Resumo em Português:

RESUMO Este trabalho consiste na avaliação do comportamento mecânico, em especial da vida de fadiga, de algumas misturas asfálticas tradicionalmente utilizadas no estado de Goiás, Brasil. Para a preparação das amostras, a granulometria dos agregados foi definida por meio da metodologia Bailey e em seguida verificada pela Fração do Agregado Dominante (FAD). Além dos ensaios de fadiga, outros ensaios laboratoriais foram realizados para avaliação do comportamento mecânico das misturas. Os resultados obtidos nesta pesquisa indicaram que somente a seleção granulométrica a partir da metodologia Bailey não foi suficiente para que as mistura estudadas apresentassem melhorias quanto à deformação permanente, sendo necessário, portanto, a análise da porosidade FAD bem como da realização de ensaios mecânicos como o ensaio uniaxial de carga repetida para determinação do Flow Number. As misturas estudadas apresentaram bom comportamento quanto à fadiga se enquadrando na Classe 4 da metodologia utilizada no software brasileiro de dimensionamento de pavimentos (MeDiNA). Assim, constata-se que quanto à fadiga, as misturas estudadas podem ser consideradas satisfatórias. No entanto, em termos de deformação permanente elas não apresentaram o desempenho necessário, sendo que a adequação granulométrica baseada apenas na metodologia Bailey não foi suficiente para melhorar o Flow Number. A partir desses resultados, recomenda-se que a faixa indicada para o FAD seja atendida e que outros tipos de ligantes asfálticos sejam incorporados nessas misturas para obter melhor desempenho.

Resumo em Inglês:

ABSTRACT This paper consists in the evaluation of asphalt mixtures regarding their mechanical behavior, especially the fatigue life of some asphalt mixtures traditionally used in the state of Goiás, Brazil. For sample preparation, the grain size distribution of the aggregates was defined using the Bailey methodology and then checked by the Dominant Aggregate Size Range (DASR). Besides the fatigue tests, other laboratory tests were performed to evaluate the mechanical behavior of the mixtures. The results obtained in this research were able to demonstrate that only the particle size selection from the Bailey methodology was not enough for a given mixture to present improvements in terms of permanent deformation. Therefore, analysis of the DASR porosity as well as mechanical tests such as the uniaxial repeated load test for determination of the Flow Number were necessary. The studied mixtures presented good fatigue behaviour and fit in Class 4 of the methodology used in the Brazilian design software (MeDiNA). Thus, this study points that for fatigue performance, the studied mixtures can be considered satisfactorily. However, in terms of permanent deformation they do not showed the necessary behavior, and the grain size adjustment based only at the Bailey method was not enough to improve the Flow Number. From these results, it is recommended that the DARS porosity range must be considered and other types of asphalt binders be incorporated into these mixtures to achieve their best performance.

Resumo em Português:

RESUMO A busca por materiais na construção civil ecoeficientes pode ser realizada adicionando ou substituindo as matérias-primas por resíduos gerados em outros setores industriais. Muitos destes resíduos são classificados como perigosos, sendo que a inertização dos compostos que conferem periculosidade pode ser realizada através da estabilização por solidificação (E/S) que ocasiona o encapsulamento e a fixação química de substâncias tóxicas. No entanto, no Brasil não há uma norma regulamentada ou mesmo uma recomendação técnica, que seja específica para produtos E/S utilizados como componentes de construção. Neste contexto, o presente estudo teve como objetivo avaliar a lixiviação do cromo em matriz de concreto de cimento Portland pelos métodos de imersão e irrigação, com vistas ao emprego destes métodos na avaliação ambiental de materiais e componentes da construção civil. Para isso, foram confeccionados corpos de prova de 25x200x400 mm com e sem adição de 2% de Cr2O3 (óxido de cromo) em relação a massa do cimento Portland, os quais foram submetidos a testes de lixiviação por imersão e irrigação. Os resultados obtidos permitiram verificar o encapsulamento do cromo no concreto e que os testes de lixiviação propostos em monólitos de concreto, durante a fase de uso, mostraram-se aplicáveis em 28 dias.

Resumo em Inglês:

ABSTRACT The search for materials in eco-efficient civil construction can be carried out by adding or replacing raw materials with waste generated in other industrial sectors. Many of these residues are classified as hazardous, and the inertization of compounds that confer dangerousness can be performed through stabilization by solidification (S/S) that causes the encapsulation and chemical fixation of toxic substances. However, in Brazil there is no regulated standard or even a technical recommendation, which is specific for S/S products used as building components. In this context, the present study aimed to evaluate the leaching of chromium in Portland cement concrete matrix by immersion and irrigation methods, with a view to the use of these methods in the environmental assessment of materials and components of civil construction. For this, specimens of 25x200x400 mm were made with and without the addition of 2% Cr2O3 (chromium oxide) in relation to the Portland cement mass, which were subjected to immersion and irrigation leaching tests. The results obtained allowed to verify the encapsulation of chromium in the concrete and that the leaching tests proposed in concrete monoliths, during the use phase, proved to be applicable in 28 days.

Resumo em Inglês:

Concrete with cactus is a new type of concrete with high fluidity, strength, and durability with more remarkable advantages. The present paper discusses the role of Euphorbia tortilis cactus (ETC) to achieve the strength, durability, and corrosion resistance properties of concrete specimens. In this work, M20 (2900psi) concrete was designed as per Indian standards, and cactus were used as an additive. ETC extracts from Tamilnadu (India) were replaced with water (1%, 3%, 5%, 7%, 9%) by weight. The performance of cactus concrete was analyzed through destructive and non-destructive tests to investigate strength properties. In addition to that, specific tests such as sorptivity, permeability, half-cell potential test, etc. have been performed further for durability and corrosion resistance. ETC concrete improves the fluidity, thereby enhancing the workability of the mixture. Concrete was analyzed through Scanning Electron Microscopy (SEM) to identify the particle distribution. Experimental investigation shows that the strength properties of concrete have been enhanced by 29% due to Polysaccharides at optimum level. However, durability is achieved at a high, which stimulates the effective filling of voids in concrete. It shows that better performance of concrete gives at optimum dosage. On Euphorbia tortilis cactus concrete, no literature has been discovered.

Resumo em Inglês:

ABSTRACT For decades, prisms and wallette have been used to explore masonry’s strength and deformation capabilities under uniaxial compression; moreover, the link between these two main test methods needs to be better established. Using standard masonry design expressions and data, the prism or wallette test can determine compression qualities. The researchers compared the standards and came to judgments on their conservatism or lack thereof, independent of how the rules for those design standards were formed. As a result, an attempt was made to link the behaviour of the enormous masonry prism to the wallette pressure behaviour. Prisms and wallette were made and tested by three different types of units and three mortar compositions. According to test results, the compressive strength of prism tests is consistently higher than that of identical wallette samples. It has remained demonstrated that a linear relationship concerning the compressive strengths of prisms and wallette is tolerable. To test data from the prisms and wallette, a simplified analytical model for the deformation properties of masonry is given.

Resumo em Português:

RESUMO A geração de resíduos da construção civil (RCC) e o consumo não racional de agregados naturais (AN) são adversidades enfrentadas no âmbito da Indústria da Construção Civil. Para mitigar este conflito, são investidos esforços, tais como a não geração, a redução, o reuso e a reciclagem, associadas a inserção de produtos não convencionais, como os geossintéticos. A reciclagem e a viabilidade técnica e econômica do emprego de agregados reciclados (AR) tem sido objeto de distintas pesquisas que buscam ampliar a gama de aplicação destes materiais, a fim de atingir aceitação e consolidação no mercado. Na engenharia geotécnica, os AR são empregados em muros de solo reforçado como material de preenchimento de blocos segmentais. Este artigo traz a investigação do emprego de agregados reciclados de concreto (ARCO) como material de preenchimento de blocos segmentais em muros de solo reforçado com geogrelhas (GGR), como proposta de substituição aos AN empregados nesta aplicação. Para tanto, os ARCO e AN na zona granulométrica de 9,5/25 mm (agregados graúdos) foram submetidos a ensaios de caracterização física e ensaios de resistência de conexão sob tensões normais de 40 kN/m2, 50 kN/m2, 60 kN/m2, 80 kN/m2 e 100 kN/m2, a fim de avaliar o desempenho dos elementos de interface quando submetidos à tração. Após a realização dos ensaios de resistência de conexão em equipamento de grande porte, verificou-se que os ARCO são indicados para o emprego como material de preenchimento de blocos segmentais em muros de solo reforçado com GGR de altura não superior a 5 metros. O aumento das tensões normais contribuiu para a redução mais expressiva das características físicas e do desempenho da resistência de conexão dos ARCO em relação aos resultados ensaios com emprego de AN.

