Mostrando recursos 1 - 20 de 74

  1. Cement-wood composites : effects of wood species, particle treatments and mix proportion

    Garcez, Mônica Regina; Garcez, Estela Oliari; Machado, A. O.; Gatto, Darci Alberto
    The aim of this research was to investigate the effects of wood species, particle treatments and mix proportion on the physical (density) and mechanical (compressive strength and dynamicmodulus of elasticity) properties of cement-wood composites. Different mix proportions were investigated, based on the cement: wood ratio of 0.3:0.7, in volume, with Pinus elliottii and Eucalyptus grandis sawdust percentages of 0-100, 25-75, 50-50, 75-25 or 100-0. Sawdust particles were pre-treated with either lime or cement coating to improve cement and wood compatibility. Results show that wood species, particle treatments and mix proportions may influence the physical and mechanical properties of cement-wood composites....

  2. Use of the swat model for hydro-sedimentologic simulation in a small rural watershed

    Uzeika, Talita; Merten, Gustavo Henrique; Minella, Jean Paolo Gomes; Moro, Michele
    Mathematical models have great potential to support land use planning, with the goal of improving water and land quality. Before using a model, however, the model must demonstrate that it can correctly simulate the hydrological and erosive processes of a given site. The SWAT model (Soil and Water Assessment Tool) was developed in the United States to evaluate the effects of conservation agriculture on hydrological processes and water quality at the watershed scale. This model was initially proposed for use without calibration, which would eliminate the need for measured hydro-sedimentologic data. In this study, the SWAT model was evaluated in...

  3. Influencia del tiempo de hidrólisis en la obtención de película híbrida con adición de iones cerio para la protección de aceros galvanizados

    Kunst, Sandra Raquel; Ludwig, Gustavo Alberto; Matos Mandujano, José Fidel; Malfatti, Célia de Fraga
    Las películas hibridas actúan como una barrera entre el substrato y el medio, reduciendo la velocidad de entrada del agua, electrolito, oxígeno y la penetración deiones agresivos hasta el metal, disminuyendo la velocidad de corrosión del substrato. Los principales factores que influyen en la resistencia a la corrosión de las películas híbridas son: el tiempo de curado, la concentración del baño, el pH de la solución de hidrólisis y el tiempo de hidrólisis. En este trabajo, se realizaron las pruebas con cuatro diferentes tiempos de hidrólisis (1, 3, 24 y 48 horas), el acero galvanizado fue revestido con una película...

  4. Influencia del tiempo de hidrólisis en la obtención de película híbrida con adición de iones cerio para la protección de aceros galvanizados

    Kunst, Sandra Raquel; Ludwig, Gustavo Alberto; Matos Mandujano, José Fidel; Malfatti, Célia de Fraga
    Las películas hibridas actúan como una barrera entre el substrato y el medio, reduciendo la velocidad de entrada del agua, electrolito, oxígeno y la penetración deiones agresivos hasta el metal, disminuyendo la velocidad de corrosión del substrato. Los principales factores que influyen en la resistencia a la corrosión de las películas híbridas son: el tiempo de curado, la concentración del baño, el pH de la solución de hidrólisis y el tiempo de hidrólisis. En este trabajo, se realizaron las pruebas con cuatro diferentes tiempos de hidrólisis (1, 3, 24 y 48 horas), el acero galvanizado fue revestido con una película...

  5. Airline customer loyalty through analysis of stated preference

    Lucchesi, Shanna Trichês; Nodari, Christine Tessele; Larrañaga Uriarte, Ana Margarita; Senna, Luiz Afonso dos Santos
    This study evaluates airline customer loyalty and estimates the switching costs for a domestic airline route in Brazil through a stated preference survey. Several structures of discrete choice models were tested to represent the choice of behavior: multinomial logit, mixed logit random coefficients, multinomial logit incorporating systematic variations of preferences, mixed logit error component and mixed logit error component incorporating systematic variations of preferences. The results showed that loyal passengers are more likely to choose the dominant Brazilian airline Tam. The switching costs of passengers loyal to Tam, for this sample, are equivalent to 15% of the fare, which represents...

