Le soudage du bois est une technique d'assemblage sans adhésif de deux pièces de bois, leur soudure étant produite par friction mécanique sous pression des deux pièces. Ce procédé, applicable à des pièces de bois plates, d'essences identiques ou différentes, se prête à la fabrication de meubles et à la menuiserie. Cependant, le joint obtenu n'est pas de classe "extérieur", ce qui le réserve à un usage "intérieur". En effet, un joint destiné à une utilisation extérieure ou en milieu à humidité variable doit présenter une résistance élevée à l'eau. L'objectif principal de cette thèse est d'étudier la résistance à l'eau du bois soudé. A cet effet, des méthodes d'essais complémentaires et non-destructrices ont été utilisées, comme le scanner ou l'imagerie par résonance magnétique (IRM). L'influence des paramètres de soudage et des propriétés du bois sur, d'une part, la formation et la propagation des fissures dans la ligne de soudure, et sur, d'autre part, la densité et l'absorption d'eau de la soudure a été ainsi étudiée. Les expériences de cette thèse seront menées sur des échantillons de pin (Pinus sylvestris) de dimensions 200 mm x20 mm x 40 mm, coupés dans la direction longitudinale du fil du bois. La Norme Européenne EN 205 a servi de cadre pour déterminer la résistance des échantillons de pin en traction-cisaillement. Les méthodes d'essais (non-destructrices) ont été utilisées selon leur pertinence: le scanner a servi à étudier la formation et la propagation des fissures; l'imagerie par résonance magnétique (IRM) a permis quant à elle de caractériser la pénétration et l'infiltration d'eau dans le bois soudé.Le mécanisme d'adhérence du pin a été étudié grâce à la RMN MAS (spectrométrie à résonance magnétique nucléaire avec polarisation croisée et rotation à l?angle magique) du carbone13 et à la micro-densitométrie par rayons X. Ces différentes méthodes, non destructrices, offrent l'avantage d'une analyse non invasive et l'élimination de facteurs parasites liés à la préparation et à la coupe du bois. Voici en résumé les résultats obtenus les plus marquants: (1) Le scanner et l'imagerie par résonance magnétique (IRM) sont des méthodes de recherche particulièrement polyvalentes et adaptées à l'étude des bois soudés. (2) L'utilisation de bois de coeur, une pression de soudage de 1.3 Mpa et un temps de soudage de 1.5 s permettent d'augmenter la résistance à l'eau du pin soudé. (3) Des tests d'optimisation ont montré que la résistance du pin en traction-cisaillement est plus sensible aux variations de temps de soudage qu'au temps de refroidissement et qu'elle peut être optimisée à plus de 9.7 MPa en respectant une pression de 1.3 Mpa, un temps de soudage > 3.5 s et un temps de refroidissement < 60 s. (4) La résistance à l'eau du bois soudé peut être améliorée dans une certaine mesure en faisant varier paramètres de soudage et propriétés des essences, mais dans tous les cas, le recours à un imperméabilisant naturel et écologique reste nécessaire. (5) Le pin soudé possède une résistance à l'eau et en traction-cisaillement inhabituellement élevée, cela pouvant s'expliquer par une teneur en composés extractifs augmentée. (6) Des essais sous IRM ont montré que les causes de rupture du joint varient suivant l'essence: faible résistance à l'eau de la ligne de soudure dans le cas du hêtre soudé, retrait et expansion du bois dans le cas du pin soudé. (7) Les extractifs du pin améliorent nettement la résistance à l'eau du joint soudé, mais à un niveau qui ne lui permet cependant pas la certification "extérieur" sans protection. En revanche, il peut être certifié "semi-extérieur" avec protection. / Wood welding is a mechanical friction process allowing the assembly of timber without any adhesives. The process consists of applying mechanical friction, under pressure, alternately to the two wood surfaces to be welded. This process can be applied to weld two flat pieces of timber, originating from the same or different tree species, and can be used in the manufacture of furniture and wood joinery. The only limitation is that the joint is not exterior-grade, but only suitable for interior joints. Exterior use, or use in an environment with varying humidity demands water resistance of the welded joints. The main objective of this thesis is to study the water resistance of the welded wood. This is complemented with special attention to non-destructive test methods such as X-ray Computed Tomography (CT-) scanning and Magnetic Resolution Imaging (MRI). The influence of welding parameters and wood properties on crack formation and crack propagation in the weldline was investigated. The influence of these parameters on weldline density and water absorption in the weldline were also studied. Investigations in this thesis are based on welded samples of Scots pine (Pinus sylvestris) of the dimensions 200 mm × 20 mm × 40 mm which were cut in the longitudinal direction of the wood grain. The tensile-shear strength of the welded Scots pine samples were determined using European standard EN 205. Different non-destructive methods such as X-ray Computed Tomography (CT-) scanning to study crack formation and propagation, and magnetic Resolution Imaging (MRI) to characterize water penetration and the distribution mechanism in welded wood were used. Solid state CPMAS 13C NMR spectrometry and X-ray microdensitometry investigations were carried out to study the mechanism of adhesion in Scots pine. These various non-destructive methods offer the advantage of non-invasive analysis and the elimination of any artifacts present due to preparation and sectioning. The most important results are summarized as follows: (1) X-ray Computed Tomography (CT-) scanning and Magnetic Resolution Imaging (MRI) are versatile research methods applicable to investigations of welded woods. (2) Water resistance of welded Scots pine can be increased using heartwood, a welding pressure of 1.3 MPa, and a welding time of 1.5 s. (3) Optimization tests showed that the tensile-shear strength of Scots pine was more sensitive to welding time changes than holding time and could be optimized to more than 9.7 MPa using 1.3 MPa welding pressure, > 3.5 s welding time, and < 60 s holding time. (4) Changing welding parameters and wood properties can increase water resistance of welded wood to some extent, but treating the weldline with certain natural and environmentally-friendly water repellents is still necessary. (5) Welded Scots pine shows unusually high water resistance and tensile-shear strength. This may be explained by there being more extractives compounds in Scots pine. (6) MRI experiments showed that the origin of the joint failure in welded beech is poor water resistance of the weldline, while swelling and shrinkage of wood are the main reasons for joint failure of welded Scots pine. (7) Extractives in Scots pine dramatically improve water resistance of the welded joint, but not to a level to classify the joint as an unprotected exterior grade. However, it can qualify as a joint for protected semi-exterior application.

