En la presente investigación se ha estudiado la formación de recubrimientos de Ti y TiB2 sobre sustrato de Ti mediante la técnica de Laser Cladding (recubrimiento láser) coaxial usando un láser de Tipo Nd YAG de 1 kW de tipo continuo, analizando los efectos que tienen sobre el recubrimiento, los porcentajes de aleación del material adicionado, los elementos aleantes presentes en el sustrato y los cambios que se presentan en la ZAC (zona afectada por el calor) en el material de sustrato. Para un apropiado análisis experimental, los principales parámetros del proceso, potencia y velocidad de barrido del láser y flujo de polvos han sido cambiados gradualmente dentro de rangos elegidos. Se ha realizado correlaciones entre las variables principales del proceso, la geometría de los cordones individuales y las transformaciones de los polvos adicionados. Una vez elegidos los cordones con mejor combinación de características geométricas, microestructura y dureza se ha realizado el solapamiento de cordones para producir los recubrimientos analizando el efecto térmico en la redistribución de fases y en la difusión de elementos químicos. Se ha obtenido recubrimientos con buenas áreas de cordón, y bajas áreas de dilución con microestructuras compuestas de matriz de titanio y compuestos de TiB y TiB2 distribuidos en la matriz de forma homogénea con buena unión a ella, y con durezas de hasta 8 veces la dureza original del titanio. Se ha identificado los parámetros adecuados para la obtención de los polvos, mediante aleado mecánico, de la aleación Ti+TiB2. Se ha logrado delimitar la ventana de proceso para la fabricación de recubrimientos de Ti+TiB2. Se ha logrado establecer la composición aproximada de boro mediante el empleo de la técnica de WDS (wavelenght dispersive spectrometry). Se ha caracterizado mecánicamente los compuestos encontrados mediante técnicas de nanodureza. Finalmente se ha identificado mediante la técnica de EBSD (Electron backacatter diffraction) las fas / Angarita Moncaleano, II. (2012). ANÁLISIS DE RECUBRIMIENTOS DE Ti REFORZADOS CON TiB2 MEDIANTE TÉCNICAS DE RECUBRIMIENTO LÁSER [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16882 / Palancia

The feasibility of in-situ alloying of AISI 410L martensitic stainless steel with nitrogen during Nd-YAG laser cladding was investigated with the aim of achieving a nitrogen content of at least 0.08 wt% and fully martensitic microstructures in the final clad deposit. Two in-situ nitrogen alloying techniques were studied. In the first set of experiments, the absorption of nitrogen from nitrogen-rich gas atmospheres was studied. Laser cladding with commercially available AISI 410L powder was performed using nitrogen-rich shielding and carrier gas. A marginal increase in deposit nitrogen content was observed, with the clad deposit displaying low hardness and mostly ferritic microstructures. Poor nitrogen absorption from nitrogen-containing atmospheres during Nd-YAG laser cladding is generally attributed to the short thermal cycle and to suppression of plasma formation above the weld pool. In the remaining experiments, Si3N4 powder was investigated as an alternative source for nitrogen during cladding. The addition of Si3N4 to the AISI 410L powder feed resulted in clad microstructures consisted of columnar -ferrite grains with martensite on the grain boundaries, higher hardness and an increase in deposit nitrogen content (to a maximum of 0.064 wt% nitrogen). Higher nitrogen contents in the clad deposit, however, significantly increased the volume percentage porosity in the clad layer. This prompted an investigation into the feasibility of raising the nitrogen solubility of the alloy through additions of manganese and nickel to the powder feed. Thermodynamic modelling revealed that the addition of manganese to AISI 410L powder increases the nitrogen solubility limit due to its negative interaction parameter with nitrogen. The addition of up to 3.5 wt% manganese to AISI 410L powder containing Si3N4 significantly increased the nitrogen solubility in the deposit. A martensitic microstructure with 0.12 wt% nitrogen and a peak hardness of 410 HV was achieved without any adverse increase in porosity in the clad layer. The clad nitrogen content easily exceeded the minimum requirement of 0.08 wt%. High nickel concentrations in AISI 410L stainless steel expand the austenite phase field at the expense of -ferrite and alter the solidification mode from ferritic to austenitic-ferritic. The addition of up to 5.5 wt% nickel, or combinations of nickel and manganese, to the nitrogen-alloyed AISI 410L powder feed raised the deposit nitrogen content, but not to the same extent as those deposits alloyed with manganese only. Since more austenite is present on cooling in nickel-alloyed AISI 410L deposits, less nitrogen is rejected to the liquid phase on solidification, resulting in higher nitrogen contents and less porosity in the room temperature microstructures. The amount of dilution during single-track laser cladding is mainly influenced by the specific energy per unit mass delivered by the laser beam. The clad height is strongly influenced by the powder deposition rate, whereas the bead width is influenced by the wettability of the deposits during laser cladding. During multi-track cladding, the observed percentage porosity is a function of the aspect ratio of the individual beads making up the clad layer, the deposition rate and the clad height. High deposition rates result in thicker layers, increasing the distance that N2 gas bubbles have to travel to escape to the atmosphere, while a high aspect ratio favours interbead porosity. The results suggest that in-situ nitrogen alloying during laser cladding should preferably be performed at low deposition rates to ensure higher clad nitrogen contents and hardness, lower clad heights, less dilution and less porosity. / Dissertation (MEng)--University of Pretoria, 2016. / Materials Science and Metallurgical Engineering / MEng / Unrestricted

