Resumo em Inglês:

ABSTRACT The present work is a continuation of the research carried out in a previous work, with the aim of improving the production of Ti35Nb alloy by reducing the particle size of Ti (from 50–149 Μm to < 53 Μm) and Nb (from 31–500 Μm to < 62 Μm) powders. Micro (MI) and Macroporous (MA) Ti35Nb alloy samples were processed by powder metallurgy. Ammonium bicarbonate (AB) was utilized as pore former additive for processing MA samples. The powders were mixed, uniaxially pressed and then sintered at 1300 ºC for 2 hours under argon atmosphere. The samples were characterized by SEM/EDS, XRD, profilometry, and Vickers hardness test. The porosity levels were determined by geometric method, Archimedes’ principle and quantitative metallographic analysis. The results showed that the processing parameters used in this work successfully produced porous Ti35Nb alloys with completely stabilized β-Ti phase, indicating an enhancement in the methodology when compared with those reported in previous work. Smaller particle sizes influenced positively on the chemical-physical properties of MI and MA samples, since they demonstrated an improvement in the their characteristics, such as: more homogeneous microstructure; better particle consolidation; homogeneous elemental distribution with no relevant chemical contamination; porosity values in accordance with literature; presence of low amounts of titanium oxides on the surfaces which can improve the biocompatibility features; suitable surface roughness parameters for bone implant applications and favouring adhesion of bioceramic coatings; more uniform microhardness values for both samples which make the material with a further predictable mechanical behavior.

Resumo em Português:

RESUMO O gesso tem conquistado, ao longo do tempo, cada vez mais espaço na área da construção civil. Apesar dos avanços obtidos no emprego do gesso, este material ainda apresenta limitações, dentre elas a absorção de água devido ao seu caráter hidrofílico, o que limita a sua aplicação em ambientes externos. Com o propósito de reduzir a absorção de água, ampliando a sua aplicação em revestimentos externos, este trabalho visa a incorporação do polímero silicone (caráter hidrofóbico) a matriz gesso. Diante disso, sintetizou-se o compósito gesso-silicone, conforme a norma NBR 12128 (2016). Utilizou-se uma razão água/gesso de 0,7 e variou-se os seguintes parâmetros, a partir de um planejamento fatorial 22: (1) teor de silicone: (−) 1% e (+) 5% (silicone/gesso) e (2) teor de clorofórmio: (−) 0% e (+) 12%. Os materiais obtidos foram caracterizados por microscopia eletrônica de varredura (MEV), espectroscopia de absorção na região do infravermelho (FTIR), difração de raios X (DRX), análises térmicas e Raman. Determinou-se também a resistência mecânica a compressão, o tempo de impermeabilização e o tempo de pega. Percebeu-se que a incorporação do silicone conferiu ao gesso uma redução na absorção de água e um retardamento no tempo de pega. Notou-se que ao adicionar o silicone ao gesso, não houve mudança na resistência à compressão, porém ao adicionar silicone com clorofórmio ocorreu uma redução em 1MPa comparado com a matriz gesso. O compósito gesso-silicone possui potencial aplicação em revestimentos, visto promover uma redução na absorção da água.

Resumo em Inglês:

ABSTRACT Gypsum has conquered, over time, more and more space in the area of civil construction. Although the advances obtained in the use of gypsum, this material still has limitations, including water absorption due to its hydrophilic character, which limits its application in external ambience. The purpose of reducing water absorption, expanding its application in external coatings, this work aims at the incorporation of the silicone polymer (hydrophobic character) to the gypsum matrix. Therefore, the gypsum-silicone composite was synthesized, according to the norm NBR 12128 (2016). A water/gypsum ratio of 0.7 was used and the following parameters were varied, based on a factorial planning 22: (1) silicone content: (−) 1% and (+) 5% (silicone/gypsum) and (2) chloroform content: (−) 0% and (+) 12%. The materials obtained were characterized by scanning electron microscope (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal analyzers and Raman spectrometers. The mechanical resistance to compression, the waterproofing time and the setting time were also determined. The incorporation of silicone gave the gypsum a reduction in water absorption and retardation in setting time. When adding the silicone to the plaster, there was no change in the compressive strength, however, when adding silicone with chloroform, there was a reduction of 1MPa compared to gypsum paste. The gypsum-silicone composite has potential application in coatings, promoting a reduction in water absorption.

Resumo em Português:

RESUMO Os geopolímeros são suscetíveis à formação de eflorescência, a qual é uma manifestação patológica que afeta as propriedades mecânicas e a durabilidade dos geopolímeros. O objetivo do trabalho foi avaliar a influência da quantidade de água sobre a resistência à compressão e sobre a formação de eflorescência no estado fresco de um geopolímero a base de metacaulim. Hidróxido de sódio e silicato de sódio foram utilizados como ativadores e um tipo de metacaulim foi utilizado como precursor. Os materiais geopoliméricos foram desenvolvidos variando a razão molar total de H2O/Na2O com valores de 15,0, 15,5, 16,0, 16,5 e 17,0. Os resultados mostraram que a quantidade de água tem influência significativa sobre a formação de eflorescência na superfície dos geopolímeros, isto é, quanto maior for a razão molar H2O/Na2O, maior foi a área de eflorescência. A maior taxa de crescimento da eflorescência ocorreu aproximadamente entre 500 e 1000 minutos, após esse tempo o crescimento teve uma tendência de estabilização. Os resultados de resistência à compressão mostraram que a quantidade de água e o tempo de cura influenciaram significativamente, sendo que quanto maior a razão molar de H2O/Na2O menor foi a resistência à compressão média.

Resumo em Inglês:

ABSTRACT Geopolymers are susceptible to efflorescence formation, which is a pathological manifestation that affects the mechanical properties and durability of geopolymers. The aim of work was to evaluate the influence of the water amount on compressive strength and efflorescence formation in the fresh state of a metakaolin-based geo-polymer. Sodium hydroxide and sodium silicate were used as activators and a type of metakaolin was used as a precursor. Geopolymer materials were developed varying the total molar ratio of H2O/Na2O with values of 15.0, 15.5, 16.0, 16.5 and 17.0. The results showed that the water amount has a significant influence on the formation of efflorescence on the surface of geopolymers in the fresh state, i.e., the greater the molar ratio H2O/Na2O, the greater the area of efflorescence. Highest rate of efflorescence growth occurred approximately between 500 and 1000 minutes, after which time growth tended to stabilize. Compressive strength results showed that the water amount and the curing time significantly influenced, and the higher the molar ratio of H2O/Na2O, the lower the average compressive strength.

Resumo em Português:

RESUMO Os polímeros utilizados para impressão 3D do tipo FFF apresentam uma sensibilidade muito grande às variações de temperatura, que vai desde o processo de fabricação até o uso do produto final. Essa é uma característica importante para o processo de impressão, porém, pode representar um fator limitante para sua utilização em ambientes com grandes variações de temperatura. Portanto, o presente trabalho teve como objetivo analisar o comportamento mecânico de corpos de provas de PLA (ácido polilático) fabricados por impressão 3D utilizando a tecnologia FFF (Fabricação por Filamento Fundido) e submetido às temperaturas de 5°C, 25°C e 45°C. Foram realizados testes de tração e flexão em três pontos em corpos de prova fabricados em três orientações diferentes (flat, on-edge e upright). Foi utilizado um equipamento constituído por uma câmara térmica e um sistema de controle de temperatura anexado a uma Máquina Universal de Ensaios. Os corpos de prova foram distribuídos em grupos experimentais de 5 unidades cada. Todos os parâmetros de impressão foram iguais para todos os grupos. O PLA à 5°C apresentou um aumento significativo do módulo de elasticidade e limite de escoamento, gerando um comportamento mais frágil. À 25°C, o comportamento mecânico foi semelhante à literatura. Por fim, à 45°C, foi observado uma queda na resistência e um aumento acentuado da plasticidade do PLA, devido à proximidade da temperatura de transição vítrea. Os corpos de prova impressos nas orientações flat e on-edge apresentaram desempenho mecânico similar, enquanto os corpos de prova impressos na orientação upright apresentaram os menores valores das propriedades mecânicas analisadas.

