L’étude présentée porte sur le développement d’un modèle numérique destiné à évaluer les performances balistiques d’une structure multicouche polymère/métal frittée par procédé SPS. Les matériaux sont un alliage d’aluminium 7020 et un polyimide thermoplastique amorphe qui sont ensuite assemblés avec une résine epoxy. Le comportement mécanique de ces trois matériaux a été étudié sur de larges gammes de vitesses de déformations (de 0.0001 /s à 50.000 /s) et de températures (de -70°C à 500°C) correspondant aux conditions extrêmes rencontrées lors d’impacts à hautes vitesses. Afin d’améliorer la précision des résultats, des approches analytiques ont été développées autant pour la modélisation du métal que pour celle les polymères. Après la calibration des modèles, ces derniers ont été implémenté dans ABAQUS®/Explicit (éléments finis) via des subroutines VUMAT en code FORTRAN. Des essais d’impacts de billes à hautes vitesses ont été réalisés sur des cibles monocouches pour valider les modèles numériques. De nombreuses configurations de composites multicouches ont ensuite été étudiées numériquement et leurs performances balistiques ont été comparées. / The present study deals with the development of a numerical model to evaluate the ballistic performance of a polymer/metal multilayer structure sintered by SPS. The materials are an aluminum alloy 7020 and an amorphous thermoplastic polyimide which are then assembled using an epoxy resin. The mechanical behavior of these three materials has been studied over wide ranges of strain rates (from 0.0001 / s to 50,000 / s) and temperatures (from -70 °C to 500 °C) corresponding to the extreme conditions encountered during impacts at high velocities. In order to improve the accuracy of the results, analytical approaches have been developed both for the modeling of the metal and for the polymers. After the calibration of the models, these models were implemented in ABAQUS® / Explicit (finite elements) via VUMAT subroutines in FORTRAN code. Ball impact tests at high velocities were performed on monolayer targets to validate numerical models. Numerous configurations of multilayer composites were then studied numerically and their ballistic performances have been compared.

Ce travail de thèse a porté sur la simulation numérique du comportement thermique et mécanique d'un combustible nucléaire à particules. Il s'agit d'un composite réfractaire constitué d'une matrice de graphite comportant 45 % en fraction volumique de particules sphériquesd'UO2 revêtues de deux couches de pyrocarbone. L'objectif était de développer une modélisationmulti-échelles de ce composite afin d'estimer son comportement moyen, ainsi que les hétérogé-néités des champs mécaniques au sein des constituants. Nous avons modélisé la microstructuredu combustible et généré des échantillons numériques en 3D. Pour cela, des outils de générationde distributions aléatoires de sphères, de maillage et de caractérisation microstructurale, tellela covariance, ont été développés dans le code de calcul Cast3M. Une centaine d'échantillonsnumériques de différentes tailles ont été réalisés. Le comportement thermo-élastique du combustiblea été caractérisé à partir de ces échantillons, à l'aide de calculs de microstructures paréléments finis. Nous avons étudié l'influence de divers paramètres de la modélisation, dont lesconditions aux limites. Nous proposons une méthode pour s'affranchir des effets des conditionsaux limites sur les résultats, appelée méthode d'érosion. Elle s'appuie sur l'analyse des résultatssur un érodé du volume élémentaire. Nous avons alors déterminé les propriétés effectives ducomposite (modules d'élasticité, conductivité thermique, dilatation thermique), ainsi que lesdistributions des champs mécaniques locaux au sein de la matrice. Enfin, nous avons proposéun modèle de changement d'échelles permettant d'obtenir, non seulement les valeurs moyennesdes variables mécaniques dans chaque phase, mais également leurs variances et covariances pourtout chargement macroscopique imposé. Cette approche statistique de changement d'échellespermet ainsi d'estimer la distribution des grandeurs mécaniques au sein de chaque phase ducomposite. / The aim of this work was to perform numerical simulations of the thermal and mechanical behavior of a particle-based nuclear fuel. This is a refractory composite material made of UO2spherical particles which are coated with two layers of pyrocarbon and embedded in a