Uso da prototipagem rápida no projecto e produção de motores de combustão interna

Os motores de combustão interna são constituídos por peças de elevada complexidade, tal como a cabeça do motor. Nesta peça existem várias condutas (admissão, escape, arrefecimento), vários postiços (sedes e guias das válvulas de admissão e escape) e vários acessórios estão a ela ligada ou fazem dela parte, tal como a vela e todo o sistema de distribuição constituído por árvore de cames, balanceiros, válvulas e molas. Com tal complexidade torna-se difícil fazer o projecto, mas principalmente efectuar a produção da peça. Em particular as condutas constituem zonas de difícil acesso para remoção de material, e impõem limitações de execução. A prototipagem rápida pode ajudar tanto na fase de projecto como na de produção. Técnicas diferentes de prototipagem rápida foram aplicadas à produção de peças fundidas, de modo a serem aplicadas no motor.Fundação para a Ciência e a Tecnologia (FCT) - POCI/EME/59186/2004

Fitting isochrones to open cluster photometric data III. Estimating metallicities from UBV photometry

The metallicity is a critical parameter that affects the correct determination fundamental characteristics stellar cluster and has important implications in Galactic and Stellar evolution research. Fewer than 10 % of the 2174 currently catalog open clusters have their metallicity determined in the literature. In this work we present a method for estimating the metallicity of open clusters via non-subjective isochrone fitting using the cross-entropy global optimization algorithm applied to UBV photometric data. The free parameters distance, reddening, age, and metallicity simultaneously determined by the fitting method. The fitting procedure uses weights for the observational data based on the estimation of membership likelihood for each star, which considers the observational magnitude limit, the density profile of stars as a function of radius from the center of the cluster, and the density of stars in multi-dimensional magnitude space. We present results of [Fe/H] for nine well-studied open clusters based on 15 distinct UBV data sets. The [Fe/H] values obtained in the ten cases for which spectroscopic determinations were available in the literature agree, indicating that our method provides a good alternative to determining [Fe/H] by using an objective isochrone fitting. Our results show that the typical precision is about 0.1 dex

Engine design using rapid prototyping techniques

An internal combustion engine was designed in ProEngineer. The aim of this project was to develop a proposefull tool enabling the rapid design/development of the required engine. The first non-working model was built using a rapid prototyping machine. A visual analysis of the engine head model shown various fields where improvements could be made on the engine design. Therefore, the head was re-designed taking that into account. The second phase of the project involves the actual production of low cost direct casting moulds straight from the engine design. Design and manufacture integration now possible through Rapid Prototyping techniques enabled drastic reductions of the design-development-casting process effort.Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional Ciência e Inovação (POCI)

Processing of titanium aluminides by ceramic crucible induction melting

This work describes the processing results of TiAl alloys melted in controlled atmosphere induction furnace, using crucibles made of calcia and zirconia stabilised with yttria, calcia and magnesia, solidified and inside the crucible, in order to simulate the worst situation using this processing. In the results are presented segregation profiles of residual elements and its relation with micro hardness and “alpha-case” extension, in the microconstituents present at room temperatur

The production of TiAl by foundry processes

This paper describes a foundry technique that enables the production of TiAl employing an adapted melting procedure that uses an induction furnace with suitable refractory crucibles, inside a controlled atmosphere chamber. The developed technique allows the production of samples with a low and controlled amount of residual elements, with a thin superficial hard skin – known as “alpha-case” – and allows the use of higher superheating temperatures, when compared with alternative melting procedures. The micro-hardness and the residual contamination profiles, from the outside to the interior of samples, are presented and correlated to crucible refractory material and foundry practice.(undefined

Life cycle assessment of a vanadium flow battery

The 6th International Conference on Energy and Environment Research, July 22–25, 2019, University of Aveiro, PortugalBattery storage technologies have been showing great potential to address the vulnerability of renewable electricity generation systems. Among the various options, vanadium redox flow batteries are one of the most promising in the energy storage market. In this work, a life cycle assessment of a 5 kW vanadium redox flow battery is performed on a cradle-to-gate approach with focus on the vanadium electrolytes, since they determine the battery’s storage capacity and can be readjusted and reused indefinitely. The functional unit is 1 kWh stored by the battery. The initial results show that the environmental hotspots reside mainly in the structural and material components of the battery, evidencing the need for alternative or recycled materials, preferably produced locally. Since the quantity of electrolytes determine the amount of storable electricity, an analysis was conducted on the variation of the impacts with the increase of storage capacity. An alternative scenario with reused electrolytes was also performed. Results show that with the increase of storage capacity, the contribution of the electrolytes to the impacts decrease significantly by stored kWh. In the reused electrolytes scenario, impacts were reduced mainly for the Acidification and Mineral, fossil and renewable resource depletion categories.This work was financial supported by projects “SunStorage – Harvesting and storage of solar energy”, with reference POCI-01-0145-FEDER-016387, funded by European Regional Development Fund (ERDF), through COMPETE 2020 – Operational Programme for Competitiveness and Internationalization (OPCI), and to FCT — Fundação para a Ciência e a Tecnologia, Portugal I.P., project IF/01093/2014/CP1249/CT0003, research grants IF/01093/2014 and SFRH/BPD/112003/2015. Support from POCI-01-0145-FEDER-006939 (Laboratory for Process Engineering, Environment, Biotechnology and Energy — LEPABE, UID/EQU/00511/2019) funded by FEDER, Spain through COMPETE2020-POCI and by national funds through FCT/MCTES (PIDDAC), Portugal.info:eu-repo/semantics/publishedVersio