Resumo em Inglês:

ABSTRACT Polymers used for 3D printing with FFF technology are very sensitive to temperature variations, which occurs from its manufacturing process to its final usage. This is an important characteristic for the printing process, however it can represent a limiting factor for its use in environments with large temperature variations. Therefore, this paper aimed to analyze the mechanical behavior of PLA (polylactic acid) specimens manufactured by 3D printing using the FFF (Fused Filament Fabrication) technology and subjected to temperatures of 5°C, 25°C and 45°C. Tensile and three-point bending tests were performed on specimens manufactured in three different orientations (flat, on-edge and upright). An equipment, consisting of a thermal chamber and a temperature control system attached to the Universal Testing Machine, was used to control the temperature in the environment where the specimens were subjected to the mechanical tests. The specimens were distributed in experimental groups of 5 units each. All printing parameters were the same for all groups. PLA at 5°C showed a significant increase in the modulus of elasticity and yield strength, causing a more fragile behavior. At 25°C the mechanical behavior was similar to the literature. Lastly, at 45°C, a decrease in strength and a high increase in PLA plasticity were observed, due to the proximity of the glass transition temperature. The specimens printed in the flat and on-edge orientations presented similar mechanical performance, while the ones printed in the upright orientation presented the lowest values of the analyzed mechanical properties.

Resumo em Inglês:

ABSTRACT Besides the strength enhancement and strain improvement (strain-hardening behavior), the use of natural fibers as reinforcement in cement-based matrices can also be highlighted as an economical and eco-friendly alternative for the future of the construction industry. In the present work, cement-based composites reinforced by natural sisal fibers were produced and tested under direct tensile loading. The Portland cement was partially replaced by pozzolans (metakaolin – MK and fly ash – FA), aiming to produce a calcium hydroxide-free matrix to ensure the durability of the fibers. The natural sisal fibers were used in a 5% volume fraction (in mass), divided into three layers. The mechanical properties of composite plates were compared to other literature results and demonstrated to be compatible with recent research. The crack pattern was analyzed by Digital Image Correlation (DIC) for a better understanding of their failure mechanisms. The material presented a tensile strength increase after the first crack formation, marked by multiple cracking partners from this point. Finally, a comparison between direct (LVDTs) and indirect (DIC) methods of strain measurement was done and demonstrated minor results for the DIC, approximately 84% of those obtained from the LVDTs.

Resumo em Português:

RESUMO A caracterização dos elementos construtivos é um conhecimento essencial para garantir a estabilidade e resistência estrutural de qualquer construção. A resistência dos materiais é uma predição efetiva prescrita por normas técnicas, as quais delimitam comportamentos resistivos em diferentes condições. As propriedades físico-mecânicas da madeira permitem a aplicação racional desse biorrecurso em projetos estruturais. Porém, testes para determinar as propriedades mecânicas requerem equipamentos de grande porte e mão-de-obra capacitada, requerimentos os quais são encontrados em poucas instituições e centros de pesquisa específicos. Uma alternativa para entender as propriedades da madeira pode ser estabelecida pela microscopia e modelos de regressão. O presente artigo objetivou demonstrar a viabilidade de estimar as propriedades mecânicas da madeira de Eucalyptus em função de suas características anatômicas e da densidade aparente. Dez lotes de diferentes espécies de eucalipto foram selecionados para prever a tração paralela às fibras, tensão perpendicular às fibras e o módulo de elasticidade na tração paralela às fibras, bem como três diferentes parâmetros anatômicos (fibras, vasos e raios) das amostras de madeira de acordo com duas normas técnicas brasileiras. Na prática, os modelos de regressão propostos foram excelentes, pois os valores de R2 foram iguais a 90,55, 86,55 e 67,95% para estimar Et0, ft0 e ft90, respectivamente.

Resumo em Inglês:

ABSTRACT Characterization of construction materials is a piece of essential knowledge to ensure the structural stability and strength of any building. The strength of materials is an effective prediction prescribed by technical standards, which delimit the resistive behaviors in different conditions. Physical-mechanical properties of timber allow the rational application of this bioresource in structural projects. However, tests to determine mechanical properties require large equipment and a skilled workforce, found in few institutions and specific research centers. The microscopy and regression models may establish an alternative to understanding the properties of wood. The present paper aimed to demonstrate the feasibility of estimating the mechanical properties of Eucalyptus wood as a function of its anatomical characteristics and apparent density. Ten batches of different eucalypt species were selected to predict the tensile strength parallel to the grain, tensile strength normal to grain, and modulus of elasticity in tensile parallel to the grain, as well as three different anatomical parameters (fibers, vessels, and rays) of the wood samples according to two Brazilian standard documents. In practice, the proposed regression models were excellent, as the R2 values were equal to 90.55, 86.55, and 67.95% for estimating Et0, ft0, and ft90, respectively.

Resumo em Inglês:

ABSTRACT This paper attempts to solve the turbine failures reported by a hydropower station, namely, the violent vibration in the runner region under a special working condition and the blade cracking on the outlet edge near the lower ring. For this purpose, the entire flow channel of the turbine was simulated by computational fluid dynamics (CFD) on ANSYS, and the runner strength and mode of shaft assembly system (SAS) were computed by the liquid-solid coupling algorithm. The calculation results show that severe low (negative) pressure appeared on the outlet edge near the lower ring, excess stress was observed in that area, and the resonance occurred as the fifth and sixth order natural frequencies of the SAS were the same with the rotation frequencies of the blade. On this basis, the original blade was modified repeatedly. Through the modification, the flow field distribution in the runner region and the blade strength were both greatly improved, and the SAS natural frequencies were kept away from the various external excitation frequencies, laying a solid basis for the safe and stable operation of the turbine.

Resumo em Português:

RESUMO O presente trabalho teve como objetivo sintetizar membranas lamelares de óxido de grafeno reduzido (rGO – reduced graphene oxide) sobre um suporte de acetato de celulose e compará-las quanto à rejeição de azul de anilina, por meio de duas metodologias de produção do rGO: redução agregante e não agregante. Inicialmente foram produzidas dispersões de óxido de grafeno (GO – graphene oxide) por uma modificação do método de Hummers, as quais passaram por tratamento termoquímico para redução do GO e foram utilizadas para deposição sobre um suporte de acetato de celulose, utilizando-se o método de filtração assistida por vácuo. Para caracterização das dispersões e membranas foram utilizadas as técnicas de difração de raios X (DRX) e microscopia eletrônica de varredura (MEV), sendo que nas membranas produzidas foram conduzidos testes de estabilidade em água. Para análise da rejeição de azul de anilina, utilizado como material a ser filtrado, os permeados de cada uma das membranas, bem como do substrato como recebido, foram analisados por espectrofotometria UV-Vis, sendo que a concentração do permeado pôde ser estimada a partir de uma curva de calibração previamente produzida. Foram observadas diferenças de estabilidade da membrana, a depender da metodologia de redução utilizada, bem como expressivo incremento de rejeição de azul de anilina em relação ao substrato como recebido de acetato de celulose.

Resumo em Inglês:

ABSTRACT The present work aimed to synthesize lamellar membranes of reduced graphene oxide (rGO) on a cellulose acetate substrate and to compare them for the rejection of aniline blue, using two different rGO production methodologies: aggregating and non-aggregating reduction. Initially, dispersions of graphene oxide (GO) were produced by a modification of the Hummers method, which underwent thermochemical treatment to reduce GO and were used for deposition on a cellulose acetate substrate, using the vacuum-assisted filtration method. To characterize the dispersions and membranes, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used, and stability tests in water were conducted on the produced membranes. To analyze the rejection of aniline blue, used as the material to be filtered, the permeates of each of the membranes, as well as the substrate as received, were analyzed by UV-Vis spectrophotometry, and the concentration of the permeate could be estimated from of a previously produced calibration curve. Significant differences in membrane stability were observed, depending on the reduction methodology used, as well as an expressive increase in the rejection of aniline blue in relation to the substrate as received from cellulose acetate.