Abstract The wood industries to this day use almost exclusively petroleum derived adhesives that are based mainly on the reaction of formaldehyde with urea, melamine or phenol. These adhesives have low cost and good adjustable properties which makes it hard for bio-based alternatives to compete. Phenol formaldehyde (PF), as an example of a synthetic adhesive, has been in use for over 100 years. In some parts of the world, legislation around formaldehyde is changing, and there is an increasingly voluntary awareness about the toxicity and unsustainability of formaldehyde. Industries realize that raw materials from oil is unstainable. The latter is currently a driving factor behind research on alternatives to amino based adhesives. Also, consumer interest in healthy and sustainable products, such as emitting less formaldehyde indoors, increases the need for bio based adhesives. Cellulose contained in plant cell walls is a renewable, abundant and nontoxic resource. During the last decades, many innovations have been achieved around cellulose and this trend does not seem to be slowing down. Cellulose shows excellent mechanical properties, high strength, high elastic modulus as well as having a low density. Research about cellulose reinforced adhesives has been increased the last years. This thesis studied the enhancement of phenol formaldehyde adhesive with Crystalline Nano Cellulose (CNC) at 5wt% and 10wt% loading levels for producing plywood boards. Indecisive results when using CNC higher than 3wt%, especially with PF resin, have been reported by other authors. In this thesis, European standards were applied. EN 314 was applied to test the panels shear strength. Three (3) treatment classes were selected, indoor room condition as well as pre-treatments 5.1.1 and 5.1.3. Other properties measured were modulus of elasticity, thickness swelling, formaldehyde emissions. Results showed a shear strength increase for all pre-treatment classes. 10wt% CNC mixture with phenol formaldehyde in water bath, pre-treatment (5.1.1) for 24h showed the highest increase in shear strength (+73,9%). The 10 wt% CNC mixture panels also showed the highest wood fibre failure of all panel types produced. A decrease in MOE has been observed with 10 wt% CNC compared to the 5 wt% CNC panels. Formaldehyde emissions tests were inconclusive, but since less PF was used, there was a general reduction in emissions. The 5 wt% CNC panels were superior in terms of modulus of elasticity and swelling and also showed improved shear strength.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-03-01T13:44:47Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Andrés Fernando Montenegro.pdf: 11976346 bytes, checksum: fa909dec838336e8c5a4ed73180bb65b (MD5) / Made available in DSpace on 2018-03-01T13:44:47Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Andrés Fernando Montenegro.pdf: 11976346 bytes, checksum: fa909dec838336e8c5a4ed73180bb65b (MD5) Previous issue date: 2017-10-16 / O objetivo deste estudo foi verificar o efeito da densidade de energia e o tempo de exposição de fotopolimerizadores LED de terceira geração em uma resina ortodôntica disponível comercialmente nos valores de microdureza, cisalhamento, índice de remanescente de resina e grau de conversão. Para tanto, foram realizados 3 experimentos: Experimento 1, o objetivo foi avaliar o grau de conversão (DC) e microdureza vickers (MHV) da resina ortodôntica utilizando dois LEDs de terceira geração, assim como, protocolos de fotoativação diferentes. Foram necessários 80 brackets cerâmicos e 80 brackets metálicos, sendo divididos em 16 grupos experimentais (n=10) tendo os seguintes grupos para cada LED: um grupo controle, diminuição da metade do tempo de exposição do grupo controle, um quarto do tempo do grupo controle, função turbo ou plasma para os LEDs Bluephase e Valo, respetivamente. Imediatamente após a polimerização, foram realizados os ensaios de DC e MHV. O experimento 2, objetivou verificar a influência de diferentes densidades de energia emitidas por dois fotoativadores LED de alta potência nas propriedades físicas e mecânicas de uma resina ortodôntica em brackets metálicos. Foram necessários 80 pré-molares superiores, sendo usadas as superfícies vestibulares dos dentes para a colagem dos 80 brackets metálicos. Os dentes foram divididos aleatoriamente em 8 grupos experimentais (n=10), sendo: um grupo controle, redução da metade do tempo de exposição do grupo controle, um quarto do tempo do grupo controle, função plasma ou turbo para cada LED estudado, sendo Valo e Bluephase. Após 24 horas da polimerização, foram realizados os testes de cisalhamento (SBS), índice remanescente de resina (ARI) e MHV. O objetivo do experimento 3 foi verificar a influência de diferentes densidades de energia depositadas por dois fotoativadores LED diferentes de alta potência nas propriedades físicas e mecânicas de uma resina ortodôntica em brackets cerâmicos. Foram necessários 80 dentes pré-molares superiores hígidos, sendo utilizadas as superfícies linguais ou palatinas dos dentes para colagem dos 80 brackets cerâmicos. Os dentes foram divididos aleatoriamente em 8 grupos experimentais (n=10), foram formados grupos iguais para cada LED Valo e Bluephase: um grupo controle, diminuição da metade do tempo de exposição do grupo controle, um quarto do tempo do grupo controle, função turbo do LED Bluephase