Este estudo avaliou a eficiência do uso do laser de CO2 com comprimento de onda de 10,6 m como auxiliar na remoção de bráquetes estéticos cerâmicos. Para este estudo foram utilizados 105 pré-molares inferiores humanos recentemente extraídos, que receberam irradiações com laser de CO2 antes da descolagem dos bráquetes. Na primeira fase deste estudo, o objetivo foi mensurar e comparar a temperatura no compósito de colagem do bráquete e na câmara pulpar após aplicação do laser de CO2 , para observar a segurança para o esmalte, bem como se a temperatura era suficiente para fragilizar o compósito, facilitando a remoção do bráquete. Nesta etapa foram utilizados 30 pré-molares inferiores recentemente extraídos, sendo que cada um recebeu 4 irradiações com diferentes protocolos de maneira aleatória. Foram testados 12 diferentes protocolos variando o tempo de irradiação (3 e 5s), a duração do pulso (0,01 e 0,03s) e a potência (5, 8 e 10W). Cada protocolo foi utilizado por 10 vezes (n=10), totalizando 120 irradiações. Em todas as irradiações os corpos-de-prova foram imersos em banho térmico com água a 37º C. Foram encontrados 4 protocolos cuja variação da temperatura na polpa foi menor que 5,5º C, portanto compatível com a saúde da polpa. Na segunda etapa do estudo, o objetivo foi avaliar a resistência ao cisalhamento após a aplicação do laser utilizando os protocolos cuja temperatura na polpa não fosse superior a 5,5º C. Setenta e cinco pré-molares inferiores humanos foram divididos em 5 grupos, dos quais um não foi submetido à irradiação, sendo considerado Controle (C). Nos 4 grupos restantes, irradiações foram realizadas como descrito a seguir: Grupo I (potência 5W; tempo de pulso 0,01s; tempo de aplicação 3s), Grupo II (5W; 0,03s e 3s), Grupo III (8W; 0,01s e 3s) e Grupo IV (10W; 0,01s e 3s). Cada grupo foi formado por 15 corpos-de-prova (n=15). Após a descolagem do bráquete foi avaliado o Índice de Remanescente Adesivo (IRA). Após as mensurações e aplicação da Análise de Variância (ANOVA) e do teste de Tukey foi constatado que o único grupo que apresentou diminuição na força de remoção foi o IV (7,33 MPa) em relação ao grupo C (10,81 MPa) sendo assim considerado seguro e eficaz na diminuição da resistência do compósito. / This study evaluates the efficacy CO2 10,6 m laser-assisted debonding esthetic ceramic brackets. For this purpose it was used 105 recently extracted lower human premolars that were irradiated with CO2 laser before debonding. In the first phase, the objectives were to measure and compare the temperature in composite for bracket bonding and at the pulp chamber after CO2 laser irradiation, to observe the safety for enamel, as well the temperature was enough to softening the composite, making debonding bracket easier. In this part it was used 30 lower premolar recently extracted, and each one received 4 irradiations with different protocols, randomly choose. It was tested 12 different protocols varying time of irradiation (3 and 5s), pulse duration (0,01s e 0,03s) and power (5, 8 and 10W). Each protocol was repeated for 10 times (n=10), resulting 120 irradiations. In every irradiation the teeth tested were immerse in warm water bath at 37o C. It was found 4 protocols with pulp temperature lower than 5,5º C, so this is compatible with pulp health. In the second phase of this study, the objective was to evaluate the shear bond strength after laser irradiation, using the protocols with pulp chamber temperatures lower than 5,5º C. Seventy-five lower human premolars was shared in 5 groups. One group did not receive laser irradiation and considered Control (C) and the other groups the irradiation was made as it follows: Group I (power density 5W; pulse duration 0,01s; irradiation time 3s), Group II (5W; 0,03s, 3s), Group III (8W; 0,01s; 3s) and Group IV (10W; 0,01s; 3s). After results ANOVA and Tukey tests were made. Group IV presented lowering in SBS force (7,33 MPa) when compared with C (10,81MPa). This protocol was founded as a safe and efficient in softening composite layer.