Resumo em Inglês:

ABSTRACT The generation of civil construction waste (CCW) and the non-rational consumption of natural aggregates (NA) are adversities faced within the scope of the Civil Construction Industry. Efforts are invested, such as non-generation, reduction, reuse, and recycling, associated with the insertion of unconventional products, such as geosynthetics. Recycling and the technical and economic feasibility of using recycled aggregates (RA) have been the object of other research that seeks to expand the range of applications of these materials to achieve acceptance and consolidation in the market. In geotechnical engineering, RA can be used in segmental retaining walls (SRW) as filling material for segmental blocks. This article presents the investigation of recycled concrete aggregates (RCA) as filling material for segmental blocks in SRW reinforced with geogrids (GG) as a replacement proposal for the NA used in this application. Therefore, the RCA and NA in the granulometric zone of 9.5/25 mm, were subjected to physical characterization and connection strength tests under normal stresses of 40 kN/m2, 50 kN/m2, 60 kN/m2, 80 kN/m2, and 100 kN/m2 to evaluate the interface elements’ performance when subjected to load tensile. After carrying out the connection resistance tests on large equipment, it was verified that RCA are indicated for filler material for segmental blocks in SRW with GG with a height not exceeding 5 meters. The increase in normal tensions contributed to a more expressive reduction in the physical characteristics and performance of the connection resistance of the RCA about the test results with the use of NA.

Resumo em Português:

RESUMO Esta pesquisa experimental tem como objetivo produzir bioconcretos de casca de arroz (BCCs) com uma matriz de misturas ternárias de cimento, cinza da casca de arroz e cinza volante. A primeira etapa consistiu na avaliação da influência de um aditivo superplastificante e um aditivo polifuncional no comportamento reológico de pastas cimentícias. O objetivo dessa etapa foi testar diferentes teores dos aditivos a fim de desenvolver uma pasta fluida que, após a adição de altas frações volumétricas de casca de arroz (CA), permita obter BCCs leves que possuam trabalhabilidade adequada para adensamento por vibração mecânica. Realizou-se uma trituração e um tratamento químico da CA, no intuito de melhorar sua aderência com a matriz. Os resultados experimentais mostram que o aditivo do tipo PF apresentou melhor compatibilidade com a matriz a um teor de 0,3%. Assim, os BCCs produzidos apresentaram-se coesos e sem segregação, com espalhamento de 210 ± 30 mm. A massa específica seca e a resistência à compressão foram determinadas aos 28 dias de idade. Com os resultados obtidos, os BCCs apresentaram massa específica entre 1000 e 1300 kg/m3 e resistência à compressão superiores a 8,0 MPa, indicando a possibilidade de utilização na produção de painéis leves e autoportantes.

Resumo em Inglês:

ABSTRACT This experimental research aims to produce rice husk bio-concretes (RBCs) with a matrix of ternary mixtures of cement, rice husk ash and fly ash. The first step consisted in an evaluation of the influence of a superplasticizer additive and a polyfunctional additive on the rheological behavior of cementitious pastes. The purpose of this step was to test different levels of additives in order to develop a paste that, after adding high volumetric fractions of rice husk, allows obtaining RBCs that have adequate workability for compaction by mechanical vibration. A grinding and chemical treatment process was carried out on the rice husk to improve its adhesion with the matrix. The experimental results show that the PF type additive showed better compatibility with the ternary combination at an optimal content of 0.3%. Thus, the RBCs produced were cohesive, without segregation, with spreading of 210 ± 30 mm. The dry specific mass and compressive strength of the RBCs were determined after 28 days of age. Based on the results obtained, the BCCs presented specific mass between 1000 and 1300 kg/m3 and compressive strength higher than 8.0 MPa, indicating the possibility of use in the production of lightweight and load bearing panels.

Resumo em Inglês:

ABSTRACT In this research article, soil stabilisation is carried out by the latest method: nanotechnology. The stabilizer nano-aluminum oxide is used as a stabilising agent in concentrations of 0.2%, 0.4%, 0.6%, 0.8%, 1%, and 1.2%. Because it is 99% pure and nanoscale, it has a large surface area for analysing the properties and strength of soil tests such as Atterberg's limit, pycnometer, proctor compaction test, California bearing ratio test, and unconfined compressive strength. These tests are done for parent soil and soil with different percentages of nanomaterials. The nanostabilizer addition increases the unconfined compressive strength, California bearing ratio, liquid limit, and optimum moisture content value. One percentage of nano-aluminium oxide is considered an optimum dosage. Beyond the optimum amount, there is a change in soil property. The CBR value, liquid limit, and OMC of soil all go down, so it is recommended to use 1% nano-aluminum oxide to improve sub-grade clay soil.

Resumo em Inglês:

ABSTRACT As concrete being widely used in the field of construction, the demand for the materials used is increased ­rapidly. To meet the growing demand it is necessary to use alternative materials to meet the requirements. The Pineapple leaf fibre (PALF) is a highly available material in larger quantity with lesser water content and higher fiber content which makes it as a desirable material as natural fibre. The workability characteristics of Self ­compaction Concrete (SCC) like flowability, filling ability, passing ability, resistance to segregation and bleeding of concrete were out by using slump cone, U-box, L-box, V- Funnel and J-ring test. The test result shows satisfactory results on the workability of SCC. The fresh and hardened properties of concrete were found at the ages 7 days, 14 days and 28 days for various addition of PALF and various replacements of granite powder with the fine aggregate. The addition of PALF has achieved maximum compressive strength and split tensile strength in all ages of concrete at PALF0.2. The replacement of granite powder with fine aggregate seems to be promising in achieving the maximum compressive strength and split tensile strength at the 10% of replacement.

Resumo em Inglês:

Aerospace and military defense fields are posing higher requirement on the lightweight feature of structures. Subject of this study is the Aluminum Alloy 5A02 /CFRTP (Carbon Fiber Reinforced Thermo-Plastic) laminates. In the paper, aluminum alloy was anodized, compression molding and 3D printing were adopted to prepare Carbon Reinforced Aluminum Laminates (CARALL) with two different structures: the solid core structure and the honeycomb structure, and the prepared specimens were then tested for mechanical properties via tensile test and three-point bending test, and compared with the performance of the conventional aluminum alloy. The results show that under the condition of a same thickness, the tensile strength of CARALL specimens with the molded solid core structure and the 3D printed honeycomb structure reaches 256Mpa and 186MPa, respectively, which is 85.5% and 34.8% higher than that of the tensile strength of Al 5A02; under different bending modes, the maximum bending strength is 682Mpa and 525Mpa, respectively, which is 62.4% and 25.5% higher than that of Al 5A02. When the specimens are subject to tensile force, the separation of the metal layer and the fiber layer is the primary failure form, the fiber layer fractures, and the metal layer exhibits the necking phenomenon as the metal fibers are being pulled out. During the bending process, for different bending forms, there’re great differences in the bending strength of CARALL specimens prepared by the same method, the failure modes of the specimens vary greatly as well, and this is determined by the tensile strength of the carbon fiber layer and the tensile strength of AL 5A02. Enhancing the bonding strength between the metal layer and the fiber layer can improve the mechanical properties of CARALL. These research findings can provide a reference for the lightweight design of metals and Fiber Metal Laminates (FMLs).

Resumo em Inglês:

Abstract Glycerol has applications as a raw material in different industrial processes, however, its supply exceeds demand. An alternative to increase the added value of this feedstock is its conversion into high added-value chemical products through dehydration and hydrogenation reactions, from which 1,2-PDO and 1,3-PDO can be obtained. To develop catalysts that increase the conversion and selectivity of these processes, materials of 2% Pt and 10% WO3 supported on SBA-15 were studied. Two methods were used for incipient wetness impregnation: sequential impregnation, with impregnation steps for each species, and co-impregnation, with a single impregnation step for both species. From the analysis of XRD, XRF, N2 isotherms, SEM, EDS, FTIR, and pyridine FTIR spectroscopy, it was possible to observe the influence of these methods on the structural and textural properties. It was verified that the co-impregnation provided a better dispersion of the WO3 species on the surface of the SBA-15 and that the reduction process, for both methodologies employed, showed an improvement in the metallic dispersion. The better dispersion of WO3 species also resulted in a greater formation of Brønsted acid sites for the co-impregnation method, with a predominance of Lewis sites in the structure of the catalysts obtained by both methods.

Resumo em Inglês:

ABSTRACT This research mainly focuses on the nature of Fiber-Reinforced Polymers (FRP) wrapped piles for the axial compression load. Normally, the degradation of Reinforced Cement Concrete (RCC) structures occurred due to corrosion, inadequate quality materials, aging, live load increments, fatigue, damages and deterioration, and so forth. RCC pile foundations are commonly affected by the above reasons. So, these structures can be strengthened with suitable methods such as jacketing, stitching, overlaying, sealing, grouting, coating, Near Surface Mounted (NSM) systems, FRP wrapping, repairing, and blanketing. FRP wrapping is well suited for strengthening pile structures because of its easy application, and this method is done without using heavy tools and skilled labor. Due to its being non-metallic, FRP reinforcing has desirable properties such as high resistance to chemicals as well as heat, flexibility, large tensile strength, permeability, and also no oxidation. Thus, FRP wrapping was selected as the chosen approach for this ongoing research. In this study, we apply an axial compression load as well as a skin friction condition to a pile member that has been modified to assess its performance and behavior.

