Orientador: Manoel Cleber de Sampaio Alves / Banca: Marcos Valério Ribeiro / Banca: Eduardo Carlos Bianchi / Banca: Ivaldo Domênico Valarelli / Banca: Fabio Minoru Yamaji / Resumo : O processo de lixamento é indispensável para situações onde os processos anteriores de fabricação não foram capazes de garantir as dimensões finais da peça produzida ou quando a qualidade superficial desejada não foi atingida. Este processo é muito usado em indústrias de painéis e de móveis, no entanto, quase sempre é empregado de forma empírica, sem o conhecimento adequado. No presente trabalho analisou-se a influência da granulometria, do desgaste abrasivo e do material abrasivo no lixamento plano da Corymbia citriodora e do Pinus elliottii. O objetivo do trabalho foi estudar e compreender a correlação entre os fatores de entrada (granulometria da lixa, desgaste do abrasivo, tipo do abrasivo) sobre as variáveis de saída (potência de lixamento, emissão acústica, vibração, rugosidade e integridade superficial) no processo de lixamento. O sistema desenvolvido e utilizado foi composto por uma lixadeira plana, um sistema de aquisição de dados e um sistema eletromecânico de ensaios com acionamento pneumático. Para a análise da influência da granulometria, do desgaste e do tipo do abrasivo foram utilizadas três granulometrias (80, 100 e 120 mesh), três tipos de grão abrasivos (óxido de alumínio, carbeto de silício e óxido de zircônio), três níveis de desgaste do grão abrasivo (sem desgaste, desgaste intermediário, desgaste severo) e duas espécies de madeira sendo realizadas seis repetições para cada configuração de ensaio, totalizando 324 ensaios. Os resultados foram analisados estatisticamente através de análise de variância (ANOVA) com nível de significância de 5%, acompanhado do teste de Tukey, que compara as variações aos pares. O sistema eletromecânico de ensaios de lixamento projetado mostrou-se bastante eficiente na aquisição dos dados. O desgaste do grão abrasivo influenciou significativamente ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The sanding process is indispensable for situations where the manufacturing processes were not sufficient to ensure the final dimensions or when the desired surface quality was not achieved. This process is frequently used in panels and furniture industries, however, is almost always used empirically, without the proper knowledge. In the present study we analyzed the influence of particle size, abrasive wear and the abrasive type on Corymbia citriodora and Pinus elliottii sanding. The objective was to study and understand the correlation between the input factors (particle size, abrasive wear, abrasive type) on the output variables (power sanding, acoustic emission, vibration, roughness and surface integrity) in sanding process. The system developed and used consists of a flat sander, a data acquisition system and an electromechanical testing system with pneumatic actuation. It was used three particle sizes (80, 100 and 120 mesh), three types of grain abrasives (aluminum oxide, silicon carbide and zirconium oxide), three levels of abrasive wear (no wear, intermediate wear, severe wear) and two species of wood for the analysis, it was made six replications for each test configuration, totaling 324. The results were statistically analyzed using variance analysis (ANOVA) with a significance level of 5%, followed by the Tukey test, which compares the variations in pairs. The electromechanical testing system designed sanding proved to be very efficient in data acquisition. The abrasive wear influenced significantly roughness in both species and all abrasive grains types. The variables that wear influenced less were acoustic emission and vibration. The best values of roughness were obtained for aluminum oxide grains and the worst for silicon carbide grains. The SEM images and topography were important to understand the interaction of the abrasive grain with wood surface / Doutor

Orientador: Ricardo Marques Barreiros / Banca: Fred Willians Calônego / Banca: Fábio Minoru Yamaji / Banca: José Cláudio Caraschi / Banca: Franciane Andrade de Pádua / Resumo : Métodos tradicionais de proteção de madeira empregam produtos químicos que são considerados tóxicos e podem prejudicar a saúde humana e o meio ambiente. O aumento da preocupação com as questões ambientais, com a saúde dos operadores de processos de tratamento preservativo e dos consumidores da madeira, e ainda com o reaproveitamento destas madeiras tratadas após seu uso, tem gerado a necessidade de desenvolvimento de tratamentos preservativos menos agressivos à saúde e ao meio ambiente. O objetivo deste estudo foi testar a potencialidade de três condições de amostras de Tall Oil, em duas espécies para as madeiras de reflorestamento: Pinus elliottii e Eucalyptus grandis. As alternativas de Tall Oil