OBJECTIVES: To evaluate different surface treatment effects on physical and mechanical properties of various types of zirconia subjected to hydrothermal aging. MATERIALS AND METHODS: This is an in vitro study on four different types of monolithic zirconia material: VITA-Zahnfabrik VITA-YZ T, VITA-YZ HT, VITA-YZ ST, VITA-YZ XT. A total of 240-disc specimens were prepared by core-drilling and sectioned with a diamond blade. Specimens were sintered according to the manufacturer’s recommendations. Half of the specimens in each group were then glazed and subjected to low temperature degradation. Three different locations were evaluated for surface roughness each group of the four different materials by using Mitutoyo SJ-201 contact profilometer with a 5μm diamond stylus tip. A Bruker D2 Phaser diffractometer was used for X-ray diffraction (XRD) measurements. Crystallographic phase identification and analysis were performed through Rietveld refinements on XRD raw data. Biaxial flexural strength was determined and the fractography was analyzed. Descriptive data such as surface roughness, crystallographic phase contents, and flexural strength were indicated as mean and standard deviation (SD). Statistical analysis was performed using multi-way ANOVA and linear regression model followed by the post hoc Tukey tests. RESULTS: All VITA YZ zirconia non-glazed control specimens showed higher means of biaxial flexural strength values compared to glazed specimens. VITA YZ HT specimens showed the highest mean of biaxial flexural strength in this study with values of 781 – 1305 MPa. On the other hand, VITA YZ XT expressed the lowest mean of biaxial flexural strength values of 466 – 972 MPa. The surface roughness of monolithic VITA YZ materials was statistically significantly low for the various zirconia materials. Aging of various zirconia materials showed statistically significant effect of aging on glazed specimens was not statistically significant. There was no significant difference in the tetragonal phase content of all VITA YZ materials (p > 0.05). There was significant difference in the cubic phase content of all VITA YZ materials (p < 0.05). On the other hand, aging process as well as the interaction between the material type and aging had no significant effect on the cubic phase content of YZ specimens (p > 0.05). There was significant difference in the rhombohedral phase of all VITA YZ materials as well as aging process (p < 0.05). CONCLUSIONS: Biaxial flexural strength was significantly affected by glazing, type of material, treatment protocol. Biaxial flexural strength was significantly affected by the interaction between type of material and treatment protocol, glazing and type of material. The VITA YZ ST control had the lowest surface roughness among all the groups. The difference was statistically significant. The type of material, aging, and the interaction effect between the material and aging were significantly different for XRD in non-glazed material. The VITA YZ T showed the lowest mean of yttrium oxide (Y2O3) molecular fraction. On the other hand, YZ XT showed the highest mean of Yttrium oxide (Y2O3) molecular fraction.

No

This thesis investigates the damping effects of a metamaterial, on structural vibration, by inducing periodic voids in the base damping material as opposed to infusing the damping material with other material. Metamaterials have been used previously to improve the damping of vibrational waves and acoustic waves through wave scattering and wave reflection at periodic impedance changes. Impedance changes can occur at both material boundaries and geometric changes of the medium. Impedance changes cause wave scattering, wave reflection, and changing of wave speed. The low frequency region of the vibration spectrum is generally harder to dampen due to the longer wavelengths. By slowing the waves down, the wavelength can be shortened and the viscoelastic material will be more effective at damping the waves. The metamaterial in the thesis has one, two, three, and four periodically located voids in the viscoelastic damping material to determine the effectiveness of the damping compared to the same beam with no damping material applied and the beam covered completely with the standard viscoelastic damping material. This research will include both finite element models of the beam and concept testing to explore the damping effects of the metamaterial. / Master of Science / In the field of mechanical engineering vibrations are one of the main causes of failure of machinery components. Reducing vibrations greatly effects the longevity and effectiveness of a machine. The research in this thesis focuses on how to reduce the vibration in a beam by using a metamaterial. Standard damping materials provide damping, reduction of vibration, at various quantities depending on the frequency and wavelength of the vibrational wave. Metamaterials are particular materials designed to reduce vibration by influencing the physical phenomena of a wave as it travels through the material usually by periodic wave scatters. The metamaterial in this research is designed to slow the flexural waves down, therefore shortening the wavelength, making it easier to dampen the vibration compared to a standard damping material. The damping effectiveness of the metamaterials explored in this research will be quantified via finite element modeling and testing in a laboratory.