Resumo em Português:

RESUMO Este trabalho avaliou o comportamento de fratura da liga de alumínio AA7075-T6 submetida a carregamento de fadiga. Ambos os corpos de prova entalhados e não entalhados foram submetidos a um tratamento térmico de retrogression and re-aging (RRA) e nitretação a plasma antes dos ensaios mecânicos. A nitretação a plasma, que tem sido um método escolhido para aumentar a dureza superficial e as resistências à fadiga, desgaste e corrosão de diversas ligas, foi realizada com tela ativa com fonte DC de 20 Hz e ciclo de trabalho de 40 Hz. O tratamento RRA, que é utilizado para aumentar a resistência e a dureza da liga de alumínio AA7075 e obter melhorias nos comportamentos de fadiga e corrosão, foi realizado a 200 °C por 20 minutos com resfriamento a água (resolubilização), seguido de 24 horas a 120 °C (reenvelhecimento). Os ensaios de fadiga axial de corpos de prova entalhados e não entalhados foram realizados com R = 0,1, frequência de 14 Hz, e em nível de tensão de 150 MPa para corpos de prova entalhados e 500 MPa para corpos de prova não entalhados. A fratura por fadiga foi então realizada via estereomicroscopia e microscopia eletrônica de varredura. Para os corpos de prova não entalhados, as condições AA7075-T6 e AA7075-RRA apresentaram características de fratura semelhantes, com boa definição dos três estágios de falha por fadiga; a condição nitretada AA7075 não apresentou evidência de fratura por fadiga típica. Os corpos de prova entalhados apresentaram fractografias semelhantes à condição de concentração de tensão severa, com marcas superficiais convexas à região de nucleação.

Resumo em Inglês:

ABSTRACT This work assessed the fracture behavior of the AA7075-T6 aluminum alloy subjected to fatigue loading. Both the notched and unnotched specimens underwent a retrogression heat treatment and re-aging (RRA) and plasma nitriding before the mechanical tests. Plasma nitriding, which has been a method chosen to increase the surface hardness and the fatigue, wear and corrosion resistances of various alloys was carried out with an active screen with a 20 Hz DC source and a 40 Hz duty cycle. The RRA treatment, which is used to increase the strength and hardness of AA7075 aluminum alloy and obtain improvements in the fatigue and corrosion behaviors, was performed at 200 °C for 20 minutes with water cooling (resolubilization), followed by 24 hours at 120 °C (re-aging). The axial fatigue tests of notched and unnotched specimens were carried out with R = 0.1, frequency of 14 Hz, and at stress level of 150 MPa for notched specimens, and 500 MPa for unnotched specimens. The fatigue fracture was then performed via stereomicroscopy and scanning electron microscopy. For the unnotched specimens, AA7075-T6 and AA7075-RRA conditions presented similar fracture features, with good definition of the three stages of fatigue failure; the AA7075 nitrited condition presented no evidence of typical fatigue fracture. The notched specimens presented fractographies similar to the severe stress concentration condition, with surface marks convex to the nucleation region.

Resumo em Inglês:

ABSTRACT The selection of key additive materials for a new type of oil-based drilling fluid was studied in this paper. The oil-based drilling fluid can strengthen well walls and ensure safety. It is suitable for high-temperature and high-pressure wells, deep wells and ultra-deep wells. A new type of high-temperature white oil-based drilling fluid was prepared by using 5# white oil as continuous phase, HIS as thickening agent, SDBS as emulsifier, and asphalt powder oxidized at 180°C as filtration agent. The results showed that the saturation concentration of sodium dodecyl benzene sulfonate (SDBS) was 4%, the saturation concentration of asphalt powder oxidized at 180°C was 4%, the saturation concentration of Tween-80 was 10%. The final resistance of high temperature and high pressure oil based drilling fluid formulation material is: No. 5 white oil + 4% SDBS + 5% modified bentonite + 4% asphalt powder oxidized at 180°C + 10% Tween-80 + 1.5% Barite + CaO. The performance evaluation of the new oil-based drilling fluid shows that shale expansion is 0.21mm, anti-temperature up to 220°C, and anti-pollution ability is good. The rheological properties, resistance of high-temperature high- pressure have been greatly improved. Therefore, the new white oil-based drilling fluid can resistance of high- temperature and also has low toxicity, which can meet the exploration and development of more complex wells.

Resumo em Inglês:

ABSTRACT The attempt to face the limitations of wood-based materials, especially concerning the relationship with water, is still a considerable gap in research on this subject. The present work proposes the accomplishment of thermal treatment in fiberboard-type hardboard, using different temperatures and times, to evaluate the effect on the physical-mechanical properties. The parameters of the heat treatment were temperatures of 120 and 160 °C and times of 20 and 40 min. The hardboards were individually heat treated in a kiln. The characterization was performed from physical tests such as bulk density, moisture content, water absorption (2 and 24 h), thickness swelling (2 and 24 h); and mechanical properties of flexural strength. The treatment with a temperature of 160 °C for 40 min showed the lowest values of water absorption in 24 h (34%). Thickness swelling was lower compared to control, for all the treatments applied. Regarding flexural strength, the treatment that adopted the 160 °C for 20 min showed the highest MOR value (26.3 MPa). In general, the performance of heat treatments positively influenced the physical and mechanical properties of the hardboards, being an interesting alternative in the development of products for applications in internal environments.

Resumo em Inglês:

ABSTRACT Brazil has immense potential in the production of quartz and its gem varieties, consequently generating huge amounts of waste. This research aims to utilize the amethyst quartz tailings from the Alto Bonito mine-Brazil accumulated for decades in waste dumps, through a specific study of cementitious mortar production, considering the mineralogical and chemical characterization; evaluation the use of tailings as a fine aggregate for mortar production; estimate the technical feasibility through mechanical tests and; characterize of specimens by SEM after breakage. The tailings are quartz associated with mica. Quartz is polycrystalline with medium to fine grain, being SiO2 the main component. The comminuted tailings showed a very fine fineness modulus, affecting the formulations. With cement:tailings (1:3) traces the mechanical tests show 5.65 Mpa and 1.05 Mpa to compressive and flexural strength respectively, slightly below the reference. The fine-sized and metamorphic morphology of the tailings affects the mechanical strength of the mortar. The process adopted in the production of mortars with total replacement of the fine aggregate have a great impact contributing to the reduction of waste in dumps, minimizing the environmental impact of mining, in addition to benefiting the Amethyst Miners Cooperative.

Resumo em Português:

RESUMO Compósitos formados de óxidos semicondutores têm sido sintetizados e testados quanto às suas propriedades e aplicações, também, como fotocatalisador de restauração de aquíferos por meio da degradação ou descoramento de corantes orgânicos. Foi preparado o nanocompósito Fe2O3-SnO2 pelo método Poliol, técnica não encontrada para este compósito até o momento na literatura, em refluxo em etilenoglicol. O compósito e os óxidos isolados foram sintetizados pelo mesmo processo, caracterizados e avaliados como fotocatalisadores da Rodamina-B em solução aquosa (10 mg.L⁻1). Os materiais coletados após o refluxo realizado em intervalos de tempo de 1 h e 8 h geraram Fe2O3 e SnO2, respectivamente e foram analisados por TGA/DTA e por DRX. Constatou-se a obtenção de α-Fe2O3 a 400 °C e do SnO2 a 650 °C. O compósito foi tratado a 700 °C por 1 h. A MEV comprovou a formação de um compósito nanoestruturado com nanopartículas de SnO2. As curvas BET indicaram materiais não porosos com áreas superficiais de 18, 45 e 20 m2.g⁻1 para as amostras preparadas de Fe2O3, SnO2 e o compósito, respectivamente. Os band gaps estimados em 1,9 eV, 3,5 eV e 1,8 eV, na mesma sequência anterior. Os ensaios de descoramento de Rodamina-B, pH 5,5 em exposição a luz visível e ultravioleta, mostraram propriedades completamente diferenciadas. As partículas de Fe2O3 mostraram adsorção física capaz de reduzir a absorção luminosa em 75% nos 15 minutos iniciais, porém não houve o descoramento ao longo dos 75 minutos seguintes. A presença do SnO2 na solução mostrou descoramento máximo de 45% após 120 minutos. O descoramento obtido pelo nanocompósito em 180 minutos foi de 20%, resultado atribuído ao total recobrimento da superfície das partículas do α-Fe2O3 pelas nanopartículas de SnO2, impedindo tanto a adsorção física do corante sobre o óxido de ferro como o andamento do mecanismo de absorção da luz seguido da degradação do corante.