graphitematrix at a high volume fraction (45 %). The objective was to develop a multi-scale modelingof this composite material which can estimate its mean behavior as well as the heterogeneity ofthe local mechanical variables. The first part of this work was dedicated to the modeling of themicrostructure in 3D. To do this, we developed tools to generate random distributions of spheres,meshes and to characterize the morphology of the microstructure towards the finite elementcode Cast3M. A hundred of numerical samples of the composite were created. The secondpart was devoted to the characterization of the thermo-elastic behavior by the finite elementmodeling of the samples. We studied the influence of different modeling parameters, one of themis the boundary conditions. We proposed a method to vanish the boundary conditions effectsfrom the computed solution by analyzing it on an internal sub-volume of the sample obtained byerosion. Then, we determined the effective properties (elastic moduli, thermal conductivity andthermal expansion) and the stress distribution within the matrix. Finally, in the third part weproposed a multi-scale modeling to determine the mean values and the variance and covarianceof the local mechanical variables for any macroscopic load. This statistical approach have beenused to estimate the intra-phase distribution of these variables in the composite material.

O final da vida útil de pavimentos com bases rígidas se caracteriza pelo aparecimento de trincas de blocos e de fadiga. Neste cenário, a reciclagem das camadas de base e revestimento asfáltico, com adição de cimento, surge como técnica importante para reabilitação dessas estruturas. Além de se tratar de uma solução vantajosa do ponto de vista técnico, é competitiva em termos econômicos, além de sustentável. Entretanto, a escassa normatização nacional dificulta sua aplicação, destacando-se a falta de um procedimento de dosagem. Objetivando contribuir para o desenvolvimento de um método de dosagem de camadas recicladas com cimento, desenvolveu-se um programa experimental, contemplando a caracterização mecânica (resistência e rigidez), a variação volumétrica e a erodibilidade de misturas contendo fresado asfáltico, materiais de bases rígidas (brita graduada tratada com cimento e solo-cimento) e cimento Portland. Foram analisados os efeitos da porcentagem de fresado, do teor de cimento e do tempo de cura, compactando-se os corpos de prova na energia Modificada. Com auxílio de um software estatístico, foi elaborado um planejamento experimental para definição das misturas analisadas, contemplando-se diversos níveis para as variáveis independentes (teores de cimento entre 1% e 7%, e porcentagens de fresado variando entre 8% e 92%, aproximadamente). Os tempos de cura considerados foram extrínsecos ao planejamento e variaram de acordo com o ensaio, sendo de 3, 7 e 14 dias para os ensaios de comportamento mecânico e de 7 dias para os demais ensaios. Obtiveram-se modelos com efeitos estatisticamente significativos, com exceção da expansão. Os demais modelos apresentaram coeficientes de determinação de médios a elevados, tendo em vista a heterogeneidade dos materiais estudados, além do tamanho amostral considerável. Foi verificado que todas as variáveis afetam as propriedades analisadas, sendo que o teor de cimento demonstrou maior efeito, sendo que sua adição melhora consideravelmente o comportamento das misturas empregadas, frente à ação do tráfego e da água. Foram alcançados resultados bastante elevados de resistência à compressão simples (1,00 MPa a 6,49 MPa) e resistência à tração na compressão diametral (0,17 MPa a 1,22 MPa); já a rigidez das misturas apresentou uma ampla variação de resultados (484 MPa a 20.031 MPa). Com relação aos materiais de base empregados (brita graduada tratada com cimento e solo-cimento), não se observou uma tendência única; as misturas com solo-cimento apresentaram maior resistência, entretanto, com comportamento ligeiramente inferior quanto à variação volumétrica e à erodibilidade. Na análise da rigidez, os materiais de base mostraram comportamento bastante similar. Para concluir, foi verificado que o procedimento proposto por Fedrigo (2015) também é satisfatório para a dosagem de misturas recicladas constituídas por antigas bases cimentadas e fresado asfáltico, restando ainda quantificar a possível retração por secagem das misturas estudadas. / The end of the useful life of pavements with rigid