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- Determinação do factor concentração de tensões em placas utilizando a extensometria com validação numéricaPublication . Fonseca, E.M.M.; Caleiro, C.M.S.; Lopes, Hernani; Vaz, M.A.P.; Mesquita, L.M.R.É apresentada uma metodologia experimental para determinação do factor concentração de tensões, com base na técnica de extensometria, em placas com furos circulares. Pretende-se efectuar a comparação dos resultados experimentais com resultados numéricos obtidos em códigos comerciais: ANSYS e COSMOS/M. É ainda apresentada a mesma solução usando um programa de elementos finitos desenvolvido FEMSEF.
- Avaliação da resistência do colo do fémur utilizando o modelo de elementos finitosPublication . Teixeira, Cristina; Fonseca, E.M.M.; Barreira, LuísaEste trabalho tem como objectivo avaliar a resistência do colo do fémur, através da distribuição de tensões na extremidade proximal, quando solicitado em diferentes actividades quotidianas (caminhar, descer escadas e posição ortostática), considerando a espessura do osso cortical do colo do fémur aos 30anos e aos 80anos.
- Fire resistance of wooden cellular slabs with rectangular perforationsPublication . Meireles, J.M.; Fonseca, E.M.M.; Piloto, P.A.G.; Ferreira, DéboraThis paper presents a numerical approach with finite element method in order to predict both the behaviour and the performance of the wooden slabs with rectangular perforations under fire exposure. These typical constructions have good sound absorption, thermal insulation and relevant architectonic features, they are used in many civil engineering applications as: concert and conference halls, classrooms, nurseries, airports, hotels, shopping, universities, and many other private and public buildings. These slabs are normally installed at lower level in building constructions essentially due to an easy maintenance requisite. Depending on the installation requirement, the perforated wooden slabs could have an additional insulation material inside the cavities [1]. The proposed numerical model could be applied to different design constructive slab solutions. For this purpose a 3D numerical simulation was conducted with particular attention to the wood thermal properties variation with temperature [2]. The numerical results were compared with those obtained experimentally in laboratory, for two wooden slabs. The fire resistance (performance criteria related to the insulation (I) and integrity (E)) was evaluated, as well as the effect of rectangular perforations into the residual cross section of the slab. This study was conducted in accordance with European Standard EN 1365-2 [3] and using a fire resistance furnace which complies the requirements of EN 1363-1 [4] in the experimental test.
- Cálculo da espessura carbonizada em estruturas de madeira quando submetidas à acção do fogoPublication . Barreira, Luísa; Fonseca, E.M.M.A utilização da madeira em construção levanta algumas questões nomeadamente no cumprimento dos aspectos normativos contra riscos de incêndio. No entanto, quando comparada com outros materiais de construção, a madeira apresenta uma boa resistência ao fogo. Com o presente trabalho, pretende-se determinar a espessura da camada carbonizada em função do tempo em elementos estruturais, para diferentes cenários de exposição ao fogo, segundo a curva ISO834, utilizando-se uma ferramenta de elementos finitos.
- Dynamic numerical simulation of different drill bit diameter on the polyurethane foams drillingPublication . Fernandes, M.G.A.; Fonseca, E.M.M.; Teixeira, Tiago A.S.; Jorge, Renato N.Drilling is one of the most common processes involved in different cutting operations and may affect the mechanical properties of the workpiece by creating residual stresses around the opened hole and highly stressed on the newly formed surface. Nevertheless, when it comes to the living tissues, drilling assumes more attention to guarantee a non-invasive procedure. Drilling of bone is common in orthopaedic surgical process, to produce a hole to screw insertion to fix the fractured members for immobilization, or even in dental implant interventions. This work describes a conventional drilling process performed on solid rigid polyurethane foams blocks with similar mechanical properties to the human bone. A dynamic and numerical study was conducted to evaluate the use of different drill diameters (4, 5 and 6mm) on the stresses generated during the process.
- Temperature assessment in the drilling of ex vivo bovine and porcine cortical bone tissuePublication . Fernandes, M.G.A.; Fonseca, E.M.M.; Natal, Renato; Dias, Maria Isabel RibeiroThermal damage in boné tissue is a common problem in drilling processes. The main goal of this work is to analyze the cutting conditions that generate the lower temperature, avoiding the occurrence of thermal boné necrosis. In this work, the effects of the drill speed and the feedrate were studied during the drilling ofcortical bovine and porcine boné tissue. !n the ex vivo drilling operations, two methodologies were performed on several fresh femur boné samples. The present study showed that the combinations of cutting conditions in the drilling process of ex 1//Vo cortiça! bovine and porcine boné tissue, produced temperatures far below the criticai values. It was concluded that the temperature increases with an increasing drill speed and decreases with high feed-rates. To the drill speed, the difference is less clear than that the the feed-rate. The drilling temperatures on the bovine samples were higher than porcine samples.