Resumo em Inglês:

ABSTRACT Composites formed from semiconductor oxides have been synthesized and assessed for their properties and applications, as well as a photocatalyst for restoring aquifers through the degradation or bleaching of organic dyes. The Fe2O3-SnO2 nanocomposite was prepared by the Polyol method, a technique not found for this composite so far in the literature, under reflux in ethylene glycol. The composite and the isolated oxides were synthesized by the same process, characterized, and evaluated as photocatalysts of Rhodamine-B in aqueous solution (10 mg.L⁻1). The materials collected after the reflux performed at time intervals of 1 h and 8 h generated Fe2O3 and SnO2, respectively, were analyzed by TGA/DTA and by XRD. It was found that α-Fe2O3 was obtained at 400 °C and SnO2 at 650 °C. This composite was treated at 700 °C for 1 h. The SEM proved the formation of a nanostructured composite with SnO2 nanoparticles. The BET curves indicated non-porous materials with surface areas of 18, 45 and 20 m2.g⁻1 for the samples prepared from Fe2O3, SnO2 and the composite, respectively. The band gaps estimated at 1.9 eV, 3.5 eV and 1.8 eV, in the same sequence as above. The bleaching tests of Rhodamine-B, pH 5.5 in exposure to visible and ultraviolet light, showed completely different properties. The Fe2O3 particles showed physical adsorption capable of reducing light absorption by 75% in the initial 15 minutes, however, there was no bleaching over the next 75 minutes. The presence of SnO2 in the solution showed a maximum bleaching of 45% after 120 minutes. The discoloration obtained by the nanocomposite in 180 minutes was 20%, a result attributed to the total covering of the surface of the α-Fe2O3 particles by the SnO2 nanoparticles, preventing both the physical adsorption of the dye onto the iron oxide and the progress of the absorption mechanism. light followed by dye degradation.

Resumo em Espanhol:

RESUMEN La vida en servicio de elementos de máquinas utilizados en la industria del gas y del petróleo puede ser extendida con el uso de recubrimientos que permiten mejorar las propiedades superficiales, como la resistencia al desgaste y a la corrosión. Los recubrimientos DLC son conocidos por su bajo coeficiente de fricción, alta resistencia al desgaste e inercia química. Las películas del tipo TiSiCN son cerámicas duras, por lo que otorgan una buena resistencia al desgaste abrasivo y erosivo. En este trabajo se analizan de forma comparativa estos dos recubrimientos cuando son depositados sobre un acero de media aleación AISI 4140. Se midió espesor y se hizo caracterización por XPS, DRX y espectroscopía Raman. Se realizaron ensayos de desgaste adhesivo tipo Pin-on-Disk y desgaste abrasivo (ASTM G65). Se evaluó la adhesión por Scrach Test. La resistencia a la corrosión se evaluó mediante cámara de niebla salina y ensayos potenciodinámicos. El DLC presentó un bajo coeficiente de fricción μ ~ 0,2, con una pérdida de volumen dos veces menor que el TiSiCN, mientras que este último presentó una resistencia al desgaste abrasivo 30 veces superior. La adhesión del TiSiCN también fue superior. El DLC mostró una mayor resistencia a la corrosión.

Resumo em Inglês:

Abstract Service life of machine parts used in the oil and gas industry can be expanded by using coatings that improve surface properties such as wear and corrosion resistance. DLC coatings are known for their low friction coefficient, high wear resistance and chemical inertness. TiSiCN films are hard ceramics, so they provide good resistance to abrasive and erosive wear. In this work, these two coatings deposited on alloy steel AISI 4140 are comparatively analyzed. Thickness was measured and the coatings were characterized by XPS, DRX and Raman spectroscopy. Pin-on-disk adhesive wear and abrasive wear tests (ASTM G65) were carried out. Adhesion was evaluated by scratch test. Corrosion resistance was evaluated by salt spray test and potentiodynamic tests. DLC coatings presented low friction coefficient μ ~ 0,2, and a volume loss twice as low as TiSiCN, whereas the latter presented 30 times the abrasive wear resistance. The adhesion of TiSiCN was also superior. DLC showed higher corrosion resistance.

Resumo em Português:

RESUMO Este artigo verificou o comportamento estrutural à flexão de três configurações de vigas mistas de madeira e perfis de aço, por meio do método de homogeneização da seção mista, ensaios experimentais e simulação computacional. Foram analisadas viga de madeira sem reforço (V-SR), com perfis de chapa de aço dobrada fixada com parafuso tipo prisioneiro (V-PRI) e autoatarraxante (V-AUT). Foram realizados ensaios de flexão por 3 pontos, obtendo a força de ruptura e deslocamentos. Verificou-se que a forma ruptura das vigas foi similar em todas as configurações, ocorrendo na parte tracionada, sem apresentar flambagem lateral dos perfis de aço ou deformação plástica dos parafusos. Notou-se que a inserção dos perfis de aço ocasionou um aumento na resistência das vigas mistas, sendo de 100% nas vigas com perfis de chapa de aço dobrada fixada com parafuso tipo prisioneiro (V-PRI) e de 32% nas vigas com perfis de chapa de aço dobrada fixada com parafuso tipo autoatarraxante (V-AUT). As simulações pelo método dos elementos finitos apresentaram valores mais próximos ao comportamento na flexão das vigas V-SR e V-PRI no regime elástico (ELS). O método de homogeneização da seção mista mostrou-se mais próximo dos resultados experimentais nas vigas de madeira reforçadas (V-PRI e V-AUT).

Resumo em Inglês:

ABSTRACT This paper verified the structural behavior of three configurations of composite beams of wood and steel profiles, analytically by the mixed section homogenization method (MHSM), by experimental tests and simulated by the finite element method (FEM). Unreinforced wooden beam (V-SR), with bent steel sheet profiles fixed with stud (V-PRI) and self-tapping (V-AUT) screws were analyzed. The flexural behavior was analyzed by 3 points of these elements, represented by the load and displacement. It was found that the beam failure form was the same in all configurations, occurring in the tensioned part, without lateral buckling of the steel profiles or plastic deformation of the screws. It was noted that the insertion of steel profiles caused an increase in the strength of the composite beams, being 100% in the V-PRI sample and 32% in the V-AUT. The FEM simulations showed values closer to the bending behavior of the V-SR and V-PRI beams in the elastic regime (ELS). The experimental results of the V-AUT beams were more compatible with the mixed section homogenization model.

Resumo em Português:

RESUMO A característica mais comum dos cimentos geopoliméricos é que eles contêm uma quantidade relativamente pequena de óxidos de ferro. Isso se deve ao fato de que vários cientistas desconfiam da ação nociva de alguns compostos ferrosos no desenvolvimento da reação geopolimérica. Para alguns pesquisadores o Fe pode interferir negativamente no processo de geopolimerização do material, enquanto que, em alguns novos estudos o papel do Fe tem revelado resultados interessantes. No intuito de verificar a resistência mecânica alcançada pelo geopolímero obtido a partir do rejeito da lavagem da bauxita, que possui em sua composição alto teor de ferro, a presente pesquisa pretende utilizar 100% dessa matéria-prima calcinada como precursor, e reagentes como o NaOH e Na2SiO3 como ativadores no processo. Todos os materiais foram caracterizados perante suas propriedades físicas e mineralógicas, a fim de possibilitar a correta dosagem dos materiais. Com os geopolímeros obtidos, avaliou-se a resistência a compressão, variando a concentração de NaOH em 8 M e 10 M para diferentes tempos de cura (7 e 28 dias). Análise de difração de raios X (DRX), Espectroscopia de Infravermelho com Transformada de Fourier (FTIR), análise granulométrica e testes de resistência mecânica. Mesmo com aproximadamente 25% de ferro, os geopolímeros apresentaram comportamento mecânico compatível com funções atribuídas e similares a normativa estabelecida para o cimento Portland, com resistência máxima de 25,85 MPa.

Resumo em Inglês:

ABSTRACT The most common feature of geopolymer cements is that they contain a relatively small amount of iron oxides. This is due to the fact that several scientists suspect the harmful action of some Fe++ ferrous compounds in the development of the geopolymeric reaction. For some researchers, Fe can interfere negatively in the geopolymerization process of the material, while, in some new studies, the role of Fe has revealed interesting results for geopolymers. In order to verify the mechanical resistance achieved by the geopolymer obtained from the bauxite washing waste, which has a high iron content in its composition, the present research intends to use 100% of this calcined raw material as a precursor, and reagents such as NaOH and Na2SiO3 as activators in the process. All materials were characterized in terms of their physical and mineralogical properties, in order to enable the correct dosage of materials. With the geopolymers obtained, the compressive strength was evaluated, varying the concentration of NaOH in 8 M and 10 M for different curing times (7 and 28 days). X-ray diffraction analysis (DRX), Fourier Transform Infrared Spectroscopy (FTIR), granulometric analysis and mechanical resistance tests. Even with approximately 25% of iron, the geopolymers presented a mechanical behavior compatible with assigned functions and similar to the norms established for Portland cement, with a maximum resistance of 25.85 MPa.

