Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2017-12-20T11:21:00Z No. of bitstreams: 1 brenofortesbittar.pdf: 2144210 bytes, checksum: e81cc0440d6624e220a83357474498f4 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-12-22T11:56:27Z (GMT) No. of bitstreams: 1 brenofortesbittar.pdf: 2144210 bytes, checksum: e81cc0440d6624e220a83357474498f4 (MD5) / Made available in DSpace on 2017-12-22T11:56:27Z (GMT). No. of bitstreams: 1 brenofortesbittar.pdf: 2144210 bytes, checksum: e81cc0440d6624e220a83357474498f4 (MD5) Previous issue date: 2017-08-14 / Este estudo avaliou a influência da pigmentação extrínseca na degradação hidrotérmica e resistência à flexão biaxial de cerâmica de zircônia Y-TZP (InCoris TZI – Sirona – EUA) submetidas a diversos tipos de tratamento de superfície. Foram confeccionados discos seguindo a norma ISO 6872 (12x1,2 mm) a partir de blocos de zircônia Y-TZP pré-sinterizados. As amostras foram pigmentadas (InCoris TZI Coloring Liquid A3,5 – Sirona – EUA) pela técnica da imersão por 5 minutos. Foram, então, separadas em grupos de acordo com o critério de se receberam (P), ou não (S), pintura extrínseca (n=60) e posteriormente, de acordo com o tipo de tratamento de superfície a que foram submetidas (n=15): 1 – (C) controle (sem tratamento de superfície); 2 – (R) Rocatec®; 3 – (G) Glazeamento; 4 – (GA) Glazeamento e condicionamento com ácido fluorídrico 10%. Duas amostras adicionais foram, também, analisadas via (1) perfilômetro ótico, para se determinar a influência dos tratamentos de superfície na rugosidade superficial; (2) análise em difração de raio-X (DRX) para se avaliar possíveis transformações de fase; (3) espectrometria por energia dispersiva (EDS) para se avaliar a composição química das amostras; e (4) microscopia eletrônica de varredura (MEV) para caracterização superficial e quantificação do tamanho médio dos grãos. As amostras foram submetidas à ciclagem mecânica (1,2x106, carga de 200N e frequência de 3.8Hz) e ensaio de resistência à flexão biaxial (1mm/min e célula de 1000kg até a fratura catastrófica). A análise dos dados obtidos pela perfilometria permitem afirmar que a pigmentação extrínseca e os tratamentos superficiais empregados alteraram de forma significativa a rugosidade superficial. A análise do DRX permite concluir que o subgrupo SR sofreu alteração de fase T → M (3,5%) e o subgrupo PR apresentou fase cúbica. A análise dos dados permite afirmar que, no grupo S, o tratamento de superfície influenciou de maneira estatisticamente significante a resistência à flexão biaxial (p=0,014), sendo que o subgrupo SR apresentou maior resistência (642,8±112,1 MPa) e o grupo SGF, a menor (542,9±80,96 MPa). O mesmo não ocorre em P, onde não foi observado diferenças estatisticamente significantes (p=0,113). Desta forma, é possível afirmar que a pigmentação extrínseca promove alterações na estrutura do material analisado. / This study evaluated the influence of extrinsic pigmentation on the hydrothermal degradation and biaxial flexural strength of zirconia ceramics Y-TZP (InCoris TZI - Sirona - USA) submitted to several surface treatments. Discs-shape specimens (ISO 6872 - 12x1.2 mm) were prepared from pre-sintered Y-TZP zirconia blocks. The specimens received pigmentation (InCoris TZI Colouring Liquid A3,5 – Sirona – USA) by immersion technique for 5 minutes. Then they were separated into groups according to the criteria of whether they received (P) or not (N), extrinsic pigmentation (n = 60) and then according to the surface treatment they were submitted to (n = 15): 1 - (C) control (as sintered); 2 - (R) Rocatec®; 3 - (G) Glaze; 4 - (GA) Glaze and conditioning with 10% hydrofluoric acid. Two additional samples were also analyzed via (1) optical profilometer to determine the influence of surface treatments on surface roughness; (2) X-ray diffraction (XRD) analysis to evaluate possible phase transformations; (3) dispersive energy spectrometry (EDX) to evaluate the chemical composition of