O objetivo deste trabalho foi o de avaliar a resistência à flexão e a quantidade de monômero residual superficial em resinas acrílicas para bases de próteses totais. Para tanto foram confeccionados corpos-de-prova nas dimensões de 2.5mm x 10mm x 65mm, utilizados em ambas as análises. Padronizou-se o processo de inclusão no qual foram empregadas muflas plásticas reforçadas por fibras de vidro. Sete grupos foram constituídos, de acordo com o tipo de processamento empregado na polimerização das resinas: Ac (Acron-MC) e Vw (Vipi-Wave) de ativação por energia de microondas; Lt (Lucitone 550 – grupo controle) e Vc (Vipi-Cril), resinas de ativação térmica convencional em banho de água aquecida no ciclo longo; Qc (QC-20), uma resina de ativação térmica em ciclo rápido e, dois grupos cuja resina era a mesma de ativação química (Vipi-Flash), processada em duas condições – à temperatura ambiente (Vf1) e, por aquecimento adicional em banho de água (Vf2). Os resultados mostraram diferenças estatisticamente significantes, onde o grupo Ac obteve as maiores médias para resistência flexural e os menores níveis de monômero liberado em relação às demais resinas. Os grupos Qc e Vf1 evidenciaram os piores resultados para ambos os testes, e a princípio, pareceu haver uma relação de causa e efeito entre, os elevados níveis de monômero residual encontrado nestes grupos, e a baixa resistência flexural observada. Verificou-se ainda que a imersão em água aquecida por 30min, da resina de ativação química, propiciou um ganho em qualidade do material para as características avaliadas. / The purpose of this work was the evaluation of flexural strength and quantity of superficial residual monomer in acrylic resin for complete denture. To perform both analyses it was developed specimens with a dimension of 2.5mm x 10mm x 65mm. The inclusion process was standardized by the use of plastic flasks reinforced with fiberglass. Seven groups were constituted in accordance with the type of resin polymerization process: Ac (Acron-MC) and Vw (Vipi-Wave) activated by microwave energy; Lt (Lucitone 550 – control group) and Vc (Vipi-Cril), conventional water bath curing cycles of heat activated acrylic resin; Qc (QC-20), fast cycle thermal activation; and two groups of self cured resin (Vipi-Flash), processed in two distinguished conditions: ambient temperature (Vf1) and additional heating in water bath (Vf2). The results have shown statistical significant differences. The Ac group had the highest mean to flexural resistance and the least level of released monomer in comparison with others resins. The Qc and Vf1 groups had the worst results for both tests. The initial conclusions showed a cause-effect relation between higher levels of residual monomer and lower flexural strength to this group. Additionally, it was verified that the immersion for 30 minutes of self cured resin in heated water gave an improvement of material quality to evaluated characteristics.