Resumo em Português:

RESUMO A concentração de minérios fosfáticos ricos em carbonatos através de flotação convencional é dificultada devido às similaridades de suas propriedades superficiais. Assim, surge a flotação reativa baseada na retenção de dióxido de carbono produzido pelos carbonatos em meio ácido. Diante das atuais demandas de novas técnicas de concentração, este trabalho investigou a flotação reativa do minério fosfático sílico-carbonatado. Para tanto, amostras das faixas granulométricas, –10# +20# (–1,70 mm +0,84 mm) e –20# +65# (–0,84 mm +0,210 mm) foram empregadas durante o processo. Os ácidos, sulfúrico e fosfórico, bem como o polímero álcool polivinílico (PVA) foram avaliados por intermédio de ensaios de planejamento fatorial. O ácido fosfórico favoreceu a redução da relação CaO/P2O5, bem como a elevação do teor de P2O5, sendo o melhor resultado, aquele que proporcionou aumento de cerca de 30% no teor de P2O5 (12,3 para 16%) na faixa –20# +65#, ao utilizar 10% (v/v) de ácido fosfórico e 0,5% (m/v) de PVA. Embora tenha-se conseguido atingir, em alguns testes, o parâmetro industrial para a relação CaO/P2O5 (inferior a 1,6), o mesmo não ocorreu para os teores de MgO (inferior a 1%). Os resultados são promissores, entretanto, novos estudos com alternativas mais sustentáveis são extremamente necessários atualmente.

Resumo em Inglês:

ABSTRACT The concentration of carbonate-rich phosphate ores through conventional flotation is difficult due to the similarities in their surface properties. Thus, the reactive flotation based on the retention of carbon dioxide produced by carbonates in an acid medium arises. Given the current demands of new concentration techniques, this work investigated the reactive flotation of silica-carbonated phosphate ore. For that, samples from the granulometric ranges, –10# +20# (–1.70 mm +0.84 mm) and –20# +65# (–0.84 mm +0.210 mm) were used during the process. Through factorial design tests, the reagents employed were sulfuric and phosphoric acids and polymer polyvinyl alcohol (PVA). Phosphoric acid favored the reduction of the CaO/P2O5 ratio and the increase of the P2O5 grade. The best result was the one that provided an increase of about 30% in the P2O5 grade (12.3 to 16%) in the range –20# +65#, when using 10% (v/v) phosphoric acid and 0.5% (m/v) PVA. Although it was possible to reach, in some tests, the industrial parameter for the CaO/P2O5 ratio (less than 1.6), the same did not occur for the MgO contents (less than 1%). The results are promising however, new studies with more sustainable alternatives are extremely necessary nowadays.

Resumo em Inglês:

ABSTRACT With its excellent fatigue performance and high damage tolerance and other irreplaceable advantages, FMLs have gradually increased the demand in aerospace, rail transit, ship and other fields, and have put forward higher requirements for the speed and accuracy of its performance test and index evaluation. In this paper, the methods of performance test, analysis and index evaluation of FMLs are introduced from three aspects with carbon fiber and composite materials, mechanical properties and numerical simulation technology, details the common test methods, the latest technology and progress, and analyzes their advantages and disadvantages, so as to provide direction and reference for the performance test method and index evaluation of FMLs. Finally, the main development directions of the current performance testing methods and index evaluation of FMLs are briefly discussed.

Resumo em Português:

RESUMO A baixa resistência mecânica e a suscetibilidade à água restringem a aplicação do gesso de construção em elementos sem fins estruturais e em locais protegidos da umidade. Em contrapartida, a conformação sob pressão tem sido apontada como uma alternativa para se obter peças de gesso de elevado desempenho. No entanto, a influência de fatores de processamento e relacionados à mistura sobre as propriedades das pastas de gesso conformado sob pressão é pouco conhecida. Este artigo tem como objetivo investigar os efeitos da pressão (P), massa conformada (M) e relação água/gesso (X) nas propriedades físicas e mecânicas do gesso conformado sob pressão (GCP). Um projeto fatorial 2k foi utilizado para avaliar os efeitos destes fatores de conformação e das suas interações. Neste projeto, P variou de 5 a 15 MPa, M de 350 a 550 g e X de 0,18 a 0,22. A espessura (t), a porosidade (η), o módulo de elasticidade dinâmico (E), a resistência à tração na flexão (Rt) e a resistência à compressão (Rc) de corpos de prova prismáticos foram as propriedades analisadas. Os resultados mostraram que a pressão e a relação água/gesso tiveram efeitos significativos em todas as propriedades, exceto na espessura, e a massa conformada afetou de forma significante, apenas, a espessura dos corpos de prova. A conformação do gesso sob pressão mostrou-se ser uma técnica promissora para o desenvolvimento de pastas de elevado desempenho mecânico (E = 20,0 GPa, Rt= 12,6 MPa e Rc= 53,5 MPa) e baixa porosidade (η= 20,1%). Os resultados apontaram a necessidade do uso de um aditivo retardador para garantir a compactação do gesso antes do início da pega e melhorar o empacotamento dos cristais de di-hidrato. A técnica de conformação por prensagem mostrou-se propícia para o desenvolvimento de componentes pré-fabricados de gesso de alta resistência mecânica para uso na construção civil.

Resumo em Inglês:

ABSTRACT The low mechanical strength and susceptibility to water restrict the application of gypsum plaster in non-structural elements and places protected from moisture. On the other hand, pressure-formed gypsum plaster has been pointed out as an alternative to obtaining high performance plaster pieces. However, the influence of processing and mixing-related factors on the properties of pressure-formed gypsum plaster pastes has yet to be discovered. This article aims to investigate the effects of pressure (P), formed mass (M), and water/gypsum ratio (X) on the physical and mechanical properties of pressure-molded gypsum plaster (PMG). A 2k factorial design was used to evaluate the effects of these forming factors and their interactions. In this project, P varied from 5 to 15 MPa, M from 350 to 550 g, and X from 0.18 to 0.22. Thickness (t), porosity (η), dynamic modulus of elasticity (E), flexural tensile strength (St), and compressive strength (Sc) of prismatic specimens were the analyzed properties. The results showed that the pressure and the water/plaster ratio had significant effects on all properties except thickness, and the formed mass affected only the specimens’ thickness. Plaster molding under pressure proved to be a promising technique for developing plaster pastes with high mechanical performance (E = 20.0 GPa, St= 12.6 MPa, and Sc= 53.5 MPa) and low porosity (η= 20.1%). The results indicated the need for a retarder to guarantee the plaster compaction before the setting and to improve the dihydrate crystals packaging. The press-forming technique proved suitable for developing prefabricated gypsum components with high mechanical strength for civil construction.

Resumo em Inglês:

ABSTRACT The urine bag is a thermo-labile medical-hospital device used in clinical/surgical procedures in urine drainage and collection. As it is a thermolabile material, it is commonly sterilized by ethylene oxide, a highly toxic, mutagenic and carcinogenic cyclic ether gas. Currently, several countries require, through documents and standards, the quantification of ethylene oxide in medical and hospital devices. Thus, this work describes the development and validation of a method employed for the quantification of ethylene oxide (ETO) in urine bags. The method was developed based on the guidelines of ISO 10993-7, ANVISA and INMETRO. The work range, linearity, limits of detection and quantification, repeatability, intermediate precision and selectivity were evaluated. Statistical tools such as Levene's test, Grubbs, residual analysis, F-test of two variances, paired sample T test and ANOVA table, were also applied to evaluate the method. The linearity of the work range (10 – 400 mg.L-1) showed an adequate correlation coefficient (r > 0.9993), with a homoscedastic profile with absence of outliers while the limit of detection and quantification were 1,95 and 6,5 mg.L-1 respectively. After validation, 45 samples of urine bags of different batches were evaluated, which demonstrated levels of ETO below the limit of detection (1,95 mg.L-1). The results highlight a simple method that meets several regulations with a wide working range, high sensitivity and capability to quantify ETO not only in urine bags but also in other medical devices.

Resumo em Português:

RESUMO O uso dos compostos poliméricos se limita às alvenarias de vedação no Brasil, devido aos critérios da NBR 16590 [1]. No entanto, deve-se avaliar o quanto este material pode contribuir quando aplicado em alvenarias estruturais. Sendo assim, esse estudo investigou o funcionamento de um tipo de composto polimérico, quando aplicado em alvenarias estruturais, realizando ensaios de caracterização química e física do material e de aderência na interface entre bloco e o ligante. Além dessas, foram investigadas a resistência à compressão axial de paredes em escala real, sendo uma amostra executada com as juntas horizontais preenchidas por argamassa cimentícia e outras duas contendo composto polimérico, com 2 e 4 filetes para assentamento dos blocos. Os resultados de caracterização do material ligante e interface mostraram que o composto polimérico possui maior resiliência e melhor desempenho à aderência, quando comparado à argamassa cimentícia. Já na análise global do sistema, verificou-se que a alvenaria construída com 4 filetes de composto polimérico atingiu a mesma resistência à compressão da amostra construída com argamassa cimentícia convencional (~138 kN/m na ruptura), a amostra com 2 filetes apresentou maior deformação vertical, 25 % em relação as demais, mostrando o potencial de utilização do composto polimérico em alvenaria estrutural.

