Submitted by Maria Medeiros (maria.dilva1@ufcg.edu.br) on 2018-08-20T14:23:35Z No. of bitstreams: 1 GLERYSTON THIAGO GOMES DA SILVA - DISSERTAÇÃO (PPGEM) 2017.pdf: 4116473 bytes, checksum: 5df445f57ab1b4d9326f681288378141 (MD5) / Made available in DSpace on 2018-08-20T14:23:35Z (GMT). No. of bitstreams: 1 GLERYSTON THIAGO GOMES DA SILVA - DISSERTAÇÃO (PPGEM) 2017.pdf: 4116473 bytes, checksum: 5df445f57ab1b4d9326f681288378141 (MD5) Previous issue date: 2017-05-03 / Capes / O presente trabalho avalia a adesão entre fios e fitas de uma liga com memória de forma (LMF) de Ni-Ti e uma borracha de silicone, para o desenvolvimento de estruturas flexíveis. A avaliação da adesão foi realizada através de ensaios de extração (Pull Out). Para realização dos ensaios, foram produzidos seis tipos de corpos de prova (CPs) em que os fios e as fitas foram embebidos em uma matriz de borracha de silicone. Primeiramente, as fitas foram obtidas laminando a frio fios de Ni-Ti superelástico. Após a laminação as fitas foram submetidas a tratamento térmico em temperaturas e tempos diferentes, a fim de obter dois tipos de fitas: uma com característica de superelasticidade (SE) e outra com o efeito memória de forma (EMF). Um promotor de adesão Dow Corning 1200 Primer foi aplicado nas superfícies dos fios e das fitas para aumento da adesão. Os fios e as fitas de Ni-Ti e a borracha de silicone foram individualmente caracterizados por Calorimetria Exploratória Diferencial (DSC), Análise Dinâmico-Mecânica (DMA) e tração uniaxial, analisando o comportamento do fator de amortecimento, módulo de elasticidade, tensões de transformação e temperaturas de transformação de fase. O ensaio de carregamento – descarregamento em tração na borracha de silicone também foi realizado para analisar a presença do efeito Mullins. Para verificação qualitativa do aumento da rugosidade e da adesão geradas pelo processo de laminação e pela aplicação do primer, respectivamente, foram realizadas imagens por Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Energia Dispersiva (EDS) nos fios e nas fitas de Ni-Ti antes e após o ensaio de extração (Pull Out). A partir dos resultados obtidos, observa-se que o fio superelástico e as fitas de Ni-Ti laminadas e tratadas termicamente sem aplicação do primer não apresentam adesão suficiente para o desenvolvimento de estruturas flexíveis compostas por borracha de silicone e elementos atuadores como fios e fitas de Ni-Ti, sendo necessária a aplicação de um promotor de adesão (primer) nas superfícies das LMF. / The present work evaluates the adhesion between Ni-Ti Shape Memory Alloy (SMA) wires and ribbons embedded into a silicone rubber, for the development of flexible structures. Adhesion evaluation was performed through pullout tests. To perform the tests, six types of specimens were produced, in which the wires and ribbons were embedded in a silicone rubber matrix. Firstly, the ribbons were obtained by cold rolling of a superelastic Ni-Ti wire. After the cold rolling, the ribbons were subjected to heat treatment at different temperatures and times in order to obtain two types materials: one with Superelasticity (SE) property and other with Shape Memory Effect (SME). A Dow Corning 1200 Primer adhesion promoter was applied to the surfaces of the wires and ribbons to improve adhesion. Ni-Ti wire and ribbons and silicone rubber were characterized by Differential Scanning Calorimetry (DSC), Dynamic-Mechanical Analysis (DMA) and uniaxial tensile tests, to obtain loss factor behavior, elastic modulus, tensile stress transformations and phase transformation temperatures. Analysis of tensile loading - unloading test on silicone rubber was also performed to evaluate the presence of the Mullins effect. For the qualitative verification of the roughness and adhesion improvement, generated by the cold rolling process and the application of the primer, respectively, images of Scanning Electron Microscopy (SEM) and Dispersive Energy Spectroscopy (EDS) in the Ni- Ti wire and ribbons were performed before and after the pullout tests. The obtained results indicate that the Ni-Ti superelastic wires and heat treated cold rolled ribbons without primer do not present sufficient adhesion for the development of silicone rubber flexible structures with embedded Ni-Ti wires and ribbons, requiring the application of an adhesion promoter (primer) on the surfaces of the SMA.