ou plasma do LED Valo. Após 24 horas da polimerização, foram realizados os testes de SBS, ARI e MHV. Os resultados de cada experimento foram analisados através de testes estatísticos específicos, para determinar se houve ou não diferença estatisticamente significativa. Para o experimento 1 foram realizados ANOVA de duas vias e teste de Tukey (α=0,05), para o experimento 2 e 3 foram realizados Anova de duas vias com testes de Tukey (α=0,05). O experimento 1 mostrou que os grupos dos brackets cerâmicos tem baixa variação, porém pequenas mudanças no aumento dos valores da energia aplicada em Joules totais aumentam os valores de DC e MHV, nos brackets metálicos pelo fato de impedir a passagem da luz o DC e HVK diminuem significativamente, permanecendo dentro dos parâmetros considerados normais. O experimento 2 mostrou que ambos LED utilizados foram efetivos tanto na função standard como na turbo ou plasma, sendo que as funções turbo ou plasma ofereceram resultados similares aos do controle, efetivando mesmo com a redução do tempo para a polimerização dos brackets metálicos. No experimento 3 não houve diferença estatisticamente significativa nos grupos analisados. Os LEDs estudados proporcionaram valores suficientes de Joules em alguns grupos experimentais sendo este suficiente para atingir bons valores no DC, SBS e MHV. O uso de LEDs com uma potência adequada, sendo o mínimo de 1200 mW/cm2, ou o uso de uma potência elevada de entre 2400 a 3200 mW/cm2 e um curto período de tempo de exposição entre 3 a 6 segundos, são efetivos para a colagem de acessórios ortodônticos. / The objective of this study was to verify the effect of energy density and the time of exposure of third generation LED light curing agents on a commercially available orthodontic resin in the values of microhardness, shear, resin remaining index and degree of conversion. Three experiments were carried out: Experiment 1, the objective was to evaluate the degree of conversion (DC) and microhardness vickers (MHV) of the orthodontic resin using two third generation LEDs, as well as different photoactivation protocols. 80 ceramic brackets and 80 metallic brackets were required and divided into 16 experimental groups (n=10), with the following groups for each LED: control group, one half, one quarter of the control group time, turbo or plasma function for the Bluephase and Valo LEDs, respectively. Immediately after the polymerization, the DC and MHV assays of the specimens were performed. The experiment 2, aimed to verify the influence of different energy densities emitted by two high power LED photoactivators on the physical and mechanical properties of an orthodontic resin in metallic brackets. For this experiment, 80 carious cavity-free, superior human premolar teeth were used, and the buccal surfaces of the teeth were used for the bonding of the 80 metal brackets. The teeth were randomly divided into 8 experimental groups (n=10), with the following groups being a control group, half the time of exposure of the control group, one quarter of the time in the control group, plasma or turbo function for each LED studied, being Valo and Bluephase. After polymerization, the teeth and specimens were stored 24h at 37°C to perform the shear tests (SBS), resin remaining index (ARI) and MHV. The objective of experiment 3 was to verify the influence of different energy densities deposited by two different LED light-curing on the physical and mechanical properties of an orthodontic resin in ceramic brackets. For this experiment, it was necessary to have 80 carious free upper premolar human teeth, using the lingual or palatine surfaces of the teeth for bonding the 80 ceramic brackets. The teeth were randomly divided into 8 experimental groups (n=10), equal groups were formed for each Valo and Bluephase LEDs: one control group, one half-time control group exposure time, one-fourth time control group, function LED Bluephase turbo or LED Valo Plasma. After polymerization, the teeth and specimens were stored 24 hours at 37°C to perform the SBS, ARI and MHV tests. The results of each experiment were analyzed by specific statistical tests to determine whether or not there was a statistically significant difference. For experiment 1, 2 and two-way ANOVA and Tukey's test (α=0.05) were performed. Experiment 1 showed that the groups of ceramic brackets have low variation, but small changes in the increase of the values of the applied energy in total Joules increase the values of DC and MHV in the metallic brackets because it prevents the passage of light the DC and HVK decrease significantly, remaining within the parameters considered normal. Experiment 2 showed that both LEDs were effective both in the standard function and in the turbo or plasma, and the turbo or plasma functions gave similar results to the control, even effecting with the reduction of the time for the polymerization of the metal brackets. In the experiment 3 there was no statistically significant difference in the analyzed groups. The studied LEDs provided sufficient values of Joules in some experimental groups being sufficient to reach good values in DC, SBS and HVK. The use of LEDs with adequate power, being at least 1000 mW/cm2, or the use of a high power of between 2400 and 3200 mW/cm2 and a short period of exposure of between 3 to 6 seconds, are sufficient for the bonding of orthodontic accessories.