Resumo em Inglês:

ABSTRACT The use of polymeric compounds is limited to sealing masonry in Brazil, due to the criteria of the NBR 16590 [1]. However, one must evaluate how much this material can contribute when applied to structural masonry. Thus, this study investigated the operation of a type of polymeric compound when applied in structural masonry, performing chemical and physical characterization tests and adhesion at the interface between block and binder. Besides these, we investigated the axial compressive strength of full-scale walls was investigated. One sample was made with horizontal joints filled with cementitious mortar and two containing polymeric compound, with 2 and 4 fillets for settlement the blocks. The characterization results of the binder material and interface showed that the polymeric compound has greater resilience and better adherence performance when compared to cementitious mortar. In the overall analysis of the system, it was found that masonry built with 4 fillets of polymeric composite achieved the same compressive strength of the sample built with conventional cement mortar (~ 138 kN/m at break), the sample with 2 fillets presented higher vertical deformation, 25% in relation to the others, showing the potential use of the polymeric compound in structural masonry.

Resumo em Português:

RESUMO A escolha do tipo de piso dentro do sistema de produção animal é um fator importante, já que está associado a grande incidência de alterações na locomoção, lesões de cascos e descarte de rebanho, o que tem levado aos produtores modificar o tipo de piso por materiais mais confortáveis, duráveis e secos, como é o caso dos emborrachado, no entanto, a matéria-prima torna o investimento muito alto. Devido os resíduos poliméricos serem potencialmente recicláveis, apresentar boas propriedades térmicas e mecânicas, torna-se viável o desenvolvimento de pesquisas que visem caracteriza-los de modo a verificar sua viabilidade de aplicação como piso para instalação de produção animal. A presente pesquisa analisou a combinação entre o resíduo de EVA e a borracha regenerada oriunda de pneus, onde foram produzidas amostras em 4 diferentes concentrações: 0, 25, 50 e 75% de borracha regenerada. As amostras foram analisadas através da microscopia eletrônica de varredura e submetida a testes de tração, deformação permanente à compressão, abrasão e dureza. A amostra com 75% apresentou maior maciez e menor deformação residual, sendo este um efeito positivo devido a redução da rigidez devido a inserção de borracha aos compostos, no entanto, devido a incompatibilidade das blendas e declínio significativo das propriedades mecânicas analisadas, a amostra sem borracha regenerada apresenta melhor potencial de reciclagem e de aplicação a qual a pesquisa a destina. Estima-se que a melhoria de propriedade pode ser alcançada com uso de agente compatibilizante que favoreça a adesão entre os materiais.

Resumo em Inglês:

ABSTRACT The choice of floor type within the animal production system is an important factor, as it is associated with a high incidence of changes in locomotion, hoof injuries and herd disposal, which has led producers to modify the type of flooring for more comfortable, durable and dry materials, such as rubber, however, the raw material makes the investment very high. Because polymeric waste is potentially recyclable and has good thermal and mechanical properties, it is feasible to develop research aimed at characterizing them in order to verify their feasibility of application as flooring for animal production installations. The present research analyzed the combination between the EVA residue and the regenerated rubber from tires, where samples were produced in 4 different concentrations: 0, 25, 50 and 75% of regenerated rubber. The samples were analyzed by scanning electron microscopy and submitted to tensile, permanent deformation under compression, abrasion and hardness tests. The sample with 75% showed greater softness and less residual deformation, which is a positive effect due to the reduction of stiffness due to the insertion of rubber in the compounds. However, due to the incompatibility of the blends and a significant decline in the mechanical properties, the sample without regenerated rubber has a greater potential for recycling and application for which the research aimed for. It is estimated that the property improvement can be achieved with the use of a compatibilizing agent that favors the adhesion between the materials.

Resumo em Inglês:

ABSTRACT In view of the poor weldability of electrodes in resistance spot welding (RSW) of galvanized steel sheets, the life of oriented multi-walled carbon nanotubes reinforced Cu matrix composites (Cu@MWCNTs/Cu) electrodes was studied, in which Cu coated multi-walled carbon nanotubes (MWCNTs) are arranged along the flow direction of working electric/force. By analyzing the macro/microscopic morphology, microstructure, hardness, texture and composition of the failed composite electrodes and the commercially CuCrZr electrode, the mechanism of the weldability enhancement and failure of electrodes was discussed. The results show that the life of Cu@MWCNTs/Cu electrodes (2150 welds) is 3 times longer than that of CuCrZr electrode (600 welds), and the degradation rate is much slower. The hardness of Cu@MWCNTs/Cu electrodes is 30–40Hv higher. The content of recrystallized and recovery grains of Cu@MWCNTs/Cu electrodes is less. This is due to the pinning effect of MWCNTs, and straight and long MWCNTs are arranged along the electrical/force direction. These improve the hardness, mechanical properties, conductivity, and resistance to thermal deformation, cracking, and pitting of Cu@MWCNTs/Cu electrodes, which effectively slows down the failure rate and makes the spot welding life of Cu@MWCNTs/Cu electrodes longer. This work provides a new idea for the application of CNTs/Cu composites.

Resumo em Português:

RESUMO A soldagem de aços dissimilares, como os aços inoxidáveis duplex e superausteníticos é muitas vezes utilizada em aplicações industriais. O efeito da energia de soldagem na zona termicamente afetada (ZTA) e zona de fusão (ZF) apresenta lacunas de conhecimento a serem pesquisadas em relação às propriedades metalúrgicas e mecânicas destes aços. Variações na aplicação da energia da soldagem podem favorecer a presença de maior volume das fases ferrítica ou austenítica, e em casos mais críticos, ocasionar a formação de precipitados deletérios à resistência a corrosão. Este trabalho tem o objetivo avaliar as propriedades metalúrgicas, mecânicas e a resistência à corrosão da soldagem dissimilar composta de aço inoxidável duplex S32205, como metal de base, e aço inoxidável superaustenítico como metal de solda. Verificou-se os efeitos na microestrutura, sensitização e anisotropias com aplicação de diferentes aportes térmicos. Na análise microestrutural foi verificado a formação de constituintes de primeira fase, como a austenita de contorno de grãos (GBA), austenita de witmanstatten (WA), austenita intragranular (IGA) e austenita secundária (γ2). Os valores de microdureza encontrados foram superiores aos referenciados na literatura. Nos ensaios de corrosão, em ambientes com cloretos oxidantes, as amostras apresentaram corrosão por pitting, sendo detectada elevada perda de massa nos corpos de prova. Conclui-se que na ZTA as características metalúrgicas se mantiveram após a variação do aporte térmico e na ZF houve incremento da perda de massa no ensaio de corrosão nas amostras analisadas.

Resumo em Inglês:

ABSTRACT The welding of dissimilar steels such as duplex and superaustenitic stainless steels is often used in industrial applications. The effect of welding energy on the heat-affected zone (ZTA) and fusion zone (ZF) presents knowledge gaps to be researched in relation to the metallurgical and mechanical properties of these steels. Variations in the application of welding energy can favor the presence of a greater volume of the ferritic or austenitic phases, and in more critical cases, cause the formation of precipitates harmful to corrosion. This work aims to evaluate the metallurgical, mechanical properties and corrosion resistance of dissimilar welding composed of duplex stainless steel S32205, as base metal, and superaustenitic stainless steel as weld metal, verifying the effects on microstructural, sensitization and anisotropies with the application of different heat inputs. In the microstructural analysis, the formation of first phase constituents, such as grain boundary austenite (GBA), witmanstatten austenite (WA), intragranular austenite (IGA) and secondary austenite (γ2) was verified. The microhardness values found were higher than those reported in the literature. In the corrosion tests, in environments with oxidizing chlorides, the samples showed pitting corrosion, with a high loss of mass in the specimens being detected. It is concluded that in the ZTA the metallurgical characteristics were maintained after the variation of the thermal input and in the ZF there was an increase in the loss of mass in the corrosion test in the analyzed samples.