This thesis is focused on quantifying the dynamic performance of lightweight metal sandwich systems under confined explosions, where this effort represents the first of a multi-phase comprehensive research program that is focused on developing blast damage mitigation techniques in submerged structures. A confined explosion occurrence inside such facilities may lead to paralyzing all operations depending on the functions of the affected sections. Subsequently, using sacrificial cladding placed as a physical barrier over critical components that might be vulnerable to a potential explosion is considered to be an effective blast damage mitigation technique. Furthermore, sandwich panels can be an ideal system to be used as sacrificial cladding, as it can be manufactured to possess high stiffness-to-weight ratio and superior energy absorption capabilities. Consequently, an experimental program was performed to investigate the performance of lightweight cold-formed steel sandwich panels under both quasi-static loads and confined explosions, where a total of fifty-seven sandwich panels were tested, considering various core configurations, different core sheet thickness, and different blast load intensity levels. The American ASCE/SEI 59-11 and The Canadian CSA/ S850-12 blast design standards predict the dynamic response of a structure component based on the static resistance function by applying dynamic increase factors. Subsequently, the static resistance functions for the proposed panel configurations were investigated experimentally and compared with the introduced analytical model, in order to quantify accurately the inelastic panel response. The quasi-static test program was performed in two stages, where the first included eighteen single layer core sandwich panels, which represented longitudinal and transverse corrugated core configurations. The results of the first stage configurations demonstrated an efficient strength and stiffness, but showed a lack in energy absorption capabilities and ductility capacity. Therefore, in the second stage, different core configurations were developed, including twenty-one panels representing Bi-directional and X-core double layered core configurations and its counterpart Uni-directional single layer core configuration. The results of the second stage demonstrated an enhancement in the ductility and energy absorption capabilities compared to the configurations tested in the first stage. The residual deformations and failure modes demonstrated were assessed and discussed in details, where web crippling, local buckling and global buckling induced by shear or flexurewere determined. In general the static resistance functions for each tested panel were used to quantify the panels’ yield loads, ultimate capacities, and corresponding displacement levels. Moreover, the influences of both the core configuration and the core sheet thickness on the panels’ stiffness, ductility levels and energy absorption were quantified. Based on the conclusions of the static testing and considering the ductility, capability of energy absorption, and the behavior beyond the elastic zone, two different core configurations were chosen to be tested under confined explosions. Eighteen panels were tested in a cylindrical shape blast chamber representing a typical submerged structure under different scaled distances ranged from 2.82 to 1.09 m/kg1/3, in order to demonstrate different damage state levels in accordance with the blast design standards (ASCE/SEI 59-11, CSA/ S850-12). In the blast testing results, the incident and reflected pressure time histories of the blast wave were measured, while the modified Friedlander equation was used to fit the first positive phase of the reflected pressure histories. In addition, the displacement response histories of the back face of the tested panels were recorded. The measured values of peak incident pressure, peak reflected pressure, incident impulse and the reflected impulse were compared to the predicted values using ConWep (Hyde 1990) considering the spherical explosion, and have shown a good agreement. Furthermore, the failure modes and the post blast damage were determined and compared to the static observations. In order to complement the experimental program, a nonlinear inelastic single degree of freedom model was developed in order to predict the dynamic response of the sandwich panels. The model used the recorded blast load and the static resistance while applying the dynamic increase factors recommended by the standards (ASCE/SEI 59-11, CSA/ S850-12). The model results were in a good agreement with the experimental data. Furthermore, the different ductility and support rotation values obtained experimentally and predicted analytically were related to the different damage levels specified by blast standards. Finally, the influence of sandwich panel core configuration on the dynamic blast response of the tested sandwich panels was discussed. / Thesis / Doctor of Philosophy (PhD)