Made available in DSpace on 2017-07-24T19:22:27Z (GMT). No. of bitstreams: 1 Adriana de Oliveira Silva.pdf: 854698 bytes, checksum: 0fe1099b901133907165a1d0a216a8e3 (MD5) Previous issue date: 2004-07-27 / The aim of this study was to evaluate the flexural strength of two fibers glass and two ceramics systems used like substructure of prosthesis fixed partial using a three point bending test. Four groups, with ten specimens and dimensions of 25+ 2mm X 2+ 0,1mm X 2+ 0,1mm (ISO 10477) to fibers glass and 25+ 5 mm X 4+ 0,25 mm X 1,2+ 0,2 mm (ISO 6872) to ceramics were prepared according to the manufacturer’s instructions, where: GI-Vectris Pontic® (Ivoclar/Vivadent), GII-Fibrex Medial® (Angelus Soluções Odontológicas), GIII- IPS Empress ®2(Ivoclar/Vivadent) e GIV- VITA In- Ceram® Zircônia. The specimens were dry stored, in plastic recipient, without light on room temperature and submitted on three point test at universal machine Instron® Corp. 2KN(crosshead speed of 0,75mm/min) and the results of the mean values of flexural strength were 516,04 + 58,44 MPa to GI , 505,23 + 85,57 MPa to GII, 182,73+ 50,33 MPa to the GIII and 442,37 + 99,89 MPa to GIV. The predominance of failure was incomplete fracture to fibers glass and complete fracture to ceramics. The results were submitted on statistical analysis, Anova (p<0,05) and there were observed differences statistically insignificant among the fibers’ group (p=0.7460) and differences statistically significant among the ceramics’ group. Concluded that fibers tested presented similar performance of flexural strength and the result suggested the possibility of fibers glass be used like alternative of alloy in good indication of clinical situation of prosthesis fixed partial. The ceramics presented not similar performance of flexural strength being VITA In-Ceram® Zircônia system able to support more load when compared with IPS Empress® 2 Ivoclar/Vivadent system. / O objetivo deste estudo foi avaliar a resistência flexural de dois sistemas de fibras de vidro unidirecionais e duas cerâmicas utilizadas como subestrutura de próteses parciais fixas, através do teste de três pontos. Quatro grupos, com 10 corpos-deprova cada, e dimensões de 25+2mm X 2+0,1mm X 2+0,1mm (ISO 10477) para as fibras de vidro e 25+ 5 mm X 4+ 0,25 mm X 1,2+ 0,2 mm (ISO 6872) para as cerâmicas, foram obtidos seguindo as orientações dos fabricantes, sendo: GIVectris Pontic® (Ivoclar/Vivadent), GII- Fibrex Medial® (Angelus Soluções Odontológicas), GIII- IPS Empress ®2(Ivoclar/Vivadent) e GIV- VITA In-Ceram® Zircônia. Os corpos-de-prova foram armazenados, secos, à temperatura ambiente, em recipientes plásticos, sem interferência de luz e submetidos ao teste de três pontos em uma máquina de ensaio Instron® Corp. 2KN (velocidade de 0,75mm/min) obtendo-se valores médios de resistência à flexão de 516,04 + 58,44 MPa para GI, 505,23 + 85,57 MPa para GII, 182,73+ 50,33MPa para o GIII e 442,37 + 99,89 MPa para o GIV. O padrão de falha observado foi de fratura incompleta para as fibras de vidro e fratura completa para as cerâmicas. Os valores médios de resistência foram submetidos à análise estatística, teste Anova (p<0,05) e verificou-se a inexistência de diferenças estatísticas significantes entre os grupos de fibras de vidro (p=0.7460) e a existência de diferenças estatísticas significantes entre os grupos de cerâmicas. Concluiu-se que as fibras de vidro utilizadas no experimento apresentaram desempenhos de resistência flexural semelhantes e os resultados sugeriram a possibilidade da utilização das fibras de vidro como alternativa às ligas metálicas em situações clínicas bem indicadas de próteses parciais fixas. As cerâmicas apresentaram diferentes desempenhos de resistência flexural, sendo o sistema VITA In-Ceram® Zircônia capaz de resistir a maior carga aplicada comparada ao sistema IPS Empress® 2 Ivoclar/Vivadent.

This paper presents an analytical method for estimating the flexural strength of reinforced concrete (RC) beams strengthened with externally bonded fibre-reinforced polymer (FRP) laminates. The method is developed from the strain compatibility and equilibrium of forces. Based on the size of external FRP laminates, several flexural failure modes may be identified, namely tensile rupture of FRP laminates and concrete crushing before or after yielding of internal steel reinforcement. Upper and lower limits to the size of FRP laminates used are suggested to maintain ductile behaviour of strengthened RC sections. Comparisons between the flexural strength obtained from the current method and from experiments show good agreement. Design equations for calculating the size of FRP laminates externally bonded to RC sections to enhance their flexural strength are proposed.

