autoregressive Distributed Model (ARDL), Vector Autoregression (VAR) or Vector Error Correction Model were developed by using time series and panel data. The results reveal a bidirectional relationship between globe economic growth and energy consumption. Moreover, the existence of heterogeneous relationships in different globe regions is proven to mostly not come from the use of different methodologies. Overall, the results support a path of diversification, not only on the used primary energy components, but also on economic outputs sources. It has also been proven that there are countries, such as China, that can influence the globe nexus. Regarding other factors influencing the globe nexus, it was observed that there are different globalization components impacting on globe economic growth and energy consumption.
- Software de apoio à reabilitação térmica de edifícios utilizando cortiçaPublication . Oliveira, Carlos Filipe Ferreira de; Lanzinha, JoãoA globalização tecnológica presenciada na atualidade permite obter na palma da mão toda a informação desejada sem grande dispêndio de tempo e recursos. Hodiernamente e devido à evolução da regulamentação, os edifícios são pensados logo aquando da realização do projeto, ostentando caraterísticas ótimas de conforto e sustentabilidade. Contudo a problemática está nos edifícios antigos. Estando estes ausentes de qualquer solução de isolamento térmico têm como consequência baixo conforto térmico e inclusive aumento dos consumos energéticos. Com isto surgiu a necessidade de desenvolver um protótipo de uma aplicação móvel denominada “Pocket Engineer” com o objetivo de facilitar o trabalho aos intervenientes na ação de reabilitação térmica dos elementos opacos da envolvente dos edifícios de habitação, evitando-se a implementação de soluções não fundamentadas no cálculo, bem como consciencializar todos os intervenientes com a temática da importância na colocação de isolamento térmico. Todo o desenvolvimento da aplicação teve como base o Regulamento do Desempenho Energético de Edifícios de Habitação (REH) aplicado em Portugal que apresenta valores máximos e de referência para os coeficientes de transmissão térmica dos elementos opacos dos edifícios. Utilizando estes coeficientes como referência, é possível garantir o cumprimento das exigências mínimas e determinar opções de reabilitação mais favoráveis através de uma comparação com os coeficientes de transmissão térmica da envolvente dos edifícios existentes, criando para tal níveis de qualidade térmica. Seguindo um conjunto de opções interativas será fornecida ao utilizador a solução de espessura ideal proposta para o reforço de isolamento térmico com cortiça, consoante o nível de qualidade pretendido.
- Advanced CaZrO3-MgO Ceramic Compositions for High Responsability ApplicationsPublication . Nunes-Pereira, J.; Pereira Silva, A; Pena, Pilar; Baudin, CarmenThe development of new advanced materials for harsh environment operation conditions, such as high temperature, wear and severe erosion and corrosion, is of growing interest, namely for transport and energy industries, due to the ecological and energetic current concerns on a global scale. Particularly, in aerospace industry the increase of working temperature of engines and turbines combined with weight reduction will give rise to higher thrust and lower fuel consumption and consequently less emissions. [...]
- Ficha de inspeção técnica aplicável a edifícios multifamiliares existentesPublication . Marcelino, Inês Isabel Gonçalves; Lanzinha, JoãoO parque edificado existente em Portugal tem um número significativo de edifícios correntes com alguma idade, havendo uma necessidade de os reabilitar para adequar as condições de utilização e conforto às exigências atuais, assegurando desta forma uma melhor qualidade de vida dos residentes. A ausência de inspeção e de ações de manutenção durante a vida útil de um edifício sem grande qualidade da construção inicial, potencia o mau estado de conservação. Quando um edifício apresenta necessidades de intervenção, é importante que o residente/condomínio contacte um técnico especializado para melhor definir a estratégia e modelo de intervenção, visto que a origem dos problemas pode muitas vezes não ser detetada e as anomalias podem agravar-se e tornar-se muitas vezes definitivas. Em Portugal ainda não existe um método oficial e obrigatório de inspeção técnica de edifícios. Por essa razão, há necessidade de aplicar medidas de inspeção sistemáticas de avaliação e prevenção de forma a evitar degradação progressiva do património edificado. Neste trabalho apresenta-se uma proposta de metodologia de inspeção de edifícios multifamiliares existentes, fundamentada em modelos similares e com a aplicação direta a um caso de estudo. A ficha de avaliação tem como principal objetivo avaliar o estado de conservação do edifício e a extensão de intervenção, realizar o levantamento dos materiais presentes, avaliar as infraestruturas gerais disponíveis e as condições de acessibilidade. O registo é efetuado em diferentes folhas que dizem respeito ao exterior, às zonas comuns e circulações e a cada compartimento de cada fogo. Apresentam-se também os resultados da aplicação efetuada.
- Reflexões sobre inspeção técnica, diagnóstico de patologias e reabilitação do edificadoPublication . Lanzinha, JoãoApresentação na 6ª Conferência de Patologia e Reabilitação de Edifícios
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