Resumo em Inglês:

ABSTRACT The application of intelligent materials in drilling fluids has greatly reduced the investment of human resources and effectively made up for the shortcomings of traditional drilling fluids, such as insufficient directivity, poor adaptive ability and difficult monitoring. Therefore, the research of intelligent drilling fluids is a valuable direction for the future oil and gas industry. In this study, the temperature-sensitive modified bentonite NIPAM-B developed by Pan Yi et al. was used as the drilling fluid base slurry, and the drilling fluid additives were optimized to complete the modulation of the intelligent drilling fluid inspection system. In addition, the rheology, filtration, shale wellbore stability and stability of the intelligent drilling fluid inspection system will be evaluated. The results show that the intelligent drilling fluid has good temperature-sensitive thickening performance, and the rheology is not affected by temperature changes, which can realize intelligent heating and thickening. In addition, compared with the original bentonite drilling fluid system, the intelligent drilling fluid has good fluid loss reduction ability and shale borehole wall protection ability, and the shale rolling recovery rate reaches more than 95 %.

Resumo em Inglês:

ABSTRACT Introduction: Surface treatment is an important technique to increase adhesion between implants and bones, improving its mechanical characteristics and consequently the patient’s comfort. Objectives: Ni-Cr alloys were the object of study in this work, with the purpose of analyzing and evaluating the effect of thin films deposition of titanium nitride via plasma, on its surface and comparing with cathodic cage (CC) and hollow cathode (HC) methods, for dental applications. Methods: Eighteen samples were prepared and the experiment was conducted in two steps: the pre-sputtering (1h, 350 °C, gases: Ar and H) and sputtering (4h, 450 °C, gases: Ar, Ni, and H). To characterize and compare the samples with those of reference, the Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Vickers Microhardness and wettability tests were used. Results: The results presented by SEM showed that during the surface treatment using CC, voids were formed, and using HC, the samples showed a more homogenous behavior. In microhardness tests, using a 25gf load, it was possible to observe that the HC method allowed an increase of 87% when compared to the reference and treated samples. Significance: Lastly, it can be concluded that both methods are suitable for Ni-Cr alloy surface treatment, and the HC technique, a method already used by dental professionals, presents better results due to the formation of a thicker film layer.

Resumo em Inglês:

ABSTRACT The function of the automotive braking system is to reduce the vehicle’s speed or stop within a stipulated time. An efficient braking system dissipates all heat generated during braking into the environment before subsequent braking is applied. The heating and cooling cycles, in combination with mechanical loads during braking operation, cause thermal stresses on the surface of the brake disc. The resulting thermomechanical fatigue (TMF) on the brake disc is a life-limiting factor and causes failure. Understanding their impact, given experimental investigation using a full-scale inertia brake dynamometer is the paramount aspect. The reference disc, that is used for the experiment is a wheel-mounted brake disc. During the investigation, it is observed that (i) friction coefficient is sensitive to vehicle speed and braking pressure (ii) fade test records a maximum brake disc temperature of 403°C (iii) repeated thermal and mechanical cycles induced plastic deformation and cracks on the brake disc. The study provides insight into the parameters contributing to the damage at the friction surface of the brake disc that is subjected to Thermo Mechanical Fatigue (TMF).

Resumo em Português:

RESUMO Usualmente, no desenvolvimento de projetos, adota-se que o comportamento das ligações viga-pilar do sistema estrutural é idealizado por meio de dois extremos: as ligações flexíveis em que nenhum momento é transmitido entre o pilar e a viga e esses elementos se comportam independentemente; e as ligações totalmente rígidas nas quais ocorre a transmissão total do momento. Entretanto, nas estruturas reais, investigações experimentais têm demonstrado que a maioria das conexões devem ser tratadas como ligações semirrígidas. Esse comportamento é descrito por intermédio de curvas momento-rotação, que, por sua vez, devem ser incorporadas à análise estrutural para que se obtenha informações mais precisas sobre o desempenho da conexão. Para tanto, este artigo apresenta a aplicação do método dos Mínimos Quadrados para a simulação do comportamento semirrígido de ligações de pórticos planos metálicos, por intermédio do acoplamento com um modelo numérico-computacional para predição de pórticos com comportamento não linear geométrico e ligações semirrígidas. Para tanto, utiliza-se a formulação Corrotacional de Elementos Finitos, considerando a teoria de viga de Euler-Bernoulli. A ligação entre os membros estruturais é simulada por um elemento híbrido. O sistema de equações não lineares é solucionado pelo procedimento incremental-iterativo de Potra-Pták, associado à técnica de continuação Comprimento de Arco Cilíndrico. Quatro estruturas encontradas na literatura são analisadas com o código computacional desenvolvido, em que é possível verificar que o método proposto apresentou bons resultados numéricos quanto à obtenção do caminho de equilíbrio da estrutura considerando a deterioração da ligação.

Resumo em Inglês:

ABSTRACT Usually, in the development of projects, it is assumed that the behavior of the connections between the beam-column of the system is idealized through two extremes: the flexible connections in which no moment is transmitted between the column and the beam and these elements are behave independently; and the fully rigid connections in which full moment transmission occurs. However, in real structures, experimental investigations have shown that most connections should be treated as semi-rigid connections. This behavior is described by means of moment-rotation curves, which, in turn, must be incorporated into the structural analysis in order to obtain more accurate information about the performance of the connection. Therefore, this article presents the application of the method of Ordinary Least Squares for the simulation of the semi-rigid behavior of connections of metallic plane optics. Through coupling with a numerical-computational model for prediction of frames with geometric nonlinear behavior and semi-rigid connections. For this purpose, the Corrotational Finite Element formulation is used, considering the Euler-Bernoulli beam theory. The connection between the structural members is simulated by a hybrid element. The system of nonlinear equations is solved by the incremental-iterative procedure of Potra Pták, associated with the Cylindrical Arc Length technique. Four structures found in the literature are analyzed, when compared, it is possible to affirm that the proposed method presented excellent results, faithfully representing the equilibrium path of the structure considering the deterioration of the connection.

Resumo em Inglês:

ABSTRACT Cracks in concrete structures are caused due to contraction and expansion irregularities, from potential damages caused in the buildings. These irregularities and damages are assessed by the engineers manually or through identification and prediction models with machine learning techniques to evaluate the impact and significance of the structural health in buildings. This research aims at applying machine learning based on VGG16-Net model for the detection of cracks in concrete structures. The proposed model is of CNN (convolutional neural network) + VGG neural network based architecture. The study uses the gradient boosting algorithm for image segmentation. The datasets are obtained from “Kaggle” resource and the library used is ‘Hugging Face Transformers’. To evaluate the developed models’ performance metrics such as “accuracy, precision, recall and f1-score” are used. The ‘accuracy’ score obtained is compared against the ‘ViT’ (Google transformer) accuracy rate, for comparison. The proposed model achieved 98% validation accuracy rate with 0.3% loss. Thus the developed research contributes an innovative and a novel ML model that predicts and identifies the cracks in concrete structures with less loss and higher accuracy with CNN architecture than ViT (vision transformer) models. Current study also provides more input upon CNN being more accurate than ViT models for future researchers for comparative analyses.

Resumo em Português:

RESUMO A argamassa estabilizada tem como característica o tempo de pega estendido. O emprego de aditivos incorporadores de ar e estabilizadores de hidratação são fundamentais para manter o estado fresco da argamassa em obra e com trabalhabilidade adequada. Esse trabalho analisou a influência combinada desses aditivos, com o objetivo de contribuir com a dosagem de argamassas. Foram ensaiadas nove formulações, as quais variaram o teor de aditivos, entre o máximo e o mínimo recomendado pelo fabricante. Os ensaios no estado fresco foram: índice de consistência, densidade de massa e teor de ar incorporado e Squeeze-flow; e no estado endurecido para: resistência à tração na flexão e à compressão e resistência de aderência à tração. Verificou-se a eficiência dos aditivos em manter as propriedades reológicas das argamassas, mantendo-as trabalháveis, porém também se identificou perda das propriedades mecânicas no estado sólido, devido a problemas de hidratação decorrente do excesso de aditivo estabilizador de hidratação e pela formação de vazios pelo uso de incorporador de ar. Dessa forma, conclui-se sobre a importância da compatibilização entre os aditivos em conjunto e o controle tecnológico na dosagem das argamassas, para que elas se mantenham trabalháveis sem perder as propriedades mecânicas necessárias para um bom desempenho e durabilidade.

Resumo em Inglês:

ABSTRACT The stabilized mortar feature is an extended setting time. The use of air-entraining admixture and hydration control admixtures are essential to maintain the fresh stage of the mortar on site and with adequate workability. This paper analysed the combined influence of these additives, aiming to contribute to the mortar dosage. Nine formulations were tested, which varied the content of additives, between the maximum and the minimum recommended by the manufacturer. The tests in the fresh stage were: consistence index, specific gravity and air entrained content and Squeeze-flow; and in the hardened stage were: flexural and the compressive strength and tensile bond strength. The efficiency of the additives in maintaining the rheological properties of the mortars, keeping them workable, was verified, but a loss of mechanical properties in the solid stage was also identified, due to hydration problems due to excess hydration control admixtures and the formation of voids by use of air-entraining admixture. Thus, it is concluded about the importance of compatibility between admixtures together and technological control in the dosage of mortars, so that they remain workable without losing the mechanical properties necessary for good performance and durability.