Submitted by Eunice Novais (enovais@uepg.br) on 2018-07-24T14:32:21Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) RENATA TERUMI JITUMORI.pdf: 3093609 bytes, checksum: 92de6bf22e06953ec3a932faaf478f71 (MD5) / Made available in DSpace on 2018-07-24T14:32:21Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) RENATA TERUMI JITUMORI.pdf: 3093609 bytes, checksum: 92de6bf22e06953ec3a932faaf478f71 (MD5) Previous issue date: 2018-02-21 / Avaliou-se o efeito da irrigação prévia na adesão de cimentos resinosos autoadesivos ao canal radicular na cimentação de pinos de fibra de vidro (PFV). Foram utilizados 120 dentes permanentes unirradiculares, os quais tiveram suas coroas removidas e suas raízes tratadas endodonticamente. Após uma semana, foi realizado o preparo padronizado dos condutos para posterior cimentação dos PFV. Nesse momento, as raízes foram divididas aleatoriamente em dez grupos, de acordo com a combinação dos seguintes fatores: cimento resinoso autoadesivo – RelyX U200 (3M ESPE) e Multilink Speed (Ivoclar Vivadent), e agente irrigante aplicado previamente à cimentação dos PFV – água destilada (AD), NaOCl 2,5% (Na), EDTA 17% (ED), ácido poliacrílico 26% (AP) e associação EDTA 17% + NaOCl 2,5% (EN). Duas raízes de cada agente irrigante foram utilizadas para avaliação do grau de desobliteração dos túbulos dentinários (DeTd) por microscopia eletrônica de varredura (MEV). Após a cimentação dos PFV, sete raízes por grupo foram avaliadas em resistência de união (RU) pelo teste de push-out, quatro em nanoinfiltração (NI) por MEV e microdureza Vickers (VHN); para esse propósito cada raiz foi seccionada transversalmente em seis fatias. Os dados obtidos da DeTd foram submetidos a Kruskall Wallis e Student-Newman-Keuls (α=0,05) e dos testes de RU, NI e VHN a ANOVA dois fatores e Tukey (α=0,05). Na avaliação da DeTd, os agentes que promoveram maior abertura dos tubúlos dentinários foram ED, AP e EN. Para o cimento RelyX U200, o Na, AD e ED obtiveram os maiores valores de RU e VHN; enquanto que para o Multilink Speed esses valores foram superiores no grupo irrigado com AD. Para ambos os cimentos, o AP apresentou valores inferiores e a associação EN valores intermediários de RU e VHN. Não houve diferença estatística significante nos resultados de NI (p>0,05). Pode-se concluir que para cada agente cimentante deve haver um protocolo de irrigação prévia ideal na cimentação de pinos de fibra de vidro ao canal radicular. / It was evaluated the effect of previous irrigation on the adhesion of on the adhesion of self-adhesive resin cements to the root canal in the cementation of glass fiber posts. A total of 120 unirradicular permanent teeth were used, which had their crowns removed and their roots treated endodontically. After one week, the standard preparation of the post space was made for the cementation of the GFP. At this time, the roots were randomly divided into ten groups, according to the combination of the following factors: self-adhesive resin cement - RelyX U200 (3M ESPE) and Multilink Speed (Ivoclar Vivadent), and irrigating agent applied prior to GFP cementation - distilled water (DW), 2.5% NaOCl (Na), 17% EDTA (ED), 26% polyacrylic acid (PA) and 17% EDTA followed by 2.5% NaOCl (EN). Two roots of each irrigating agent were used for evaluation the degree of open dentinal tubules (ODeT) by scanning electron microscopy (SEM). After the cementation of the GFP, seven roots per group were evaluated in bond strength (BS) by the push-out test, four in nanoleakage (NL) by SEM and in Vickers microhardness (VHN); for this propose each root was sectioned transversely into six slices. The data obtained from ODeT were submitted to Kruskall Wallis and Student-Newman-Keuls (α=0.05) and from the tests of BS, NL and VHN to ANOVA two-way and Tukey (α=0.05). In the evaluation of the ODeT, the agents that promoted greater opening of the dentin tubules were ED, PA and EN. For RelyX U200 cement, the Na, DW and ED obtained the highest values of BS and VHN; while for Multilink Speed these values were higher in the group irrigated with DW. For both cements, the PA presented lower values and the association EN intermediate values of BS and VHN. There was no statistically significant difference in NL results (p>0.05). It can be concluded that for each cementing agent there must be an optimal prior irrigation protocol for the cementation of glass fiber posts to the root canal.