Miniaturised cylinder head production by rapid prototyping

This work shows the development of the design and manufacturing of a very small engine, namely its head. The engine works under the 4-stroke cycle, therefore having a very complex cylinder head, housing the camshaft, valves and its auxiliaries (seats, guides, springs), spark plug, inlet and exhaust passages and a coolant chamber. The geometries, both inner and outer are highly intricate which makes the production of such a part a very difficult job. In addition, when the engine is very small, as it is the case of this engine, all dimensions are miniaturized therefore making it extremely difficult to design, cast and finish. The cooling chamber, in particular, has a critical inner core removal problem due to reduced accessibility, imposing casting limitations. The cores place also a problem of air and gas removal during metal filling and solidification. Rapid prototyping may be the only solution to build the cores, and may help in the design and manufacturing phases of the casting tools. 3D printing with a plaster based material as a rapid prototyping technique presents itself as a tool to drastically reduce the design-development-casting process effort and time cycle. This technique enables the designer to obtain new moulds for castings on the shortest time possible, following redesign and new casting simulations. This paper illustrates the various tasks involved in the design and development stages leading to the production of a running prototype of the cylinder head for this small engine.Fundação para a Ciência e a Tecnologia (FCT) - POCI/EME/59186/2004, MIT-Pt/EDAM-SMS/0030/200

Development of an anthropomorphic mobile manipulator with human, machine and environment interaction

An anthropomorphic mobile manipulator robot (CHARMIE) is being developed by the University of Minho's Automation and Robotics Laboratory (LAR). The robot gathers sensorial information and processes using neural networks, actuating in real time. The robot's two arms allow object and machine interaction. Its anthropomorphic structure is advantageous since machines are designed and optimized for human interaction. Sound output allows it to relay information to workers and provide feedback. Allying these features with communication with a database or remote operator results in establishment of a bridge between the physical environment and virtual domain. The goal is an increase in information flow and accessibility. This paper presents the current state of the project, intended features and how it can contribute to the development of Industry 4.0. Focus is given to already finished work, detailing the methodology used for two of the robot's subsystems: locomotion system; lower limbs of the robot.- This project has been supported by the ALGORITMI Research Centre of University of Minho's School of Engineering

Evaluation of Y2O3 as front layer of ceramic crucibles for vaccum induction melting of tial based alloys

During the last decades titanium alloys were found to be valuable engineering materials for many different applications. Formerly used in critical applications like aerospace, aeronautic and military equipment, where the factor cost is not relevant, titanium alloys are finding now new and different markets. However, the development of such new markets will depend on an effective cost reduction of titanium parts, in order to achieve a selling cost suitable with its application in consumer goods. A possible solution to decrease production costs might be the use of traditional casting techniques to produce near net shape functional parts. During the last years, the authors have developed extensive research work on this field, and a new technique both for melting and moulding, using ceramic multi-layered crucibles and investment casting shells was developed. This paper presents some of the results obtained during that research work: Ti-48Al alloy were melted and cooled inside CaO, MgO and Y2O3 stabilized ZrO2 crucibles with inside layer of Y2O3. The chemical composition, hardness and microstructure at the metal-crucible interface, studied by secondary ion mass spectrometry, SEM/EDS and XRS are presented. On a second step, the same alloy was melted on the same crucibles, and poured into graphite moulds, and the crucibles wall was characterized by SEM/EDS and XRS.(undefined

Characterization of TiAl alloys by secondary Ion mass spectrometry

Titanium aluminides are arising as a valuable alternative to superalloys in applications where the ratio resistance/density is important. Together with excellent mechanical and corrosion properties at high temperatures, such characteristics are very attractive for applications in the aeronautical, aerospace and automotive industries. However, the current high selling price, due to high costs of production and raw materials and the need of very specific equipment, are limitative factors for further applications. With the end of the cold war, and the decrease of traditional markets of TiAl, the strategy to develop other applications, strongly depends on the decrease of production costs. An alternative to the present production routes might be the use of traditional casting techniques, by induction melting of the alloy in a ceramic crucible and pouring into ceramic moulds, made by the investment casting process. However, due to the high reactivity of Ti alloys, the use of traditional ceramic materials cannot be used, as they lead to oxide formation and oxygen pick up both from the crucible and the moulding materials. In this work, the relative oxygen concentration of Ti-48Al castings was measured by SIMS — Secondary Ion Mass Spectrometry. This technique provides a direct measurement of the isotopic composition with high sensitivity. The cylindrical samples were specially prepared to allow the analysis of the area close to the border. Oxygen profiles were acquired for samples obtained by with different mould materials. The comparison of such profiles with hardness profiles, give insight in the significance of the oxygen concentration in the properties of the alloy and in the choice of the most suitable materials for TiAl production(undefined