bases characterizes by the appearance of block and fatigue cracking. The full-depth reclamation with cement (FDR-C) of this layer combined with the asphalt layer seem to be a good choice for the rehabilitation of the pavement structure. Besides being an advantageous solution from a technical point of view, it is competitive in economic terms, besides being sustainable. However, the Brazilian standards are scarce thus limiting its application, highlighting the lack of an appropriated mix design method to this technique. In order to contribute for the development of an FDR-C mix design method, an experimental program was developed aiming to test the mechanical characterization (strength and stiffness), volumetric variation and the erodibility of mixtures made of reclaimed asphalt pavement (RAP), rigid base materials (cement treated crushed stone and soil-cement) and Portland cement. There were analyzed the effects of the RAP percentage, the cement content and the curing time of the specimens. For that, the compaction effort used was the Brazilian Modified one. Through a statistic software, an experimental planning was prepared for mixtures determination, with several levels for the independent variables (cement content between 1% and 7%, and RAP percentage varying by 8% up to 92%, approximately). The curing time analyzed was outward of experimental planning and it varied according to the kind of test. The specimens of mechanical performance were cured for 3, 7 and 14 days, and the other tests were examined at the 7th day of curing time. Models with statically significant effects were obtained, except the swell one. The others had medium and high coefficients of determination, given the heterogeneity of the studied materials, in addition to considerable sample size. It was found that all variables affect the analyzed properties, and the cement content proved to be with the greatest effect among the analyzed factors. Cement addition improves considerably the behavior of the mixtures for the traffic and water actions. Moreover, higher results were achieved for UCS (1.00 MPa up to 6.49 MPa) and ITS (0.17 MPa up to 1.22 MPa) tests. While the mixtures stiffness presented a wide range of results (484 MPa up to 20,031 MPa). Regarding the studied materials, it was observed that they do not have a single trend. The mixtures with soil-cement presented stronger, but with slightly lower behavior for volumetric variation and erodibility. At the stiffness analysis, different materials showed very similar behavior. All in all, it was found that the mix design method proposed by Fedrigo (2015) is also suitable for employment in semi-rigid FDR-C, still remaining to measure the possible drying shrinkage of specimens.

A indústria da construção civil utiliza grandes volumes de recursos naturais e, concomitantemente, produz elevadas quantidades de resíduos de construção e demolição (RCD), que são pouco reaproveitados e, às vezes, descartados de forma inadequada. Por reduzir a quantidade de matérias-primas extraídas da natureza, a construção de pavimentos aparece como destino nobre para os RCD. Contudo como esses materiais podem apresentar elevada heterogeneidade em sua composição, questiona-se se isso pode influenciar seu comportamento mecânico. A pesquisa relatada nesta dissertação buscou analisar as características físicas e comportamento mecânico de RCD de concreto (RCD cinza), e desse material misturado com RCD cerâmico (RCD vermelho). Acrescentando-se de 0 a 50% de tijolos maciços britados aos resíduos de concreto, reproduziram-se composições encontradas em obras civis. A partir de resultados de ensaios de granulometria, compactação, abrasão, compressão triaxial e módulo de resiliência (MR), compararam-se os comportamentos das mesmas. Com auxílio do software Everstress 5.0, foram feitas análises mecanísticas de pavimentos com bases compostas desses materiais, de forma que fossem estimados seus desempenhos frente a diferentes mecanismos de degradação. Observou -se que o aumento na porcentagem de RCD cerâmico afeta significativamente o comportamento mecânico do RCD misto, aumentando a perda de massa por abrasão e o teor de umidade ótimo de compactação, reduzindo o peso específico aparente seco máximo, a coesão e o módulo de resiliência e tornando o material menos dependente do estado de tensões. Conclui-se que a composição de resíduos de construção e demolição afeta seu comportamento mecânico e tem influência