To determine the effects of thermal accelerated aging on flexural strength and flexural modulus of conventional and CAD/CAM provisional crown and bridge restorative materials. Six provisional crown and bridge materials were selected for this study. Three conventional resins: Jet Set 4 (Lang), Luxatemp (DMG), and Protemp Plus (3M ESPE); and three CAD/CAM materials: ArtBloc Temp (Merz), Telio CAD-Temp (Ivoclar Vivadent), and Vita CAD-Temp (Vita). Specimens of conventional materials were fabricated using a custom-made aluminum mold 25 2 2 mm. CAD/CAM blocks were sectioned to the same dimensions. A total of 180 bar-shaped specimens were obtained (30 of each material) and were divided into three groups per treatment. Groups 1 and 2 were immersed in 37°C water for 24 hours, and 6 days, respectively. Group 3 was subjected to 5,000 thermal cycles between 5°C and 55°C in water with 35 seconds dwelling time. All specimens where tested for flexural properties using three-point bending protocol on an Instron 5566A at a crosshead speed of 0.5mm/min. The results were analyzed by one-way ANOVA and post hoc Tukey test with material type and aging conditions as the main variables. Significance level was set at (p<0.05).  Overall CAD/CAM materials demonstrated significantly higher flexural strength and flexural modulus over conventional resins. No significant difference in flexural strength and flexural modulus was found among three treatments except for: Luxatemp, which showed significant increased flexural strength and flexural modulus after thermal cycling, and Protemp Plus which showed increased flexural strength after 6 days of water storage.

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No. of bitstreams: 2 Dissertação - Pedro Ivo de Carvalho - 2017.pdf: 4004894 bytes, checksum: 33f2a48487a0eb9767e85161eae677b4 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Several researches aim to discover a best development of new glass-fiber-reinforced composite resins for the manufacture of intraradicular posts with better mechanical properties has been the aim of several researches lately. The reinforcement of composite resin with glass fibers can improve the mechanical properties, such as flexural strength, fracture resistance and compressive strength. Considering that the resin matrix monomers, the photoinitiator system and the interaction with the glass fibers interfere in the homogenization of the composite and in the degree of polymer conversion, the present work had as Objective: To evaluate the influence of different proportions of the monomers Bis-EMA / Bis-GMA / TEGDMA and photoactivator systems based on DFI and camphorquinone on the mechanical properties of a experimental fiberglass reinforced composite resin. Methodology: Ten groups were created (n = 10) using an experimental resin based on methacrylate, having as study factors: 1. Different matrices according to the proportions of monomers Bis-GMA (BG), TEGDMA (TE) and Bis-EMA (BE): And 2. The photoinitiator system: without DFI (SD) salt or DFI (CD) salt. The samples were prepared for the flexural strength (RF) and diametral tensile strength (RTD) tests. Statistical analysis showed that for RF (Mpa) there was significance in the interaction between the factors under study (p = 0.047). The highest result occurred for Group 10 (267.815 ± 45.05) c, followed by Group 9 (242.440 ± 44.83) bc; Group 8 (241.05 ± 44.83) b Group 3 (236.152 ± 26.42) abc. The lowest result occurred in Group 9 (192.450 ± 12.60) a, followed by Group 7 (202.35 ± 28.36) ab; Group 6 (207,240 ± 30,07) ab; Group 2 (209.530 ± 23.16) ab; Group 5 (216,760 ± 30,14); And Gruop 1 (218,880 ± 41,49). For RTD only the presence of DFI salt showed statistical significance (p = 0.001). The addition of the DFI salt in the composite significantly increased results for flexural strength and diametral tensile strength, while the increase of Bis-EMA was significant for better flexural strength results. / A busca pelo desenvolvimento de novos compósitos reforçados com fibra de vidro para a confecção de pinos intrarradiculares com melhores propriedades mecânicas tem sido a base de várias pesquisas atuais. O incremento fibras de vidro silanizadas nas resinas promove melhora nos valores de resistência à flexão, resistência à fratura e resistência compressiva. Tendo em vista que os monômeros da matriz resinosa, o sistema fotoiniciador e a interação com as fibras de vidro interferem na