Objetivo: Este estudo se propõe a verificar a influência do adesivo, material de preenchimento e hibridização da dentina na força de retenção de pinos intra-radiculares na técnica direta indireta e comparar o teste de tração de push out com o pull out. Métodos: 60 raízes de dentes bovinos com comprimento de 12 mm foram tratadas endodonticamente e divididas aleatoriamente em 6 grupos (n=10): grupo 1 (técnica direta-indireta, adesivo fotopolimerizável, cimento resinoso, teste de pull out); grupo 2 (idem ao grupo 1 porém o cimento resinoso foi substituído pela resina composta); grupo 3 (idem ao grupo anterior porém o adesivo fotopolimerizável foi substituído pelo químico); grupo 4 (idem ao anterior porém o teste utilizado foi o de push out); grupo 5 (idem ao grupo anterior porém o adesivo utilizado foi o auto condicionante); e grupo 6 (idem ao grupo anterior porém a dentina foi pré hibridizada). A força de retenção foi determinada através do teste de tração usando Universal Testing Machine (Instron). Todos os dados foram analisados usando one-way analysis of variance (ANOVA) com a significância de p<0.05 e complementadas com teste de Tukey. Após o teste, as interfaces adesivas onde ocorreram as falhas foram examinadas e classificadas. Resultado: Houve diferença estatística na comparação de materiais (adesivo, material de preenchimento). A hibridização da dentina não apresentou melhoras na retenção dos pinos . A maior parte das fraturas ocorreu na interface dentina/resina. Conclusão: Com base nos resultados obtidos, concluímos que material de preenchimento, o tipo de adesivo, influenciaram na retenção de pinos de fibra; e a pré-hibridização da dentina não apresentou melhoras a retenção dos pinos. O teste de push out apresentou mais detalhes para verificar o valor da adesão de cada terço da raiz; e o teste de pull out, para a força de retenção do pino ao longo do interior do conduto e o tipo de falha. / Objective: The aims of this study is to verify the influence of adhesive, filling material and dentin hybridization on fiber post retention force in diretc -indirect technique and compare the tensile test of push out with pull out. Methods: 60 bovine single roots with a length of 12 mm were endodontically treated and randomly divided into 6 groups (n = 10): group 1 (direct-indirect technique, light-curing adhesive, resin cement, pull out test), group 2 (same as group 1 but the resin cement was replaced by composite resin), group 3 (same as previous group but the light-curing adhesive was replaced by the chemical), group 4 (same as group 3 but the test was used was push out test), group 5 (same as group 4 but the adhesive used was the self etching) and Group 6 (same as previous group but the dentin was pre-hybridized). The retention force was determined by Universal Testing Machine (Instron). All data were analyzed using one-way analysis of variance (ANOVA) with significance of p <0.05 and complemented with Tukey test. After testing, the adhesive interfaces were examined and classifie. Result: There was a significant difference between comparison of materials (adhesive and filling material). The hybridization of dentin showed no improvement in the retention post. Most fractures occurred at the interface dentin / resin. Conclusion: Based on the results, we conclude that filling material, adhesive, influenced the retention of fiber posts, and the prehybridization of dentin did not improve the retention of fiber post. The push out test showed more details to verify the bonding between the post and dentin, and the pull out test for the retention force of the post inside the canal.

