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Large-dimensional wooden products are highly demanded within the construction sector. Theprimary motive of the thesis is to find a solution to connect small timber elements by meansof special steel devices. It is auspicable that the resulting hybrid structure could match theload-carrying capacity of a corresponding homogenous timber element with the same size.The focus in this thesis is to study one type of shear-key connection. Three types of beams(pure glulam beam, hybrid beam either with or without the splice connection at mid-span) arestudied regarding their structural behaviours by means of theoretical analysis, numericalmodelling and experimental tests.Hybrid beam without the splice connection shows higher bearing capacity and higher stiffnessthan pure glulam beam no matter which method is used. The structural behaviours for hybridbeam without the splice connection obtained from each method are more or less similarexcept the failure mode.Hybrid beam with the splice connection shows the bearing capacity higher than pure glulambeam but lower than hybrid beam without the splice connection. The stiffness for hybrid beamwith the splice connection is approximately the same as that of the pure glulam beam basedon analytical and numerical calculation. However, around 30% - 40% lower stiffness isachieved in experiment. Factors that might influence the result are discussed in the main text.Two analytical methods (Partial composite action (PCA) Method and Gamma Method) areutilized for hybrid beam without the splice connection. Although Gamma method is asimplified method, the results are similar with that from PCA method. Therefore, GammaMethod is reliable to be used for the hybrid beam without the splice connection in this thesisproject.In addition, it is found that the alignment of shear-key connectors, slip modulus betweenshear-key and notch, diameter of rod and the vertical distance between glulam and rod areconsidered as the main sensitivity parameters that would influence the structural behaviours for hybrid beams a lot.

No description available.

This comprehensive study is the first to quantify the fatigue performance, failure loads, and microstructure of resistance spot welding (RSW) in 6061-T6 aluminum (Al) alloy according to welding parameters and process sensitivity. The extensive experimental, theoretical and simulated analyses will provide a framework to optimize the welding of lightweight structures for more fuel-efficient automotive and military applications. The research was executed in four primary components. The first section involved using electron back scatter diffraction (EBSD) scanning, tensile testing, laser beam profilometry (LBP) measurements, and optical microscopy(OM) images to experimentally investigate failure loads and deformation of the Al-alloy resistance spot welded joints. Three welding conditions, as well as nugget and microstructure characteristics, were quantified according to predefined process parameters. Quasi-static tensile tests were used to characterize the failure loads in specimens based upon these same process parameters. Profilometer results showed that increasing the applied welding current deepened the weld imprints. The EBSD scans revealed the strong dependency between the grain sizes and orientation function on the process parameters. For the second section, the fatigue behavior of the RSW’ed joints was experimentally investigated. The process optimization included consideration of the forces, currents, and times for both the main weld and post-heating. Load control cyclic tests were conducted on single weld lap-shear joint coupons to characterize the fatigue behavior in spot welded specimens. Results demonstrate that welding parameters do indeed significantly affect the microstructure and fatigue performance for these welds. The third section comprised residual strains of resistance spot welded joints measured in three different directions, denoted as in-plane longitudinal, in-plane transversal, and normal, and captured on the fusion zone, heat affected zone and base metal of the joints. Neutron diffraction results showed residual stresses in the weld are approximately 40% lower than the yield strength of the parent material, with maximum variation occurring in the vertical position of the specimen because of the orientation of electrode clamping forces that produce a non-uniform solidification pattern. In the final section a theoretical continuum modeling framework for 6061-T6 aluminum resistance spot welded joints is presented.