  6. Mineral processing and characteristics of coal waste to be used as fine aggregates for concrete paving blocks

    Santos, Cassiano Rossi dos; Tubino, Rejane Maria Candiota; Schneider, Ivo Andre Homrich
    Commercial coal production in the southern region of Brazil has been occurring since the beginning of the twentieth century. Due to the geological characteristics of the region, large amounts of solid wastes are generated. The aim of this work was to evaluate the use of coal waste to produce concrete paving blocks. A procedure to process the coal waste with the purpose of reducing the sulfur content and changing the particle size distribution of the material to meet the specification of fine aggregates was developed. The methodology considered the following steps: (a) sampling of a coal mining waste; (b) gravity...

  7. Processamento de rejeito de carvão visando a redução de custos no tratamento da drenagem ácida de minas : estudo de caso na região carbonífera de Santa Catarina

    Weiler, Jessica; Amaral Filho, Juarez Ramos do; Schneider, Ivo Andre Homrich
    Rejeitos de carvão contêm vários minerais, entre os quais a pirita, que se oxida e gera a drenagem ácida de minas (DAM), um efluente ácido com alto poder poluidor. Atualmente, o setor de mineração de carvão brasileiro controla a DAM por meio do tratamento pelo método de neutralização/precipitação de metais, que consome substanciais quantidades de reagentes e gera um grande volume de lodo. O objetivo deste trabalho foi estudar a minimização da geração da DAM por outra abordagem, o método preventivo de isolamento e exclusão de sulfetos. O processo consiste na remoção da pirita da massa de resíduos, reduzindo a...

  8. Modelagem baseada em agentes para a simulação da dispersão de poluentes em cursos d'agua

    Fan, Fernando Mainardi; Bravo, Juan Martín; Collischonn, Walter
    A atividade antrópica em bacias hidrográficas frequentemente gera efluentes que poluem cursos d’água e tendem a gerar problemas ambientais diversos. Uma ferramenta muito útil para auxiliar a avaliação desses problemas é a modelagem matemática. Uma classe específica de modelos matemáticos com aplicações promissoras na área de recursos hídricos e controle da poluição são os modelos baseados em agentes. Neste trabalho se demonstrou como um modelo baseado em agentes pode ser desenvolvido e utilizado para a simulação de plumas de constituintes conservativos e não conservativos em cursos d’água. Foram apresentadas as suposições feitas para a representação dos fenômenos de advecção, dispersão...

  9. Free opening performance of steel ladle as a function of filler sand properties

    Cruz, Ricardo Thomé da; Pelisser, Gustavo Frassini; Bielefeldt, Wagner Viana; Braganca, Saulo Roca
    The secondary steel refining process uses filler sand as a thermal insulating barrier that separates the liquid metal from direct contact with slide-gate system of the steel ladle. The effective use of this practice must provide a high free opening rate, impacting on increased productivity and quality of steel, reducing the number of stops, thermal loss and even the steel re-oxidation. Both operational parameters and material properties have influence on the free opening rate. In the present work, two chromite-silica sands were analyzed, and some composition changes were proposed. The properties of these materials and the relevant process parameters were...

  10. Effect of the shot peening process on the corrosion and oxidation resistance of AISI430 stainless steel

    Peltz, Jefferson da Silva; Beltrami, Lílian Vanessa Rossa; Kunst, Sandra Raquel; Brandolt, Cristiane de Souza; Malfatti, Célia de Fraga
    Ferritic stainless steels are used in specific applications where corrosion resistance, oxidation resistance and a high mechanical resistance are required. Shot peening is a process applied to add residual compression stresses in metallic surfaces with the intent of improving the material when exposed to corrosion due to stress and fatigue. Some studies about the effect of the shot peening process on the fatigue resistance, bending fatigue behavior, and residual surface stress in the ferritic stainless steels have been performed. However, the effect of the shot peening process on the corrosion and oxidation resistance of the stainless steel is not well...