qualidade do compósito e no grau de conversão polimérica, o presente trabalho teve como objetivo avaliar as propriedades mecânicas de um compósito experimental reforçado por fibra de vidro composto por 30% de matriz orgânica, 47,5% de partícula de carga e 22,5% de vibras de vidro curta(3mm), variando proporções de monômeros Bis-EMA, Bis-GMA e TEGDMA e o efeito do sal de difenil-iodônio (DFI) em um sistema fotoiniciador à base de canforoquinona. Dez grupos foram criados (n=10) utilizando uma resina experimental a base de metacrilato, tendo como fatores em estudo: 1. Diferentes matrizes de acordo com as proporções dos monômeros Bis-GMA, TEGDMA e Bis-EMA e 2. O sistema fotoiniciador: sem sal DFI (SD) ou com sal DFI (CD). As amostras foram preparadas para os testes resistência flexural (RF) e resistência à tração diametral (RTD). Análise estatística mostrou que para RF (Mpa) houve significância na interação entre os fatores em estudo (p=0,047). Os melhores resultados foram encontrados para os grupos: Grupo 10 (267,815±45,05)c, seguido por Grupo 9 (242,440±44,83)bc. Para RTD somente a presença do sal DFI demonstrou significância estatística (p=0,001). Em MPa foram observados os maiores resultados: Grupo 10, (35,36±2,61b); Grupo 8, (35,07±6,89b). A adição do sal DFI no compósito aumentou significativamente resultados para resistência flexural e resistência à tração diametral, enquanto que a presença de Bis-EMA foi significante para melhores resultados somente em resistência flexural.

O objetivo deste trabalho foi o de avaliar a resistência à flexão e a quantidade de monômero residual superficial em resinas acrílicas para bases de próteses totais. Para tanto foram confeccionados corpos-de-prova nas dimensões de 2.5mm x 10mm x 65mm, utilizados em ambas as análises. Padronizou-se o processo de inclusão no qual foram empregadas muflas plásticas reforçadas por fibras de vidro. Sete grupos foram constituídos, de acordo com o tipo de processamento empregado na polimerização das resinas: Ac (Acron-MC) e Vw (Vipi-Wave) de ativação por energia de microondas; Lt (Lucitone 550 – grupo controle) e Vc (Vipi-Cril), resinas de ativação térmica convencional em banho de água aquecida no ciclo longo; Qc (QC-20), uma resina de ativação térmica em ciclo rápido e, dois grupos cuja resina era a mesma de ativação química (Vipi-Flash), processada em duas condições – à temperatura ambiente (Vf1) e, por aquecimento adicional em banho de água (Vf2). Os resultados mostraram diferenças estatisticamente significantes, onde o grupo Ac obteve as maiores médias para resistência flexural e os menores níveis de monômero liberado em relação às demais resinas. Os grupos Qc e Vf1 evidenciaram os piores resultados para ambos os testes, e a princípio, pareceu haver uma relação de causa e efeito entre, os elevados níveis de monômero residual encontrado nestes grupos, e a baixa resistência flexural observada. Verificou-se ainda que a imersão em água aquecida por 30min, da resina de ativação química, propiciou um ganho em qualidade do material para as características avaliadas. / The purpose of this work was the evaluation of flexural strength and quantity of superficial residual monomer in acrylic resin for complete denture. To perform both analyses it was developed specimens with a dimension of 2.5mm x 10mm x 65mm. The inclusion process was standardized by the use of plastic flasks reinforced with fiberglass. Seven groups were constituted in accordance with the type of resin polymerization process: Ac (Acron-MC) and Vw (Vipi-Wave) activated by microwave energy; Lt (Lucitone 550 – control group) and Vc (Vipi-Cril), conventional water bath curing cycles of heat activated acrylic resin; Qc (QC-20), fast cycle thermal activation; and two groups of self cured resin (Vipi-Flash), processed in two distinguished conditions: ambient temperature (Vf1) and additional heating in water bath (Vf2). The results have shown statistical significant differences. The Ac group had the highest mean to flexural resistance and the least level of released monomer in comparison with others resins. The Qc and Vf1 groups had the worst results for both tests. The initial conclusions showed a cause-effect relation between higher levels of residual monomer and lower flexural strength to this group. Additionally, it was verified that the immersion for 30 minutes of self cured resin in heated water gave an improvement of material quality to evaluated characteristics.