This qualitative phenomenological study explored the perceptions and experiences of the middle school students who participated in learning center support as elementary students in independent schools. There were 16 participants from three sites included in the study: six students, seven parents, and three learning specialists. The research questions guiding this study included: (1) What are the perspectives of students on the impact of the learning center experience in regard to reading development? (2) How does the child's discernment of how he or she is perceived academically by his or her reading teacher contribute to/hinder the process of learning to read? (3) How does a child's sensitivity to being identified as needing extra support in learning to read affect/support the experience? (4) What do students, parents, and teachers think about learning centers? (5) How do children perceive reading teacher effectiveness and successful reading instruction? (6) How does a child's perception of a model of reading intervention inform the planning of teachers, interventionists, and reading specialists? (7) What do students think about the activities they participate during learning center time? Literature reviewed for the study included the existence of the reading problem in the United States, models of reading intervention, strategies shown to accelerate reading growth, teacher knowledge, and student perspectives. Data was collected in the form of interviews and observations, and was reviewed in consideration of narrative inquiry, typological analysis, and polyvocal analysis. All participant responses were considered across cases with specific attention given to the guiding research questions. The six students interviewed believed that their participation in the learning center helped them in some way. Some of them were able to verbalize what was helpful, while others provided few details. Nonetheless, the student participants offered specific recommendations on how to improve the learning center structure. Parent interviews shored up varying perspectives and recommendations for ways that the structure of the learning center should remain the same and also how it should change. Finally, learning specialists shared their views and experiences and added a richer understanding to the study in general. Three major themes emerged from the data. First, that students and parents attach a stigma to resource support. Second, that students and parents feel like they had to give something up because of their participation in the learning center. And third, methodological issues on the structure of the interviews were raised. Findings and current research were connected, and considerations for future research were made.

Os ensaios de arrancamento e de cisalhamento direto são os ensaios de laboratório mais usados para mensurar a resistência da interface solo geossintéticos. Em algumas ocasiões somente os ensaios de arrancamento avaliam convenientemente bem o comportamento das inclusões em meio ao maciço de solo. Esse trabalho apresenta um equipamento de ensaios de arrancamento em geossintéticos, de grandes dimensões, e resultados de ensaios executados com ele. Os resultados foram analisados segundo uma metodologia sugerida por Ochiai et al. (1996), levemente modificada pelo autor. Dos dados de ensaios de arrancamento, pôde-se concluir que o equipamento se presta à finalidade a que se destina, além disso, analisando-se os resultados segundo o método mencionado, verificou-se que a resistência ao arrancamento de geogrelhas se concentra na sua porção inicial, quando são aplicadas pequenas cargas. À medida que se aumenta a força aplicada, a resistência é gradativamente mobilizada nos trechos posteriores até à ruptura generalizada por arrancamento. / The pull-out and direct shear tests are the more used laboratory test for measure the resistance of soil-geosynthetic interface. In some occasions only the pull-out test evaluate well the behaviour of the inclusions amid the massive of soil. This work presents an pull-out test equipment, of great dimensions, and results of tests executed with him. The results were analysed according to a methodology suggested by Ochiai et al. (1996), slightly modified by the author. From the pull-out tests data, it may be concluded that the equipment is rendered to the purpose that it is destined, besides, being analysed the results according to the mentioned method, it was verified that the pull-out resistance of geogrids concentrates in initial portion, when it is applied small loads. When the applied force increases, the resistance is mobilized in the posterior portions and occur to the generalised pull-out rupture.