significativa no desempenho de pavimentos em que forem usados. Verifica-se que tanto os RCD cinza, quanto os mistos podem suportar as solicitações do tráfego, fortalecendo-se a filosofia de aliar a construção de pavimentos aptos estruturalmente a um modo de construir que contribua para a redução da exploração e degradação do meio ambiente. / The construction industry uses large volumes of natural resources and, at the same time, produces a high amount of construction and demolition waste (CDW), which are little reused and sometimes discarded inappropriately. In order to reduce the amount of raw materials extracted from nature, the construction of pavements appears as a noble destination for the use of CDW. However, since these materials may present high heterogeneity in their composition, it is questioned whether this may influence their mechanical behavior. The research reported in this dissertation aimed at analyzing the physical characteristics and mechanical behavior of recycled concrete aggregate (RCA) and this material mixed with crushed bricks. Adding from 0 to 50% of ceramic CDW to concrete residues, compositions found in civil works were reproduced. From the results of grain size distribution, abrasion, triaxial compression and resilience modulus tests, their behavior was compared. Using Everstress 5.0 software, mechanistic analysis of pavements with bases made of these materials were performed, so that their performances against different degradation mechanisms were estimated. It was observed that the increase in the percentage of ceramic CDW influences the behavior of the mixed CDW, increasing the abrasion mass loss and the optimum compaction moisture content, reducing the apparent maximum dry unit weight, cohesion and the modulus of resilience and making the material less dependent on the stress state. It is concluded that the composition of construction and demolition waste directly influences its mechanical behavior and has a significant influence on the performance of pavements in which they are used. Both RCA and mixed CDW have the potential to withstand traffic loads, strengthening the philosophy of combining the construction of pavements structurally capable with a construction mode that contributes to the reduction of exploration and degradation of the environment.

Made available in DSpace on 2015-04-22T22:08:55Z (GMT). No. of bitstreams: 1 Dissertacao Karine Jussara da Costa.pdf: 6916532 bytes, checksum: 872f531f6e30b510bea0beb9ae62b8a9 (MD5) Previous issue date: 2010-04-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This teses research analyses, m ky trough an experimental project, the mechanical behavior of hot-mix asphalt, with dust of sand. The dust of sand residue was utilized as a filler in hot-mix asphalt, replacing in the Manaus city used material the Portland cement CP II. The general purpose of this work is to test hypothesis that the residue can be use as a filler in hot-mix asphalt. The reuse of these industrial residues leads to environmental gains; it not only helps to avoid the open-air deposition of this by-product but it also reduces. All the mixtures were characterized mechanically through the testing of Resilient Modulus, Static Tensile Strength, fatigue of diametrical compression under controlled stress and static creep. The results of this research show that the addition of industrial residue in hot-mix asphalt increases the binder consumptio / Esta pesquisa analisa por meio de um estudo experimental, o comportamento mecânico de misturas asfálticas, utilizando o resíduo pó de areia. O objetivo geral desta pesquisa é testar a hipótese que o resíduo pode ser utilizado como fíler em misturas asfálticas. O resíduo pó de areia foi utilizado como fíler em mistura asfáltica tipo CBUQ, em substituição ao cimento Portland CP II usado na cidade de Manaus. A reutilização destes resíduos industriais traz benefícios ambientais, pois auxilia a questão de deposição destes rejeitos. Todas as misturas foram caracterizadas mecanicamente através dos ensaios de Módulo de Resiliência, Resistência à Tração estática por compressão diametral, fadiga por compressão diametral à tensão controlada e compressão axial estática (creep estático). Os resultados obtidos demonstraram que a adição do resíduo industrial estudado em mistura asfáltica aumenta o consumo de ligante da mistura. Os resultados dos ensaios mostram desempenho adequado da mistura confeccionada com o pó de areia.