the samples; And (4) scanning electron microscopy (SEM) for surface characterization and quantification of the mean grain size. The samples were submitted to mechanical cycling (1.2x106, 200N load and 3.8Hz) and biaxial flexural strength test (1mm / min and 1000kg cell until catastrophic fracture). The analysis of the data obtained by the profilometer allows to state that the extrinsic pigmentation and the surface treatments employed significantly altered the surface roughness. The XRD analysis allows to conclude that the subgroup SR underwent T → M phase change (3.5%) and the subgroup PR presented also cubic phase. Data analysis allowed us to state that, in the N group, the surface treatment had a statistically significant influence on biaxial flexural strength (p = 0.014), and the SR subgroup presented higher resistance (642.8 ± 112.1 MPa) and the SGF group, the lowest (542.9 ± 80.96 MPa). The same does not occur in P, where no statistically significant differences were observed (p = 0.113). Thus, it is possible to conclude that the extrinsic pigmentation promotes changes in the structure of the analyzed material.

L’évaluation de la résistance probable des éléments dissipatifs d’énergie sismique lors du dimensionnement parasismique des charpentes d’acier au Canada repose sur la limite élastique probable de l’acier. Les taux de déformation élevés dans les éléments dissipatifs au cours d’un tremblement de terre ont pour effet d’augmenter la limite élastique de l’acier dans ces éléments. Le comportement dynamique de l’acier étudié par le biais d’essais uniaxiaux conventionnels ne permettent pas nécessairement de valider le comportement d’un élément dissipateur d’énergie sismique pouvant être sollicité selon deux dimensions. Les cadres contreventés excentriques, où le lien ductile subi des déformations biaxiales par les effets combinés du cisaillement et de la flexion en est un exemple. Le projet de recherche présenté dans ce mémoire de maîtrise vise à évaluer l’effet du taux de déformation sur la limite élastique de l’acier structural de grade 350W lors de sollicitations impliquant un état planaire de contrainte. La conception d’une éprouvette cruciforme optimale en acier basée sur des recommandations proposés dans la littérature et sur des analyses par éléments finis a été effectuée. Six essais de traction uniaxiaux et quatre essais de traction équibiaxiaux sur éprouvettes cruciformes ont été réalisés à différents taux de déformation entre 0.0001/sec et 2.4/sec. Durant ces essais, les déformations moyennes à travers la partie centrale des éprouvettes ont été mesurées par un système de potentiomètre conçu dans le cadre de ce projet. Quatre essais biaxiaux sur éprouvettes cruciformes selon des rapports de déformation distincts ont également été réalisés à un taux de déformation quasi-statique. Chaque essai a été simulé numériquement à l’aide d’un modèle éléments finis dans lequel la limite élastique a été calibrée afin de reproduire le comportement observé lors des essais. Le critère d’écoulement plastique de Von Mises ainsi qu’une formulation d’écrouissage non-linéaire ont été adoptés lors des analyses numériques. Les modèles calibrées ont permis de déterminer la limite élastique dynamique observée lors de chaque essai. Les résultats des analyses confirment que la limite élastique de l’acier augmente en fonction du taux effectif de déformation. Sept lois de prédiction de la limite élastique de l’acier ont été étudiées. Trois lois ont permis de représenter la limite élastique dynamique de l’acier testé dans la plage des taux de déformation étudiée. La loi qui semble la mieux adaptée à être implémentée dans un logiciel de modélisation a été identifiée. La loi de Drysdale et Zak utilisé dans le logiciel ADINA ne permet pas d’évaluer correctement le comportement dynamique observé lors des essais impliquant un taux élevé de déformation. Une étude numérique préliminaire sur le lien ductile est également présentée dans ce mémoire.