- The measuring of the cortical bone thickness in L4 vertebra and comparison with bone mass densityPublication . Fonseca, E.M.M.; Barreira, Luísa; Dinis, Jairson C.; Pereira, Ana I.The aim of this work is to identify the cortical bone thickness in L4 vertebra, through a digital methodology using Computed Tomography and an experimental methodology with the rapid prototyping, and to compare with the body mass density for each vertebra in analysis. The study presents clinic results of sixteen women from the Northwest of Portugal, with age between 52 and 83 years, collected from May to June 2011. The patients underwent a dual energy X-ray densitometry scan system (Lunar, DPX Pro, daily calibrated) at L4 vertebra for body mass density determination, and simultaneous a lumbar spine Computed Tomography scan (Lightspeed Plus, GE Medical System) was performed. All clinical data were obtained in a Medical Imaging Centre of Radiology. Discussions of results regarding the measuring of the cortical bone thickness and the relation with body mass density in L4 vertebra are presented in this work. The L4 vertebra is one of the most common spinal sites that lead to chronic lower back pain. The goal of this study is to acquire accurate values, concerning cortical bone thickness, which could improve the prediction of vertebral fractures.
- Avaliação da resistência óssea da vértebra L3 em diferentes pacientes do género femininoPublication . Silva, Sónia F.D.; Fonseca, E.M.M.; Barreira, LuísaO principal objetivo deste estudo é avaliar a resistência óssea da vértebra L3 em 16 pacientes do género feminino. Foram obtidas imagens médicas da coluna vertebral de diferentes pacientes por tomografia computorizada (TC). Em cada imagem, foi selecionada a vértebra L3 para o estudo 3D, posterior avaliação e medição da espessura cortical. Os valores obtidos da espessura cortical em cada vértebra serão comparados com os valores de registo da densidade mineral óssea (DMO) e do T-Score para cada paciente, através de exames médicos adicionais de densitometria óssea.
- Avaliação experimental do comportamento ao fogo de lajes celulares em madeira com diferentes perfuraçõesPublication . Meireles, J.M.; Piloto, P.A.G.; Fonseca, E.M.M.; Santos, H.S.; Barreira, LuísaAs lajes em madeira são elementos estruturais com aplicação crescente, em particular na reabilitação de elementos existentes, na adequação de grandes espaços interiores e na construção de novas estruturas. As excelentes propriedades mecânicas, associadas a elevadas propriedades térmicas e acústicas fazem deste material uma solução ideal para lajes de pavimentos e de coberturas. Para avaliação do comportamento ao fogo, foram realizados dois ensaios em lajes celulares (3 células) com diferentes perfurações (pequenos e grandes retângulos). Estas lajes são constituídas por vigas de secção retangular (tricapa casquinha) ligadas a uma armadura (vigas Kerto), com conetores metálicos SIMPSON e painéis de teto e pavimento tricapa casquinha. As lajes foram instrumentadas com termopares tipo K, termopares de discos de cobre para superfície não exposta e termopares de placa para medição da temperatura no compartimento de incêndio e nas células. Foi utilizado um forno de resistência ao fogo, com a prescrição da curva ISO834. Neste trabalho são apresentados os resultados da evolução da temperatura nos painéis perfurados, nas vigas, conetores, superfície não exposta e apresentados resultados da taxa de carbonização de cada célula.
- Cellular slabs with and without insulation submitted to fire conditionsPublication . Djaafer, Haddad; Belkacem, Lamri; Fonseca, E.M.M.The wooden cellular slabs are lightweight structures, easy to assemble, and with excellent architectural features, as thermal and acoustic conditions. The wooden cellular slabs with perforations are typical and very common engineering solutions, used in the ceiling or flooring plates to improve the acoustic absorption of compartments, and also have a good insulation and relevant architectonic characteristics. However, the high vulnerability of wooden elements submitted to fire conditions requires the evaluation of its structural behavior with accurately. The main objective of this work is to present a numerical model to assess the fire resistance of wooden cellular slabs with different perforations. Also the thermal behavior of the wooden slabs will be compared considering material insulation inside the cavities.