  11. The influence of long chain branches of LLDPE on processability and physical properties

    Dartora, Paula Cristina; Santana, Ruth Marlene Campomanes; Moreira, Ana Cristina Fontes
    Two polyethylene-based on single-site metallocene catalyst (mLLDPE) were selected to characterize the effect of long chain branching (LCB) on blown film processability, optical and mechanical properties. 13C NMR and parallel plate rheology were used to identify LCB presence on LLDPEs. Blown films were produced from 100% LLDPEs using three different machine direction (MD) stretch ratios. When the same processing conditions for the two LLDPEs grades were used, better processability was observed for LLDPE with LCB. In relation to mechanical and physical properties, Elmendorf tear and optical properties were highly influenced by the presence of LCB. Tear resistance is affected by...

  12. Slope stability analysis at highway BR-153 using numerical models

    Hundelshaussen Rubio, Ricardo José; Flórez Gálvez, Jorge Hernán; Zingano, Andre Cezar
    An existing cut slope on Highway RS-471/BR-153 is studied. The slope is composed of the Serra Geral Formation's material: a highly altered volcanic breccia and above it a slightly altered and very fractured rhyolite. A numerical analysis of the slope is carried out in two dimensions. Fracturing of the rhyolite necessitates the use of a constitutive model for materials with families of discontinuities (Ubiquitous-joint). To simplify the analysis of the problem and to examine some of the most sensitive variables, two more analyses are made, replacing the initial model by a Mohr’s constitutive model, which considers the material as continuous....

  13. Avaliação das propriedades mecânicas e morfológicas de compósitos de PEAD com pó de Pinus taeda e alumina calcinada

    Grison, Karine; Turella, Taís Caroline; Scienza, Lisete Cristine; Zattera, Ademir José
    Neste estudo foram desenvolvidos compósitos utilizando PEAD, pó de madeira (Pinus taeda), alumina calcinada e dois diferentes tipos de agentes compatibilizantes para avaliação das propriedades morfológicas e mecânicas dos mesmos. Para aumentar a interação entre a matriz polimérica e o pó de madeira foram utilizados 2% de polietileno graftizado com anidrido maleico em todas as formulações. Para efeito comparativo foi desenvolvida uma formulação com viniltrietoxisilano como compatibilizante para a alumina calcinada. O teor de cargas variou de 4% a 33% para os compósitos de carga única e mantiveram o percentual de 28% para os compósitos com as duas cargas. A...

  14. In situ synchrotron X-ray powder diffraction study of the early hydration of α-tricalcium phosphate/tricalcium silicate composite bone cement

    Morejón Alonso, Loreley; Motisuke, Mariana; Correa, José Raúl; García Carrodeguas, Raúl; Santos, Luis Alberto dos
    Bioactivity, osteogenicity and mechanical properties of α-tricalcium phosphate (α-TCP) based phosphates cements can be improved by adding tricalcium silicate (C3S); however, the addition of C3S delays the precipitation and growth of calcium deficient hydroxyapatite (CDHA). Thus, the aim of this work was the study of in situ setting reaction of α-TCP/C3S composite bone cement under high energy X-ray generated by a synchrotron source within the first 72h. The results showed that the addition of C3S induces the precipitation of nanosized CDHA at early times depending on the added content. Calculated crystallite sizes showed that the higher the content of C3S,...

  15. Problemas suportados pelos pilotos agrícolas e suas relações com segurança e saúde ocupacional

    Zanatta, Mateus; Amaral, Fernando Goncalves
    Este estudo faz um levantamento da informação qualitativa dos estudos que abordam os problemas suportados pelos pilotos agrícolas na execução de seu trabalho, que podem estar relacionados à saúde e segurança do trabalho. O objetivo é investigar se a evolução das tecnologias utilizadas na aviação agrícola é acompanhada de uma melhoria das condições de trabalho. Para isto, foi realizada uma revisão sistemática da literatura procurando, através de mecanismos de busca informatizados, reunir a informação existente sobre este tema. A síntese dos dados incluiu os fatores de exposição apresentados e as respectivas relações com segurança do trabalho e saúde ocupacional. Os...