Les procédés de mise en forme des tôles métalliques sont largement utilisés dans l’industrie mécanique. La simulation numérique des opérations de mise en forme nécessite une caractérisation précise des modèles de comportement rhéologique des matériaux. Dans de nombreuses opérations de mise en forme des tôles métalliques telle que l’emboutissage, l’hydroformage, …, de grandes déformations et des vitesses de déformations dites intermédiaires peuvent être atteintes sous des états biaxiaux de déformation ou de contrainte. L’objectif de ce travail est de montrer le potentiel de l’essai de traction bi-axiale pour caractériser l’écrouissage des tôles métalliques pour de grandes déformations et dans une gamme de vitesse de déformation dite intermédiaire. A partir de simulations numériques, une forme optimale d’éprouvette en croix, permettant d’atteindre 30% de déformation plastique équivalente dans la zone centrale de l’éprouvette sous un chargement équibiaxial, a été proposée. Par la suite, des essais quasi-statiques et dynamiques de traction bi-axiale ont été réalisés sur la forme d’éprouvette proposée à partir d’une machine dédiée d’essais servo-hydraulique à quatre vérins. Dans un premier temps, le matériau choisi est un alliage d’aluminium AA5086 ne présentant pas de dépendance à la vitesse de déformation. Les déformations expérimentales sont déterminées à partir de la technique de corrélation d’images. L’écrouissage isotrope de différents modèles est identifié à partir d’une procédure inverse basée sur une modélisation éléments finis de l’essai de traction biaxiale. Trois critères de plasticité (Mises, Hill 48 et Bron et Besson) ont été successivement utilisés pour l’identification des paramètres des lois d’écrouissage. Les résultats obtenus montrent d’une part que la modélisation est très sensible au critère de plasticité choisi, et d’autre part que le critère de Bron et Besson permet d’obtenir une très bonne corrélation entre les courbes d’écrouissage identifiées à partir de l’essai bi-axial et de l’essai uni-axial. Pour les tests dynamiques bi-axiaux, les phénomènes de résonance du dispositif mécanique, générés à l’impact initial de début d’essai et matérialisés par de fortes oscillations du signal d’effort, sont atténués par l’interposition d’un élément en élastomère dans le système d’ancrage de chaque bras de l’éprouvette. Pour finir, la méthodologie d’identification proposée est appliquée à la caractérisation du comportement viscoplastique d’un acier dual phase DP600. Les courbes d’écrouissage identifiées à partir des essais bi-axiaux ont été comparées à celles obtenues par des essais uni-axiaux pour une gamme de vitesse de déformation allant de 10- 3s-1 à 101s-1. Le DP600 présente une même sensibilité à la vitesse de déformation quelque soit la sollicitation, uni-axiale ou bi-axiale. Les lois d’écrouissage de Ludwick et de Voce, identifiées jusqu’à 30% de déformation plastique équivalente sur la base de données expérimentales constituées des essais bi-axiaux, sont relativement proches. Les différences observées entre ces courbes d’écrouissage et celles identifiées à partir des essais de traction uni-axiaux montrent tout l’intérêt de l’essai de traction bi-axiale sur éprouvette en croix. / Sheet metal forming processes are widely adopted to produce panels, tubes, profiled parts in manufacturing industry. The numerical simulation of the forming processes requires accurate constitutive models of material. In many sheet metal working operations such as stamping, hydroforming, …, large strains and intermediate strain rates can be reached under biaxial strain or stress states. The objective of this work is to show the potential of the biaxial in-plane tensile test to characterize the hardening behaviour of metal sheets up to large strain levels. By numerical investigation, an optimal cruciform shape is designed to obtain large equivalent plastic strain, up to 30%, at the central zone under equi-biaxial strain path. As expected, the initial cracks of tested specimens are always observed at the central zone. Then, quasi-static and dynamic biaxial tensile