testadas foram o Crude Tall Oil (CTO), que é um subproduto no processamento de polpa de coníferas resinosas, para produção do papel Kraft, e dois subprodutos do refino do CTO, o Ligth Oil (LO) e o Óleo Ejetor (OE). Estas alternativas foram testadas em solução isopropílica a 25% e em combinação com ácido bórico em solução aquosa a 2%. Foram realizados ensaios de hidrofobicidade e de exposição ao fungo de podridão branca (Trametes versicolor (L.; Fr.) Pilát) nas amostras com os sistemas de proteção aplicados. O ensaio de hidrofobicidade foi realizado pela medida do ângulo de contato em um Goniômetro. O ensaio de apodrecimento foi conduzido dispondo os corpos de prova tratados em solo com o fungo inoculado. Os resultados obtidos mostraram que as condições de Tall Oil possuem potencialidade para proteger a madeira contra ataque do fungo de podridão branca e esta proteção não está diretamente relacionada com o grau de hidrofobicidade do tratamentos aplicados nas amostras de madeira. Os resultados mais satisfatórios foram obtidos com os tratamentos com Óleo Ejetor, que apresentou hidrofobicidade de 55%, tanto para ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Traditional methods of wood protection employ chemicals that are considered toxic and can harm human health and the environment. Increasing concern about environmental issues, with the health of process operators to preservative treatment of timber and consumers, and with the reuse this timber treated after use, has generated the need for development of less aggressive treatments condoms to health and the environment. The aim of this study was to test the capability of three conditions of samples from Tall Oil in two species for reforestation wood: Pinus elliottii and Eucalyptus grandis. The alternatives were tested tall oil Crude tall oil (CTO), which is a by-product in the processing of coniferous softwood pulp for the production of kraft paper and two by-products from the refining of CTO, the ligth Oil (LO) and the Oil ejector (OE). These alternatives were tested isopropyl and 25% solution in combination with boric acid in a 2% aqueous solution. In samples with the systems of protection; tests hydrophobicity and exposure to white rot fungus (Fr.) Pilát Trametes versicolor (L.) were performed. The hydrophobicity assay was performed by measuring the contact angle on a goniometer. The test was conducted rotting providing the specimens treated soil inoculated with the fungus. The most satisfactory results were obtained with treatments with Ejector Oil, which showed hydrophobicity of 55%, both for pine as for eucalyptus, and mass loss of 39.07% for eucalyptus and 39.18% for pine after test exposure apodrecedor fungus. And for systems with boric acid mass loss was lower, being for AB + OE mass loss was 19.05% for eucalyptus and 19.96% for pine; and the OE / AB system and 13.43% for eucalyptus and 14.16% for pine / Doutor

Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-09-26T14:20:44Z No. of bitstreams: 1 CLÁUDIA DA SILVA BATISTA - TESE (PPGEP) 2009.pdf: 3258402 bytes, checksum: 334bd2bbc1cb52f81aa523fd16f4b763 (MD5) / Made available in DSpace on 2018-09-26T14:20:44Z (GMT). No. of bitstreams: 1 CLÁUDIA DA SILVA BATISTA - TESE (PPGEP) 2009.pdf: 3258402 bytes, checksum: 334bd2bbc1cb52f81aa523fd16f4b763 (MD5) Previous issue date: 2009-11-06 / Este trabalho teve por objetivo principal apresentar um estudo teórico e experimental da vazão mássica e do fluxo de produtos granulares para subsidiar o projeto estrutural em silos. Foi desenvolvido um modelo matemático para predizer a vazão de descarregamento para distintos produtos. Estudou-se as características físicas e de fluxo de cinco produtos granulares: painço, areia fina e três farelos de milho, e avaliou-se o comportamento do fluxo das partículas em um silo cilíndrico, equipado com fundo plano e tremonhas de 30 e 45 de inclinação com a vertical; diferentes orifícios de descarga, 3,5 e 5 cm de diâmetro; e três rugosidades das paredes, 0,06, 6,56 e 11,9 m. Concluiu-se que a rugosidade da parede, para a faixa estudada, não influenciou na vazão de descarregamento, para todos os produtos. As maiores vazões de descarregamento no silo foram registradas para a areia e as menores foram observadas para o farelo de milho M1, cuja razão aproximada foi de 2,5 para as diversas formas de descarregamento. As maiores vazões de descarga foram observadas quando o diâmetro do orifício de saída foi de 5 cm chegando a um valor de 1,35 kg/s. As menores vazões de descarregamento dos produtos foram registradas quando se utilizou a tremonha com inclinação de 30 com o valor de 0, 16 kg/s para o produto que apresentou as menores vazões, farelo de milho M1.O fenômeno “slip stick” foi verificado para as diferentes granulometrias do farelo de milho, sendo mais intenso para o M2. O modelo