Otimização de parâmetros mecânicos e microestruturais dos moldes em areia de sílica ligados quimicamente pelo processo de cura a frio em fundição de aço

Surface defects on steel parts borne costs of smelting industries due to the need of rework. Sand molds are frequently used in foundry industries and largely responsible for providing surface defects. This study aims to optimize the levels of the molding process variables to minimize the occurrence of surface defects in steel castings in silica sand molds chemically linked by cold cure process. The methodology used the experimental design with split plot, being considered in the study the resin percentage factors in the mold formulation, addition of iron oxide, type of paint, the paint application method, amount of ink layers, use of hot air along the lines and waiting time of the mold before casting. They were analyzed as response variables erosion defects, sand inclusion, penetration, porosity and surface finish. Tensile strength tests were performed to evaluate the influence of factors on mechanical parameters and the microstructural parameters were carried out the analysis of X-ray diffraction, scanning electron microscopy (SEM) and thermal analysis (TG / DSC / dilatometry). The results elucidate that for the faulty erosion, the only significant factor with a 95% confidence level was the type of ink and the ink alumina-based superior results obtained. For the sand inclusion of defect, there were three significant factors, with best results obtained with alumina-based paint and spray applied using hot air in the mold before casting the metal. For the defect penetration, there were four significant factors, the best results being achieved with 0.8% of resin and addition of iron oxide in the molding formulation, the paint being applied by brush and standby time of 24 hours before leak. For the defect porosity with a 95% confidence level, no significant factors. For the defect surface finish, the best results were achieved with the 0.8% formulation of the resin in the mold and application of the paint brush. To obtain the levels of the factors that optimize all defects simultaneously, we performed a weighted average of the results of each type of fault, concluding that the best levels of the factors were: 0.8% resin and addition of iron oxide in the formulation of the template, application of two coats of paint applied with a brush or spray, using hot air in the mold before casting and 24 hours of waiting ready the mold before casting. These levels of the optimized factors were used in an experiment to confirm that ratified the results, helping to reduce rework and consequently reducing costs of cast steel parts.

Duplicação rápida de prótese total: passo-a-passo

This study presents a simple, fast and low cost technique for fabrication new conventional dentures from the duplication of old prosthesis in use by the patient. Colorless acrylic resin was poured into the moulds obtained by duplication of prosthesis. With the replicas obtained a functional impressions using polyether should be performed and they are stabilized with occlusal registration in acrylic resin. The molds need to be castings and mounted on an semi-adjustable articulator. The artificial teeth are positioned with the assistance of a guide made condensation silicone to reproduce the positioning of the teeth of the old prosthesis and fixed with wax 7. After approval of the teeth on the trial in wax, without adjustment of the planes, the prosthesis may be processed in the laboratory. After occlusal adjustment in the articulator the same can be installed.

Caracterização do ciclo da marcha em amputado transtibial com prótese inteligente

This work presents an application of optical fiber sensors based on Bragg gratings integrated to a transtibial prosthesis tube manufactured with a polymeric composite systrem of epoxy resin reinforced with glass fiber. The main objective of this study is to characterize the sensors applied to the gait cycle and changes in the gravity center of a transtibial amputee, trough the analysis of deformation and strengh of the transtibial prosthesis tube. For this investigation it is produced a tube of the composite material described above using the molding method of resin transfer (RTM) with four optical sensors. The prosthesis in which the original tube is replaced is classified as endoskeletal, has vacuum fitting, aluminium conector tube and carbon fiber foot cushioning. The volunteer for the tests was a man of 41 years old, 1.65 meters tall, 72 kilograms and left-handed. His amputation occurred due to trauma (surgical section is in the medial level, and was made below the left lower limb knee). He has been a transtibial prosthesis user for two years and eight months. The characterization of the optical sensors and analysis of mechanical deformation and tube resistance occurred through the gait cycle and the variation of the center of gravity of the body by the following tests: stand up, support leg without the prosthesis, support in the leg with the prosthesis, walk forward and walk backward. Besides the characterization of optical sensors during the gait cycle and the variation of the gravity center in a transtibial amputated, the results also showed a high degree of integration of the sensors in the composite and a high mechanical strength of the material.

A longevidade das organizações no cenário da nova economia

A década de 90 inscreveu as organizações num novo cenário caracterizado pelo aparecimento da denominada nova economia. Outros desafios se colocaram e a luta pela sobrevivência tornou- se uma constante diária para as empresas que operam em actividades altamente competitivas. O presente artigo visa analisar este contexto. Discutem-se as novas preocupações e problemáticas, designadamente as novas competências-chave, a moldagem de futuros competitivos, onde o conhecimento e a aprendizagem são as principais armas de diferenciação entre as organizações. Consequentemente, a informação, a capacidade de absorção e adaptação incessantes e o fascínio pela inovação fazem o diferencial competitivo de algumas empresas centenárias.

