Browsing by Author "Ferreira, F."
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- Comparative study about heating systems for pultrusion processPublication . Silva, Francisco J. G.; Ferreira, F.; Costa, C.; Ribeiro, M. C. S.; Meira Castro, Ana C.Different heating systems have been used in pultrusion, where the most widely used heaters are planar resistances. The primary objective of this study was to develop an improved heating system and compare its performance with that of a system with planar resistances. In this study, thermography was used to better understand the temperature profile along the die. Finite element analysis was performed to determine the amount of energy consumed by the heating systems. Improvements were made to the die to test the new heating system, and it was found that the new system reduced the setup time and energy consumption by approximately 57%.
- Effect of peak power on microstructure, mechanical and tribological properties of W-Ti-C-N(O) ceramic films produced by hybrid sputteringPublication . Ataie, S.A.; Soltanieh, M.; Naghizadeh, R.; Cavaleiro, A.; Fernandes, F.; Ferreira, F.This research investigates the impact of peak power (from 44 to 105 kW) on the structural and tribological properties of W-Ti-C-N(O) films. Chemical analysis of the coatings, using energy-dispersive spectroscopy and Raman spectroscopy, indicates that increasing target power results in a rise in the oxygen (from 2.6 to 12.0 at%), carbon (from 19.7 to 32.4 at%), and sp3 (from 9.8% to 24.3%) content. Morphological and topographical analysis reveal that an increase in target power causes a transition from a columnar structure (with nodular grains) to a dense structure (with textured grains). The indentation and dry sliding tests demonstrate that the maximum level of H/E2 (0.00047 GPa-1) is achieved, along with a low wear rate of 8.1 × 10-7 mm3/N.m.
- Effect of substrate bias voltage on structural and tribological properties of W-Ti-C-N thin films produced by combinational HiPIMS and DCMS co-sputteringPublication . Ataie, S.A.; Soltanieh, M.; Naghizadeh, R.; Cavaleiro, A.; Evaristo, M.; Fernandes, F.; Ferreira, F.Protective multi-component thin films at the surface of cutting tools have been significantly developed to reduce wear and friction. The present work investigates the effect of substrate bias voltage on the structural-tribological relations of W-Ti-C-N thin films produced by HiPIMS and DCMS co-sputtering. Chemical analysis of the coatings is obtained and composite phase structure is revealed. Morphology of the coatings illustrates that defectless surfaces may be achieved. Topographical parameters are investigated by employing graphical software. Indentation, scratch and pin-on-disk tests (pin is AISI 52100 steel) are applied to study mechanical behaviors of the films. To produce a wear-resistant film, a median bias voltage ( 60 V) and as a result, optimum content of tungsten concentration (19.2 at. %), grain size (42.8 nm) and average peak interval (188 nm) is required. Finally, a model based on the representative volume element is developed to show crack propagation and delamination.
- Ensaios preliminares para caracterização de um solo sujeito a fogo controladoPublication . Meira Castro, Ana C.; Albergaria, José Tomás; Meixedo, João Paulo; Delerue-Matos, Cristina; Vivas, António; Ferreira, F.; Costa, M.; Freitas, A.; Ribeiro, S. R.No presente trabalho são apresentados os resultados obtidos num estudo realizado na região do Norte de Portugal, onde uma equipa multidisciplinar, em estreita cooperação com a Autoridade Florestal Nacional, estudou as variações de pH e teores de humidade e matéria natural orgânica do solo antes e após a execução de um fogo controlado. Foi avaliada também a evolução destes parâmetros nos 90 dias seguintes após a queimada no sentido de estudar o nível de recuperação natural dos solos. Deste estudo foi possível concluir-se que o fogo controlado causou um aumento do pH do solo e uma redução no teor de humidade. Relativamente à recuperação natural dos solos, foi verificada uma recuperação parcial das características do solo não se tendo atingido, ao fim de 90 dias, os valores observados antes da acção do fogo. Os trabalhos de monitorização/ avaliação prosseguirão com periodicidade trimestral.
- Finite Element Analysis (FEA) applied to heat transfer optimization process of pultrusion die systemsPublication . Silva, Francisco J. G.; Ferreira, F.; Costa, C.; Meira Castro, Ana C.; Meixedo, João Paulo; Alvim, Mário Rui; Santos, R. P. C.; Ribeiro, M. C. S.; Fiúza, António; Dinis, M. L.The aim of this study is to optimize the heat flow through the pultrusion die assembly system on the manufacturing process of a specific glass-fiber reinforced polymer (GFRP) pultrusion profile. The control of heat flow and its distribution through whole die assembly system is of vital importance in optimizing the actual GFRP pultrusion process. Through mathematical modeling of heating-die process, by means of Finite Element Analysis (FEA) program, an optimum heater selection, die position and temperature control was achieved. The thermal environment within the die was critically modeled relative not only to the applied heat sources, but also to the conductive and convective losses, as well as the thermal contribution arising from the exothermic reaction of resin matrix as it cures or polymerizes from the liquid to solid condition. Numerical simulation was validated with basis on thermographic measurements carried out on key points along the die during pultrusion process.
