Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2014-09-02T11:26:28Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação Joao Francisco Machado do Nascimento.pdf: 721039 bytes, checksum: 2a145e907cf0cfc7e15f26459ae30aff (MD5) / Made available in DSpace on 2014-09-02T11:26:28Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Dissertação Joao Francisco Machado do Nascimento.pdf: 721039 bytes, checksum: 2a145e907cf0cfc7e15f26459ae30aff (MD5) Previous issue date: 2013-08-14 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / For patients poorly adapted to conventional dentures, the single-implant mandibular overdenture has been proposed as a simplified alternative for the two-implant treatment, together with the use of immediate loading of the implant. The aim of this in vitro study was to compare the photoelastic characteristics of stress transfer to the implant in a single-implant mandibular overdenture using different types of attachments. A photoelastic model of an edentulous mandible with a resilient edentulous ridge and a unique implant located at the symphyseal region was obtained to reproduce a single implant-retained mandibular overdenture. Six 2.0 mm height attachments were selected and inserted in the same photoelastic model in a random order. A universal material testing machine was used to induce axial vertical loads of 70 N applied in the central incisor and in the central region of the first right molar without contact on the contralateral side. The photoelastic analysis was performed using a polariscope integrated into the testing machine. Standard separate views were photographed and evaluated visually for stress-induced fringes, to comparatively rank the different attachment systems. All attachments showed a similar tension distribution concentrated in the apical third, and the highest stress concentration at the apical level. There was a low stress concentration at the coronal third of the implant, with no discernible stress in the first threads of the implants, except for Dalla Bona which showed low stress at the coronal part of the implant (one fringe). No identifiable fringes were observed when the load was applied in the molar region, which resulted from the low amount of stress transmitted by the implant for all attachments. It was concluded that the load transferred to a single mandibular implant is low and within the limits of functional loading, irrespective of the type of retention system. / Implantes osseointegrados vêm sendo utilizados com sucesso para restaurar a função e a estética de pacientes desdentados totais e parciais. No entanto há necessidade de tornar o tratamento de pessoas com necessidade de overdenture retida com implante menos oneroso e mais eficiente. O objetivo deste trabalho foi verificar pela técnica fotoelástica (Qualitativa) as tensões geradas ao redor do implante pela aplicação de carga sobre overdenture mandibular retida por um implante unitário na sínfise da mandibular. Foi confeccionado um modelo de resina fotoelástica Araldite, reproduzido de uma mandibular anatômica, onde foi fixado na região sínfise um implante 3.75x11mm (Titamax Ti Cortical, Neodent, Curitiba, Brasil). Com um modelo foi confeccionada uma prótese total e gingival artificial. Todos os pilares foram posicionados sobre o implante e apertado com 10 Ncm, a fêmea foi capturada de forma direta à prótese, com a réplica da mucosa em posição. Todos foram sucessivamente capturados e levados ‘à máquina de ensaio universal. Com uma carga axial de 70 Ncm na fossa central do 46 e incisal do 41. Foram fotografados em um polariscópio as franjas resultantes das tensões. Foram feitas análises qualitativa dos resultados das tensões sobre o attachment. De acordo com os resultados obtidos pode-se concluir que a carga transferida para o implante, é baixo, independente do sistema de retenção.

[en] The present work is concerned with the optimal location of piping supports. A Weighted average of the stress resultants at specified points is used as the objective function to be minimized. ANSI piping codes are considered for the constrained functions. The minimization process is carried out using the conjugate gradient method on an interior penalty function. Numerical examples are presented at the end of the work. / [es] Se presenta el problema de localización de los soportes de una tuberia como un problema de optimización donde se busca minimizar una media ponderada de las tensiones que actúan en las bocas de los equipamientos ligados a la línea. La localización de estos soportes debe ser realizada de manera que los esfuerzos que actúan en la tubería debido a los varios cargamentos posibles estén dentro de los límites especificados por las normas ANSI. Para el proceso de optimización se hace uso del método de gradientes conjugados aplicado a una función de penalidad que trasforma el problema inicial con restricciones en uno sin restricciones. Por último se presentan algunos resultados numéricos.