O comportamento estrutural do concreto armado depende da união entre o concreto e a armadura. Esta união se estabelece por meio da aderência, que funciona como um mecanismo de transferência de tensões e garante a compatibilidade de deformações entre a armadura e o concreto. Este trabalho tem como objetivo investigar os efeitos da adição de fibras de aço e armadura transversal no comportamento da ancoragem. A investigação experimental foi feita por meio de dois tipos de ensaio de arrancamento de barras, sendo eles o modelo-padrão do RILEM-CEB-FIP e modelo proposto pelo autor, este considerando barras de pontas retas e com ganchos de 90º. Todos os modelos utilizaram comprimento aderente igual a cinco vezes o diâmetro da barra. As armaduras longitudinais eram compostas por barras de 10 mm e 16 mm e a resistência à compressão média do concreto era igual a 50 MPa no dia do ensaio. Foram utilizadas fibras de aço com ganchos nas extremidades, com relação de aspecto igual a 65, comprimento igual a 35 mm e fração volumétrica de 2% (157 Kg/m³). Também foram realizadas comparações com modelos teóricos, analisados através do estudo de bibliografias existentes e das normas NBR 6118:2003 e ACI-318-08. Os resultados experimentais mostraram que os estribos e as fibras exercem influência significativa na resistência ao fendilhamento do concreto. Observou-se ainda que, para os corpos de prova com barras de aço de 10 mm e 16 mm com pontas retas, as fibras estudadas exerceram pequena influência na resistência ao arrancamento. / The structural behavior of reinforced concrete depends on connection behavior of concrete and steel. This union is established by means of bond, which serves as a mechanism to transfer forces and ensure the compatibility of deformation between the reinforcement and the concrete. This research aims investigating the effects of the use of steel fibers and stirrups on the behavior of the anchorage. An experimental investigation was carried out by means of pull-out tests according to the RILEM-CEB-FIP standard model and pull-out tests of straight and with 90º hooked bars, with a bonded length of five times the bar diameter. The longitudinal reinforcement bars were of 10 mm and 16 mm and concrete compressive strength was 50 MPa at the day of test. Steel fibers with hooked ends, aspect ratio of 65, and length of 35 mm and volumetric fraction of 2% (157 kg /m³) were used. Comparisons with theoretical models, analyzed through the literature review and recommendations of NBR 6118:2003 and ACI-318-08 were also performed. The experimental results showed that the stirrups and the fibers have significant influence on the cracking of the concrete. It was also observed that, for the specimens with steel bars of 10 mm and 16 mm with straight anchorage, the fibers had small influence on the pull-out resistance.

A presente pesquisa propõe analisar, avaliar e validar o uso de ensaios de aderência açoconcreto para estimativa da resistência à compressão axial do concreto in loco nas primeiras idades em canteiros de obras, como alternativa ao controle de qualidade tradicional. Alguns pesquisadores propuseram a utilização de um ensaio de aderência modificado, que denominaram Appropriate Pull-Out Test (APULOT), como uma adaptação do método pullout test (POT) tradicional, normalizado pela norma EN12504-3. Para viabilizar o uso do ensaio APULOT como ensaio que possa ser implementado na prática do controle tecnológico do concreto em canteiros de obras e seja representativo da resistência in loco é necessário definir um padrão para o mesmo. O presente trabalho desenvolveu um molde específico para o ensaio, analisou a influência do processo da cura nos resultados da tensão máxima de aderência, estudou como a medição da maturidade no concreto pôde auxiliar na determinação do momento certo para fazer o ensaio de arrancamento e comparou resultados dos ensaios feitos em corpos de prova para teste de aderência com ensaios de arrancamento de barras de aço em painéis de concreto. Para tanto foram feitos nove concretagens empregando diferentes tamanhos e configurações de corpos de prova, ensaios de arrancamento, extrações de testemunhos de painéis de concreto, ensaios à compressão simples e medições de maturidade dos concretos empregados. Também se realizaram registros de temperatura ambiente e velocidade do vento na vizinhança dos painéis, buscando estabelecer relações entre a maturidade e as condições ambientais do canteiro. Os ensaios descritos anteriormente realizaram-se às idades de 3, 5, 7 e 28 dias. Os resultados obtidos mostram que, sob condições padronizadas de ensaio, existe ótima correlação entre a tensão máxima de aderência e a resistência à compressão do concreto e por tanto o ensaio de aderência pode ser utilizado para fazer uma estimativa da resistência à compressão do concreto in loco nas primeiras idades. / This research aims to analyze, evaluate and validate the use of steel-concrete bond tests to estimate the axial compression strength of in situ concrete at early ages on construction sites, as alternative to conventional strength control tests. Some researchers have proposed the use of a modified bond test, named Appropriate Pull-Out Test (APULOT), as an adaptation of the traditional pull-out test method (POT) standardized by the EN12504-3. To implement the APULOT as a strength control procedure for concrete on construction site, standardization is needed. This study developed a specific mold for the test; analyzed the influence of curing process on the results of the maximum bond stress; studied how measuring the maturity in the concrete could help to determine when is the right time to make the pull-out test; compared results of tests made on cores for testing the bond and pull-out tests on steel bars in concrete panels. Therefore, it have been made nine concrete events, pull-out tests using different sizes and configurations of cylindrical concret specimen, pull-out tests and extraction of cores from concrete panels, compressive test and maturity measurements of specific employees. Also, temperature and wind speed records have been performed in the panel´s sourrundings, seeking to establish relationships between maturity and ambiental conditions on construction site. The tests described above were carried out at 3, 5, 7 and 28 days. The results show that, under standardized test conditions, a correlation between the maximum bond stress and the concrete compression strength exists, and therefore, bond test can be used to estimate the in situ compression strength of the concrete in the first ages.