  16. Mechanical and metallurgical properties of DP 1000 steel square butt welded joints with GMAW

    Rocha, Ianto Cáceres Leite; Machado, Ivan Guerra; Mazzaferro, Cintia Cristiane Petry
    In this work, Gas Metal Arc Welding (GMAW) was used to study the influence of heat input (i.e. cooling rate) on mechanical/metallurgical properties of square butt welded joints of DP 1000 sheets. The influence of filler metals of different strengths on the mechanical properties of joints was also tested. A significant decrease in hardness was observed in the Heat Affected Zone (HAZ) due to martensite tempering, in regions where peak temperature was close to isotherm AC1 (calculated in 735 oC for these steel); coincidently, fracture in every tensile test occurred in regions where martensite was tempered, even when a wire...

  17. Efeitos da taxa de resfriamento na soldagem do aço API 5L-X80

    Moojen, Roberto Gomes; Machado, Ivan Guerra; Mazzaferro, Jose Antonio Esmerio; Gonzalez, Arnaldo Ruben
    Uma das principais razões para o desenvolvimento do aço API 5L-X80 foi seu uso em Regiões Polares, onde se faz necessário alta tenacidade em baixas temperaturas. Neste trabalho foi estudado o efeito da taxa de resfriamento na soldagem sobre as propriedades mecânicas e metalúrgicas deste tipo de aço. Estas diversas taxas de resfriamento simulam também diversas energias de soldagem. As diferentes taxas de resfriamento foram obtidas através de cinco distintos pré-aquecimentos. A temperatura de interpasse foi igual à temperatura de pré-aquecimento de cada uma das juntas em duplo V com face de raiz, sendo as soldagens robotizadas realizadas por arco...

  18. Residual stress analysis of drive shafts after induction hardening

    Lemos, Guilherme Vieira Braga; Hirsch, Thomas; Rocha, Alexandre da Silva; Nunes, Rafael Menezes
    Typically, for automotive shafts, shape distortion manifests itself in most cases after the induction hardening by an effect known as bending. The distortion results in a boost of costs, especially due to machining parts in the hardened state to fabricate its final tolerances. In the present study, residual stress measurements were carried out on automotive drive shafts made of DIN 38B3 steel. The samples were selected in consequence of their different distortion properties by an industrial manufacturing line. One tested shaft was straightened, because of the considerable dimensional variation and the other one not. Firstly, the residual stress measurements were...

  19. Role of thermodynamics in the shape transformation of embedded metal nanoparticles induced by swift heavy-ion irradiation

    Ridgway, M.C.; Giulian, Raquel; Sprouster, David J.; Kluth, Patrick; Araújo, Leandro Langie; Llewellyn, D. J.; Byrne, A. P.; Kremer, Felipe; Fichtner, Paulo Fernando Papaleo; Rizza, G.; Amekura, H.; Toulemonde, M.

  20. Influence of coupling agent in compatibility of post-consumer HDPE in thermoplastic composites reinforced with eucalyptus fiber

    Catto, André Luis; Stefani, Bruno Vicari; Ribeiro, Vanda Ferreira; Santana, Ruth Marlene Campomanes
    This study investigates the feasibility of using recycled high density polyethylene (HDPE) and wood fiber from species Eucalyptus grandis (EU) to manufacture experimental composite panels. The use of maleated polyethylene as coupling agent (CA) improved the compatibility between the fiber and plastic matrix. The mechanical properties of the resultant composites were compared with polymer with and without compatibilizer. The influence of the coupling agent (CA) in the polymer matrices and composites were evaluated at different concentrations, checking the physical, mechanical and thermal properties of wood plastic composites (WPC). Results of mechanical, physical and thermal properties showed that concentration of 3%...

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