Resumo em Português:

RESUMO A utilização de fibras celulósicas em matrizes cimentícias pode apresentar um efeito inibitório causando incompatibilidade química e inviabilizando o processo de produção de materiais de construção civil reforçados com fibras de celulose. Já as microceluloses geralmente aceleram a produção de gel de hidrato de silicato de cálcio (CSH) acelerando o grau de hidratação do cimento. Assim, o presente trabalho tem por objetivo o entendimento das interações combinadas entre microcelulose cristalina e fibra de celulose (MCC e FC) no processo de hidratação das pastas cimentícias. Os resultados obtidos no ensaio de inibição das pastas apontaram uma boa compatibilidade das fibras celulósicas e do sistema FC/MCC com as pastas cimentícias. Já para pastas cimentícias com substituição de cinza volante, o sistema FC/0,6%MCC apresentou moderada inibição apresentando diferença estatística significativa em relação aos demais tratamentos. Através do ensaio de difração de raios—X foi possível concluir que tanto as fibras celulósicas quanto o sistema FC/MCC não influenciaram na mineralogia dos compósitos, onde os padrões de difração mostraram os produtos de hidratação típicos dos aglomerantes minerais. Na análise de DRX foi possível identificar a redução dos picos de magnitude da Portlandita, com a incorporação de celulose MCC nas pastas cimentícias, o que indica menor disponibilidade de produtos C-S-H, podendo correlacionar com o retardo na hidratação das pastas cimentícias contendo celuloses FC/MCC.

Resumo em Inglês:

ABSTRACT The use of cellulose fibers in cement matrix can present an inhibitory effect causing chemical incompatibility. The production process of civil construction materials reinforced with cellulose fibers can be rendered unfeasible. On the other hand, microcelluloses usually accelerate the production of calcium silicate hydrate gel (CSH) accelerating the cement hydration degree. The present work aims at understanding the combined interactions between crystalline microcellulose and cellulose fiber (MCC and FC) in the hydration process of cement pastes. The results obtained in the paste inhibition test pointed out a good compatibility of cellulose fibers and the FC/MCC system with cement pastes. For cement pastes with fly ash substitution, the FC/0,6%MCC system showed moderate inhibition with a statistically significant difference from the other treatments. Through the X-ray diffraction test it was possible to conclude that both cellulosic fibers and the FC/MCC system did not influence the mineralogy of the composites, where the diffraction patterns showed the typical hydration products of mineral binders. In the XRD analysis it was possible to identify the reduction of the Portlandite magnitude peaks, with the incorporation of cellulose MCC in the cement pastes.

Resumo em Inglês:

ABSTRACT Stable natural graphene occurs in graphite- and phyllosilicate-bearing low-grade metamorphic rocks. The present work simulates the process of geological formation of graphene using a piston-cylinder apparatus, promoting diffusion between talc and graphite at 700ºC and 900 MPa for a period of 24 h. The experimental products were analyzed by optical and scanning electron microscopy for description of the microstructures formed between the mineral precursors. The talc-graphite diffusion zone was also analyzed by Raman spectroscopy. Results indicate that graphite becomes progressively more deformed near the talc diffusion zone and eventually undergoes cleavage. Graphene becomes stable on the talc substrate in the center of diffusion zone. Therefore, the search for deposits of natural graphene and other nanomaterials in geological context is promising.

Resumo em Português:

RESUMO O presente trabalho tem como objetivo analisar o efeito de diferentes espécies de madeiras e de bambu (Pinus taeda, Cereus jamacaru e Bambusa vulgaris) na hidratação de matrizes cimentícias. Para tanto, os materiais lignocelulósicos foram moídos e caracterizados antes e depois de tratamento em água quente. Posteriormente, o efeito da adição de diferentes níveis (5, 10 e 33,3%) de madeiras, pré-tratadas ou não, em pastas de cimento foram analisados a partir dos ensaios de calorimetria isotérmica e termogravimetria. Os resultados demonstraram que as partículas de cada espécie lignocelulósica apresentaram um aumento das propriedades de umidade e absorção concomitante a diminuição de suas densidades e níveis de extrativos a partir do pré-tratamento aplicado. Os outros componentes químicos destes elementos, majoritariamente, todavia, não foram afetados. Por outro lado, foi observado que quanto maior o teor de tais materiais lignocelulósicos, pré-tratados ou não, nas matrizes de cimento, maior o impacto na hidratação do cimento, segundo o ensaio de calorimetria. Já com relação ao resultado do ensaio de termogravimetria observou-se uma tendência geral, com ou sem pré-tratamento de partículas ou adição de água de compensação, de aumento dos produtos hidratados, fato atribuído, principalmente, a presença de água livre e gases nos materiais lignocelulósicos.

Resumo em Inglês:

ABSTRACT The present work aims to analyze the effect of different species of wood and bamboo (Pinus taeda, Cereus jamacaru and Bambusa vulgaris) on the hydration of cementitious matrices. For this, the lignocellulosic materials were ground and characterized before and after treatment in hot water. Subsequently, the effect of adding different levels (5, 10 and 33.3%) of wood, pre-treated or not, in cement pastes were analyzed using isothermal calorimetry and thermogravimetry tests. The results showed that the particles of each lignocellulosic species showed an increase in moisture and absorption properties concomitant with a decrease in their densities and extractive levels from the pre-treatment applied. The other chemical components of these elements, however, were mostly unaffected. On the other hand, it was observed that the higher the content of such lignocellulosic materials, pre-treated or not, in the cement matrices, the greater the impact on cement hydration, according to the calorimetry test. Regarding the result of the thermogravimetry test, a general trend was observed, with or without pre-treatment of particles or addition of make-up water, of an increase in hydrated products, a fact mainly attributed to the presence of free water and gases in the lignocellulosic materials.

Resumo em Português:

RESUMO Ações para tratamento, reutilização e destinação adequada de resíduos perigosos (RP), a exemplo dos gerados em serviços de saúde, atividades agrossilvopastoris e oficinas mecânicas ganham importância, observando que o descarte inadequado pode ocasionar problemas ambientais. Algumas pesquisas têm apontado uso das cinzas oriundas de RP, em substituição parcial do cimento Portland ou como agregado miúdo em matrizes cimentícias, conforme as propriedades dos materiais. O objetivo desta pesquisa foi identificar as características físicas, químicas e mineralógicas das cinzas geradas em uma incineradora de RP situada no estado da Bahia/Brasil, sendo essas submetidas aos ensaios de caracterização, tanto in natura quanto após etapa de calcinação à 1000 °C, denominadas de cinza pesada (CP) e cinza calcinada (CC), respectivamente. Determinou-se a distribuição granulométrica, perda ao fogo, propriedades térmicas, composição química, morfologia, carbono orgânico total e reatividade, sendo as amostras classificadas pela norma da ABNT NBR 12653/2014. Os resultados obtidos indicam significativas diferenças entre os materiais analisados, nos aspectos físicos, químicos e mineralógicos. O uso das técnicas e métodos possibilitou classificar as amostras estudadas de forma que não atendem os requisitos mínimos normativos, entretanto, não é possível descartar a utilização das CC em matrizes cimentícias.

Resumo em Inglês:

ABSTRACT Actions for the treatment, reuse and proper disposal of hazardous waste (WH), such as those generated in health services, agroforestry activities and mechanical workshops gain importance, noting that improper disposal can cause environmental problems. Some researches have pointed to the use of ash from WH, in partial replacement of Portland cement or as a fine aggregate in cementitious matrices, according to the properties of the materials. The objective of this research was to identify the physical, chemical and mineralogical characteristics of the ash generated in a RP incinerator located in the state of Bahia/Brazil, which were subjected to characterization tests, both in natura and after the calcination step at 1000 °C, called heavy ash (AH) and calcined ash (AC), respectively. The granulometric distribution, loss on fire, thermal properties, chemical composition, morphology, total organic carbon and reactivity were determined, and the samples were classified according to the ABNT NBR 12653/2014 standard. The results obtained indicate significant differences between the analyzed materials, in the physical, chemical and mineralogical aspects. The use of techniques and methods made it possible to classify the studied samples in a way that they do not meet the minimum normative requirements, however, it is not possible to rule out the use of AC in cementitious matrices.