O município de Caxias do Sul está inserido em um importante contexto geológico-geotécnico do estado do Rio Grande do Sul e, em sua área urbana, são observados vários acidentes de ordem geotécnica. O conhecimento dos solos e das rochas que constituem os perfis da área urbana carece de uma caracterização mecânica que, diante de qualquer acidente geotécnico, possa servir como ponto de partida para a solução de tal evento. Esta dissertação apresenta um estudo a respeito do comportamento mecânico de um solo residual de Dacito Canyon encontrado na área urbana do município de Caxias do Sul – RS. Foram realizados ensaios de cisalhamento direto e compressão triaxial com corpos de prova indeformados e reconstituídos e também foram executados um ensaio edométrico com um corpo de prova remoldado com a umidade próxima ao limite de liquidez. Os resultados obtidos com a realização dos ensaios mostraram que o material possui uma forte influência da estrutura do solo que foi especialmente evidenciada nos resultados dos ensaios de cisalhamento Foi possível estabelecer, com base em ensaios remoldados, uma curva NCL coerente com os parâmetros N da ordem de 2,1452 e e λ similar a 0,135. Entretanto não foi possível a definição de uma CSL pelo fato do material apresentar uma forte estrutura e os ensaios em amostras remoldadas e indeformadas não indicaram uma estabilização dos índices de vazios finais. O comportamento mecânico dos ensaios indeformados varia de acordo com o nível de deformação e de acordo com os ensaios. Nos ensaios de cisalhamento direto houve uma redução da coesão (de 50kPa para ~24kPa) e aumento do ângulo de atrito com as deformações (de 23 para 24 graus). Com a remoldagem esta tendência aumentou (o ângulo de atrito alcançou 28,5 graus). Já no ensaios triaxiais, o ângulo de atrito se manteve em torno de 29-30 graus e a coesão reduziu de 26kPa para 15kPa para grandes deformações. / The municipality of Caxias do Sul is part of an important geological-geotechnical context in the state of Rio Grande do Sul and several geotechnical accidents have been observed in its urban area. The knowledge of the soils and rocks that make up the profiles of the urban area lacks a mechanical characterization which, in the face of any geotechnical accident, can serve as a starting point for the solution of such an event. This dissertation presents a study about the mechanical behavior of a residual soil of Dacito Canyon found in the urban area of the city of Caxias do Sul - RS. Direct shear and triaxial compression tests were carried out with undisturbed and reconstituted test specimens and an edometric test carried out with a test specimen remolded with humidity close to the liquidity limit. The results obtained with the tests showed that the material has a strong influence of the soil structure that was specially evidenced in the results of the shear tests It was possible to establish on the basis of remolded tests an NCL curve coherent, with the N parameter of the order of 2.1452 and λ similar to 0.135. However, it was not possible to define a CSL because the material had a strong structure and the tests on remolded and undisturbed samples did not indicate a stabilization of the final void ratios. The mechanical behavior of the undeformed tests varied according to the level of deformation and according to the test type. In the direct shear tests there was a reduction of cohesion (from 50kPa to ~ 24kPa) and an increase in the angle of friction with the deformations (from 23 to 24 degrees). In tests with the remolded soil this trend increased (the angle of friction reached 28.5 degrees). In the triaxial tests on undisturbed specimens the friction angle remained around 29-30 degrees, similar to peak, and the cohesion reduced from 26kPa to 15kPa for large deformations.