[pt] A calibração de padrões atômicos de tempo e freqüência, na forma atualmente realizada, apresenta o inconveniente de ter que se fazer o transporte do Padrão de Transferência até os laboratórios onde se encontram os padrões a serem calibrados. Isto se dá pelo fato destes laboratórios não possuírem uma maneira adequada para enviarem seus padrões ao Departamento do Serviço da Hora do Observatório Nacional (DSH/ON), órgão responsável perante o INMETRO na calibração em tempo e freqüência e detentor do Padrão Nacional. Propõe- se aqui a substituição do procedimento atual por um sistema de calibração automática via Internet, o que elimina a necessidade do deslocamento do Padrão de Transferência. Neste novo sistema de calibração, a referência passa a ser um receptor de GPS (Global Position Sistem), que assume o papel de Padrão de Transferência, ao qual o padrão a ser calibrado é ininterruptamente comparado. O acesso e armazenamento dos dados pelo DSH/ON é feito por meio de um programa que controla remotamente a calibração no laboratório via conexão pela Internet. O presente trabalho envolve uma comparação entre o sistema atual e o proposto aqui, todo o desenvolvimento e apresentação do programa computacional, a montagem de um sistema completo de simulação prática, inclusive com acesso remoto via Internet, a coleta e tratamento dos dados e a apresentação do procedimento utilizado para se chegar à incerteza de medição do sistema. Procura-se ressaltar a vantagem de um sistema de calibração automático, quanto à coleta dos dados, assim como a não dependência do transporte do Padrão de Transferência para a realização da calibração, evitando- se com isto a sua deterioração . Na conclusão deste trabalho a incerteza obtida é comparada com a do procedimento atualmente em prática e a partir desta comparação são feitas considerações quanto à implementação do novo sistema e ao uso do r eceptor de GPS como Padrão de Transferência. / [en] The time and frequency calibration of atomic standards presents the inconvenience of the need of transportation of the Transfer Standard to the laboratories in which stay the standards to be calibrate. This happens because the laboratories do not possess a way to send its standards to the Departamento do Serviço da Hora do Observatório Nacional (DSH/ON), organ representative of INMETRO in Time and Frequency calibrations and detainer of the National Standard. This work intends the substitution of the procedure adopted today by a system of automatic calibration using Internet, eliminating the need of the displacement of the Transfer Standard. In this new procedure, the reference is t he Global Position Sistem (GPS) receiver, assuming the role of the Transfer Standard, to which the standard to be calibrate is compared continuosly. The access and storage of the data for the DSH/ON are made by means of a computer code that remotely controls the calibration through an Internet connection. The present work involves a comparison among both systems, the whole development and presentation of the computer code, the assembling of a complete system of practical simulation, the acquisition and data treatment and the presentation of the procedure used to obtain the measurement of the uncertainty. The advantage of an automatic calibration system, as well as of the collection of the data, is the fact that it not depending of the transportation of the Reference Standard for the accomplishment of the calibratio. As a conclusion of this work the obtained uncertainty is compared with the one in use today and based in this comparison we made considerations about the implementation of the new system and the use of the GPS receiver as Transfer Standard. / [es] La calibración de padrones atómicos de tiempo y frecuencia, en la forma actualmente realizada, tiene el inconveniente de tener que realizar el transporte del Padrón de Transferencia hasta los laboratorios donde se encuentran los padrones que serán calibrados. Esto se debe al hecho de que estos laboratorios no poseen una manera adecuada para enviar sus padrones al Departamento de Servicio de la Hora del Observatorio Nacional (DSH/ON), óprgano responsable frente al INMETRO en la calibración en tiempo y frecuencia y detentor del Padrón Nacional. Se propone aqui la substituición del procedimiento actual por un sistema de calibración automática vía Internet, que elimina la necesidad del desplazamiento del Padrón de transferencia. En este nuevo sistema de calibración, la referencia pasa a ser un receptor de GPS (Global Position Sistem), que asume el papel de Padrón de Transferencia, al cual el padrón a ser calibrado es ininterruptamente comparado. El acceso y almacenamiento de los datos por el DSH/ON se realiza a través de un programa que controla remotamente la calibración en el laboratorio vía conexión por Internet. El presente trabajo compara el sistema actual con el aqui propuesto, todo el