Estudo da adição de argila expandida na formulação de concretos leves

Lightweight concrete has been the subject of several studies towards the development of new building materials. Emphasis has been given on the particle size effect and nature of aggregates used as raw materials. The present study includes an analysis of the materials that make this kind of concrete, analyzes of mechanical properties such as compressive and tensile strength, in addition to assessments of the interface concrete aggregate/matrix interface, porosity and absorption profile of chloride ions in lightweight concrete based on expanded clay. The experiments were carried out by molding cylindrical samples 100 mm in diameter and 200 mm in height. The dosage experiments were performed without additives or with the addition of minerals: (T1) 1: 2.01: 1.10: 0.78 (T2) 1: 2.00: 1.32 : 0.62 - (T3) 1 :1.93 :1.54: 0.47 (cement : sand : expanded clay 0500 : expanded clay 1506).The water to cement ratio was set to 0.43. Expanded clay minerals with different average particle sizes were used, i.e., 9.5 mm/0500 and 19 mm/1506. The larger aggregate was coated by a glassy layer, yielding lower water absorption characteristics to the concrete. The results showed that the use of light expanded clay aggregates is a technically interesting solution to the production of lightweight concrete for construction applications

Aprendizaje, voluntariado y comunidades de aprendizaje

Esta comunicación forma parte del proyecto “Ecologías del aprendizaje en contextos múltiples: análisis de proyectos de educación expandida y conformación de ciudadanía”, con referencia EDU2014-51961-P y financiado por MIMECO. La experiencia que se presenta se viene llevando a cabo desde el curso pasado en la Facultad de Ciencias de la Educación, a través de las asignaturas de Organización y Gestión de Centros e Instituciones e Intervención educativa y diversidad sociocultural del Grado de Primaria y consiste fundamentalmente en el desarrollo de un proceso de colaboración con dos centros educativos que son comunidades de aprendizaje. Iniciamos la experiencia desde la conformación de un grupo de voluntarias y voluntarios que semanalmente y de forma rotativa asisten a uno de los centros para participar en grupos interactivos y en el otro centro asisten semanalmente, de forma continua, para participar en todas las actividades del centro. Dos modalidades diferentes de colaboración de acuerdo con las necesidades y el estado de los proyectos de los centros educativos. La experiencia del alumnado que asiste a los centros, se convierte en materia de reflexión para todo el grupo-clase y se comparte con otros grupos de otras universidades, como es el caso de la Facultad de Educación de Soria. La reflexión que se instala en las clases abre diversas vías de aprendizaje: por un lado, el sentido de ser voluntaria y voluntario en la formación de la ciudadanía, por otro, el reconocer la realidad educativa en contexto, en situación y por último la posibilidad de compartir saberes y conocimientos con los demás estudiantes. Entendemos que los procesos de enseñanza y aprendizaje en la universidad no pueden quedar encerrados en las cuatro paredes del aula cuando todas las investigaciones señalan la complejidad del conocimiento, el avance de las redes sociales y la transformación del aprendizaje en procesos más abiertos, menos jerárquicos, más participativos y poniendo en relación a toda la comunidad educativa. Desde una primera valoración de la experiencia a través de relatos orales del alumnado participante compartido con los demás estudiantes y de procesos de autoevaluación al finalizar la asignatura, podemos observar que el sentirse parte de un proyecto institucional así como la participación en el aprendizaje de niños y niñas son aspectos relevantes para su formación y para pensar en que otra escuela es posible al aprender todos de todas.

Estudo da incorporação da cal em composições binárias de solo-cimento para produção de tijolos maciços

The use of binders in the soil for the production of solid bricks is an old construction technique that has been used by several civilizations over time. At the same time, the need for environmental preservation and the tendency of scarcity of natural resources make the construction invest in researching new concepts, methods and materials for building systems for the sustainability of their economic activities. Thus arises the need to obtain building materials with low power consumption, capable of reducing the growing housing shortage of rural and urban population. Currently, research has been conducted on this topic to better understand the cementitious and pozzolanic reactions that occur in the formation of the microstructure of the soil-cement when added to other materials such as, for example, lime, and the relationship between microstructure and formed interfaces with the physical, mechanical and chemical analysis in compounds made from these ternary compositions. In this context, this study aimed to analyze the results of the influence of the incorporation of lime to the soil-cement to form a ternary mixture to produce soil-cement bricks and mortar without structural purposes. From the inclusion of contents of 6 %, 8 %, 10% and 12% lime to the soil, and soil-cement mixes in amounts of 2 %, 3 %, 4 % and 5 % were shaped-bodies of -cylindrical specimens to determine the optimum moisture content and maximum dry apparent specific weight. Then they were cured, and subjected to the tests of compressive strength, absorption and durability modified. Compositions obtained the best results in the tests performed on the bodies-of-proof cylindrical served as a parameter for molding of solid bricks, which underwent the same experimental methodology previously cited. The raw materials used, as well as compositions in which the bricks were molded solid, were characterized by physical and chemical tests, X-ray diffraction and scanning electron microscopy. The results obtained in the study indicate that the compositions studied, that showed the best results in terms of compressive strength, water absorption and durability ternary composition was soil, 10 % cement and 2 % lime

Processamento e caracterização de compósitos Poli(METACRILATO DE METILA)/Sílica (PMMA/SiO2)