tests on in-plane cross specimens have been performed on a dedicated servo-hydraulic machine. These biaxial tensile tests have been carried out on aluminium alloy AA5086 to validate the identification methodology of hardening behaviour under biaxial loading. This alloy has been chosen since its hardening behaviour is not dependent on the strain rate. Digital Image Correlation (DIC) technique is used for strain measurement. The parameters of isotropic hardening models are identified by inverse analysis based on the finite element model of the biaxial tensile test. Three yield criteria of Mises, Hill48 and Bron and Besson are compared for the parameter identification of different hardening laws. It is shown that the hardening law identified by biaxial test is precise only if an appropriate yield function is preliminarily determined. The biaxial flow stress curve identified with Bron and Besson yield function have been found in good agreement with the experimental flow stress curve obtained from uniaxial tensile tests. For biaxial tests at intermediate strain rates, damping layers are adopted to reduce oscillations on force versus time curves. The comparison of flow stress curves, identified from quasi-static and dynamic biaxial in-plane tensile tests on the non strain rate-dependent material AA5086, validates the identification methodology of strain-rate dependent hardening models. Finally, the proposed methodology is applied to the hardening characterization of a strain-rate dependent Dual Phase steel DP600 at room temperature. Identified biaxial flow stress curves have been compared with uniaxial ones for different strain rates ( . = 10-3s-1, 10-1s-1 and 101s-1). DP600 steel exhibits the same positive strain rate sensitivity for uniaxial and biaxial strain states. The biaxial flow stress curves identified on the basis of Ludwick and Voce hardening models are close, up to equivalent plastic strains of 30%. The benefits of the proposed methodology, based on a biaxial in-plane tensile test carried out on cross specimen, are clearly shown since the hardening behaviour identified in this case for large strains (up to 30%) is very different from the one identified from uniaxial tensile test on a smaller strain range.

Within the master thesis a computational model of biaxial tension test of soft biological tissues was developed. The tested specimen can be attached using clamps or hooks. The number and the size of clamps and hooks have a significant impact on the distribution of stress and strain in the centre of the specimen, where deformation is measured. Using the developed computational model, a sensitivity analysis of number and size of clamps and hooks and a sensitivity analysis of placement of clamps was elaborated. The number and size of clamps and hooks were optimized in such a way that the material’s parameters obtained by the tension test correspond to the utmost to the actual parameters of the material. By analyzing the placement of clamps, the influence of selected deviations on the outcome of the tension test was determined. Finally, a plan of the next course of action has been proposed.

The paper treats the question of feasibility of measuring intrinsic thin film stresses due to nanoindentation. A variety of different methods is proposed and analysed with respect to their applicability. As this accuracy-estimation results in boundary conditions for the measurements which can not be fulfilled yet, the whole topic is considered from a purely academic point of few. With the help of a special software package [25] the following methods are considered: 1. Taking the moment of beginning plastic flow within the substrate as indictor, 2. Taking the moment of beginning plastic flow within the film as indictor, 3. Applying mixed loads (normal and lateral forces), 4. Applying the concept of the effectively shaped indenter. While the methods 2 to 4 appear to be in principle feasible, method 1 can completely be ruled out as being of no practical use. The mentioned software package (FilmDoctor prototype) is part of the supplemental material of this study.