- How to reduce energy consumption on pultrusionPublication . Ferreira, F.; Costa, C.; Silva, Francisco J. G.; Meira Castro, Ana C.The global warming due to high CO2 emission in the last years has made energy saving a global problem nowadays. However, manufacturing processes such as pultrusion necessarily needs heat for curing the resin. Then, the only option available is to apply all efforts to make the process even more efficient. Different heating systems have been used on pultrusion, however, the most widely used are the planar resistances. The main objective of this study is to develop another heating system and compares it with the former one. Thermography was used in spite of define the temperature profile along the die. FEA (finite element analysis) allows to understand how many energy is spend with the initial heating system. After this first approach, changes were done on the die in order to test the new heating system and to check possible quality problems on the product. Thus, this work allows to conclude that with the new heating system a significant reduction in the setup time is now possible and an energy reduction of about 57% was achieved.
- Internal audits: an ally in the promotion of a radiation protection culturePublication . Cunha, L.; Roda, A. L.; Ratão, P.; Capoulas, M.; Ferreira, F.; Sousa, M.; Vasconcelos, H.; Moreira, A. S.; Metelo, Luís FranciscoInternal audits are between the most important tools supporting the management board of any organization. Regardless if they are conducted by na internal or an external auditor, the goals are to assist the organization in defining areas of improvement, while providing precise information needed to accomplish the established goals. We aim to contribute to improving the community awareness of the value of conducting regular audits and its impact on promoting a culture of radiation protection.
- Mechanical behaviour analysis of polyester polymer mortars modified with recycled GFRP waste materialsPublication . Ribeiro, M. C. S.; Meixedo, João Paulo; Fiúza, António; Dinis, M. L.; Meira Castro, Ana C.; Silva, Francisco J. G.; Costa, C.; Ferreira, F.; Alvim, Mário RuiIn this study the effect of incorporation of recycled glass-fibre reinforced polymer (GFRP) waste materials, obtained by means of milling processes, on mechanical behaviour of polyester polymer mortars was assessed. For this purpose, different contents of recycled GFRP waste powder and fibres, with distinct size gradings, were incorporated into polyester based mortars as sand aggregates and filler replacements. Flexural and compressive loading capacities were evaluated and found better than unmodified polymer mortars. GFRP modified polyester based mortars also show a less brittle behaviour, with retention of some loading capacity after peak load. Obtained results highlight the high potential of recycled GFRP waste materials as efficient and sustainable reinforcement and admixture for polymer concrete and mortars composites, constituting an emergent waste management solution.
- Optimising the energy consumption on pultrusion processPublication . Silva, Francisco J. G.; Ferreira, F.; Ribeiro, M. C. S.; Meira Castro, Ana C.; Castro, M.R.A.; Dinis, M.L.; Fiúza, A.This study is based on a previous experimental work in which embedded cylindrical heaters were applied to a pultrusion machine die, and resultant energetic performance compared with that achieved with the former heating system based on planar resistances. The previous work allowed to conclude that the use of embedded resistances enhances significantly the energetic performance of pultrusion process, leading to 57% decrease of energy consumption. However, the aforementioned study was developed with basis on an existing pultrusion die, which only allowed a single relative position for the heaters. In the present work, new relative positions for the heaters were investigated in order to optimise heat distribution process and energy consumption. Finite Elements Analysis was applied as an efficient tool to identify the best relative position of the heaters into the die, taking into account the usual parameters involved in the process and the control system already tested in the previous study. The analysis was firstly developed based on eight cylindrical heaters located in four different location plans. In a second phase, in order to refine the results, a new approach was adopted using sixteen heaters with the same total power. Final results allow to conclude that the correct positioning of the heaters can contribute to about 10% of energy consumption reduction, decreasing the production costs and leading to a better eco-efficiency of pultrusion process.
- Optimização do processo de pultrusãoPublication . Costa, C.; Ferreira, F.; Silva, Francisco J. G.; Meira Castro, Ana C.; Ribeiro, C.; Alvim, Mário RuiCada vez mais é necessário inovar e optimizar, sendo todos os processos susceptíveis a melhorias contínuas. A inovação e empenho no desenvolvimento destas novas soluções resultam do “know-how” já existente e da necessidade permanente de incrementar a produtividade com vista a uma maior competitividade, a flexibilidade e assegurar simultaneamente a qualidade dos produtos manufacturados. Com vista a incrementar a flexibilidade, torna-se necessário reduzir significativamente os tempos de “set-up” e o ”lead-time”, com vista a assegurar a entrega dos produtos de forma cada vez mais rápida. Este objectivo pode ser conseguido através de uma normalização dos elementos que constituem a linha de pultrusão. Implicitamente, observa-se um aumento de produtividade com esta medida. Neste trabalho pretende-se optimizar e flexibilizar todo o processo de pultrusão de perfis estruturais. Foram considerados todos os elementos do sistema, desde o armazém das fibras (“rack”) até à fieira de pultrusão. Foi dedicada particular atenção ao sistema de guiamento das fibras e mantas, à tina onde as fibras são impregnadas em resina, normalizadas as placas de posicionamento das fibras em direcção à entrada da fieira e revisto todo o processo de montagem e fixação da fieira, assim como o sistema de aquecimento da mesma. Com a implementação destes novos sistemas foi conseguida uma poupança significativa de tempo de “set-up” e foram claramente reduzidos os custos unitários de produção. A garantia de qualidade foi também incrementada.