proposto apresentou ajuste razoável em relação aos dados experimentais. / This work was aimed at presenting a theoretical and experimental study of the mass flow and the flow of granular products to support the structural design of silos. We developed a mathematical model to predict the flow of discharge for different products. We studied the physical characteristics and flow of five granular products: millet, fine sand and three meals of corn, and evaluated the flow behavior of particles in a cylindrical silo, equipped with flat bottom hoppers 30 and 45 inclination to the vertical, different discharge outlets, 3.5 and 5cm in diameter and three m.roughness of the walls, 0.06, 6.56 and 11.9 It was concluded that the roughness of the wall, in the range studied did not influence the flow of discharge for all products. The highest rates of discharge were recorded in the silo for sand and the lowest was observed for the corn bran M1, whose approximate ratio was 2.5 for the various forms of discharge. The highest rates of discharge were observed when the diameter of the exit hole was 5 cm reaching a value of 1.35 kg / s. The lowest flow rate of discharge of the products were recorded when using the to the value of 0, 16 kg/s for the product hopper with an inclination of 30 that had the lowest flow rates, corn bran M1.O phenomenon "slip stick" was observed for different particle size of corn bran, being more intense for the M2. The proposed model presented a reasonable adjustment in relation to the experimental data.

Dense flows of grains are commonplace throughout natural and industrial environments, from snow-avalanches down the sides of mountains to flows of cereal down chutes as it is transported from one part of a factory to another. A ubiquitous feature in all of these flows is their ability to separate the different grain types when shaken, stirred, sheared or vibrated. Many flows are sheared through gravity and these flows are particularly efficient at segregating particles based on their size, with small particles percolating to the bottom of the flow and large particles collecting at the top. Within this mechanism, an asymmetry between the large and small particles has been observed, with small particles percolating downwards through many large particles at a faster rate than large particles rise upwards through many small particles. This alternative format thesis presents a revised continuum model for segregation of a bidisperse mixture that can account for this asymmetry. A general class of asymmetric segregation flux functions is introduced that gives rise to asymmetric velocities between the large and small grains. Exact solutions for segregation down an inclined chute, with homogenous and normally graded inflow conditions, show that the asymmetry can significantly enhance the distance for complete segregation. Experiments performed using a classical shear-box with refractive index matched scanning are able to quantify the asymmetry between large and small particles on both bulk and particle scales. The dynamics of a single small particle indicate that it not only falls down faster than a single large particle rises, but that it also exhibits a step-like motion compared to the smooth ascent of the large grain. This points towards an underlying asymmetry between the different sized constituents. The relationship between the segregation-time and the volume fraction of small grains is analysed, and solutions presented for the steady-state balance between segregation and diffusive remixing. These help to show the good agreement between the asymmetric model and experimental data. Segregation at the front of natural avalanches produces a recirculation zone, known as a `breaking size-segregation wave', in which large particles are initially segregated upwards, sheared towards the front of the flow, and overrun before being resegregated again. Solutions for the structure of this recirculation zone are derived using the asymmetric flux model, revealing a novel `lens-tail' structure. Critically, it is seen that a few large particles starting close to the bottom of the flow are swept a long way upstream and take a very long time to recirculate. The breaking size-segregation waves highlight the important interplay between segregation and the bulk velocity field. The properties of flowing monodisperse grains are explored through experiments on a cone that produce a beautiful radial fingering pattern. Equations developed in a conical coordinate system reproduce the measured linear relationship between fingering radius and initial flux, whilst also predicting the slowing and thinning dynamics of the flow. Overall, these results illustrate the complex nature of the granular rheology and provide perspectives for future modelling of segregation in dense granular flows.