Resumo em Português:

RESUMO A intensa atividade industrial na região Amazônica gera grande quantidade de resíduos, entre eles, os resíduos lignocelulósicos não madeireiros. O presente estudo avaliou a utilização do tegumento de murumuru (Astrocaryum murumuru Mart.) na produção de um compósito de madeira plástica, em que se utilizou a proporção 70/30 de polipropileno e tegumento de murumuru e 2% de anidrido maleico. Os compósitos de madeira plástica foram moldados por compressão em uma prensa termo hidráulica. O tegumento de murumuru foi caracterizado quanto ao seu teor de lignina e celulose e quanto a sua morfologia através de Microscopia Eletrônica de Varredura (MEV). Os compósitos foram avaliados quanto a sua morfologia por meio do MEV e quanto as suas propriedades mecânicas por meio do ensaio de resistência a flexão, onde as placas de PP puro apresentaram desempenho mecânico 21,7% superior ao compósito com 30% de resíduo, para valores de significância (P < 0,05) não houve diferença estática entre as placas. Os padrões de espectrometria de infravermelho indicaram que a composição da carga vegetal se caracteriza de constituintes como lignina, celulose e hemicelulose. Os resultados obtidos indicaram bom desempenho da madeira plástica, desta forma, o objetivo deste trabalho foi alcançado.

Resumo em Inglês:

ABSTRACT The intense industrial activity in the Amazon region generates a large amount of waste, including non-wood lignocellulosic waste. The present study evaluated the use of murumuru tegument (Astrocaryum murumuru Mart.) in the production of a plastic wood composite, in which a 70/30 proportion of polypropylene and murumuru tegument and 2% maleic anhydride were used. The wood-plastic composites were compression molded in a thermo-hydraulic press. The murumuru tegument was characterized as to its lignin and cellulose content and as to its morphology through Scanning Electron Microscopy (SEM). The composites were evaluated for their morphology through SEM and for their mechanical properties through the flexural strength test, where the pure PP plates showed a mechanical performance 21.7% higher than the composite with 30% residue, for Significance values (P < 0.05) there was no static difference between the plates. The infrared spectrometry patterns indicated that the composition of the vegetal filler is characterized by constituents such as lignin, cellulose and hemicellulose. The results obtained indicated good performance of plastic wood, thus, the objective of this work was achieved.

Resumo em Português:

RESUMO A demanda por concreto autoadensável cresce continuamente devido aos investimentos em novas infraestruturas, atualizações ou substituição de infraestruturas antigas. Esse tipo de concreto é capaz de se moldar nos espaços destinados a ele por conta própria, preenchendo estes espaços, sem a necessidade de vibração ou compactação externa. Para isso, precisa alcançar três propriedades principais: fluidez, habilidade passante e resistência à segregação. Monitorar essas propriedades, a qualidade, e aumentar o desempenho das estruturas de concreto é essencial para acompanhar esse crescimento da demanda. Neste trabalho, exploramos o efeito da adição de um composto comercial à base de óxido de cálcio supercalcinado, como aditivo compensador de retração, nas propriedades do concreto fresco e endurecido, particularmente na retração e cura de corpos de prova de concreto autoadensável (CAA). Além disso, é proposto um protocolo experimental para a análise de impedância elétrica de amostras de concreto. Foram realizados testes de fluidez, compressão, retração, módulo de elasticidade e espectroscopia de impedância, além de imagens de microscopia eletrônica de varredura. O aditivo modifica levemente as propriedades do concreto no estado fresco e, no concreto endurecido, há um aumento da resistência à compressão e do módulo de elasticidade, além da redução da retração com 2,8% do aditivo.

Resumo em Inglês:

ABSTRACT The demand for self-compacting concrete grows continuously due to investments in new infrastructure, upgrades, or replacement of old infrastructure. This type of concrete can mold itself into the spaces intended for it on its own and fill them without the need for any vibration or external compaction. It must achieve three main properties: fluidity, passing ability, and resistance to segregation. Monitoring these properties, the quality, and the increase in the performance of concrete structures is essential to keep up with this growth. In this work, we explore the effect of adding a commercial over calcined calcium oxide-based compound, as a shrinkage-compensating admixture, on the properties of fresh and hardened concrete, particularly on the shrinkage and curing of self-compacting concrete specimens (SCC). Also, an experimental protocol is proposed for the electrical impedance analysis of concrete samples. Fluidity, compression, shrinkage, elastic modulus, and impedance spectroscopy tests were performed, in addition to scanning electron microscopy images. The additive slightly modifies the concrete properties in the fresh state. In hardened concrete, the compressive strength and modulus of elasticity increase, in addition to a reduction in shrinkage with 2.8% of the additive.

Resumo em Inglês:

ABSTRACT During production and heat treatments of aluminum alloys, numerous second phase particles form, which maximizes their mechanical properties. This work aimed to perform a correlation between Vickers hardness and X-ray diffraction results, when 7475-T7351 aluminum alloy processed by the cross rolling is subjected to annealing heat treatments (AHT) at 500 °C for different soaking times (15, 30 and 60 minutes) and for a soaking time of 15 minutes at different temperatures (200, 300 and 400 °C). The influence of the AHT (500 °C / 15 minutes) on the microstructure, via scanning and transmission electron microscopy, and tensile tests properties was also investigated. The results show evidence that the Vickers hardness decreased for AHT performed at 200 and 300 °C / 15 minutes and increase for greater temperatures and times. This behavior is probably due to modifications in the constituent/dispersoid particles and aluminum matrix observed from the X-ray analysis. Partial recrystallization and a coarsening of the precipitates was observed after the AHT at 500 °C / 60 minutes, whose brought harmful effects on the tensile mechanical properties.

Resumo em Inglês:

Inconel 718 alloy which was prepared using selective laser melting (SLM) forming technology underwent various annealing treatments. Optical microscope, scanning electron microscope, electron backscattered diffraction and MTS testing machine were used to study the microstructure, mechanical and fatigue properties of Inconel 718 alloy melted by selective laser melting under different annealing treatments. The results show that the microstructure of Inconel 718 alloy after homogenization and doubleaging annealing is the most obvious, and the microstructure of the alloy is mainly recrystallized. The microstructure contains a large number of annealing twins and the grain boundaries are flat. The yield strength, tensile strength and microhardness of Inconel 718 alloy formed by selective laser melting after different annealing treatments are greatly increased, while the elongation after fracture is significantly decreased. The fatigue properties of Inconel 718 alloy after double aging annealing and solution dual aging annealing are improved slightly, while the fatigue properties after uniform double aging annealing are decreased slightly.

Resumo em Inglês:

ABSTRACT The paving technique ensures the guarantee of functional traffic conditions, optimizing the performance of the structure in providing travel with comfort and safety. Considering that due to time and the action of traffic, when the pavement reaches the end of its useful life, interventions are necessary, aiming at a gain in serviceability, comprised of the thinning of the coating, generating waste, for later execution of a new layer, which can be recycled. This recurrent technique for road pavements has been widely applied to the use of RAP (reclaimed asphalt pavement), to compose new layers of pavement, given its mechanical performance, especially in terms of permanent deformation, and given the sustainable and economical premise. The paper sought to evaluate, using a laboratory study, the mechanical performance of hot recycled asphalt mixtures with the incorporation of 25%, 45%, and 100% of RAP, and to perform an economic analysis of the applicability of the technique. The dosage methodology occurred according to the Superpave specification whose results listed a significant gain in stiffness, and good mechanical performance with proportionality in the values obtained according to the incorporation rate of RAP. As for the economic analysis, it was observed that the costs of applicability of the technique are related to the percentage of incorporation in mass and the logistical costs of processing, which may be lower than or higher than that of a conventional mixture. Above all, the results were satisfactory to prove the feasibility of the technique in paving works.