Detta arbete undersöker om metoden ’laser cladding’ skulle kunna användas för att möjliggöra återanvändandet av bromsskivor som annars skulle deponeras. Olika material undersöks ur ett miljöperspektiv, det vill säga energiåtgång och CO2-utsläpp jämförs mot en vanlig gjutjärnsskiva. För att göra detta användes programmet CES EduPack samt ytterligare beräkningar med formler som komplement då programmets databas inte är heltäckande gällande specifika materialvarianter. För att lättare kunna beräkna massor användes CAD-programmet Solid Edge för att modellera en typisk bromsskiva. Resultatet blev att laserbeläggning på utslitna bromsskivor sparar på både energi och avger mindre CO2-avtryck, förutsatt att rätt tillsatsmaterial väljs. Som mest kunde en minskning med 80,5% uppnås i energiåtgång respektive 88% för CO2-utsläpp under materialframställning och tillverkning. Metoden medför alltså tydliga positiva miljömässiga effekter. / This report investigates Laser Cladding and especially the possibility to coat worn brake discs. A selection of materials are studied with an environmental point of view in focus, the life cycle of the coated brake discs are compared to a standard new gray cast iron brake disc. The program CES Edupack is used for the life cycle analysis and it is completed by formulas of energy consumption and CO2 footprint because not all processes and materials are included in the software. Solid Edge is used to create a CAD model of a typical brake disc to easily exam the volume and weight of the disc as a function of the thickness. The result is laser cladding on worn brake discs saves energy and produces a smaller carbon footprint if the right powders used for cladding are chosen. Laser cladding with stainless steel powders provided the best results with 80.5% savings in energy consumption and 88% in CO2-footprint savings. The laser cladding technique shows clear positive environmental effects.

This thesis describes the work carried out at Brunel University to develop novel optical fibre sensors capable of monitoring the cure state of an epoxy/amine resin system. The sensors were of simple construction, consisting of an optical fibre from which the silicone cladding layer had been removed over a short length. This stripped length was embedded into the curing resin system. The sensor was successfully used in two ways: i) as an evanescent absorption sensor to monitor specific absorption bands of the resin system. The absorption of energy from the evanescent wave of the optical fibre by absorbing media allows evanescent absorption spectra to be obtained. Absorption spectra were obtained from sensors embedded in a model curing resin system over narrow wavelength ranges. These wavelength ranges corresponded to positions of known absorptions in the spectra of active components in epoxy/amine systems. By monitoring the change in these absorptions it was possible to obtain information about concentration of the amine hardener functional group throughout cure; ii) as a refractive index sensor capable of monitoring the changes in the refractive index of the resin system during cure. A laser diode was used to launch light into the sensor and the intensity of light emerging from the other end of the fibre was monitored. Changes in the resin system refractive index caused changes in the guiding properties of this the sensor. This resulted in a significant change in the intensity of light recorded by the detector and allowed the cure process to be followed. This sensor was also embedded into a unidirectional pre-preg system and was able to follow the cure of the system. The results from the two sensing methods have been compared with data obtained using FTIR spectroscopy and Abbe refractometry during the resin system cure. A theoretical model of sensor response has been developed and compared with the experimental data obtained. The sensor response has also been compared to predictions made by several models of evanescent sensor systems obtained from the literature. These models have been modified so that they can be applied to a sensor embedded into a curing resin system. An analysis of the correspondence between theory and experiment is presented.