Submitted by Eunice Novais (enovais@uepg.br) on 2018-07-31T14:08:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Julio Cezar C Filho.pdf: 2297707 bytes, checksum: 0318db2af277ea89875b724010007eb0 (MD5) / Made available in DSpace on 2018-07-31T14:08:13Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Julio Cezar C Filho.pdf: 2297707 bytes, checksum: 0318db2af277ea89875b724010007eb0 (MD5) Previous issue date: 2018-02-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Avaliou-se a influência do tipo e viscosidade da resina composta utilizada para reforço radicular (RR) em dentes com canais radiculares excessivamente alargados na adesão de pinos de fibra de vidro (PFV) ao canal radicular. Foram selecionados 78 dentes permanentes unirradiculares, os quais tiveram suas coroas removidas e suas raízes tratadas endodonticamente. Após uma semana, foi realizado o preparo dos condutos para posterior RR. Nesse momento, as raízes foram aletoriamente divididas em 6 grupos (n=13), sendo um grupo controle positivo (GCP – em que os canais não estavam alargados), um grupo controle negativo (GCN – em que os canais estavam alargados, porém sem RR), e 4 grupos de RR dos canais alargados de acordo com a combinação dos seguintes fatores: tipo de resina composta: bulk ou convencional e viscosidade da resina composta: fluida ou regular. Após a cimentação dos PFV, para cada raiz foram obtidas seis fatias (duas representativas de cada região radicular - terço coronário, médio e apical). Em seguida, para cada grupo, 7 raízes foram avaliados em resistência de união (RU) pelo teste de push-out, 6 raízes foram avaliados em nanoinfiltração (NI) e microdureza Vickers. Os dados obtidos de RU e NI foram submetidos a ANOVA dois fatores (grupo experimental vs região radicular) e Tukey (α=0,05), e de microdureza a ANOVA um fator e Tukey para cada grupo experimental (α= 0,05). Os grupos de RR com as resinas tipo bulk em ambas as viscosidades apresentaram resultados de adesão superiores estatisticamente ao GCN em todas as regiões radiculares (maior RU e menor NI). Pode-se concluir que a técnica de reforço radicular com resinas composta do tipo bulk, tanto com viscosidade regular quanto com viscosidade fluida, pode ser uma técnica alternativa interessante previamente à cimentação de PFV em raízes enfraquecidas com canais radiculares alargados. / The influence of the type and viscosity of the composite resin used for root reinforcement (RR) was evaluated in teeth with excessively wide root canals in the adhesion of glass fiber post (GFP) to the root canal. It was selected 78 uniradicular permanent teeth, which had their crowns removed and their roots treated endodontically. After one week, the conduits were prepared for later RR. At that time, the roots were randomly divided into 6 groups (n = 13): positive control group (PCG - where the root canals were not enlarged), negative control group (NCG - where the root canals were widened - but without RR), and 4 groups of RR of the widened root canals according to the combination of the following factors: type of composite resin: bulk or conventional and viscosity of composite resin: flow or regular. After the cementation of the GFP, six slices were obtained for each root (two representatives of each root region - coronary, middle and apical third). Then, for each group, 7 teeth were evaluated in bond strength (BS) by the push-out test, 6 teeth were evaluated in nanoleakage (NL) and Vickers microhardness (VHN). The data obtained from BS and NL were submitted to two-way ANOVA (experimental group vs root region) and Tukey (α = 0.05), and from VHN to one-way ANOVA and Tukey for each experimental group (α = 0.05). The RR groups with bulk composite resins at both viscosities showed statistically superior adhesion results to GCN in all root regions (higher BS and lower NL). It can be concluded that the radicular reinforcement technique with bulk composite resins, both with regular and flow viscosities, may be an interesting alternative technique prior to the GFP cementation in weakened roots with widened root canals.

Nas últimas décadas, teorias têm sido formuladas para interpretar o comportamento de solos não saturados e estas têm se mostrado coerentes com resultados experimentais. Paralelamente, várias técnicas de campo e de laboratório têm sido desenvolvidas. No entanto, a determinação experimental dos parâmetros dos solos não saturados é cara, morosa, exige equipamentos especiais e técnicos experientes. Como resultado, essas teorias têm aplicação limitada a pesquisas acadêmicas e são pouco utilizados na prática da engenharia. Para superar este problema, vários pesquisadores propuseram equações para representar matematicamente o comportamento de solos não saturados. Estas proposições são baseadas em índices físicos, caracterização do solo, em ensaios convencionais ou simplesmente em ajustes de curvas. A relação entre a umidade e a sucção matricial, convencionalmente denominada curva característica de sucção do solo (SWCC) é também uma ferramenta útil na previsão do comportamento de engenharia de solos não saturados. Existem muitas equações para representar matematicamente a SWCC. Algumas são baseadas no pressuposto de que sua forma está diretamente relacionada com a distribuição dos poros e, portanto, com a granulometria. Nestas proposições, os parâmetros são calibrados pelo ajuste da curva de dados experimentais. Outros métodos supõem que a curva pode ser estimada diretamente a partir de propriedades físicas dos solos. Estas propostas são simples e conveniente para a utilização prática, mas são substancialmente incorretas, uma vez que ignoram a influência do teor de umidade, nível de tensões, estrutura do solo e mineralogia. Como resultado, a maioria tem sucesso limitado, dependendo do tipo de solo. Algumas tentativas têm sido feitas para prever a variação da resistência ao cisalhamento com relação a sucção matricial. Estes procedimentos usam, como uma ferramenta, direta ou indiretamente, a SWCC em conjunto com os parâmetros efetivos de resistência c e &#61542;. Este trabalho discute a aplicabilidade de três equações para previsão da SWCC (Gardner, 1958; van Genuchten, 1980; Fredlund; Xing, 1994) para vinte e quatro amostras de solos residuais brasileiros. A adequação do uso da curva característica normalizada, proposta por Camapum de Carvalho e Leroueil (2004), também foi investigada. Os parâmetros dos modelos foram determinados por ajuste de curva, utilizando técnicas de problema inverso; dois métodos