Orientador: Sheila Canevese Rahal / Banca: Cláudia Valéria Seullner Brandão / Banca: Maria Jaqueline Mamprim / Banca: Fernanda De Biasi / Banca: Bruno Watanabe Minto / Resumo: O objetivo do estudo foi desenvolver uma placa óssea bloqueada em formato de T, com o intuito de ser utilizada em fraturas distais de rádio, e avaliar a resistência da montagem, por meio de ensaios mecânicos. A placa de 2,7 mm foi confeccionada em titânio, contendo eixo com três orifícios para parafusos bloqueados e um orifício para compressão dinâmica, e uma cabeça com dois orifícios para parafusos bloqueados. A cabeça da placa possuía uma chanfradura localizada na porção médio-distal e a extremidade proximal da haste da placa apresentava formato afunilado. Para os ensaios mecânicos foram usados 40 corpos de prova sintéticos em formato de T e 20 placas em T. A placa óssea foi posicionada sobre os corpos de prova, com a falha óssea segmentar de 2 mm localizada entre a cabeça e a haste da placa. Para a determinação das cargas para os ensaios de fadiga, seis montagens foram testadas até a falha, sendo três em flexão engastada e três em compressão. Para o ensaio de fadiga foram utilizadas 14 montagens, sendo sete testadas em compressão axial e sete em flexão engastada. Em ambos os ensaios foram observados valores mais altos, em todas as variáveis avaliadas, na configuração sob carga axial do que na flexão engastada. Além disso, no ensaio em fadiga em compressão axial as montagens suportaram um maior número de ciclos. Foi possível concluir que pelos testes mecânicos, o modelo oferece suficiente estabilidade para resistir as cargas axiais no tratamento de fratura radial distal / Abstract: The aim of this study was to develop a locked T-plate to be used in distal radial fractures and evaluate the mechanical properties. A titanium 2.7 mm T-plate was designed with a shaft containing three locked screw holes and one dynamic compression hole, and a head with two locked screw holes. The head of the plate had an indentation and shaft had tapered-shaped end. Forty polyurethane blocks having a T-shaped and 20 titanium T-plates were used for mechanical testing. The bone plate was positioned over the polyurethane blocks with 2 mm fracture gap between the head and shaft of the plate. Six bone-plate constructs were tested until failure, three in axial compression and three in cantilever bending, to determine the loads for fatigue testing. Fourteen bone-plate constructs were tested for failure in fatigue, seven in axial compression and seven in cantilever bending. Fatigue failure was defined as polyurethane block breakage or pullout of the screws in the polyurethane block. Tests were discontinued after one million cycles if the construct had not already failed. In both static and fatigue testing, higher values of axial compression test than cantilever bending test were observed for all variables. Moreover, the constructs under fatigue axial compression test supported a larger number of cycles to failure. The locking Tplate tested has biomechanical properties that may offer sufficient stability to resist axial loads in the treatment of a distal radius fracture / Doutor

Foram fabricadas amostras de placas combustíveis contendo núcleos de cermets U3O8-Al com concentrações de U3O8 variando de 10 a 90% em peso (3,4 a 55,5% em volume). Amostras contendo núcleos com 58% em peso de U3O8, foram fabricadas a partir de compactados com densidades variando de 75 a 95% da densidade teórica. É discutida a influência da concentração de U3O8 e da porosidade do compactado de partida sobre a porosidade e uniformidade da espessura do núcleo obtido. Os núcleos U3O8-Al foram submetidos a ensaios de corrosão por água deionizada nas temperaturas 30, 50, 70 e 90°C, onde os núcleos foram expostos através de um defeito artificial produzido no revestimento. Os resultados obtidos mostram que a corrosão dos núcleos é acompanhada pela liberação de hidrogênio. O volume total de hidrogênio liberado (V) e o tempo transcorrido até que seja observado o início da liberação de hidrogênio (tempo de incubação ti, são dependentes da porosidade do núcleo e da temperatura absoluta (T), podendo ser descritos pelas equações: V = K1 eα1 P - K2 T eα2 P e ti = eK1 + K2 P + K3 / T + K4 P / T onde P é a fração volumétrica de vazios (porosidade) e K1, K2, K3,K4, α1 e α2 são constantes. É proposto e discutido um mecanismo para o processo de corrosão de núcleos U3O8-Al. O revestimento das amostras de placas combustíveis foi submetido a ensaios de corrosão sob condições similares às encontradas no reator IEA-R1 operando às potências de 2 MW, 5 MW e 10 MW. Foi verificado o efeito da presença de heterogeneidades superficiais e de um tratamento de limpeza química sobre o comportamento da corrosão do revestimento. Os resultados obtidos mostram que a corrosão é regulada pela dissolução/erosão da camada de óxido formada e segue lei linear para as três condições de testes e que a presença de heterogeneidades superficiais ou o tratamento de limpeza química não alteram significativamente a corrosão do revestimento para tempos de exposição de até 20 dias. Estão apresentadas as velocidades de corrosão e as espessuras das camadas de óxido observadas nos três ensaios efetuados. Não foi observado ataque localizado significativo. / Fuel plate specimens containing U3O8-Al cermet cores were fabricated with the U3O8 concentration varying between 10 and 90% by weight (3.4 to 55.5% in volume). Fuel plate specimens containing 58% U3O8 by weight were also fabricated from compacts with densities varying between 75 and 95% of the theoretical density. The influence of U308 concentration and porosity of the initial compact on the porosity and uniformity of thickness of the core are discussed. The U3O8-Al cores were corrosion tested in deionized water at 30, 50, 70 and 90°C, where in the cores were exposed to the deionized water by means of an artificially produced cladding defect. The results indicate that core corrosion is accompanied by hydrogen evolution. The total volume of hydrogen evolued (V) and the time to initiation of hydrogen evolution (incubation time ti), vary with the porosity of the core and temperature (T), according to equations: V = K1 eα1 P - K2 T eα2 P e ti = eK1 + K2 P + K3 / T + K4 P / T where P is the volumetric fraction of pores and K1, K2, K3,K4, α1 e α2, are constants. A mechanism for the U3O8-Al core corrosion has been proposed and discussed. The cladding of the fuel plats specimens was also corrosion tested under conditions similar to those encountered in the IEA-R1 reactor operating at 2, 5 and 10 MW. The effect of the presence of surface heterogeneities and a chemical surface treatment on the corrosion behavior of the cladding have been studied. The results reveal that the corrosion is regulated by dissolution/erosion of the oxide layer, and follows a linear law under the three test conditions. The presence of surface heterogeneities or the chemical surface treatment did not significantly alter the cladding corrosion for test times of up to 20 days. The corrosion rates and the oxide layer thicknesses observed under the three test conditions are also presented. No significant localized attack was observed.