Within the framework of this thesis, three innovative electrochemical devices have been studied. A part of the work is devoted to an already existing device, laminates which are debonded by the application of a voltage. This type of material can potentially be used in a wide range of applications, including adhesive joints in vehicles to both reduce the total weight and to simplify the disassembly after end-of-life, enabling an inexpensive recycling process. Although already a functioning device, the development and tailoring of this process was slowed by a lack of knowledge concerning the actual electrochemical processes responsible for the debonding. The laminate studied consisted of an epoxy adhesive, mixed with an ionic liquid, bonding two aluminium foils. The results showed that the electrochemical reaction taking place at the releasing anode interface caused a very large increase in potential during galvanostatic polarization. Scanning electron microscopy images showed reaction products growing out from the electrode surface into the adhesive. These reaction products were believed to cause the debonding through swelling of the anodic interface so rupturing the adhesive bond. The other part of the work in this thesis was aimed at innovative lithium ion (Li‑ion) battery concepts. Commercial Li-ion batteries are two-dimensional thin film constructions utilized in most often mechanically rigid products. Two routes were followed in this thesis. In the first, the aim was flexible batteries that could be used in applications such as bendable reading devices. For this purpose, nano-fibrillated cellulose was used as binder material to make flexible battery components. This was achieved through a water-based filtration process, creating flexible and strong papers. These paper-based battery components showed good mechanical properties as well as good rate capabilities during cycling. The drawback using this method was relatively low coulombic efficiencies believed to originate from side-reactions caused by water remnants in the cellulose structure. The second Li-ion battery route comprised an electrochemical process to coat carbon fibers, shown to perform well as negative electrode in Li-ion batteries, from a monomer solution. The resulting polymer coatings were ~500 nm thick and contained lithium ions. This process could be controlled by mainly salt content in the monomer solution and polarization time, yielding thin and apparently pin-hole free coatings. By utilizing the carbon fiber/polymer composite as integrated electrode and electrolyte, a variety of battery designs could possibly be created, such as three-dimensional batteries and structural batteries. / <p>QC 20130403</p>

A typical buckling restrained brace (BRB) consists of a core segment and a buckling restraining mechanism. When compared to a conventional brace, BRBs provide nearly equal axial yield force in tension and compression. Buckling restraining mechanism can be grouped into two main categories. Buckling is inhibited either by using a concrete or mortar filled steel tube or by using steel sections only. While a large body of knowledge exists on buckling restrained braces the behavior of steel encased BRBs has not been studied in detail. Another area that needs further investigation is the detailing of the deboding material. For all types of BRBs a debonding material or a gap has to be utilized between the core brace and the restraining mechanism. The main function of the debonding material is to eliminate the transfer of shear force between the core brace and the restraining mechanism by preventing or reducing the friction. A two phase research study has been undertaken to address these research needs. In the first phase an experimental study was carried out to investigate the potential of using steel encased BRBs. In the second phase a numerical study was conducted to study the friction problem in BRBs. The experimental study revealed that steel encased braces provide stable hysteretic behavior and can be an alternative to mortar filled steel tubes. Material and geometric properties of the debonding layer for desired axial load behavior were identified and presented herein.

Texas Department of Transportation (TxDOT) is currently designing its highway bridge structures using the AASHTO Standard Specifications for Highway Bridges, and it is expected that TxDOT will make transition to the use of the AASHTO LRFD Bridge Design Specifications before 2007. The objectives of this portion of the study are to evaluate the current LRFD Specifications to assess the calibration of the code with respect to typical Texas U54 bridge girders, to perform a critical review of the major changes when transitioning to LRFD design, and to recommend guidelines to assist TxDOT in implementing the LRFD Specifications. This study focused only on the service and ultimate limit states and additional limit states were not evaluated. The available literature was reviewed to document the background research relevant to the development of the LRFD Specifications, such that it can aid in meeting the research objectives. Two detailed design examples, for Texas U54 beams using the LRFD and Standard Specifications, were developed as a reference for TxDOT bridge design engineers. A parametric study was conducted for Texas U54 beams to perform an in-depth analysis of the differences between designs using both specifications. Major parameters considered in the parametric study included span length, girder spacing, strand diameter and skew angle. Based on the parametric study supplemented by the literature review, several conclusions were drawn and recommendations were made. The most crucial design issues were significantly restrictive debonding percentages and the limitations of approximate method of load distribution.The current LRFD provisions of debonding percentage of 25 percent per section and 40 percent per row will pose serious restrictions on the design of Texas U54 bridges. This will limit the span capability for the designs incorporating normal strength concretes. Based on previous research and successful past practice by TxDOT, it was recommended that up to 75% of the strands may be debonded, if certain conditions are met. The provisions given in the LRFD Specifications for the approximate load distribution are subject to certain limitations of span length, edge distance parameter (de) and number of beams. If these limitations are violated, the actual load distribution should be determined by refined analysis methods. During the parametric study, several of these limitations were found to be restrictive for typical Texas U54 beam bridges. Two cases with span lengths of 140 ft. and 150 ft., and a 60 degree skew were investigated by grillage analysis method.