Resumo em Inglês:

This work presents a study on the interference of kaolinite particles, smaller than 10 µm, in the performance of the cationic flotation of quartz. The surface properties control the effects of heteroaggregation and provide the creation of a coverage of these ultrafine on the coarser particle surfaces (slime coating), which makes it difficult for the collectors to adsorb and/or contact the air bubbles. The flotation experiments revealed that the etheramine collector used is capable of recovering 76.9% of ultrafine kaolinite in the absence of coarse quartz particles. On the other hand, the flotation results carried out with the binary mixture (quartz −150 + 45 µm and kaolinite ultrafines −6 µm) and in the presence of the same reagent system showed that kaolinite floats together with quartz depending on the content of ultrafines in the suspension. Micrographs from MEV/EDS showed that a heterocoagulation between coarse quartz particles and kaolinite ultrafine with a formation of hydrophobic agglomerates can be recovered in the flotation.

Resumo em Inglês:

ABSTRACT Sorafenib is an oral multi-target kinase inhibitor that has been used to treat unresectable hepatocellular carcinoma and advanced renal cell carcinoma. The aim of the study was to prepare gum Arabic-chitosan (GA-CS) and gum Arabic-modified chitosan (GA-MCS) microcapsules containing sorafenib as the core phase by complex coacervation. The fluorescence microscopy, dynamic light scattering (DLS), drug loading, and encapsulation efficiency of the microcapsules were clarified. The GA-MCS microcapsule was successfully performed at approximate pH of 4 with a 1% modified chitosan -to- 5% gum Arabic ratio of 5:1 (v/v), while the GA-CS microcapsule was successfully prepared at pH 3.5 with a volume ratio of 1% chitosan -to- 5% gum Arabic 1:1 (v/v). Sorafenib was encapsulated in the microcapsules as shown through the fluorescence microscopy images. The formation of GA-CS and GA-MCS microcapsules with hydrodynamic sizes of 6.31 μm and 6.56 μm, respectively, was successfully achieved. The drug loading and encapsulation efficiency of the GA-MCS microcapsule was greater than that of the GA-CS microcapsule. The findings indicated that the GA-MCS microcapsule could be an appropriate formation to load sorafenib with a high encapsulation yield.

Resumo em Português:

RESUMO O presente trabalho avaliou o efeito do tratamento térmico no comportamento acústico em madeira de mogno africano (Khaya ivorensis A. Chev.) submetida a dois tipos de tratamentos, denominados tratamento a seco (TS), realizado em mufla elétrica a temperaturas de 130, 160 e 190 °C, e tratamento hidrotérmico (TH), utilizando vapor de água em autoclave nas temperaturas e pressões de 123 °C e 1,2 kgf.cm−2 e 160 °C e 6,0 kgf.cm−2, respectivamente. Os tratamentos foram realizados em conformidade com um planejamento experimental. Após os tratamentos, as amostras foram submetidas à avaliação acústica através de ensaios por vibração mecânica, utilizando a técnica de excitação por impulso transversal, como previsto na norma ASTM-E1876. As grandezas acústicas determinadas foram: frequência de ressonância transversal (fr(Tr)), decaimento logarítmico transversal (Dl(Tr)), módulo de elasticidade dinâmico específico transversal (Eesp(Tr)) e eficiência da conversão acústica transversal (ECA(Tr)). De acordo com os resultados obtidos, a madeira modificada em autoclave a 123 °C se destacou em relação aos outros tratamentos, inclusive dos conjugados. Foram verificados aumentos de 7,3 % para fr(Tr), 10,8 % para o Eesp(Tr) e 26,4 % para o ECA(Tr), e redução de 11,9 % para Dl. Tais resultados indicam otimização das propriedades do mogno africano para aplicações acústicas.

Resumo em Inglês:

ABSTRACT The present work evaluated the effect of thermal treatment on the acoustic behavior of african mahogany wood (Khaya ivorensis A. Chev.) submitted to two types of thermal treatments called dry treatment, carried out in an oven at temperatures of 130, 160 and 190 °C, and wet treatment, using steam in an autoclave at temperatures and pressures of 123 °C and 1.2 kgf.cm−2 and 160 °C and 6.0 kgf.cm−2, respectively. Conjugated treatments were also carried out, where part of the samples first went through wet treatment and after that, through dry treatment. After treatments, the samples were submitted to acoustic evaluation through mechanical vibration tests, using the transverse impulse excitation technique, as reported for in the ASTM-E1876 standard. The fundamental resonance frequency (fr), the specific transverse dynamic (Espe), the logarithmic decrement of damping (LDD) and the acoustic conversion efficiency (ACE) were determined. According to the results obtained, the wood treated only by steam in an autoclave at 123 °C stood out in relation to the other treatments, including the conjugated was. An increase of 7.3 % was verified for the fr, 10.8 % for Eesp and 26.4 % for ECA, and reduction of 11.9 % for Dl. It was observed the optimization of African mahogany’s acoustic properties.

Resumo em Português:

RESUMO Efluentes industriais contendo contaminantes orgânicos e inorgânicos são despejados em mananciais causando prejuízo aos organismos aquáticos e, consequentemente, sérias doenças ao ser humano. Nesta pesquisa foi investigada a capacidade de adsorção frente ao azo corante vermelho de metila pelo resíduo industrial proveniente da fabricação do silício metálico, os resultados foram ajustados aos modelos de isotermas de adsorção de Temkin, Freundlich e Dubinin-Radushkevich. Realizou-se a caracterização granulométrica, morfológica e química do material. Técnicas como MEV-EDS e ICP-OES foram utilizadas. Para o resíduo foi determinado o ponto de carga zero (pHPCZ) e a influência do pH e da velocidade de agitação na capacidade de adsorção. As características do equilíbrio de adsorção foram determinadas aplicando-se os modelos lineares de isotermas de adsorção de Freundlich, Tempkin e Dubinin-Radushkevich, já os processos cinéticos foram avaliados utilizando-se os modelos lineares de pseudo-primeira ordem, pseudo-segunda ordem, Elovich e difusão intrapartícula. A caracterização por MEV/EDS indicou que o resíduo apresenta um teor de 63,75% de SiO2. O percentual de remoção do corante em meio aquoso chegou a 80% a partir da concentração de 15 mg/L. O modelo de pseudo-segunda ordem, com R2 igual a 1,0000 e Q2 de 0,9999, foi o que melhor se ajustou às condições de cinética de adsorção e o de Temkin, cujos valores de R2 e Q2 foram 0,9008 e 0,7929, respectivamente, foi o que melhor representou o equilíbrio. O processo de adsorção foi caracterizado como sendo favorável e os resultados indicam que o resíduo apresenta potencial para ser utilizado como adsorvente do corante vermelho de metila.

Resumo em Inglês:

ABSTRACT Industrial effluents containing organic contaminants and inorganics are discharged into water sources, causing damage to aquatic organisms and, consequently, serious diseases to humans. In this research we investigated the adsorption capacity against methyl red dye nitrogen (adsorbent) by the industrial residue (adsorbent) from the manufacture of silicon metal, the results were adjusted to the adsorption isotherm models. The granulometric, morphological and chemical characterization of the material was performed. Techniques such as SEM-EDS and ICP-OES were used. For the residue, the zero load point (pHPCZ), influence of pH and agitation velocity on the adsorption capacity were measured. The characteristics of the adsorption equilibrium were determined by applying the Freundlich, Tempkin and Dubinin-Radushkevich linear adsorption isotherms, while the kinetic processes were availed using the linear models of pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion. The pseudo-second order model, with R2 equal to 1,0000 and Q2 of 0,9999, was the best fit to the adsorption kinetic condition and Temkin model, whose R2 and Q2 values were 0,9008 and 0,7929, respectively, was the one that best represented the equilibrium observed. The adsorption process was characterized as being favorable and the results indicated that the residue has potential to be used as an absorbent for methyl red dye.

Resumo em Inglês:

ABSTRACT The significant features of the GFRP angle make it one of the modern construction members for the present lattice-type Transmission Line Towers (TLT) made out of mild steel. The GFRP structural angle members with gusset plate connections for net-crushing strength are investigated in this study, with an emphasis on connections to transmission line towers. Forty-two specimens of single-lap, butt joints with bolted connections are considered in this study. The gusset plate and edge distance have different widths. The joint is subjected to a compression load before failure modes and the associated loads were noticed. An experimental investigation on the crushing behaviour of GFRP angle sections to determine the crushing performance against the standard crushing force of different connections such as bolted, adhesive, and hybrid (bolted + adhesive) with various joints (butt and lap) has been carried out and are presented. Additionally, the impact of plate edge distance and width on connection effectiveness is investigated. The innovation of the work is in the evaluation of the crushing value for bolted GFRP structural angle members of 2, 3, and 4 nos with gusset plate connections that have been used to predict the compressive strength.