Resumo em Inglês:

ABSTRACT In this investigation of AISI 1045 steel are tested in two stages. In the first stage of AISI 1045 steel samples, induction boriding and induction hardening of heat treatment typically 800 °C, 900 °C, 1000 °C, 1100 °C, and 1200 °C applied over the course of two seconds. Internal strains maybe mitigated using a 30 min tempering at temperature ranges 300 °C, 500 °Cand 700 °C. After that the samples subjected to the induction hardening, microhardness and tensile strength according to ASTM. The lowest hardness readings are achieved between 800 and 1100 °C, while the maximum hardness of 685HV is reported after heating to 1200 °C and then cooling in water. The second stage involves AISI 1045 steel is treated with low-temperature plasma nitro-carburizing, and its effects are studied. The specimens are treated at temperatures over 430 °C, NCr2is formed and has an effect on the corrosion resistance property. Increasing the temperature to 450 °C raises the surface hardness to approximately 1000 HV0.05. Treatment at 400 °C results in superior corrosion resistance compared to untreated steel. According to the results of the experiments, the surface hardness of AISI 1045 steel materials increases with an increase in temperature.

Resumo em Português:

RESUMO A fim de minimizar o impacto ambiental ocasionado pelas misturas asfálticas a quente surgiram as chamadas misturas asfálticas mornas. Este trabalho investigou o uso da cera de carnaúba tipo 1, nos teores de 1, 2 e 3% por peso de ligante asfáltico classificado com penetração 50/70, como aditivo incorporado às misturas asfálticas para a obtenção de misturas mornas. Os resultados apontaram uma redução de até 9 °C na temperatura de mistura e 7 °C na temperatura de compactação com o uso de 2 e 3% de cera. As misturas asfálticas foram dosadas pelo método Superpave e submetidas a ensaios mecânicos: ensaios de resistência à tração, dano por umidade induzida, módulo de resiliência, módulo dinâmico e vida de fadiga. A incorporação de 2% acarretou resultados superiores quanto ao desempenho mecânico das misturas asfálticas, principalmente ao dano por umidade induzida, e uma maior redução das temperaturas de mistura e compactação. Portanto, as misturas cumpriram as exigências mecânicas e se apresentaram viáveis tecnicamente, podendo contribuir para mitigação de danos ambientais como a redução do consumo de energia e as emissões de CO2 em usinas asfálticas.

Resumo em Inglês:

ABSTRACT In order to minimize the environmental impact caused by hot asphalt mixtures, the so-called warm asphalt mixtures emerged. This work investigated the use of type 1 carnauba wax, at levels of 1, 2, and 3% by weight of asphalt binder classified with penetration 50/70, as an additive incorporated into asphalt mixtures to obtain warm mixtures. The results showed a reduction of up to 9 °C in the mixing temperature and 7 °C in the compaction temperature with the use of 2 and 3% wax. The asphalt mixtures were dosed by the Superpave method and submitted to mechanical tests: tensile strength tests, induced moisture damage, modulus of resilience, dynamic modulus and fatigue life. The incorporation of 2% resulted in superior results in terms of the mechanical performance of the asphalt mixtures, mainly in terms of induced moisture damage, and a more significant reduction in mixing and compaction temperatures. Therefore, the mixtures complied with the mechanical requirements and were technically viable, contributing to the mitigation of environmental damages such as the reduction of energy consumption and CO2 emissions in asphalt plants.

Resumo em Português:

RESUMO Este trabalho tem como objetivo entender a influência da oxidação nos fios de cobre e seus impactos em materiais soldados através do processo ultrassônico em componentes automotivos. 42 (quarenta e duas) amostras de cobre foram extraídas e subdividas em 7 (sete) grupos com 6 (seis) amostras cada um para o experimento, onde o primeiro grupo contou com amostras sem oxidação e o último grupo conta com amostras que foram envelhecidas em 360 dias. Estas amostras foram soldadas através do processo ultrassom com parâmetros que garantiram os requisitos mínimos de soldabilidade, critérios visuais e a união completa dos filamentos de cobre na junta. Após isso, os materiais soldados foram submetidos a validação da soldagem através da medição da força de tração de cisalhamento para garantir os requisitos mínimos exigidos por norma interna do setor automotivo. As amostras sem oxidação atenderam aos parâmetros de engenharia e resultaram nos maiores valores de força de tração de cisalhamento. Nas amostras com presença de oxidação, o aumento da energia de soldagem proporcionou a redução da força de cisalhamento dos 6 (seis) grupos, apresentando 1 amostra que ficou abaixo do parâmetro mínimo estabelecido para força de cisalhamento.

Resumo em Inglês:

ABSTRACT The main objective of this work is to understand the influence of oxidation on copper wires and its impacts on materials welded through the ultrasonic process in automotive components. 42 (forty-two) copper samples were extracted and subdivided into 7 (seven) groups with 6 (six) samples each for the experiment, where the first group had samples without oxidation and the last group had samples that were aged in 360 days. These samples were welded through the ultrasonic process with parameters that ensured the minimum requirements for solderability, visual criteria and the complete union of the copper filaments in the joint. After that, the welded materials were submitted to welding validation by measuring the shear traction force to guarantee the minimum requirements demanded by the internal standard of the automotive sector. The samples without oxidation met the engineering parameters and resulted in the highest values of shear tensile strength. In the samples with the presence of oxidation, the increase in welding energy provided a reduction in the shear force of the 6 (six) groups, with 1 sample that was below the minimum parameter established for shear force.

Resumo em Inglês:

ABSTRACT Self-healing in asphalt mixtures can be induced by adding particles that are susceptible to heating by electromagnetic microwaves. This process allows the closure of microcracks caused by the fatigue phenomenon and can extend the service life of the asphalt pavement. In this article, the self-healing index of asphalt mixtures without and with the addition of steel slag (15% and 65.7%), steel fibers, (0.2% and 0.4%), and graphite powder (15% and 65.7%) was evaluated. The index was determined after subjecting the mixtures to fatigue damage, microwave heating, rest, and fatigue damage again. Results showed that all additions led to mixtures susceptible to microwave heating and with healing capacity. A higher self-healing index was observed when the mixture was produced with slag than with graphite powder. It was found that the use of a higher content of steel fibers was more effective for healing, and for successful healing, the mixtures must be heated to temperatures ranging between 50°C and 75°C. The results also showed that it is possible to achieve high healing values without having to subject the mixtures to microwave heating.

Resumo em Português:

RESUMO Este trabalho estuda o efeito da forma de tratamento termomecânico (calcinação e moagem) do resíduo de ardósia com foco na ativação das propriedades pozolânicas. O programa experimental consistiu em avaliar as propriedades físicas, químicas, minerais e morfológicas do resíduo. O material foi cominuído por 1 hora e 45 minutos, peneirado e, em seguida, as amostras passantes em 45 µm foram submetidas ao tratamento térmico, as quais foram expostas a temperatura 1000ºC, mantendo-se constante por um período de até 5 horas e foram moídas novamente. As análises cristalográficas demonstraram que processo de calcinação gerou uma redução da cristalinidade pela diminuição dos picos e formação de um possível halo de amorfização. Os resíduos de ardósia após tratamento térmico, aumentaram o tamanho médio devido ao efeito de aglomeração pela fusão das partículas o que interferiu no efeito da ativação pozolânicas, sendo que uma maior moagem garantiu um ótimo resultado de ativação, comprovando que a granulometria mais elevada interfere na reatividade do material. Ficou evidenciado que para ativação do resíduo de ardósia se faz necessária a utilização de moagem antes do processo de aquecimento (partículas menores de 45 µm) e após (partículas menores de 38 µm).