Magnesium alloys are widely used in engineering applications, including aerospace and automobile industries, due to their desirable properties, such as lower density, high damping capacity, relatively high thermal conductivity, good machinability, and recyclability. Researchers have, therefore, been developing new magnesium materials. However, mechanical and corrosion properties are still limiting many commercial applications of magnesium alloys. In this Ph.D. thesis research, I developed Mg-Ti composite materials to offer some solutions to further improve the mechanical behavior of magnesium, such as titanium-magnesium (Ti-Mg) claddings, Mg-Ti multilayers, and Ti particle enforced Mg alloys. Low cost manufacturing processes, such as hot roll-bonding (RB) and accumulative roll-bonding (ARB) techniques, were used to produce Mg-Ti composites and sheets. The microstructural evolution and mechanical properties of composites were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), nanoindentation, and tensile tests. In the first part of this study, I investigated the bonding strength of the AZ31/Ti to understand the mechanical properties of Mg/Ti composites. Using a single pass RB process, I fabricated AZ31/Ti multilayers with the thickness reduction in a range of 25% to 55%. The hot-rolled AZ31/Ti multilayers were heat-treated at 400 °C for 6, 12, and 24 hours, respectively, in an argon atmosphere. Tensile-shear tests were designed to measure the bonding strength between AZ31/Ti multilayers. Furthermore, the experimental results revealed good bonding of the AZ31/Ti multilayers without forming any intermetallic compounds in the as-rolled and heat-treated AZ31/Ti multilayers. The good bonding between Ti and AZ31 is the result of diffusion bonding whose thickness increases with increasing heat-treatment time and thickness reduction. The shear strength of the Ti/AZ31 multilayer increases with increasing bonding layer thickness. In the second part of this study, I characterized the microstructure and texture of three-layered Ti/AZ31/Ti clad sheets which were produced by single-pass hot rolling with a reduction of thickness 38% (sheet I) and 50% (sheet II). The AZ31 layer in sheets I and II exhibited shear bands and tensile twins {1012}⟨1001⟩ . The shear bands acted as local strain concentration areas which led to failure of the clad sheets with limited elongation. Heat treatment caused changes in the microstructure and mechanical properties of clad sheets due to static recrystallization (SRX) on twins and shear bands in the AZ31 layer. Recrystallized grains usually randomize the texture which causes weaken the strong deformed (0001) basal texture. Twins served as nucleation sites for grain growth during SRX. Tensile tests at room temperature showed significantly improved ductility of the clad sheets after heat treatment at 400°C for 12h. The results showed that the mechanical properties of clad sheets II are better than clad sheet I: The clad sheet II shows elongation 13% and 35% along the rolling direction (RD) for as-rolled and annealed clad sheet, respectively whereas the clad sheet I shows elongation 10% and 22% along RD for as-rolled and annealed clad sheet, respectively. In the final part of this study, I examined the effects of dispersed pure titanium particles (150 mesh) with 0, 2.3, 3.5, 4.9, and 8.6 wt. % on the microstructure and mechanical properties of AZ31-Mg alloy matrix. Mg-Ti composites were processed through three accumulative roll bonding (ARB) steps using thickness reductions of 50% in each pass followed by heat treatment at 400 °C for 12 h in an argon atmosphere. ARB is an efficient process to fabricate Mg-Ti composites. Mechanical properties of Mg- 0Ti and Mg-2.3Ti composite were enhanced by ~ 8% and 13 % in yield strength and ~ 30% and 32 % in ultimate tensile strength, respectively. Meanwhile, the elongation of the composites were decreased by 63% and 70%, respectively. After heat treatment, the results showed a decrease in yield strength and increase in elongation to fracture. The mechanical properties of the Mg-0 and Mg-2.3Ti composite were enhanced: ultimate tensile strength by 9% and 7%, and elongation by 40% and 67%, while the yield strength was decreased by 28% and 36% compared with the initial AZ31. Enhancements of strength and ductility were the results of two mechanisms: a random matrix texture by ARB and ductile titanium particle dispersion.