foram usados: algoritmo genético (AG) e Levenberq-Marquardt. Vários parâmetros que influênciam o comportamento da SWCC são discutidos. A relação entre a sucção matricial e resistência ao cisalhamento foi avaliada através de ajuste de curva utilizando as equações propostas por Öberg (1995); Sällfors (1997), Vanapalli et al., (1996), Vilar (2007); Futai (2002); oito resultados experimentais foram analisados. Os vários parâmetros que influênciam a forma da SWCC e a parcela não saturadas da resistência ao cisalhamento são discutidos. / In the last decades, theories have been formulated to interpret the behavior of unsaturated soils and found to be consistent with the experimental response. Besides, several techniques for field and laboratory testing have been developed, as well. However, the experimental determination of unsaturated soil parameters is costly, time-consuming, requires particular test equipments and experienced technicians. As a result, these theories application are limited to academic researches and are barely used in engineering practice. To overcome this issue, several researchers proposed equations to mathematically represent the experimental behavior unsaturated soils. These propositions are based on physical indexes, soil characterization, and current laboratory tests or simply curve fitting. The relationship of soil-water content and matric suction, conventionally referred to as the soil-water characteristic curve (SWCC) is also useful tool in the prediction of the engineering behavior of unsaturated soils. There are many equations to mathematically represent SWCC. Some are based on the assumption that its shape is directly related to the pore distribution, and, therefore, the grain size distribution. In these propositions the parameters are calibrated by curve adjustment of the experimental data. Others assume that the curve can be directly estimated from physical properties of soils. These proposals are simple and convenient for practical use, but are substantially incorrect since they disregard the influence of moisture content, stress level, soil structure and mineralogy. As a result, most of them have limited success depending on soil types. Some attempts have also been made to predict the variation of the shear strength with respect to matric suction. These procedures use SWCC as a tool either directly or indirectly along with the saturated strength parameters c and &#61542;. This work discusses the applicability of three SWCC equations (Gardner, 1958; van Genuchten, 1980; and Fredlund and Xing, 1994) for twenty four residual soils from Brazil. The suitability of the normalized soil-water characteristic curve, proposed by Camapum de Carvalho and Leroueil (2004), was also investigated. Models parameters were determined by curve fitting, using inverse problem techniques; two optimization methods were used: Genetic Algorithm (GA) and Levenberq-Marquardt method. Several parameters that influence the SWCC behavior are discussed, as well. The relationship between matric suction and shear strength was evaluated by curve fitting using the equations proposed by Öberg and Sällfors (1995, 1997), Vanapalli et al., (1996), Vilar (2007) and Futai (2002); eight experimental results were analyzed. Several parameters that influence the SWCC behavior and the unsaturated shear strength are discussed, as well.

Made available in DSpace on 2014-06-11T19:31:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-07Bitstream added on 2014-06-13T20:21:49Z : No. of bitstreams: 1 coldebella_cr_dr_arafo.pdf: 1165027 bytes, checksum: 68372d3e55cbf9fcc5b26e1b2514cf7c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Proposição: O objetivo deste trabalho, dividido em três estudos, foi investigar o efeito após a aplicação de ondas de ultrassom sobre cimentos de ionômero de vidro (CIV) (1) a dureza da dentina subjacente, hígida e afetada por cárie; (2) a resistência de união à dentina hígida e afetada por cárie (3) e à rugosidade do material após ensaio de escovação. Materiais e métodos: Nos três estudos foram utilizados os CIV Vitremer (VT) e Ketac Molar Easymix (KM). Para o estudo 1 foram realizados preparos cavitários (3 mm de largura, 5 mm de comprimento e 2 mm de profundidade) na face vestibular de 80 incisivos bovinos. Foi realizada a indução de lesão de cárie artificial pelo método microbiológico (n=40). Os dentes foram distribuídos em 8 grupos (n=10), segundo o substrato (hígido ou afetado por cárie), material utilizado (VT ou KM) e o tratamento recebido (com ou sem a aplicação de ondas de ultrassom). A aplicação de ondas de ultrassom foi realizada por 30 segundos. Após 30 dias de armazenagem em água os dentes foram seccionados e as leituras de dureza Knoop realizadas na dentina subjacente ao material até 200 μm de distância da interface dentina/CIV. No segundo estudo foram confeccionados 20 blocos de dentina bovina para cada material, sendo que 10 deles foram submetidos ao processo de indução de lesão de cárie artificial e subsequente remoção da dentina contaminada. Em cada bloco foram confeccionados dois corpos de prova com 1,5 cm de altura e 3 cm de diâmetro, sendo o primeiro com e o segundo sem a aplicação de 30 segundos de ondas de ultrassom. Após 24 horas, os corpos de prova foram submetidos ao ensaio mecânico de cisalhamento. No terceiro trabalho 32 espécimes de cada material, VT e KM, foram confeccionados em matriz de dente bovino, sendo que a metade recebeu ondas... / Aim: This work was divided into three studies. The objective was to investigate the effect of ultrasound application on glass ionomer cement (GIC), analyzing underlying dentin hardness, bond strength to noncarious dentin and cariesaffected dentin and the material roughness after toothbrushing test. Materials and methods: GIC Vitremer (VT) and Easymix Ketac Molar (KM) were used in these studies. In the first study, cavities (3 mm wide, 5 mm in length and 2 mm deep) were performed on the buccal surface of eighty bovine incisors. Microbiological method was used to induce artificial caries lesions (n = 40). The teeth were divided into 8 groups (n = 10), according the substrate (noncarious dentin or caries-affected dentin), the material used (VT or KM) and the treatment received (with or without ultrasound application). The ultrasound application was performed for 30 seconds, and teeth stored in water for 30 days. After that, the specimens were sectioned and transversal hardness evaluation was performed in the underlying dentin material up to depth of 200 μm. In the second study, 20 dentin blocks were used for each material. Ten of them were artificially decayed and performed subsequent removal of infected dentin. In each block, two specimens (1.5 cm high and 3 cm diameter) were performed, the first with and the second without ultrasound application. After 24 hours the specimens were shear bonding tested. For the third study 32 specimens of each material, VT and KM, were prepared using a bovine tooth matrix. Half of them received a 30 s ultrasound application during its initial setting. The surface roughness, before and after toothbrushing test, was evaluated at 24 hours (n = 16) and 30 days (n = 16). Data were analyzed by ANOVA and Tukey tests. For all the studies, the statistical tests were considered at the present level... (Complete abstract click electronic access below)