Resumo em Inglês:

ABSTRACT This paper studies the effect of thermomechanical treatment (calcination and grinding) of slate waste focusing on the activation of pozzolanic properties. The experimental program consisted in evaluating the physical, chemical, mineral and morphological properties of the residue. The material was comminuted for 1 hour and 45 minutes, sieved, and then samples passing through 45 μm were subjected to heat treatment, which were exposed at 1000 °C temperature, remaining constant for up to 5 hours and were ground again. Crystallographic analyzes demonstrated that the calcination process generated a reduction in crystallinity by reducing the peaks and forming a possible amorphization halo. The slate waste after thermal treatment, increased the average size due to the effect of agglomeration by the melting of the particles, which interfered in the pozzolanic activation effect, and a greater grinding ensured an excellent activation result, proving that the higher granulometry interferes in the material reactivity. It was evidenced that for the slate residue activation it is necessary to use grinding before the heating process (particles smaller than 45 μm) and after (particles smaller than 38 μm).

Resumo em Inglês:

ABSTRACT Surface treatments such as heat treatments, paints, plasma treatments and galvanizing are important in metal working industry. In those treatments, the required adhesion characteristics can be limited if contaminants are present, so there is a need to clean these surfaces. Conventional processes can be costly, some generated waste may be environmentally hazardous and, in some cases, due to part geometry, they are not effective. Alternatively, plasma treatments which are considered to be environmentally clean, more efficient and with lower operating costs can overcome those difficulties. Due to the reactional complexity of these treatments, there are many fields to be researched, such as which reactions are due to impacts of (neutral) chemical species and which are due to excited species and radiation. The present work aims to verify the interactions between Ar-10%O2 plasma using amino acid L-proline in an inductively coupled radiofrequency plasma. This study showed that oxidative plasma promotes high degradation of the sample. A gas analyzer (quadrupole mass spectrometer) coupled to the gas outlet was used and many gaseous products are detected during treatment, such: H2, H2O, CO, NO (Nitric Oxide) and CO2 while L-proline undergoes intense degradation. The conclusions allow to state that the interaction between the Ar/O2 plasma and L-proline promotes intense degradation through the breakdown of the heterocyclic ring of the molecule.

Resumo em Português:

RESUMO Avaliou-se o grau de passivação da superfície de tanques de bioprocessamento em aço AISI 316L com polimento mecânico e rugosidade média de 0,8 μm. Os tanques foram inspecionados após a sua construção e em diferentes condições de superfície: (i) após 12 meses em operação industrial, (ii) com a adesão de biofilme, (iii) após o tratamento de passivação química. O aparelho PassivityScan foi utilizado nas inspeções in situ do grau de passivação aplicando as técnicas de potencial de circuito aberto e polarização potenciodinâmica cíclica. Os resultados indicaram que a superfície interna polida do tanque como fabricado gerou um grau de passivação relativamente baixo (Eprot–Ecorr<150 mV) e elevada cinética de corrosão. Após 12 meses de operação reduziu-se o grau de passivação da superfície e consequentemente sua durabilidade. Notou-se um agravamento com a presença de biofilme, dado que a superfície não possuía mais a capacidade de repassivação. É importante ressaltar que o tratamento de passivação química elevou o grau de passivação para 520 mV(Ag|AgCl|KCl 3 mol/L), reduzindo a densidade de corrente de passivação de 20 para 0,7 μA cm–2. Conclui-se que um tanque passivado quimicamente apresenta melhor confiabilidade operacional, e que o tratamento de passivação a cada 12 meses restaura as propriedades de resistência da superfície.

Resumo em Inglês:

ABSTRACT The passivation level of AISI 316L bioprocessing tanks of roughness average of 0.8 μm mechanically polished was assessed. The on-site inspections were performed after tanks manufacturing and in distinct surface conditions: (i) after 12 months of industrial operation, (ii) with biofilm adhesion, (iii) after chemical passivation treatment. The PassivityScan inspection instrument was used in on-site measurements of passivation level applying the open circuit potential and cyclic potentiodynamic polarization techniques. The results showed that the tank inner surface in as-built condition obtained a relative low passivation level (Eprot–Ecorr < 150 mV(Ag|AgCl|KCl 3 mol/L) and high corrosion kinetic. The passivation level and durability of the surface were reduced after 12 months of operation. A worst-case scenario was noted with biofilm adhesion given that the surface was not able to repassivate. It worth to emphasize that the passivation treatment increased the passivation level to 520 mV(Ag|AgCl|KCl 3 mol/L) and reduced the passivation current density from 20 to 0.7 μA cm–2. It was concluded that a passivated AISI 316L tank reach a better operational reliability, and also the chemical passivation treatment should be done every 12 months in order to restorage the passive film resistance.

Resumo em Inglês:

ABSTRACT The use of permeable concrete pavements can mitigate flooding in densely populated areas by serving as a functional and sustainable mechanism for surface water absorption and drainage. However, it is found that the performance of the pavement is often limited to low and moderate flows and that the absorption capacity of the concrete matrix decreases as the flow rate increases. Therefore, the present study was developed aiming to evaluate the potential to reduce runoff in permeable concrete pavements subjected to simulations of successive events of heavy rainfall. For this purpose, 2 binary combinations of coarse aggregates were used, varying the cement consumption and the water/cement (w/c) ratio. The samples were submitted to simulations of heavy and sequential rainfall, with evaluation of the volume of water absorbed and the runoff. The mechanical and hydraulical properties of the permeable pavements were evaluated, as well as the characteristics of the area and volume of the internal and superficial pores. Among the results, specific weight stands out as the parameter that showed the highest linear correlation with the mechanical and hydraulic behavior of the specimens. It was also found that the runoff coefficient had a moderate negative linear correlation with the average pore size of the surface of the pavement. Finally, the permeable concrete pavements investigated were found to have the potential to reduce surface runoff in densely populated areas that are prone to frequent flooding, thus playing a critical role in mitigating the problems associated with stormwater runoff.

Resumo em Inglês:

ABSTRACT Pervious asphalt concrete (PAC) pavement is an environmentally friendly type of pavement due to its highly porous structure. However, with the increase in the service life of PAC, small substances such as damaged rubber particles, industrial dust, sand, and grease collected in rainwater infiltrate the voids of PAC so that it loses its original pervious structure and functions. In order to explore the effects of chemical pore-clearing methods on the infiltration rate of blocked PAC pores in the present study, chemical agents such as sodium hydroxide solution (H2O2) and hydrogen peroxide (NaOH) solution were used to rinse the voids in PAC specimens obtained from field sampling and laboratory preparation. The effectiveness of different chemical pore-clearing methods in restoring the permeability and stability of PAC was evaluated by water infiltration rate measurements, Cantabro abrasion tests, and CT scanning. The results showed that the capability of H2O2 solution to restore PAC porosity was greater than that of tap water and NaOH solution, especially when the H2O2 content in the solution was 6%. In addition, the decomposition products of H2O2 are oxygen and water, which are environmentally friendly products, this method proved highly effective in preventing groundwater contamination from pavement-cleansing chemical solutions.

Resumo em Português:

RESUMO Neste trabalho utilizou-se uma liga hipereutética Al-40wt%Cu para verificar a influência das variáveis de entrada taxa de resfriamento (°C/min) e superaquecimento (°C), na variável de saída microdureza (HV). As amostras foram vazadas em cadinhos de cerâmica e de cobre e um termopar acoplado à um sistema de aquisição de dados mediu as taxas de resfriamento que foram 20°C/min e 24°C/min, respectivamente. Avaliou-se a influência dessas taxas de resfriamento e do superaquecimento de 100°C e 200°C acima da temperatura de fusão da liga na microdureza. As medições de dureza Vickers foram realizadas na seção transversal da amostra com área de 0,8 cm2. As amostras foram caracterizadas microscopicamente para avaliar a formação microestrutural. O potencial das variáveis envolvidas no estudo foi avaliado por um planejamento fatorial completo 22. Os resultados do planejamento fatorial indicaram que as amostras solidificadas usando o superaquecimento de 200°C acima da temperatura de fusão e resfriadas a uma taxa de 24°C/min obteve maiores valores de microdureza. As ligas superaquecidas em maiores temperaturas apresentaram microestruturas mais refinadas com grãos alongados, direções de crescimento desordenadas e espaçamento dendrítico curto, provocando uma transição na microestrutura colunar para equiaxial.