Bridge decks are commonly subjected to harsh environmental conditions that often lead to serious corrosion problems triggered by blisters under the hot mix asphalt bridge deck surfacing and secretly evolving during weather exposure until damage is often detected too late. Blisters may form under both the waterproofing dense mastic asphalt layer or under the waterproofing membrane which is often applied as additional water protection under the mastic asphalt (MA). One of the main technical issues is the formation of blisters under the membrane and asphalt-covered concrete structures caused by a complex mechanism governed by bottom-up pressure and loss of adhesion. A linear viscoelastic finite-element model was developed to simulate time-dependent blister growth in a dense mastic asphalt layer under uniformly applied pressure with and without temperature and pressure fluctuation. A finite element model was developed using ABAQUS with linear viscoelastic properties and validated with a closed form solution from first-order shear-deformation theory for thick plates. In addition, the blister test was conducted on different samples of MA in the laboratory and digital image correlation measurement technique was used to capture the three-dimensional vertical deflection of the MA over time. It was found that the blister may grow continuously under repeated loading conditions over subsequent days. With respect to blistering under waterproofing membranes, mechanical elastic modeling and experimental investigations were performed for three different types of membranes under in-plane stress state. The orthotropic mechanical behavior of a polymer modified bitumen membrane (PBM) was determined from biaxial test data. Finally, blister tests by applying controlled pressure between orthotropic PBMs and concrete plates were performed for studying the elliptical adhesive blister propagation using digital 3D image correlation. The energy calculated from elliptical blister propagation was found comparable to the adhesive fracture energy from standard peeling tests for similar types of PBMs. This indicates that the peeling test assists to evaluate and rank the adhesive properties of different types of membranes with respect to blister formation at room temperature without conducting time consuming and complicated pressurized blister propagation tests using digital 3D image correlation. / <p>QC 20130625</p>

In today's automotive industries, many different simulation programs are used to optimize parts before they come into production. This has created a market for complex material models to get the best possible approximation of reality in the simulation environment. Several industries are still using older material models that can’t give an acceptable accuracy for the materials currently in use as they are based on much simpler and older materials. The problem with material models is that there is no direct comparison between the material models which leads to several sheet metal forming companies still holding on to older models like Hill`48.   The purpose of this work is to create a comparison of sheet material models from a user perspective to be able to provide recommendations of material models. Different models will be tested for different materials and will be based on AutoForm's recommendations. AutoForm is a FEM based sheet metal forming simulation program used by large names in the automotive industry. These recommendations are Vegter2017, BBC2005 or Hill`48 for steel and Vegter2017, BBC2005 or Barlat`89 for aluminum.   This work is achieved by comparing experimental data from a Limiting Dome Height (LDH) test with a simulation of this test for all material models and then comparing the results. The data that will be compared consists of the major and minor strain in the sheet as well as the punch force. These parameters are chosen as they give an overview of the model’s applicability as well as accuracy. The test will be performed on all materials available in Volvo Cars material library to create a broader overview of all material models. The material models will also be evaluated depending on their user-friendliness by analyzing what types of data are required to perform a simulation.   The result from these tests showed that BBC 2005 should be recommended for aluminum and steel for companies that have access to biaxial data and for people who put optimization in focus. Hill`48 proved far too deviant in the results for steel and should not be used if other models are available. Vegter 2017 proved perfect for steel simulations as the result were great as well as the necessary material data can be obtained through standardized tensile tests. The result also showed that Vegter2017 should not be used for aluminum since the result was too deviant from the experimental data in aspect for both form approximation and strain magnitude. Barlat`89 gave accurate results with only data from a tensile test which makes it a preferred model when working with aluminum.   