In this thesis a finite element model of a household washing machine cylinder is built and analysed in ABAQUS 6.9-2. The aim is to help Asko appliances in conducting similar analysis for future manufacturing of high capacity cylinders by reducing experimentation. The analysis is mainly concerned with an evenly distributed load at a constant angular velocity. The load is applied with the help of lead plates instead of clothes. The cylinder is loaded with three thin (2 mm) lead plates weighing 2 kg each. The plates with dimensional 370x240x2 mm are mounted with one strip of double sided foam tape inside the cylinder. To estimate the behavior of the cylinder the strains are measured when the cylinder is rotating at 1620 and 2200 revolution per minute (rpm). To validate the model the numerical analyses are compared with experimental results. The results clearly show that the numerical strain values fit with experimental strain values.

The estimation of gas hydrate volume in closed systems such as pipelines during shut-in time has a great industrial importance. A method is presented to estimate the volume of formed or decomposed gas hydrate in closed systems. The method was used to estimate the volume of formed gas hydrate in a gas hydrate crystallizer under different subcoolings of 0.2, 0.3, 0.6 and 4.6 degrees C, and initial pressures of 2000 and 2500 psi. The rate of gas hydrate formation increased with increases in subcooling and initial pressure. The aim of the second part of the study was the evaluation of the formation of gas hydrate and ice phases in a super-cooled methane-water system under the cooling rates of 0.45 and 0.6 degrees C/min, and the initial pressures of 1500, 2000 and 2500 psi, in pure and standard sea water-methane gas systems. The high cooling rate conditions are likely to be present in pipelines or around a wellbore producing from gas hydrate reservoir. Results showed that the initial pressure and the chemical composition of the water had little effect on the ice and gas hydrate formation temperatures, which were in the range of -8 +/- 0.2 degrees C in all the tests using the cooling rate of 0.45 degrees C/min. In contrast, the increase in the cooling rate from 0.45 to 0.6 degrees C/min decreased the ice and gas hydrate formation temperatures from -8 degrees C to -9 degrees C. In all tests, ice formed immediately after the formation of gas hydrate with a time lag less than 2 seconds. Finally, an analytical solution was derived for estimating induced radial and tangential stresses around a wellbore in a gas hydrate reservoir during gas production. Gas production rates between 0.04 to 0.12 Kg of gas per second and production times between 0.33 to 8 years were considered. Increases in production time and production rate induced greater radial and tangential stresses around the wellbore.

Gediz Graben is a continental extensional basin filled with Neogene sediments. Its margins are controlled by active ~E&amp / #8211 / W-trending fault systems with major system, in terms of total offset and duration of activity, located along the southern margin. The graben evolved as a half graben by the activity of the southern margin during the entire Miocene. Then, the northern margin-bounding structure initiated by Plio&amp / #8211 / Quaternary to form the current configuration of the graben with an inherited asymmetry. The southern margin-bounding fault system forms a graben-facing step-like pattern from the horst block (~2000 m) down to the graben floor (~200 m). The faults become younger towards the graben and the structural maturity decreases in the same direction. Fault plane data suggest ~N&amp / #8211 / S-oriented regional crustal extension through the entire graben history with no evidence of temporal change in the regional extension direction. Minor spatial variations are attributed to poorly defined s3-axis or local stress field anomalies caused by fault interactions. Evolution of the Gediz Graben is a dynamic process as indicated by pronounced changes in the geometry and lateral extend of the southern margin-bounding structures along strike and dip directions. This also influenced the lithofacies, depositional pattern and thickness of the graben fill units. The western Anatolian extension is episodic with earlier (Miocene) and later (Plio&amp / #8211 / Quaternary) phases of extension and intervening short phase of contraction (Late Miocene&amp / #8211 / Early Pliocene). Despite of this fact, evidence for the short-term intervening contractional phase throughout the Gediz Graben is scarce and there is local observation of folds and thrust/reverse faults affecting the AlaSehir formation. These structures suggest that the short-term phase of contraction might have existed but most probably been absorbed by the high rates of extension. This data may further imply that graben evolution from half-graben phase (Miocene configuration) to full graben phase (present day configuration) might be a discontinuous process accompanied by a short-time break in-between.