The durability of infrastructure components, such as prestressed concrete bridge beams, can be significantly affected by long-term deterioration associated with corrosion. Corrosion is a major concern for bridges in Virginia, due to the frequent use of deicing salts during the winter, as well as the number of structures in marine environments. The residual capacity of corrosion damaged prestressed I-beams and box beams needs to be accurately estimated to determine if damaged bridges need to be posted, and to help with making informed decisions related to repair, rehabilitation and replacement of damaged bridges. The initial stage of the research investigated the ability to determine the in-situ strength of members that have visible corrosion-related damage. In this stage, six corrosion-damaged beams were investigated. Prior to testing, the beams were visually inspected and damage was documented. The beams were then tested in the lab to determine their flexural strength. Following testing, samples of strands were removed and tested to determine their tensile properties while cores were taken to determine compressive strength. Powdered concrete samples were removed to perform chloride concentration tests. The tested strengths of the beams were compared to calculated strengths using two methods for damage estimation and two different calculation approaches. Two repair methods were then evaluated through large-scale experimental testing, aimed at restoring the strength of deteriorated prestressed concrete beams. The investigated repairs included External Post-Tensioning (PT) and Carbon Fiber Reinforced Polymer (CFRP) laminates applied to the bottom flange of beams for flexural strengthening. A total of five full-scale bridge members were tested to failure throughout this stage. All beams were subjected to monotonically increasing loads until failure. For beams repaired with external PT, the experimental test was accompanied by a detailed approach for determining the ultimate failure load, the ultimate stress in the external tendons, and the location of the failure. For beams repaired with CFRP, the experimental test was accompanied by a parametric study that was performed to determine the maximum reduction in flexural strength for which CFRP can be considered as a viable repair method to restore the lost capacity. This dissertation provides additional information on estimating the residual capacity of corrosion-damaged beams and shows the types of repair that can restore their original strength. With this information, Departments of Transportation (DOT) can properly determine what types of repair are a suitable for the damaged girders based on their level of corrosion. / Doctor of Philosophy / Many bridges in the United States were built using longitudinal members, called girders, made of prestressed concrete. In prestressed concrete, because concrete cannot resist high tensile forces, tensioned steel cables, called strands, are used to produce compression on the concrete member to improve its behavior when it is in service. Corrosion induces cracks in the concrete superstructure which accelerates the deterioration rate and can result in a partial loss of the concrete body and exposure of the embedded steel. This causes degradation in the load-carrying capacity of the bridge girders which raises a danger to vehicles, passengers, and pedestrians. The residual capacity of corrosion damaged prestressed I-beams and box beams needs to be accurately estimated to determine if damaged bridges need to be posted, and to help with making informed decisions related to repair, rehabilitation and replacement of damaged bridges. The initial stage of the research investigated the ability to determine the in-situ strength of members that have visible corrosion-related damage. In this stage, six corrosion-damaged beams were investigated. Prior to testing, the beams were visually inspected, and damage was documented. The beams were then tested in the lab. Following testing, samples of strands were removed and tested to determine their tensile properties while cores were taken to determine compressive strength. Powdered concrete samples were removed to perform chloride concentration tests. The tested strengths of the beams were compared to calculated strengths. Two repair methods were then evaluated through large-scale experimental testing, aimed at restoring the strength of deteriorated prestressed concrete beams. The investigated repairs included External Post-Tensioning (PT) and Carbon Fiber Reinforced Polymer (CFRP) sheets applied to the bottom of beams for flexural strengthening. A total of five full-scale bridge members were tested to failure throughout this stage. All beams were subjected to monotonically increasing loads until failure. For beams repaired with external PT, the experimental test was accompanied by a detailed approach for determining the ultimate failure load, the ultimate stress in the external tendons, and the location of the failure. For beams repaired with CFRP, the experimental test was accompanied by a parametric study that was performed to determine the maximum reduction in flexural strength for which CFRP can be considered as a viable repair method to restore the lost capacity. This dissertation provides additional information on estimating the residual capacity of corrosion-damaged beams and shows the types of repair that can restore their original strength. With this information, Departments of Transportation (DOT) can properly determine what types of repair are a suitable for the damaged girders based on their level of corrosion.