Made available in DSpace on 2014-12-17T14:07:11Z (GMT). No. of bitstreams: 1 QueremAFA_DISSERT.pdf: 6927049 bytes, checksum: 5fbf755901320194b71aa9dc0dc0b657 (MD5) Previous issue date: 2013-06-07 / Studies indicate that a variation in the degree of crystallinity of the components of a polymer blend influences the mechanical properties. This variation can be obtained by subjecting the blend to heat treatments that lead to changes in the spherulitic structure. The aim of this work is to analyze the influence of different heat treatments on the variation of the degree of crystallinity and to establish a relationship between this variation and the mechanical behavior of poly(methyl methacrylate)/poly(ethylene terephthalate) recycled (PMMA / PETrec) with and without the use of compatibilizer agent poly(methyl methacrylate-al-glycidyl methacrylate-al-ethyl acrylate) (MMAGMA- EA). All compositions were subjected to two heat treatments. T1 heat treatment the samples were treated at 130 ? C for 30 minutes and cooled in air. In T2, the samples were treated at 230 ? C for 5 minutes and cooled to approximately -10 ? C. The variation of the degree of crystallinity was determined by the proportional relationship between crystallinity and density, with the density measured by pycnometry. The mechanical behavior was verified by tensile tests with and without the presence of notches and pre-cracks, and by method of fracture toughness in plane strain (KIC). We used the scanning electron microscopy (SEM) to analyze the fracture surface of the samples. The compositions subjected to heat treatment T1, in general, showed an increase in the degree of crystallinity in tensile strength and a tendency to decrease in toughness, while compositions undergoing treatment T2 showed that the opposite behavior. Therefore, this work showed that heat treatment can give a polymer blend further diversity of its properties, this being caused by changes in the crystal structure / Estudos apontam que uma varia??o no grau de cristalinidade dos componentes de uma blenda polim?rica influencia nas suas propriedades mec?nicas. Essa varia??o pode ser obtida pela submiss?o da blenda a tratamentos t?rmicos que levam a modifica??es da estrutura esferul?tica. O objetivo desse trabalho ? analisar a influ?ncia de diferentes tratamentos t?rmicos na varia??o do grau de cristalinidade e estabelecer uma rela??o entre essa varia??o e o comportamento mec?nico da blenda poli(metacrilato de metila)/poli(tereftalato de etileno) reciclado (PMMA/PETrec) com e sem o uso do agente compatibilizante interfacial poli(metacrilato de metila-almetacrilato de glicidila-al-acrilato de etila) (MMA-GMA-EA). Todas as composi??es foram submetidas a dois tratamentos t?rmicos. No tratamento t?rmico T1 as amostras foram tratadas a 130 ?C por 30 minutos e resfriadas ao ar. No tratamento T2 as amostras foram tratadas a 230 ?C por 5 minutos e resfriadas a aproximadamente 10 ?C. A varia??o do grau de cristalinidade foi verificada pela rela??o de proporcionalidade existente entre cristalinidade e densidade, sendo a densidade medida por picnometria. O comportamento mec?nico foi verificado por ensaios de tra??o, com e sem a presen?a de entalhes e pr?-trincas, e pelo m?todo da tenacidade ? fratura em estado plano de deforma??o (KIC). Utilizou-se a microscopia eletr?nica de varredura (MEV) para analisar a superf?cie de fratura das amostras. As composi??es submetidas ao tratamento t?rmico T1, de uma forma geral, mostraram aumento no grau de cristalinidade, na resist?ncia ? tra??o e uma tend?ncia ? redu??o na tenacidade ? fratura, enquanto que as composi??es submetidas ao tratamento T2 mostraram um comportamento oposto a esse. Portanto, este trabalho mostrou que um tratamento t?rmico pode conferir a uma blenda polim?rica uma diversidade ainda maior de suas propriedades, sendo essa ocasionada pelas mudan?as na estrutura cristalina