Currently the search for new materials with properties suitable for specific applications has increased the number of researches that aim to address market needs. The poly (methyl methacrylate) (PMMA) is one of the most important polymers of the family of polyacrylates and polymethacrylates, especially for its unique optical properties and weathering resistance, and exceptional hardness and gloss. The development of polymer composites by the addition of inorganic fillers to the PMMA matrix increases the potential use of this polymer in various fields of application. The most commonly used inorganic fillers are particles of silica (SiO2), modified clays, graphite and carbon nanotubes. The main objective of this work is the development of PMMA/SiO2 composites at different concentrations of SiO2, for new applications as engineering plastics. The composites were produced by extrusion of tubular film, and obtained via solution for application to commercial PMMA plates, and also by injection molding, for improved the abrasion and scratch resistance of PMMA without compromising transparency. The effects of the addition of silica particles in the polymer matrix properties were evaluated by the maximum tensile strength, hardness, abrasion and scratch resistance, in addition to preliminary characterization by torque rheometry and melt flow rate. The results indicated that it is possible to use silica particles in a PMMA matrix, and a higher silica concentration produced an increase of the abrasion and scratch resistance, hardness, and reduced tensile strength

Sinterização de matrizes cerâmicas à base de alumina reforçadas por carbetos a partir de precursores poliméricos

Ceramic composites produced with polymerics precursors have been studied for many years, due to the facility of obtaining a complex shape, at low temperature and reduces cost. The main objective of this work is to study the process of sintering of composites of ceramic base consisting of Al2O3 and silicates, reinforced for NbC, through the technique of processing AFCOP, as well as the influence of the addition of LZSA, ICZ and Al as materials infiltration in the physical and mechanical properties of the ceramic composite. Were produced ceramic matrix composites based SiCxOy e Al2O3 reinforced with NbC, by hidrosilylation reaction between D4Vi and D1107 mixtured with Al2O3 as inert filler, Nb and Al as reactive filler. The specimens produced were pyrolised at 1200, 1250 and 1400°C and infiltred with Al, ICZ and LZSA, respectively. Density, porosity, flexural mechanical strength and fracture surface by scanning electron microscopy were evaluated. The microstructure of the composites was investigated by X-ray diffraction to identify the presence of crystalline phases. The composites presented apparent porosity varying of 31 up to 49% and mechanical flexural strength of 14 up to 34 MPa. The infiltration process improviment of the densification and reduction of the porosity, as well as increased the values of mechanical flexural strength. The obtained phases had been identified as being Al3Nb, NbSi2, Nb5S3, Nb3Si and NbC. The samples that were submitted the infiltration process presented a layer next surface with reduced pores number in relation to the total volume

Lecturas de la prensa popular: Un estudio de recepción del periódico Q'hubo en la localidad de Kennedy en Bogotá

En este trabajo de grado se aborda la relación entre las audiencias y los medios a partir de un estudio de recepción del diario Q’hubo en los sectores populares de Bogotá, específicamente en la localidad de Kennedy de esta ciudad. El estudio reconoce que las formas determinadas de interactuar con los medios están atadas a los contextos, las instituciones y los entornos culturales y sociales desde los que lector construye su realidad y se inserta en la sociedad actual. Por lo mismo, se nutre de estos elementos para entender los procesos de recepción a través de las formas cotidianas de consumo del diario Q’hubo frente al contexto mediático actual. Se sustenta que el Q’hubo se comunica con sus lectores combinando aspectos clásicos de la prensa popular y adaptando aspectos de diseño y lenguaje aportados por los nuevos medios. Lo que a su vez se relaciona con apropiaciones, usos y modos de leer de la audiencia, que reivindica interacciones tradicionales y desarrolla interacciones emergentes gracias a la convergencia de las tecnologías con la cultura letrada, oral y visual.

FICTION OF THE SELF: A GLANCE AT NANCY HUSTON’S MARCAS DE NASCENÇA

This paper analyzes two works of the canadian writer Nancy Huston: Marcas de nascença and A espécie fabuladora. The main idea is to support the reading of the former work based on the reflections raised by the latter, especially regarding the aspect concerning issues such as the Meaning and the (re) invention of the self. The relevance of these concepts will be effective in an immersion in the universe of the four main characters of the novel Marcas de nascença: Sun, Randall, Sadie and Kristina. The paper focuses on seeking the essence of Meaning in the life of each one of these characters, always considering two vital and non-discernible ​​aspects: time and space in each of them. Therefore, literature and culture concepts will be considered such as the concept of Americanness as well as the Americanization, Identity, Fiction and Recognition. Thus, this assay is divided into two parts. The first one envisions the idea matter expressed by Huston in A espécie fabuladora - the ceaseless quest for Meaning culminating in identity shaping – in order to seek understanding from this point of view the occurrence of certain cultural phenomena of which some characters from Marcas de nascença are an expression. The second part observes each of the four main characters and strengthens the suggested initial idea (that the book's characters are constituent parts of a behavioral matrix vital to human existence), then filling the gaps of the two themes developed: the birthmarks transmitted throughout four generations and how these marks are recorded over fifty-six years of history.