Resumo em Inglês:

ABSTRACT In this work a hypereutectic Al-40wt%Cu alloy was used to verify the influence of the input variables cooling rate (°C/min) and superheating (°C), on the output variable microhardness (HV). The samples were poured in ceramic and copper crucible and a thermocouple coupled to a data acquisition system measured the cooling rates that were 20°C/min and 24°C/min, respectively. The influence of these cooling rates and overheating of 100°C and 200°C above the melting temperature of the alloy on microhardness was evaluated. Vickers hardness measurements were performed on the sample cross section with an area of 0.8 cm2. The samples were characterized microscopically to evaluate the microstructural formation. The potential of the variables involved in the study was evaluated by a 22 full factorial design. The results of the factorial design indicated that the samples solidified using overheating to 200°C above the melting temperature and cooled at a rate of 24°C/min obtained higher microhardness values. The alloys superheated to higher temperatures showed more refined microstructures with elongated grains, disordered growth directions and short dendritic spacing, causing a transition in columnar to equiaxial microstructure.

Resumo em Português:

RESUMO A produção dos materiais de construção degrada o meio ambiente, assim, busca-se fontes alternativas de matéria-prima para produção de materiais, como tijolos refratários, ou como adição ao processo de produção do cimento Portland. Deste modo, este trabalho teve como objetivo analisar a viabilidade técnica da extração da sílica, obtida através da queima do farelo de trigo. Inicialmente, as análises laboratoriais envolveram dois métodos para extração do silício do farelo de trigo com quatro tipos de ácidos (acético, clorídrico, sulfúrico e cítrico), sendo o primeiro método a lavagem em meio ácido, seguido de secagem na estufa e queima em forno tipo mufla. Já o segundo método foi seguindo as etapas de queima na mufla, secagem e banho ácido, totalizando oito amostras. A sílica obtida foi analisada empregando técnicas de energia dispersiva de raios-X (EDS), microscopia eletrônica de varredura (MEV) e difração de raios-X (DRX). Os resultados com o tratamento térmico, físico e químico mostram que a cinza do farelo de trigo obteve, dentre as amostras, o maior percentual de 30,55% de silício, mantendo-se predominantemente no seu estado amorfo. Diante dos resultados, pode-se notar que a geração de sílica a partir da cinza do farelo de trigo torna-se uma fonte alternativa.

Resumo em Inglês:

ABSTRACT The production of building materials degrades the environment, thus, an attempt is made to alternative source of raw material for the production of materials such as refractory bricks, or as an addition to the Portland cement production process. Therefore, this work aims to analyze the feasibility of silica extraction, obtained by burning wheat bran. Initially, laboratory analyzes involved two methods for extracting silicon from wheat bran with four acidic types (acetic, hydrochloric, sulfuric and citrus), the first method being washing in an acidic environment, followed by drying in the oven and burning in a type oven muffle, the second method followed the steps of burning in the muffle, drying and acid bath, totaling eight samples. The silica obtained was analyzed using X-ray dispersive energy (EDS), scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. The results with the thermal, physical and chemical treatment show that the wheat bran ash obtained, among the samples, the highest percentage of 30.55% of silicon, remaining predominantly in its amorphous state. In view of the results, it can be noted that the generation of silica from the ash of the wheat bran becomes an alternative source.

Resumo em Português:

RESUMO Avaliou-se a funcionalização do sistema polimérico PVC/Carbonato diante da incorporação de resíduos de borracha SBR-r. As amostras foram preparadas em um misturador interno do tipo Haake e avaliado o torque aos serem incorporados os resíduos no sistema polimérico. Nas diversas concentrações de SBR-r estudadas e considerando as condições de equilíbrio durante o processamento, as misturas foram caracterizadas através de ensaios físico-químicos e mecânicos. Nos espectros de FTIR, pode se observar que a incorporação do resíduo, mesmo nas maiores concentrações, não alterou as bandas características do PVC/CaCO3 o que pode indicar que houve apenas interação física no sistema. A resistência mecânica foi reduzida com o aumento no percentual de incorporação do resíduo de borracha ao sistema PVC/CaCO3, e observou-se uma discreta elevação na dureza do compósito. Com o aumento das incorporações verificou-se uma redução na cristalinidade dos sistemas. Os sistemas apresentaram comportamento térmicos semelhantes, com três etapas de decomposição. Tendo o sistema PVC SBR-r-25 Ca-75 apresentado maior estabilidade térmica (178 ºC). O aumento do percentual de incoporação do SBR-r ao PVCCa, provocou uma leve diminuição das temperaturas TD10% e TD50%, no entanto, para o TD90% essa redução foi mais efetiva. Os resultados obtidos na fluidez dos sistemas, foi de 93% de eficácia do índice de escoamento, em comparação ao esperado do PVCCa100. Embora o aumento da incorporação dos resíduos de borracha tenha indicado mudanças fisicos-químicas e mecânicas das caracterizações, os resultados de uma forma geral foram bastante significativos, possibilitando neste presente trabalho uma alternativa para aplicação em escala industrial dos sistemas PVC SBR-r-25 Ca-75 e PVC SBR-r-50 Ca-50.

Resumo em Inglês:

ABSTRACT The functionalization of the PVC/Carbonate polymer system was evaluated in face of the incorporation of SBR-r rubber residues. The samples were prepared in an internal Haake-type mixer and the torque was evaluated when the residues were incorporated into the polymeric system. In the different concentrations of SBR-r studied and considering the equilibrium conditions during processing, the mixtures were characterized through physical-chemical and mechanical tests. In the FTIR spectra, it can be observed that the incorporation of the residue, even in the highest concentrations, did not change the characteristic bands of PVC/CaCO3, which may indicate that there was only physical interaction in the system. The mechanical strength was reduced with the increase in the percentage of incorporation of the rubber residue to the PVC/CaCO3 system, and a slight increase in the hardness of the composite was observed. With the increase in incorporations, there was a reduction in the crystallinity of the systems. The systems presented similar thermal behavior, with three stages of decomposition. The PVC system SBR-r-25 Ca-75 showed greater thermal stability (178 ºC). The increase in the percentage of incorporation of the SBR-r to the PVCCa caused a slight decrease in the TD10% and TD50% temperatures, however, for the TD90% this reduction was more effective. The results obtained in the fluidity of the systems, was of 93% of efficiency of the flow index, in comparison to the expected of the PVCCa100. Although the increase in the incorporation of rubber residues has indicated physical-chemical and mechanical changes in the characterizations, the results in general were quite significant, allowing in this present work an alternative for application in industrial scale of the PVC SBR- r-25 Ca-75 and PVC SBR-r-50 Ca-50.

Resumo em Inglês:

Knowing the importance of predicting acting forces during the formation process, our research has conducted 27 Single Point Incremental Forming (SPIF) experiments in hyperboloid format, followed by Finite Element Method (FEM) simulations and regression equations were determined to estimate the maximum axial force in the process. ANOVA analysis of variance was used to determine the significance of material parameters in the maximum axial force response. A multiple linear regression model was constructed to estimate the maximum axial force in the SPIF process. After the experiments, we were able to identify that the maximum axial force increases according to an increase in tool radius, sheet initial thickness, and strength coefficient values, as well as according to the decrease in the strain-hardening exponent. The FEM simulations are in agreement with the experimental values found, and the linear regression model has proven to be efficient to describe results, with R2 of 98.85% and a maximum percentage error of 11.5%.