In recent decades, a significant research has been carried out towards understanding the behaviour of plated beam. Initially designed to achieve a desired capacity, the plated beams prematurely fail in undesirable modes of failure, such as debonding and peeling. The uncertainty related with such modes of failure poses a real challenge towards quantifying them. This field is far from being clearly understood. Therefore, an attempt is made in this thesis to accurately predict the behaviour of adhesively plated beams.

Submitted by Fabio Salomão (salomaofm@me.com) on 2017-10-25T13:11:58Z No. of bitstreams: 1 TESE FINAL - POS DEFESA OK.pdf: 22130957 bytes, checksum: 001852660d064b7d48732b95f0767def (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-10-31T16:03:04Z (GMT) No. of bitstreams: 1 salomao_fm_dr_araca.pdf: 22130957 bytes, checksum: 001852660d064b7d48732b95f0767def (MD5) / Made available in DSpace on 2017-10-31T16:03:04Z (GMT). No. of bitstreams: 1 salomao_fm_dr_araca.pdf: 22130957 bytes, checksum: 001852660d064b7d48732b95f0767def (MD5) Previous issue date: 2017-08-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Objetivo: Avaliar através de simulação clínica a efetividade da remoção de resíduos fluorescentes do esmalte dental bovino, após remoção de bráquetes ortodônticos, utilizando dispositivos emissores de luz branca e fluorescente. Materiais e Métodos: 180 dentes bovinos anteriores hígidos foram seccionados em discos de esmalte/dentina. A remoção do material resinoso cimentante foi realizada por três operadores. Os dentes foram divididos em quatro grupos de estudo. Os fatores em estudo foram: a fonte de iluminação empregada durante a remoção dos materiais resinosos cimentantes de bráquetes ortodônticos em 4 níveis (n = 45): Convencional (C), LED branco (W), LED fluorescente (F) e fotopolimerizador com filtro fluorescente (FL). Foram consideradas como variáveis de resposta: o tempo para remoção dos resíduos das amostras; a área de remanescente resinoso fluorescente superficial e a mensuração da altura de material adesivo fluorescente remanescente (PICO) e a profundada de esmalte desgastado (VALE). Na comparação entre as técnicas empregou-se o teste Kruskal-Wallis seguido do pós-teste Mann-Whitney U (P≤0,05). Resultados: As Técnicas F e FL apresentaram-se, estatisticamente, semelhantes e as menores medianas de tempo consumido para a remoção do resíduo resinoso. As técnicas C e W apresentaram estatisticamente, a presença de maiores e semelhantes medianas de áreas fluorescentes remanescentes e de PICO (altura do remanescente), com relação as técnicas F e FL; enquanto que as técnicas FL e F postaram, estatisticamente, uma maior mediana de VALE que a técnica C. Conclusões: A associação de emissor de luz fluorescente com um material resinoso fluorescente, colaborou significativamente e de forma eficaz, na redução do tempo consumido para remoção e evidenciação dos resíduos resinosos cimentantes fluorescentes, possibilitando uma remoção efetiva, após a remoção dos bráquetes ortodônticos. / Objective: Evaluate, through clinical simulation, the effectiveness on the removal of fluorescent resin residues from bovine dental enamel after brackets debonding using white and fluorescent light emitting devices. Materials and Methods: 180 healthy anterior bovine teeth were sectioned on enamel / dentin disks. The removal of the resinous material was performed by three operators. The teeth were divided into four groups. The factors studied were: the light source used to remove orthodontic resin residue in 4 levels (n = 45): Conventional (C), white LED (W), fluorescent LED (F) and photocuring unit with Fluorescent filter (FL). Response variables were: the time spent to remove the sample residues; The surface area of the fluorescent remaining resin and the depth measurement of the remaining fluorescent adhesive thickness (PEAK) and the enamel thickness removed (VALLEY). In the comparison between the techniques, the Kruskal-Wallis test was used, followed by the Mann-Whitney U post-test (P≤0.05). Results: In terms of time, the groups F and FL were similar to each other and statistically different for groups C and W. The techniques C and W presented statistically, the presence of larger and similar medians of remaining fluorescent areas, in relation to te F and FL techniques. The techniques C and W presented, statistically, a larger and similar median of peaks than the F and FL techniques. The FL technique statistically demonstrated a higher median of valleys than the C technique. The W, F and FL techniques were statistically similar to each other, as were C and W techniques. Conclusions: Fluorescent light with a fluorescent resinous material, signicantly and removal of fluorescent resin residues, allowing an efficient removal after removal of orthodontic brackets. / CAPES: 1294804