Silicon Carbide (SiC) is increasingly gaining attention as a potential fuel cladding material, on account of its favorable thermo-mechanical and neutronic properties. The major limitations of such a cladding is currently associated with joining and hermetic sealing. The work presented here investigated the use of Al, Cr and Fe metals and a specialized alloy (FeCrAl) to achieve hermetic sealing of SiC tubes as well as a joining technology of SiC. Major part of solving this issue requires addressing joining of ceramic and metallic components, which are largely dissimilar in both thermal and mechanical properties. Preliminary experiments to bond SiC with FeCrAl resulted in adverse separation partially attributed to the differences in thermal expansion mismatch. To alleviate these problems, thin and thick coatings of the metals and alloys were applied to SiC. Qualitative microstructural characterization of the final product indicated satisfactory bonding between the materials.

L'architecture moderne des années 20 et 30 est en général caractérisée par un usage des nouveaux matériaux que son l'acier, le béton et le verre. Pourtant la pierre a joué également un rôle important, quoique plus modeste, dans la définition du "style moderne", rôle qui a été peu étudié dans les nombreux travaux qui ont porté sur cette période. Pendant des siècles, la "construction pierre par pierre", a été un aphorisme de la culture occidentale qui renvoyant à l'action archaïque de construire, que ce soit au niveau de bâtiment ou de la ville. C'est la raison pour laquelle elle a toujours été associée à la tradition, et délibérément occultée par le Mouvement Moderne. Cependant elle témoigne bien des transformations en cours de la phase cruciale de la "modernisation" de la société et donc de l'architecture et de la construction. La pierre est aussi un excellent lieu d'analyse de la phase délicate de transition d'un tissu technique et commerciale traditionnel, vers une industrialisation naissante et des nouvelles technologies qui lui sont liées / Reading the project of the Modern and its constructive cultures in relation to the historical conditions and the technology, allows exploring some aspects of Modern Architecture in Europe. Besides the traditional, more studied and known triad of "moderns" materials, steel, concrete and glass, the stone also played an important role, in the definition both of "modern construction and modern style". The construction in stone was always associated with the tradition and then forgotten by the Modern Movement, during the crucial phase of society's "modernization" and therefore its architecture and construction. The stone however explains this delicate transition from the traditional art of building in stone to the new technologies

A Dissertação de Mestrado em questão consiste na avaliação do uso de revestimentos cerâmicos de fachada fundamentada no estudo de caso para edifícios residenciais multifamiliares, caracterizado por prédios de apartamentos, no Município de São Paulo, região Sul, cujos lançamentos ocorreram entre 1994 e 1998. Para tanto, abordam-se inicialmente antecedentes do uso destes materiais em fachadas de edifícios no Brasil. Posteriormente são abordadas as principais características dos materiais componentes dos revestimentos cerâmicos, enfatizando suas características quando aplicados em fachadas. São explicitadas, ainda, considerações para a elaboração de projetos de revestimentos cerâmicos de fachadas, bem como para sua execução, destacando também as principais patologias que os afetam. Finalmente, é realizada uma análise do uso dos revestimentos cerâmicos em fachada, no cenário definido, acompanhada de registros fotográficos, apresentados na forma de fichas para cada bairro levantado. Acompanha também esta análise uma pesquisa realizada entre os escritórios de arquitetura responsáveis pelos projetos arquitetônicos dos edifícios em questão, visando as condicionantes de projeto para o uso dos revestimentos cerâmicos. Conclui-se com abordagens vinculadas ao estado da arte sobre o uso dos Revestimentos Cerâmicos de Fachadas baseado na pesquisa de campo e opiniões dos arquitetos. / This Dissertation is about an evaluation of the use of ceramic tiles in facades of buildings, based on the study of housing buildings located at the southern region of the city of Sao Paulo, which were built between 1994 and 1998. At the beginning, the historic aspects of use of ceramic tiles in facades are reviewed, specifically in Brazil. Later on, the main characteristics of the components of ceramic tiles in coverings are studied, emphasizing the resulting characteristics when applied to facades. The study also describes considerations for both the elaboration and implementation of projects of ceramic tile facade coverings including the main pathologies that may affect them. An analysis on the use of ceramic tile facade coverings in a specific scenery is included. Photographic files of each neighborhood are attached to this section as well as a research among architecture offices who were responsible for the projects of those buildings. Finally you will find approaches related to the state -of-art when using ceramic tile facade coverings based on an in situ research and on architect’s opinions.