Two sample statistical energy analysis (SEA) models are generated for a section of the fuselage panel of an aircraft, namely the uniform panel model which includes the frames and stringers, and the ribbed panel model in which the frames and stringers are smeared into the skin. Turbulent boundary layer (TBL) excitation is used as the primary acoustic excitation source. Stress levels are estimated from the average velocity data of the panels. The stress results are found comply with those obtained by the AGARD method. Effect of radiation from panels to exterior and interior of the sample skin panel as well as the pressurization of the skin panels are investigated separately to analyze their effects on the stress levels. The method is then used in the analysis of center fuselage skin panels on a basic training aircraft. Two models are generated for the aircraft analysis, namely the complete aircraft model and the simplified model which excludes the wings and the empennage. In addition to TBL, propeller noise is used as the primary acoustic excitation source. The effects of the wings and the empennage on the stress levels in the center fuselage skin panels are also investigated along with the radiation from panels to the exterior and interior of the aircraft and pressurization of the pilot cabin.

Textile composites can be tailored to meet specific thermo-mechanical requirements for structural applications. The focus of this research is on 2x2 biaxial braided composites since they have good stiffness and strength properties. Moreover, they have potentially better impact and fatigue resistance than laminated composites. Along with good properties, they have a reduced manufacturing cost because much of the fabrication can be automated. In order to exploit these benefits, thorough understanding of the effect of various factors on their material behavior is necessary. Obtaining effective mechanical properties is the first order of concern in any structural analysis. This work presents an investigation of the effect of various parameters like braid angle, waviness ratio, stacking sequence and material properties on the effective engineering properties of the 2x2 braids. To achieve this goal, three dimensional finite element micromechanics models were developed first. Extensive parametric studies were conducted for two material systems: 1). Glass (S2) fiber / epoxy (SC-15) matrix and 2). Carbon (AS4) fiber / Vinyl Ester (411-350) matrix. Equivalent laminated materials with angle plies and a resin layer were also analyzed to compare the difference in predictions from the full three dimensional finite element analysis of the 2x2 braided composites. A full three-dimensional stress state exists in braids even for very simple loading. In order to locate the potential damage spots, the stress distributions in both the matrix and the tows were predicted. The effect of braid angle on location and magnitude of peak stresses was determined.

Thesis (M.S.D.)--Indiana University School of Dentistry, 2009. / Title from PDF t. p. (viewed Feb. 5, 2010) Advisor(s): Jeffrey A. Platt, Chair of the Research Committee, Joseph Legan, Carl J. Andres, David Brown, Burak Taskonak . Curriculum vitae. Includes abstract. Includes bibliographical references (leaves 45-52).

Thesis--University of Oklahoma. / Bibliography: leaves 76-79.

The influence of dent imperfections on the elastic stress behavior of cylindrical shells is explored. This problem is of central importance to the prediction of fatigue failure due to dents in petroleum pipelines. Using an approximate technique called the Equivalent Load Method, a semi-analytical model of two-dimensional dent stress behavior is developed. In the three-dimensional situation, decreased dent localization, in particular dent length, and increased dent depth are confirmed to cause dent stress concentration behavior to shift from having a single peak at the dent center to having peaks at the dent periphery. It is demonstrated that the equivalent load method does not predict this shift in stress behavior and cannot be relied upon to analyze relatively small, deep imperfections. The two stress modes of dents are associated with two modes of dent fatigue behavior that have significantly different fatigue lives. A method for distinguishing longer lived Mode P dents from shorter lived Mode C dents based on two measured features of dent geometry is developed and validated. An approach for implementing this analysis in the evaluation of real dents is also suggested.