Este estudo avaliou a eficiência do uso do laser de CO2 com comprimento de onda de 10,6 m como auxiliar na remoção de bráquetes estéticos cerâmicos. Para este estudo foram utilizados 105 pré-molares inferiores humanos recentemente extraídos, que receberam irradiações com laser de CO2 antes da descolagem dos bráquetes. Na primeira fase deste estudo, o objetivo foi mensurar e comparar a temperatura no compósito de colagem do bráquete e na câmara pulpar após aplicação do laser de CO2 , para observar a segurança para o esmalte, bem como se a temperatura era suficiente para fragilizar o compósito, facilitando a remoção do bráquete. Nesta etapa foram utilizados 30 pré-molares inferiores recentemente extraídos, sendo que cada um recebeu 4 irradiações com diferentes protocolos de maneira aleatória. Foram testados 12 diferentes protocolos variando o tempo de irradiação (3 e 5s), a duração do pulso (0,01 e 0,03s) e a potência (5, 8 e 10W). Cada protocolo foi utilizado por 10 vezes (n=10), totalizando 120 irradiações. Em todas as irradiações os corpos-de-prova foram imersos em banho térmico com água a 37º C. Foram encontrados 4 protocolos cuja variação da temperatura na polpa foi menor que 5,5º C, portanto compatível com a saúde da polpa. Na segunda etapa do estudo, o objetivo foi avaliar a resistência ao cisalhamento após a aplicação do laser utilizando os protocolos cuja temperatura na polpa não fosse superior a 5,5º C. Setenta e cinco pré-molares inferiores humanos foram divididos em 5 grupos, dos quais um não foi submetido à irradiação, sendo considerado Controle (C). Nos 4 grupos restantes, irradiações foram realizadas como descrito a seguir: Grupo I (potência 5W; tempo de pulso 0,01s; tempo de aplicação 3s), Grupo II (5W; 0,03s e 3s), Grupo III (8W; 0,01s e 3s) e Grupo IV (10W; 0,01s e 3s). Cada grupo foi formado por 15 corpos-de-prova (n=15). Após a descolagem do bráquete foi avaliado o Índice de Remanescente Adesivo (IRA). Após as mensurações e aplicação da Análise de Variância (ANOVA) e do teste de Tukey foi constatado que o único grupo que apresentou diminuição na força de remoção foi o IV (7,33 MPa) em relação ao grupo C (10,81 MPa) sendo assim considerado seguro e eficaz na diminuição da resistência do compósito. / This study evaluates the efficacy CO2 10,6 m laser-assisted debonding esthetic ceramic brackets. For this purpose it was used 105 recently extracted lower human premolars that were irradiated with CO2 laser before debonding. In the first phase, the objectives were to measure and compare the temperature in composite for bracket bonding and at the pulp chamber after CO2 laser irradiation, to observe the safety for enamel, as well the temperature was enough to softening the composite, making debonding bracket easier. In this part it was used 30 lower premolar recently extracted, and each one received 4 irradiations with different protocols, randomly choose. It was tested 12 different protocols varying time of irradiation (3 and 5s), pulse duration (0,01s e 0,03s) and power (5, 8 and 10W). Each protocol was repeated for 10 times (n=10), resulting 120 irradiations. In every irradiation the teeth tested were immerse in warm water bath at 37o C. It was found 4 protocols with pulp temperature lower than 5,5º C, so this is compatible with pulp health. In the second phase of this study, the objective was to evaluate the shear bond strength after laser irradiation, using the protocols with pulp chamber temperatures lower than 5,5º C. Seventy-five lower human premolars was shared in 5 groups. One group did not receive laser irradiation and considered Control (C) and the other groups the irradiation was made as it follows: Group I (power density 5W; pulse duration 0,01s; irradiation time 3s), Group II (5W; 0,03s, 3s), Group III (8W; 0,01s; 3s) and Group IV (10W; 0,01s; 3s). After results ANOVA and Tukey tests were made. Group IV presented lowering in SBS force (7,33 MPa) when compared with C (10,81MPa). This protocol was founded as a safe and efficient in softening composite layer.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第14575号 / 工博第3043号 / 新制||工||1453(附属図書館) / 26927 / UT51-2009-D287 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 落合 庄治郎, 教授 粟倉 泰弘, 准教授 奥田 浩司 / 学位規則第4条第1項該当

Fibre reinforced plastics (FRP) have been used widely in civil engineering in order to improve the structural response (deformation and stress). Most of the current codes for the strengthening of RC structures do not provide enough provision for the design of the column-slab connections strengthened with externally bonded reinforcement (EBR) due to the lack of research covering this area. This study is to investigate, both experimentally and analytically, the effectiveness of bonding pre-stressed carbon fibre plates to the tension surface of concrete column-slab connections in both the serviceability and ultimate limit state. The experimental programme comprises five full-scale specimens that are designed and fabricated to simulate an interior column-slab connection. The prestressing technique, application