Using license plates as a context, we will analyze patterns. I will share a technique for graphing, and you will design your own license plates with given parameters. Our graphs will offer entry into transformational geometry, and a mapping from letters to numbers allows us to experience early algebra in context.

License plates are a useful context to work with numbers, and in this article you will see a range of activities in which to engage your students. Some innovative graphing concepts are presented with license plates that allow students to investigate transformations including translations, reflections, and rotations.

Using license plates as a context, we will analyze patterns. I will share a technique for graphing, and you will design your own license plates with given parameters. Our graphs will offer entry into transformational geometry, and a mapping from letters to numbers allows us to experience early algebra in context.

Using license plates as a context, we will analyze patterns. I will share a technique for graphing, and you will design your own license plates with given parameters. Our graphs will offer entry into transformational geometry, and a mapping from letters to numbers allows us to experience early algebra in context.

Using license plates as a context, we will analyze patterns. I will share a technique for graphing, and you will design your own license plates with given parameters. Our graphs will offer entry into transformational geometry, and a mapping from letters to numbers allows us to experience early algebra in context.

Ti-6Al-4V anterior cervical plates (ACP) are used in spinal fusion surgeries to fixate cervical vertebrae during graft adhesion. However, documented cases of implant failure and the potential for ACP corrosion raise concerns regarding any degradation of material resulting from extended implantation. In addition, abrasion during implantation may damage a section of the protective oxide layer, potentially exposing surrounding tissues to the harmful effects of bare titanium, aluminum, and vanadium. Thermal oxidation has been shown to improve corrosion-resistance and wear-resistance, depending on temperature and time. To quantify the attributes of the thermally grown oxide layer, Ti-6Al-4V coupons underwent thermal oxidation treatments in an atmosphere environment at 600 and 675 ˚C for 1, 4, 8, and 16 hours. Two sample types were produced: non-abraded and abraded. Non-abraded samples underwent potentiodynamic polarization according to ASTM F2129, which included open circuit potential tests. Open circuit potentials (EOC) increased with increasing treatment time, indicating that longer treatment time resulted in thicker oxides. All samples treated at 675˚C displayed higher EOC than samples treated at 600˚C, indicating an increase in oxide thickness with higher temperature. During the first hour of treatment at 675˚C, the rate of oxide growth was greater than the rate of oxide growth of all samples treated at 600˚C. Samples treated at 600˚C for 4 and 8 hours displayed pitting during potentiodynamic polarization, but all other samples withstood the applied potentials and surfaces were further passivated. To simulate damage during surgery, a single abrasion was made across samples in the abraded group with a diamond-tip indenter under a load of 471g at 4.4 mm/s. Abraded samples were subjected to potential-step tests to assess repassivation ability after abrasion. All samples displayed repassivation ability, except for the sample treated at 600˚C for 4 hours. Surface roughness was measured with atomic force microscopy before and after thermal oxidation treatments. Lower surface roughness was desired to discourage osseointegration, or the growth of bone cells. No isothermal surface roughness trends were observed, as high surface roughness outliers were seen in samples treated at 675˚C for 8 hours and 600˚C for 4 hours. Rockwell hardness and Vickers microhardness were also measured to assess bulk changes in mechanical properties and hardness of the oxidized surfaces. No statistical change was seen in Rockwell hardness. Vickers hardness increased with increasing temperature and time, with the exception of the sample treated at 600˚C for 4 hours. Metallography of the thermally oxidized samples was analyzed to determine if a change in microstructure had occurred due to thermal processing. No major change in grain size or the amount of alpha and beta grains was seen in samples treated at 600˚C, but samples treated for extended times at 675˚C showed equiaxed enlarged alpha grains and a reduction in beta grains. The breakdown of samples treated at 600˚C exemplified possible differences in the alpha-beta oxide behavior during thermal oxidation and corrosion. Outlying surface roughness and microhardness values related to the thermal oxidation treatments and resulting oxide structure. Due to delamination of oxides grown at 675˚C for 4, 8, and 16 hours, the treatment parameters would not be effective in the ACP application. Therefore, through corrosion resistance, repassivation ability, low surface roughness, increased microhardness, and no microstructural change, thermal oxidation treatments at 600˚C for more than 16 hours, and 675˚C for 1 hour or less would be suitable treatments for anterior cervical plates.

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