Concrete is a strong material as to its compressive strength. However, it is a material with a low tensile and shear strength, and brittleness at failure. Concrete has to be reinforced with appropriate materials. Steel fibre is one of the most common materials currently being used to develop reinforced concrete, which may replace partially or completely conventional steel reinforcement. Successful reinforcement of concrete composite is closely related to the bond characteristics between the reinforcing fibre and matrix. The effective utilisation of steel fibre reinforced concrete (SFRC) requires in-depth and detailed understanding of bonding mechanisms governing the tensile behaviour. In response to this demand, this study embraced two main areas: understanding the reinforcing mechanisms of fibres in SFRC and material's post-cracking behaviour. Comprehensive experimental and theoretical programmes have therefore been developed: the experimental work is subdivided into three parts. The first part was to investigate the effect of various physical parameters, such as fibre characteristics (i.e. geometry, inclination angle, embedded length, diameter and tensile strength) and matrix strength which controls the pull-out behaviour of steel fibres. The second part is concerned with the assessment of the bond mechanisms of straight and hooked end fibres after exposure to elevated temperatures and varying matrix strength. The third part is devoted to gain further insight on the bond mechanisms governing the post-cracking behaviour through uniaxial and bending tests. It was found that the varying hook geometry and matrix strength each had a major influence on the pull-out response of hooked end fibres. As the number of the hook's bends increased, the mechanical anchorage provided by fibre resulted in significant improvement of mechanical properties of SFRC. The reduction in bond strength at elevated temperatures is found to be strongly related to the degradation in properties of the constituent materials, i.e. the fibre and concrete. The most effective combination of matrix strength and fibre geometry was found to be as follows: 3DH (single bend) fibre with normal-medium strength matrix, 4DH (double bend) fibre with high strength matrix and 5DH (triple bend) fibre with ultra-high performance matrix. Two analytical models to predict the pull-out behaviour of hooked end fibres were developed. Both models were able to predict the pull-out response of SFRC made from a variety of fibre and matrix characteristics at ambient temperature. This work has established a comprehensive database to illustrate the bonding mechanisms of SFRC and anchorage strengthening of various hooked end fibres, and this should contribute towards an increasing interest and growing number of structural applications of SFRC in construction.

A utilização de placas bloqueadas e suas vantagens biomecânicas na redução de fraturas cominutivas de ossos longos em cães já foram descritas por diversos autores. O presente trabalho teve como objetivo avaliar diferentes configurações de placa bloqueadas submetidas a dois diferentes testes biomecânicos, um de flexão em quatro pontos para avaliar a influencia do preenchimento dos orifícios centrais na resistência a flexão da placa bloqueada com função de placa de apoio. O outro teste avaliou a força máxima ao arrancamento de dois diferentes tipos de placas, um com todos os orifícios perpendiculares e outro com os orifícios angulados alternadamente lateral e medialmente em relação ao eixo longitudinal da placa. Para cada teste formou-se dois grupos com dez corpos de prova cada. Não houve diferença estatística no resultado obtido no teste de flexão, a resistência a flexão do grupo com preenchimentos dos orifícios centrais foi maior em relação ao grupo sem preenchimento, porem sem significância. Já no teste de arrancamento o grupo de placas com orifícios angulados obteve um valor de forma máxima de arrancamento significantemente superior em relação ao grupo com orifícios perpendiculares em relação ao eixo longitudinal da placa. Concluiu-se que não há influencia na resistência da placa de apoio com o preenchimento dos orifícios centrais da placa bloqueada e que a configuração de placa com os orifícios angulados se mostrou mais resistente ao arrancamento. / The feasibility of locking plates and their biomechanical advantages in comminuted fractures are well known. The objective of this study was to evaluate different locking plate´s configurations submitted to a four point´s flexion test and pull out test. The flexion test evaluated the influence of screws in center position in bridging plate, the pull out test compared relative to pull out strength locking plates using parallel locking screws or angulated locking screws. For each biomechanical assay two groups of ten test materials were formed. The results found no statistical differences relative to flexion resistance in the groups with and without central screws. Relative to pull out test the group with angulated screws showed higher values of maximum pull out strength when compared with the perpendicular screws, the data were statistically significant. We concluded that there was no improvement in the resistance of bridging plate with the use of central screws, but the use of angulated screws showed a greater resistance to pull out when compared to parallel screws.