procedure and prestressing device are described in detail in this study. Different prestressing forces are applied to the FRP plates bonded to the concrete substrate. The structural response of the strengthened specimens are compared with a reference specimen in terms of punching shear strength, deflection profile, strain, crack opening displacement and failure modes. Furthermore, a finite element model using ABAQUS is built to obtain a further insight into the punching behaviour of the test slabs. Both experimental and numerical results are compared, and a parametric study on the effect of the FRP-concrete interface on the structural integrity is conducted. Results are also compared with Eurocode 2 and ACI for the prediction of the punching strength. It was found that bonding of prestressed FRP plates to the tensile face of the concrete slabs improved the serviceability, but was not able to enhance the ultimate behaviour as much as the non-prestressed FRP plates. The development of the critical diagonal crack (CDC) was the main reason for diminishing the ultimate strength of the strengthened slabs.

<div>Polymer bonded explosives (PBXs) consist of energetic material (EM) crystals embedded inside a polymeric binder. These are highly heterogeneous structures designed to explode under controlled conditions. However, accidental ignition of PBXs leading to deflagration, or even detonation, may take place due to non-shock stimulus such as low velocity impacts and vibration. Thus, assessing the safety of PBXs under non-shock stimulus is very important.</div><div><br></div><div>The ignition in PBXs depends on several microstructural features which include mechanical properties of EM particles and polymeric binder, as well as the adhesive properties of interface between EM particles and binder. It is also sensitive to initial defects in EM particles including cracks or voids. EM particle size distribution, distance between particles and their relative location are also shown to be affecting the ignition behavior of PBXs. This study focuses on PBX composition consisting of HMX as EM and Sylgard or HTPB as polymeric binder. Among several mechanisms of hot-spot formation, this study focuses on frictional heating at cracks or debonded surfaces.</div><div><br></div><div>Finite element simulations are performed on a domain containing a single EM particle embedded inside polymer binder under compressive and tensile loading at 10 m/s. The effect of the binder properties and the particle surface properties, on damage evolution and corresponding temperature rise due to frictional heat generation, is investigated. Two binders, Sylgard and HTPB, while two surface qualities for HMX particle, low and high, are compared. The adhesion strength of the particle-polymer interface is varied and damage evolution is qualitatively compared with experimental results to estimate interfacial energy release rate for HMX-Sylgard and HMX-HTPB interfaces. Simulations of two HMX particles inside Sylgard binder, subjected to vibration loading, are performed to analyze the effect of particle-particle distance and relative location of particles on the damage evolution and frictional heating in the particles.</div><div><br></div><div>The results of impact simulations show that the low surface quality HMX particle inside HTPB is likely to propagate cracks as compared to high surface quality particle. The HMX particle inside Sylgard shows crack propagation irrespective of particle surface quality. The impact simulations with the lower stiffness binder do not show a significant increase in temperature after impact. A polymer with higher stiffness induces more particle damage under impact contributing to a larger temperature rise. Furthermore, high quality surface and higher adhesion strength induces larger stresses and increase the temperature rise. The vibration simulations show that a small particle is less likely to damage when it is shielded by a large particle irrespective of its distance, within 40-200$\mu$m, from the large particle. However, the small particle is likely to damage when it is in parallel to the large particle with respect to loading. The temperature rise in the small particle is higher than the larger particle only in case of parallel configuration. The adhesion between the particles and the polymer has a direct effect on the formation of hot-spots due to friction and through local increase of compressive stresses that may cause a surge in heat generation.</div><div><br></div><div>The energetic materials often show anisotropy in elastic and crystalline properties. Fracture in HMX along the preferred cleavage plane is considered. Anisotropy in the elastic constants is also incorporated in the fracture model. The dependence of pressure on temperature is considered using Mie-Gruneisen equation of state which is shown to be important for damage evolution in HMX at impact velocity of 100 m/s.</div>