The EC Landfill Directive (1999), which is enforced in England and Wales through the Landfill (England and Wales) Regulations (2002), has increased the technical challenge associated with the design and construction of landfill containment systems, in particular those on steep side slopes. Increased numbers of lining system components, varied configurations, and complex loading scenarios require advanced analysis tools to facilitate design. This project involved the development of advanced numerical modelling techniques, based on the FLAC finite difference modelling code. The analysis toolbox can be used to predict the behaviour of multilayered geosynthetic and soil lining systems, during and after staged construction. The model can include non-linear interface and geosynthetic axial properties, represent complex loading, including downdrag from the waste mass, whilst retaining the flexibility to represent varied geometries and include engineered support structures. Whilst numerical modelling is becoming increasingly commonplace in commercial design, there is little evidence of the validation of numerical models with field or experimental data. Validation of the analysis toolbox described in this document was conducted by back analysis of published data, modelling of landfill failure mechanisms, and comparisons to large scale laboratory testing. Design of field scale instrumentation has also been carried out as part of this project. The influence of interface shear strength variability has been assessed through the compilation of a comprehensive database, and the effect of this variability on lining system behaviour assessed through reliability based analyses. This has shown probability of failures may be higher than proposed limiting values when adopting traditional accepted factors of safety. A key area of interest identified during the project was the requirement for support, potentially through reinforcement, of the geological barrier. The inclusion of randomly reinforced fibres in bentonite enhanced soil has shown the potential for increased strength, without adverse effects on hydraulic barrier performance. ii Additionally, the influence of geomembrane seams on lining system integrity has been investigated, showing that fusion welded seams can result in stress concentration and extruded seams can cause significant stress concentration.

Large scale structures such as those in aerospace flight vehicles are made in parts and assembled. Joints are inevitable in these systems and they are potential threats to the structural integrity of the flight vehicles. Fastener and bonded joints are the most commonly used methods of joining in these structures. Among these, adhesive bonding has become more popular with the advent of composite structures, due to the presence of less number of points of stress concentration and the resulting benefit for static strength and fatigue life. In modern aircraft in which maximum percentage of composite materials are being employed due to several benefits, designers are contemplating to replace discrete joints with adhesively bonded joints wherever possible. A detailed literature survey shows that the field of adhesively bonded joints has been extensively studied in the past. Initial publications appeared in late 1950’s and early 1960's, but many of the initial attempts were based on one dimensional (1-D) approximation of the adherents due to lack of computing power. With the current day emphasis on safety and damage tolerance, there is a definite need to study these joints with 2-D and 3-D idealization. In spite of valuable contributions in the literature from several researchers in past 4-5 decades, one finds that there are gaps to be filled, in particular, with reference to static strength prediction and de-bond growth to failure under fatigue loading. This thesis is intended as a modest contribution in this direction covering the methods of strength prediction and also correlations between de-bond growth and fracture parameters. Most commonly used bonded joints are single lap joints. The primary issue in their analysis is the geometric nonlinearity resulting in large deformations due to eccentricity of load path between the adherents. Further, adhesives have very low yield strength and plastic deformation in thin adhesives could affect the mechanics of load transfer. The current work is initiated by carrying out geometric and material nonlinear analysis of adhesively bonded single lap joints between metal-metal (aluminum-aluminum) adherents using standard NASTRAN finite element software. Modified Newton-Raphson iterative technique has been used to economize the computer time and also achieve fast convergence. A convergence study has been conducted to determine the order of mesh size required. Preliminary results are obtained on configurations analysed by earlier workers and the current results are compared with their results. Later, extensive experimental and numerical studies have been taken up on the numerical strength prediction of these joints correlating them to the experimental values. Cohesive failure along the centre line of the adhesive is assumed under both static and fatigue loading. The bonded joints are studied with both 2-D plane stress and plane strain nonlinear FE analysis. The issue in this type of analysis is the presence of theoretical elastic singularity at the ends of the lap length. The normally used maximum stress criterion can not be used in such circumstances. There were attempts in the past to use point stress or average stress criteria for this purpose. In point stress criterion the shear stress (or von-Mises stress) is