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This thesis presents a detailed experimental programme on understanding the mechanics of drilling in porous brittle solids. Gypsum was used as a model material for this experimental study, in which the mechanics of drilling was decoupled into equivalent problems of indentation and cutting. A comprehensive understanding of the mechanics of indentation and cutting was gained by performing experiments in 2-D conditions. A camera and microscope assembly was used to capture images at high temporal and spatial resolution to measure the in situ deformation. Particle image velocimetry (PIV) algorithm was used to measure the deformation parameters such as velocity, strain-rate, strain and volume change. In the last part of this research, drilling experiments were performed in 3-D conditions and an attempt was made for understanding the mechanics of drilling by relating the drilling experiment results to that of indentation and cutting. A series of wedge indentation experiments were performed under 2-D plane-strain conditions. Development of a parabolic zone of deformation, surrounding the indenter, was observed, wherein this size of the deformation zone and the strain accumulation in the deformation zone was a function of the geometry of the indenter. The maximum effective strain decreased and the overall strain field was more diffuse with increase in the wedge angle. Significant volume change was also observed in this deformation zone and the amount of volume change increased with increase in the porosity of the material. The zones of high volume change (compaction bands) were stacked in the form of layers oriented perpendicular to the direction of indentation. These compaction bands were more localized for the case of lower angles of wedge indenter. The extent of the compaction bands was also a function of porosity and spread over a larger area for the case of low porosity samples. A change in the material response was also observed with change in porosity and geometry of the indenter. The appearance of the crack was delayed with increase in porosity and reduction of wedge angle. The experimental results were also used to validate an analytical cavity expansion model. A better prediction of indentation pressure and the size of the deformation zone was possible after volume change corrections were incorporated into the cavity expansion formulation. A series of orthogonal cutting experiments were performed in 2-D plane-strain conditions. The e ect of tool geometry and the depth of cut on the mechanics of cutting was studied with the help of image based measurements and cutting force signatures. Different types of cutting mechanisms were observed for the case of positive and negative rake angle tool. A cyclic increase and decrease in the cutting force was observed in case of positive rake angle cutting tool. The decrease in the cutting force corresponded to the initiation of crack from the tip of the tool. The crack traversed towards the surface of the material and resulted in the removal of a material chip. With progress of cutting, the tool scratched the material surface, giving rise to the gradual increase in the cutting force as it again reached local maxima when the tool completely re-engaged with the material. For the case of negative rake angle, apart from cyclic increase and decrease of the cutting force, there was a development of a triangular dead zone at the tip of the cutting tool. The size of the dead zone varied cyclically with the progress of cutting. The length of crack, which resulted in the removal of the chip from the material, was found to be a function of the rake angle and the depth of cut. Drilling experiments were performed on gypsum samples in 3-D conditions. Two types of twist drills with different helix angles were used for this research work. Experiments were performed on the samples with two different porosities. Thrust force and torque signatures were recorded for five values of depth of cut per revolution. Since these experiments were performed in 3-D, image analysis was not performed. However, in order to ascertain a qualitative understanding of the drilling process, few experiments were performed on the edge of the material surface so that a cylindrical groove with semicircular cross section is made and the exposed surface of the material and the drill were imaged. The normalized thrust force and normalized torque were compared with indentation pressure and cutting force signatures and remarkable similarities between them was found. A transition from ductile to brittle type of response was observed with increase in the depth of cut per revolution, which was similar to what was observed in case of indentation. The magnitude of torque was found to be higher for high helix angle drills, which was counter to what was observed in cutting, which was due to the deposition of the material in helix for high helix angle drills, resulting in the reduction of the effective helix angle. An approximate estimate of the effective helix angle was made with the help of analytical solutions as well as from the qualitative analysis of the images.

This thesis is an experimental study of the fluidization of binary mixture in particulate flows. A fluidized bed with two distributors was built with water being used as carrying fluid. Three types of solid particles of nylon, glass and aluminum of the same size and different densities are used in the experiments. The wall effect on a single particle fluidization, the fluidization of binary mixture of large density difference (nylon and aluminum of density ratio of 0.42), and the fluidization of binary mixture of close density (glass and aluminum with density ratio of 0.91) were investigated. Also, the effect of distributors on mono-disperse and bi-disperse particle fluidization was investigated. Results show that the presence of narrow walls reduces the minimum fluidization velocity for a single particle by as much as nearly 40%. Also, in the case of binary mixture of close density particles, uniform mixing was easily achieved and no segregation was observed, but in the case of large density difference particles, there exists significant segregation and separation. At high velocity, the uniform distributor behaves like a transport bed. To achieve a full bed in the single jet, it requires 1.5 times velocity of the uniform distributor. This behavior determines their application in the industries.