Neste trabalho foi realizado um estudo comparativo entre juntas dissimilares produzidas pelo processo FSpW sem e com a utilização de Zn como metal intermediário tendo a finalidade de investigar a eficácia da adição deste metal no comportamento mecânico das juntas, bem como avaliar sua influência nas características microestruturais das juntas soldadas. As juntas foram produzidas com ligas de Al AA5754-H24 e Mg AZ31-O, de particular interesse do setor automotivo. Nas condições de soldagem com metal intermediário, chapas de Al revestido com Zn por galvanização foram usadas. As propriedades mecânicas das juntas foram avaliadas através de ensaios com carregamento quasi-estáticos e dinâmicos, sendo então correlacionados com as características microestruturais. Através das análises constatou-se que a aplicação de Zn como metal intermediário mostrou-se efetiva na redução do volume de compostos intermetálicos formados na interface da solda e consequentemente, obteve-se um aumento do desempenho mecânico de cerca de 48 % no ensaio de cisalhamento por tração, 230% no ensaio de tração cruzada e de 35,31 % no ensaio de fadiga quando em comparação a juntas soldadas diretamente entre as chapas de AA5754-H24 e AZ31-O. / In this research was carried out a comparative study between dissimilar joints produced by means of the process FSpW without and with applying Zn as an intermediary metal with the purpose of investigating the effectiveness of the addition of this metal in the mechanical behavior of joints, as well as to assess its influence on the microstructural characteristics of the welded joints. The joints were produced with the AA5754-H24 Al alloy and the AZ31-O Mg alloy, materials of particular interest to the automotive industry. For the welding conditions with the Zn interlayer Al sheets coated by hot deep galvanizing were used. The mechanical properties of the welded joints were evaluated in terms of quasi-static and dynamic load and then correlated with the microstructural features. Through the analyzes it has been verified that the addition of Zn as an intermediary metal proved to be effective in reducing the amount of the intermetallic compound formed at the weld interface and consequently the mechanical performance increased about 48 % in the lap shear strength test, 230 % in the cross tensile strength test and 35,31 % in the fatigue test when compared to the welded joints produced by the direct contact among the AA5754-H24 and the AZ31-O sheets.

Neste trabalho foi realizado um estudo comparativo entre juntas dissimilares produzidas pelo processo FSpW sem e com a utilização de Zn como metal intermediário tendo a finalidade de investigar a eficácia da adição deste metal no comportamento mecânico das juntas, bem como avaliar sua influência nas características microestruturais das juntas soldadas. As juntas foram produzidas com ligas de Al AA5754-H24 e Mg AZ31-O, de particular interesse do setor automotivo. Nas condições de soldagem com metal intermediário, chapas de Al revestido com Zn por galvanização foram usadas. As propriedades mecânicas das juntas foram avaliadas através de ensaios com carregamento quasi-estáticos e dinâmicos, sendo então correlacionados com as características microestruturais. Através das análises constatou-se que a aplicação de Zn como metal intermediário mostrou-se efetiva na redução do volume de compostos intermetálicos formados na interface da solda e consequentemente, obteve-se um aumento do desempenho mecânico de cerca de 48 % no ensaio de cisalhamento por tração, 230% no ensaio de tração cruzada e de 35,31 % no ensaio de fadiga quando em comparação a juntas soldadas diretamente entre as chapas de AA5754-H24 e AZ31-O. / In this research was carried out a comparative study between dissimilar joints produced by means of the process FSpW without and with applying Zn as an intermediary metal with the purpose of investigating the effectiveness of the addition of this metal in the mechanical behavior of joints, as well as to assess its influence on the microstructural characteristics of the welded joints. The joints were produced with the AA5754-H24 Al alloy and the AZ31-O Mg alloy, materials of particular interest to the automotive industry. For the welding conditions with the Zn interlayer Al sheets coated by hot deep galvanizing were used. The mechanical properties of the welded joints were evaluated in terms of quasi-static and dynamic load and then correlated with the microstructural features. Through the analyzes it has been verified that the addition of Zn as an intermediary metal proved to be effective in reducing the amount of the intermetallic compound formed at the weld interface and consequently the mechanical performance increased about 48 % in the lap shear strength test, 230 % in the cross tensile strength test and 35,31 % in the fatigue test when compared to the welded joints produced by the direct contact among the AA5754-H24 and the AZ31-O sheets.