Resumo em Inglês:

ABSTRACT As high-end equipment requires a higher and higher sealing effect, sealing forms such as packing seals expose problems such as considerable wear and high heat generated by friction. Based on the theoretical analysis of the instability at the liquid-liquid interface and the pressure resistance of the seal structure, considering the rotating speed of the rotating shaft, this paper reconstructs the formula for calculating the pressure resistance value of the seal structure. On this basis, a magnetic fluid seal structure is designed for a large horizontal shaft diameter in liquid. Based on the magnetic field analysis software Maxwell, the magnetic field of the magnetic fluid seal is analyzed, and the mapping relationship between the different tooth widths of the pole teeth, the size of the permanent magnet, and the difference in the magnetic induction intensity of the seal gap is obtained. Built in the ring seal test system, the pressure test of the horizontal large shaft diameter seal structure under different rotating speeds was carried out to verify the effectiveness of the seal structure. The results have specific theoretical research significance and engineering application value for designing and applying magnetic fluid seal structures.

Resumo em Inglês:

ABSTRACT Flanged diffuser can improve hydrokinetic turbine efficiency. However, in the current literature it is still not clear if the flange allows the possibility of cavitation on its structure, and whether it can support high pressure variation. This work presents a Computational Fluid Dynamics (CFD) study on the effect of cavitation on a flanged diffuser. The water flow through the diffuser was evaluated using a Reynolds Averaged Navier Stokes approach coupled to the Rayleigh-Plesset model to estimate the vapor production rate. The methodology was applied to a flanged diffuser and results were compared with experimental data from the literature. The minimal depth to avoid cavitation on the flanged diffuser was found. The pressure field obtained on CFD was applied as loading in structural analysis using Finite Element Method. The numerical model presented good agreement with experimental data available in the literature. The results showed that cavitation occurs more intensely at a depth of 1.0 m for the model. This intensity gradually decreases as the depth increases. Cavitation can be present in flanged diffusers, especially in the region inside the shroud, where it can directly impact the flow through the rotor. A good safety factor was obtained in the structural analysis.

Resumo em Inglês:

ABSTRACT Sugar cane bagasse ash (SA) is the result of the incineration of residues in the production of sugar which has as its final disposal the sanitary landfills generating environmental impacts. The practice of the circular economy for using SA ash as a stabilizer of clay soils in highway bases and sub-bases requires the study of the potential of ash as an alternative cement. Soil stabilization is commonly done with the addition of cement or lime; however, the production of these materials releases CO2 into the atmosphere. This research estimates the potential use of SA ash as a cementing agent considering the physical, hydraulic, and mechanical properties of clay soil mixed with percentages of 6, 8, and 10% of Uncalcined Sugarcane Bagasse Ash (USA) and Calcined Sugarcane Bagasse Ash (CSA). X-ray fluorescence spectrometry (FRX), methylene blue value test, specific gravity, dry unit weight, granulometric analysis, and Atterberg limits tests were carried out to evaluate the physical properties of the mixtures. One-dimensional consolidation tests, soil water characteristic curves (SWCC), standard Proctor compaction, unconfined compression, and direct shear were carried out to estimate the mechanical and hydraulic properties of the mixtures. An improvement in the physical, hydraulic, and mechanical properties was found with the addition of USA and CSA. Finally, based on the analysis of the physical, hydraulic, and mechanical properties of the Soil-USA and soil-CSA samples, it was determined that the best option as an alternative cementitious agent is found in the 8% Soil-CSA mixture due to the improvement in the plasticity index, gravity density, angle of friction, cohesion, and unconfined compressive in comparison with the other samples and the original soil. However, it is essential to mention that this cementitious addition can prejudice the hydraulic properties and consolidation process. It is vital to consider those parameters when realizing any geotechnical design with this mixture.

Resumo em Português:

RESUMO Pesquisas na área da ciência e engenharia dos materiais têm buscado alternativas para melhorar as propriedades e características dos compósitos cimentícios. Para tanto, o uso de nanopartículas, como as nanopartículas de sílica vem sendo uma alternativa promissora no segmento de nanocompósitos, proporcionando melhorias das propriedades físicas, químicas e na durabilidade, devido a alteração na microestrutura do material. Estudos internacionais têm demonstrado benefícios com a incorporação de pequenos teores de nanossílica em concretos, pastas de cimento e argamassa, entretanto, existem divergências quanto ao teor e ao tamanho de nanopartículas de sílica incorporada, e seus respectivos efeitos nas propriedades do estado fresco e endurecido dos materiais cimentícios. Diante disso, o presente estudo tem como objetivo analisar a influência da adição de nanopartículas de sílica em compósitos cimentícios, a partir das verificações da resistência mecânica, da absorção de água e da exposição em ambientes agressivos, através de uma análise entre quatro compósitos cimentícios, sendo uma amostra de referência, e nas demais serão adicionados teores de 0,5%, 0,75% e 1,0% de nanossílica em relação à massa de cimento. Os compósitos cimentícios foram analisados mediante o ensaio de resistência à compressão aos 3, 7 e 28 dias, absorção de água e ataque ácido, todos aos 28 dias de cura. Diante dos resultados obtidos verificou-se que a adição de nanossílica promoveu uma maior densificação da matriz cimentícia, logo, melhorou a resistência à compressão, diminuiu a absorção de água e o ataque ácido em relação à referência. Por fim, dentre as misturas avaliadas, conclui-se que o compósito com adição de 0,5% de nanossílica apresentou as melhores contribuições à pesquisa sendo, aumento de 15,6% para resistência à compressão e redução de 4,9% para absorção de água e 0,2% e 1,4% para o ataque ácido pelo método de Miranda e pela ASTM C-267-01, respectivamente.

Resumo em Inglês:

ABSTRACT Research in materials science and engineering has sought alternatives to improve the properties and characteristics of cementitious composites. Therefore, the use of nanoparticles, such as silica nanoparticles, has been a promising alternative in the nanocomposite segment, providing improvements in physical, chemical and durability properties, due to the change in the material’s microstructure. International studies have shown benefits with the incorporation of small amounts of nanosilica in concrete, cement pastes and mortar, however, there are divergences regarding the content and size of nanoparticles of incorporated silica, and their respective effects on the properties of the fresh and hardened state of the cement materials. Therefore, the present study aims to analyze the influence of the addition of silica nanoparticles in cementitious composites, from the verifications of mechanical strength, water absorption and exposure in aggressive environments, through an analysis between four cementitious composites, being a reference sample, and in the others, contents of 0.5%, 0.75% and 1.0% of nanosilica will be added in relation to the cement mass. The cementitious composites were analyzed using the compressive strength test at 3, 7 and 28 days, water absorption and acid etching, all at 28 days of curing. In view of the results obtained, it was verified that the addition of nanosilica promoted a greater densification of the cementitious matrix, therefore, it improved the compressive strength, reduced the water absorption and the acid attack in relation to the reference. Finally, among the mixtures evaluated, it is concluded that the composite with the addition of 0.5% of nanosilica presented the best contributions to the research, being an increase of 15.6% for compressive strength and a reduction of 4.9% for water absorption and 0.2% and 1.4% for acid attack by Miranda method and ASTM C-267-01, respectively.

Resumo em Inglês:

ABSTRACT Dielectric fluid is an important component in machining using Electrical Discharge Machining (EDM). Conventional dielectric fluids have disadvantages such as emit carbon dioxide and carbon mono oxide gases to the environment. Vegetable-based dielectrics are biodegradable, environment-friendly, and emit less harmful gases. This study focuses on water-in-sunflower seed oil as a replacement for conventional dielectric fluid. The quality of the performance is evaluated through selected machining responses such as material removal rate (MRR), tool wear ratio (TWR), circularity, taper conicity, and overcut of the hole. The experimental design of the project is designed based on the Taguchi L9 orthogonal array which results in 9 sets of experiments with different combinations of electrode diameter, dielectric fluids, feed rate, and capacitance. Water-in-sunflower seed oil provides the highest MRR. Besides that, it also performs well in the overcut which shows a steady spark throughout the whole fabrication.