The conclusion from this work is that the choice of material model is very dependent on what conditions you have as very few industries have access to the tests required by the BBC 2005 model. Another conclusion may be drawn for Barlat`89 with aluminum and Vegter 2017 with steel as they can be preferred when working with a small timeframe as well as when few test data is available. / Inom dagens bilindustri används det många olika simuleringsprogram för att optimera delar innan de kommer ut i produktion. Detta har då skapat en marknad för komplexa material modeller för att få en så bra approximation av verkligheten som möjligt. I flera industrier använder man sig fortfarande av äldre materialmodeller som egentligen inte håller måttet för dagens material då de är baserade på simplare material. Problemet som har skapat denna situation är att det inte direkt finns en konkret jämförelse mellan materialmodellerna vilket leder till att flera plåtformnings företag fortfarande håller kvar vid äldre modeller som t e x Hill`48.   Syftet med detta arbete är att skapa en jämförelse av plåt materialmodeller från ett användarperspektiv för att kunna ge konkreta bevis till rekommendationer av materialmodeller. Olika modeller skall testas för olika material och baseras på AutoForms rekommendationer. AutoForm är ett FEM baserat plåtformningssimulerings program som används av stora namn inom bilindustrin. Dessa rekommendationer är då att köra Vegter2017, BBC2005 eller Hill`48 för stål samt att köra Vegter2017, BBC2005 eller Barlat`89 för aluminium.   Detta arbete utförs genom att jämföra experimentella data från ett Limiting Dome Height (LDH) test med en simulering av detta test för alla material modeller och sedan jämföra resultaten. Jämförelsen mellan den experimentella och simuleringsdatan kommer att involvera major och minor strain i plåten samt stämpelkraften. Dessa parametrar har valts då de ger en bra översikt över materialmodellernas applicerbarhet och noggrannhet. Testen kommer att utföras på samtliga material som finns tillgängliga i Volvo Cars materialbibliotek för att skapa en breddare syn på samtliga modellers applicerbarhet. Materialmodellerna kommer även att utvärderas beroende på deras användarvänlighet samt vilka typer av data krävs för att använda modellen.   Resultatet visade att BBC 2005 skall rekommenderas för aluminium samt stål till de företag som har tillgång till biaxiella data samt lägger optimering i fokus. Hill`48 visade sig alldeles för avvikande för stål och bör inte användas om andra modeller är tillgängliga. Vegter 2017 visade sig perfekt för stål då resultatet var bra samt att den nödvändiga materialdatan kan införskaffas genom standardiserade dragprov. Resultatet visade även att Vegter 2017 inte bör användas för aluminium då resultatet var för avvikande. Barlat`89 gav bra resultat med endast data från dragprovstest vilket ger att den är att rekommendera för aluminium.   Slutsatsen från detta arbete är att valet av materialmodell är väldigt beroende av vilka förutsättningar som finns då väldigt få industrier har tillgång till de tester som krävs för att använda BBC 2005. I större delar av industrin där minimala optimeringar inte anses som väsentliga är Barlat`89 och Vegter 2017 att föredra då detta leder till snabbare processer.

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The modulus of aggregate base layers in pavement structures can potentially be increased through the use of geogrid. However, methods for determining how much structural benefit can be expected from a given geogrid product have not been standardized. A laboratory testing protocol is therefore needed to enable evaluation, in terms of modulus or California bearing ratio (CBR), for example, of the degree of improvement that may be achieved by a given geogrid. Consequently, the objective of this research was to identify a laboratory test method that can be used to quantify improvements in structural capacity of aggregate base materials reinforced with geogrid. For this research, National Cooperative Highway Research Program Report 598 repeated load triaxial, American Association of State Highway and Transportation Officials (AASHTO) T 307 quick shear, and CBR testing protocols were used to test unreinforced and geogrid-reinforced aggregate base materials from northern Utah. Biaxial and triaxial geogrid were investigated in multiple reinforcement configurations. Several statistical analyses were performed on the results of each test method to identify the test that is most likely to consistently show an improvement in the structural capacity of aggregate base materials reinforced with geogrid. The results of this research indicate that, for the methods and materials evaluated in this study, calculation of the modulus at 2 percent strain from the AASHTO T 307 quick shear data is the test method most likely to consistently show an improvement in structural capacity associated with geogrid reinforcement. Of the three configurations investigated as part of this research, placing the geogrid at an upper position within a specimen is preferred. Given that the end goal of the use of geogrid reinforcement is to improve pavement performance, additional research is needed to compare the results of the AASHTO T 307 quick shear test obtained in the laboratory with the structural capacity of geogrid-reinforced aggregate base materials measured in the field. In addition, correlations between the results of the AASHTO T 307 quick shear test and resilient modulus need to be investigated in order to incorporate the findings of the AASHTO T 307 quick shear test on reinforced base materials into mechanistic-empirical pavement design.

No description available.