A utilização de placas bloqueadas e suas vantagens biomecânicas na redução de fraturas cominutivas de ossos longos em cães já foram descritas por diversos autores. O presente trabalho teve como objetivo avaliar diferentes configurações de placa bloqueadas submetidas a dois diferentes testes biomecânicos, um de flexão em quatro pontos para avaliar a influencia do preenchimento dos orifícios centrais na resistência a flexão da placa bloqueada com função de placa de apoio. O outro teste avaliou a força máxima ao arrancamento de dois diferentes tipos de placas, um com todos os orifícios perpendiculares e outro com os orifícios angulados alternadamente lateral e medialmente em relação ao eixo longitudinal da placa. Para cada teste formou-se dois grupos com dez corpos de prova cada. Não houve diferença estatística no resultado obtido no teste de flexão, a resistência a flexão do grupo com preenchimentos dos orifícios centrais foi maior em relação ao grupo sem preenchimento, porem sem significância. Já no teste de arrancamento o grupo de placas com orifícios angulados obteve um valor de forma máxima de arrancamento significantemente superior em relação ao grupo com orifícios perpendiculares em relação ao eixo longitudinal da placa. Concluiu-se que não há influencia na resistência da placa de apoio com o preenchimento dos orifícios centrais da placa bloqueada e que a configuração de placa com os orifícios angulados se mostrou mais resistente ao arrancamento. / The feasibility of locking plates and their biomechanical advantages in comminuted fractures are well known. The objective of this study was to evaluate different locking plate´s configurations submitted to a four point´s flexion test and pull out test. The flexion test evaluated the influence of screws in center position in bridging plate, the pull out test compared relative to pull out strength locking plates using parallel locking screws or angulated locking screws. For each biomechanical assay two groups of ten test materials were formed. The results found no statistical differences relative to flexion resistance in the groups with and without central screws. Relative to pull out test the group with angulated screws showed higher values of maximum pull out strength when compared with the perpendicular screws, the data were statistically significant. We concluded that there was no improvement in the resistance of bridging plate with the use of central screws, but the use of angulated screws showed a greater resistance to pull out when compared to parallel screws.

The purpose of this study was to compare the achievement scores in reading/language arts and math of fourth and fifth grade special education learning-disabled students who received academic instruction in an inclusion classroom or a pull-out classroom. Student achievement scores from the 2012-2013 Tennessee Comprehensive Assessment Program (TCAP) and the Discovery Education Assessment (DEA) improvement scores were compared with regard to service location and analyzed for significant differences between the locations: inclusion and pull-out classrooms. A quantitative study was used to find the differences in reading/language arts and math achievement scores for fourth and fifth grade special education learning-disabled students in an East Tennessee school district. Eleven research questions guided the study. The results of the analyses indicated significant differences in reading/language arts and math scores between the groups in all but 2 analyses. The inclusion students scored higher than the pull-out students. The fourth grade inclusion students scored significantly higher than the fourth grade pull-out students in TCAP reading/language arts, TCAP math, and DEA math but scored with similar results in DEA reading/language arts. The fifth grade inclusion students scored significantly higher than the fifth grade pull-out students in TCAP reading/language arts, TCAP math, and DEA reading/language arts but scored with similar results in DEA math. This study supported the idea that learning-disabled students receiving academic instruction in an inclusion classroom score significantly higher on achievement tests than the students who received their instruction in the pull-out classroom.