desarrollo y presenta el programa computacional, el montaje de un sistema completo de simulación práctica, incluso con acceso remoto víaa Internet, la recolección y tratamiento de datos y la presentación del procedimiento utilizado para llegar a los erros de medición del sistema. Se resalta la ventaja de un sistema de calibración automático, así como la no dependencia del transporte del Padrón de Transferencia para la realización de la calibración, evitando con esto su deterioración. En la conclusión de este trabajo se compara el error obtenido con el del procedimiento actualmente en práctica y a partir de esta comparación se realizan consideraciones respecto a la implementación del nuevo sistema y al uso del receptor de GPS como Padrón de Transferencia.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23457号 / 理博第4751号 / 新制||理||1681(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 前里 光彦, 教授 北川 宏, 教授 竹腰 清乃理 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Proton-Exchange Membrane Fuel Cells are an alternative source of electricity generation for automobiles and stationary power plants. With increasing concerns on environmental issues, recent research has focused on maximizing the efficiency and durability as well as minimizing the costs of fuel cells. One of the main areas of research is optimizing the structure of the cathode catalyst layer. The main driving force of this thesis was the effective visualization of nanostructure of the ionomer, which is responsible for proton conduction in the cathode catalyst layer. However, challenges regarding sample preparation and radiation damage still need to be well understood. Different sample preparation techniques of catalyst inks and catalyst coated membranes were used for Scanning and Transmission Electron Microscopy, such as freeze fracturing, ultramicrotomy and Focused Ion Beam. Comparisons of the microstructure and chemical differences of all components, especially the ionomer, prepared by ultramicrotomy and Focused Ion Beam, was done with Transmission Electron Microscopy and Scanning Transmission X-ray Microscopy applied to the same catalyst coated membrane sample. Detailed spectroscopic information regarding components in both specimens was compared with C 1s and F 1s near edge X-ray absorption spectra recorded in a Scanning Transmission X-ray Microscope. Focused Ion Beam causes extensive damage to the carbon support and ionomer but prepares thinner sections than ultramicrotomy. This work makes it possible to understand the limitations of each sample preparation and compositional analysis technique in order to later apply one of them to image the ionomer in the catalyst layer at the nanoscale, hopefully using tomography techniques. / Thesis / Master of Materials Science and Engineering (MMatSE)

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I jordbävningsdrabbade områden är stabilisering av byggnader en avgörande del i husens utformning. I många av dessa delar av världen lever stora delar av befolkningen i fattigdom med begränsad tillgång till resurser och moderna byggtekniker. Byggnader i jordbävningsdrabbade områden förstärks i olika mån, beroende på jordbävningsfrekvensen och deras magnitud. Staden Arusha i utvecklingslandet Tanzania är ett sådant område som drabbas av små till måttliga jordbävningar, då och då. Där förstärks byggnader med s.k. ring beams, ringbalkar. Denna typ av förstärkning ger huset stabilitet och flexibilitet vid jordbävningar. Förstärkningen som är mest frekvent använd i dessa områden tillverkas av armerade betongbalkar. Dessa kan hantera tryck-och dragspänningar, samt skjuvspänningar som konstruktionen utsätts för vid seismisk aktivitet.   Detta arbete syftar till att, på uppdrag av organisationen Econef, utvärdera konstruktionselementet ringbalk, för att kunna förbättra hållfastheten och livslängden på framtida konstruktioner som planeras byggas i Econefs aktuella projekt. Econef har konstaterat ett antal brister med dessa konstruktionselement som kan komma att påverka hållfastheten avsevärt.  Detta i sin tur drabbar hela konstruktionen som förlorar stora delar av sin förmåga att hålla ihop under markrörelser vid seismisk aktivitet.   För att kunna besvara Econefs frågor har en grundläggande studie om seismisk aktivitet utförts. Ringbalkens byggtekniska funktion, material och materialkombinationer har utvärderats.  Det som är mest aktuellt att besvara är möjligheten att, utifrån förutsättningarna i Arusha, Tanzania, förbättra och utveckla ringbalken. Resultaten är baserade på en fältstudie i Tanzania, intervjuer och litteraturstudier. Design med hänsyn till seismisk aktivitet är ett fascinerande och komplicerat ämne. Denna text syftar endast till att översiktligt studera ringbalkens tekniska egenskaper och hållfasthet vid sådan aktivitet. Detta är fördjupningsdelen i ett arbete som också innefattar projektering och dimensionering av ett småhus.