picked at a characteristic distance away from the ends of the lap length and compared with the corresponding strength value to predict failure. In the average stress criterion the stresses are averaged over a characteristic distance from the ends of lap length and this is compared with the corresponding strength to predict failure. Determination of the characteristic distance in both the cases needs extensive experimental results on static strength of joints. The static strength data is to be correlated with numerical results to determine the characteristic distance in various specimens. In the current thesis a series of specimens with aluminum-aluminum, aluminum-CFRP composite and CFRP-CFRP composite adherents were tested to determine the static strength. In all the specimens the adhesive used was Redux 319 A. These experimental strength data was used to determine characteristic distance using point stress criterion. The consistency of estimates of the characteristic distances in all the specimens shows that the approach is capable of predicting the static strength. The above approaches are capable of predicting the strength of joints with linear material and nonlinear geometric analysis. But when the adhesive yield strength is low, a novel approach is required to predict the static strength. Numerical analysis is conducted using a combined material and geometric nonlinear analysis in NASTRAN software. The plastic zone size from the ends of the lap length is determined at different load levels. Combining the numerical results with experimental failure load data, a failure criterion based on plastic zone size (PZS) is proposed in this thesis and validated. It has been observed that the validation is with limited testing carried out and further experimental programs are required to complete the validation. To the best of the knowledge of the author PZS criterion is used for the first time for failure prediction of bonded joints. The structural integrity of the joints also requires a study of de-bond growth and damage tolerance assurances in the presence of de-bond type of defects. The first step in this direction is to estimate the fracture parameters at the tips of de-bond in the adhesive of lap joints between various adherents. Modified virtual crack closure integral (MVCCI) technique has been developed in the past for estimating Strain Energy Release Rates (SERR) in several crack problems. Large contributions for developing this technique have come from the group where the author has worked. This technique is simple and has the ability to estimate individual SERR components GI and GII in cases of mixed mode fracture. It is seen clearly that the de-bond growth in bonded joint is one of mixed mode. The mode-II component is because of shear stresses transferring the load across the adherents and mode-I component is due to peel stresses developed during the deformation. The mode I SERR component is primarily responsible for de-bond growth and the effect of mode II component on de-bond growth is insignificant. The mesh details for accurately estimating the SERR components are evaluated and those meshes are used to estimate these values for the cases of aluminum-aluminum, aluminum-CFRP composite and composite-composite joints. Obviously, when the adherents are dissimilar, mode I SERR components are the highest and assist faster de-bond growth. Painstaking fatigue de-bond growth experiments were conducted and de-bond growth rate with number of cycles of fatigue loading was determined. MVCCI method is used to estimate SERR components at maximum load and zero load in the fatigue cycle, to determine the SERR range in the fatigue cycle. Since the stress ratio, R of the loading cycle is -1, the minimum load for estimating SERR components is taken as zero. From the experimental data and numerical estimates, a Paris type of equation was developed for the de-bond growth. The thesis concludes with a summary of the achievements in the current work with respect to the structural integrity of adhesively bonded joints and also with suggestions for future work.

Past studies on sands have shown that the shear strength measured in plane strain tests was higher than that measured in triaxial tests. It was observed that this difference changed with the friction angle &amp / #966 / cv at constant volume related to the mineralogical composition. In order to investigate the difference in strength measured in the wedge shear test, which approaches the plane strain condition, in the triaxial test, and in the shear box test, Anatolian sands were obtained from different locations in Turkey. Mineralogical analyses, identification tests, wedge shear tests (cylindrical wedge shear tests (cylwests) and prismatic wedge shear tests (priswests)), triaxial tests, and shear box tests were performed on these samples. In all shear tests, the shear strength measured was found to increase with the inclination &amp / #948 / of the shear plane to the bedding planes. Thus, cylwests (&amp / #948 / = 60o) iii yielded higher values of internal friction &amp / #966 / by about 3.6o than priswests (&amp / #948 / = 30o) under normal stresses between 17 kPa and 59 kPa. Values of &amp / #966 / measured in cylwests were about 1.08 times those measured in triaxial tests (&amp / #948 / &amp / #8776 / 65o), a figure close to the corresponding ratio of 1.13 found by past researchers between actual plane strain and triaxial test results. There was some indication that the difference between cylwest and triaxial test results increased with the &amp / #966 / cv value of the samples. With the smaller &amp / #948 / values (30o and 40o), priswests yielded nearly the same &amp / #966 / values as those obtained in triaxial tests under normal stresses between 20 kPa and 356 kPa. Shear box tests (&amp / #948 / =0o) yielded lower values of &amp / #966 / than cylwests (by about 7.9o), priswests (by about 4.4o), and triaxial tests (by about 4.2o) under normal stresses between 17 kPa and 48 kPa. It was shown that the shear strength measured in shear box tests showed an increase when &amp / #948 / was increased from 30o to 60o / this increase (about 4.2o) was of the order of the difference (about 3.6o) between priswest (&amp / #948 / = 30o) and cylwest (&amp / #948 / = 60o) results mentioned earlier. Shear box specimens with &amp / #948 / = 60o, prepared from the same batch of any sample as the corresponding cylwests, yielded &amp / #966 / values very close to those obtained in cylwests.