<p>U radu se analiziraju analitički postupci za određivanje<br />opterećenja u silosima, prema teorijskim postupcima i<br />tehničkoj regulativi. Metoda integralnih relacija je<br />primenjena kod formiranja postupaka analize stanja napona u<br />silosima sa pravougaonim ćelijama i silosa sa kružnim<br />ćelijama. U analizama je uvedeno granično stanje ravnoteže i<br />asimptotsko stanje napona materijala u silosu. Na primerima<br />je dato upoređenje rezultata analize stanja napona u silosima,<br />kao i kod analize statičkih uticaja kod kružnih ćelija od<br />dejstva dodatnog lokalnog opterećenja i nesimetričnog<br />opterećenja pri pražnjenju sa velikim ekscentricitetom.</p> / <p>This paper analyzes the analytical procedures for the determination of<br />loads in silos, according to theoretical procedures and technical<br />regulations. The method of integral relations was applied for the<br />establishment of procedures for analyzing the stress state in silos with<br />rectangular cells and silos with circular cells. The analysis is<br />introduced limit state of equilibrium and asymptotic stress state of the<br />material in the silo. The examples given comparison of the results of<br />the analysis of stress state in silos, as well as in the analysis of static<br />forces of circular cells from the effects of patch load and discharge<br />loads for circular silos with large outlet eccentricities.</p>

Abstract Excess pore water pressure can be generated in subgrades of both railway and pavement sub-structures under cyclic loading caused by heavy traffic. When saturated subgrades are subjected to cyclic loading, excess pore water pressures accumulate over time which then could lead to migration of particles into overlying layers. The migration of subgrade soil particles to the upper layers would lead to clogging of pores and reducing the upper layers' drainage capacity. Both excess pore water pressure accumulation and migration of fine particles could negatively affect the long-term performance and service life of the sub-structures and eventually may lead to failure. Understanding the mechanism of both excess pore water pressure and migration of fine particles under cyclic loading is, therefore, essential for not only designing but also further proposing efficient and economical maintenance methods. The main objectives of this research are to (1) investigate excess pore water pressure generation in fine granular materials under cyclic loading and (2) evaluate migration of fine granular materials into overlying layers under cyclic loading.  A series of undrained cyclic triaxial tests were performed to study the excess pore water pressure generation in fine granular materials. Two types of fine granular materials, i.e., railway sand (natural granular material) and tailings (artificial granular material), were selected for this investigation. The cyclic characteristics of these materials, e.g., accumulated strain and excess pore water pressure, were evaluated in terms of number of cycles and applied cyclic stress ratios (CSR). As a result, axial strain and excess pore water pressure accumulated over time due to cyclic loading. However, its accumulations were significantly dependent on CSR values and material types. Finally, a relationship between excess pore water pressure and accumulated strain of the fine granular materials was discovered based on all outputs from the undrained cyclic triaxial tests (both tailings and railway sand samples).  In order to evaluate the migration of fine granular materials into overlying layers under cyclic loading, a modified large-scale triaxial system was used as a physical model test. Samples prepared for the modified large-scale triaxial system composed of a 60 mm thick gravel layer overlying a 120 mm thick subgrade layer (tailings and railway sand). The quantitative analysis on migration of the fine granular materials was based on the mass percentage and grain size of migrated materials collected at the gravel layer. In addition, the cyclic responses (strain and pore water pressure) were evaluated. As a result, the total migration rate of the railway sand sample was found to be small. There were no migrated sand particles pumped up to the gravel surface, i.e., no mud pumping, after the test terminated. The migrated sand particles were observed and collected at the bottom half of the gravel layer. The total migration rate of the tailing sample was much higher than that of the railway sand sample. In addition, the migration analysis revealed that finer tailings particles tended to be migrated into the upper gravel layer easier than coarser ones under cyclic loading. The migrated tailings particles were observed at the surface of the gravel layer after the test ended. It could be involved in significant increases in excess pore water pressure at the last cycles of the physical model test. The findings obtained in this research may provide an additional contribution to the literature dealing with the excess pore water pressure accumulation and its effects on the migration of fine particles under cyclic loading.