A atual situação sócio econômica do país tem levado as empresas construtorasa buscarem eficiência no seu processo de produção. Nesse contexto, o uso das chapas de gesso acartonado como componente de vedação vertical interna vem se tornando cada vez mais intenso, substituindo a tradicional vedação em alvenaria. Apesar da utilização crescente desse componente, há uma carência no país sobre o conhecimento da tecnologia construtiva das divisórias de gesso acartonado, que já é largamente difundida em vários países. Dessa forma, o presente trabalho caracteriza o método construtivo da vedação vertical interna de chapas de gesso acartonado, abordando sobre o seu desempenho; analisando os materiais, componentes, equipamentos e ferramentas necessários para a sua execução; apresentando os procedimentos de montagem da divisória e propondo algumas diretrizes para a elaboração de um projeto para produção e o estabelecimento de parâmetros de controle durante o processo de execução. Espera-se dessa forma contribuir para o avanço da tecnologia de produção das vedações verticais e, em especial, das divisórias de gesso acartonado. / Due to the current social and economic situation in Brazil, building construction companies are seeking ways to improve efficiency in their production processes. For this reason, gypsum plasterboard is beginning to be widely used for internal walls as a substitute for traditional masonry. In spite of the increasing utilization of this component, which is common in other countries, little research regarding gypsum plasterboard construction technology has been carried out here. In this way, this study deals with the gypsum plasterboard construction method, analyzing its performance, materials, components, equipment and tools required for installation. It also describes the procedure for assembling these partitions. Finally, some guidelines for the production design elaboration and the parameters to help to control the execution process are proposed. This study aims to contribute to improving internal wall technologies, especially gypsum plasterboard partition construction.

A utilização de tecnologias construtivas inovadoras, como os painéis pré-fabricados arquitetônicos de concreto (PPAC), tem-se configurado prática frequente do mercado brasileiro por, potencialmente, contribuir para incrementar os níveis de industrialização dos processos de produção, bem como a qualidade do produto final a custos reduzidos. No Brasil, entretanto, não existem ainda normas ou manuais técnicos que balizem a utilização dessa tecnologia construtiva. Por isso, este trabalho sistematiza o conhecimento sobre a tecnologia de PPAC para emprego em fachadas de edifícios de múltiplos pavimentos, por meio da apresentação dos principais fatores que devem ser considerados nas fases de elaboração dos projetos de empreendimentos que utilizem os PPAC em suas fachadas. Fatores esses, que condicionam o desempenho e a eficiência do processo de produção das fachadas. Após o acompanhamento do processo de produção de dois empreendimentos que utilizaram PPAC em suas fachadas, constituindo os estudos de caso, conclui-se que a tecnologia de PPAC apresenta grande potencial para incrementar os níveis de industrialização do processo de produção do edifício, se a elaboração dos seus projetos ocorrer nas fases preliminares da concepção do empreendimento, em que suas funções e interfaces sejam consideradas. / The arquitectural precast concrete panel technology has frequently been used because of its probability of increasing the industrialization levels of the building process and also improve the building product quality. On the other hand, mostly in Brasil, there are no rules ou manual books which guide the utilization of this technology. In addition, this works aims to raise the knowledge about the arquitectural precast concrete panel used as cladding (APCP-PPAC in Portuguese). Therefore, this works presents some factors that must be considered in designs of building facades, using this kind of technology. After the analysis of one study case using APCP, it was concluded that APCP technology has a great potential of increasing the industrialization levels of the building process, if its designs are done as soon as possible and if its performance and interfaces are considered.