This work uses different size of strain gages (Gage Grid Length: 10mm, 1mm, 0.2mm) to measure the stress distributions of metal (Al 6061-T6) and composite (laminates of [0/+45/90/-45]2S and [0/90]4S layers ) with a central circular hole and a crack. Both the SCF (Stress Concentration Factor) and SIF (Stress Intensity Factor) are found to consider the stress scatteredness of experimental data in contrast to micro- mechanics. To understand the strain gage size effect is our main purpose in measuring both types of materials. The size effect of strain gage we find appears obviously in the measuring position with stress changing significantly. We find that the size of strain gage is bigger; the error of stress is higher. Analyzing the stress scattering around a central circular hole, we obtain the experimental result that the stress will first reduce drastically from central circular hole edge and then keep uniform. In analysis of the stress scattering around the crack tip, we observe that first stress rises quickly from the specimen¡¦s free edge to the top of crack tip with a maximum value, and the stress keeps a nominal value in the specimen central part. Comparing the empirical result of SCF and SIF, we find that the data of 0.2mm of strain gage close to the theoretical solution, while those of 1mm and 10mm strain gages appear inexact in measuring and calculating SCF and SIF.

In order to determine fracture parameters of the body and fracture conditions, stress and strain fields in the crack zone should be precisely calculated, especially near the crack tip. These goals can be achieved by performing experiments which are very complicated and expensive. More efficient numerical finite element and boundary element methods yielding the reliable data faster than experiments are usually used for practical calculations. A great number of classical analytical, experimental and numerical investigations are restricted to solving two-dimensional problems by making different assumptions. The results may be uncertain when three-dimensional state is simplified to two-dimensional one. Therefore, it is very important to study the effect of this simplification, in other words, to investigate the influence of three-dimensionality. The dissertation research belongs to the area of numerical fracture mechanics.

Made available in DSpace on 2016-06-02T19:56:52Z (GMT). No. of bitstreams: 1 5338.pdf: 2812584 bytes, checksum: c4ea2f65f591bec0e6ad7105c6ec591e (MD5) Previous issue date: 2013-06-20 / Universidade Federal de Minas Gerais / In this work, it was studied the simultaneous isomerization and fermentation of xylose to ethanol (SIF) using xylose isomerase (XI) and S. cerevisiae co-immobilized in calcium alginate gel. XI was immobilized on chitosan gel activated with glutaraldehyde (IXI-Ch). The influence of the concentration of enzyme/yeast in the reactor, the pH, temperature and yeast strain on yield and selectivity in ethanol was studied. The concentrations of enzyme and yeast in the reactor were varied by changing the mass of IXI-Ch and yeast per gram of alginate solution, maintaining fixed the ratios of biocatalyst weight: volume of medium in the reactor (1:1). The SIFs were carried out in batch with xylose (65g.L-1), antibiotics and other salts. The first experiment, with 16% Itaiquara® yeast and 5% enzyme biocatalyst (% wenzyme or yeast/wbiocatalyst) showed that pH drop occurred during the test, preventing full conversion of xylose, due to reduced enzyme activity. calcium carbonate (0.5-1.0%) was then included in the biocatalyst, which maintained the pH between 5,2 to 5,6, allowing complete conversion of the sugar at all concentrations tested (%Yeast -Enzyme in biocatalyst): 5-20, 17-5, and 10 yeast (Itaiquara ®) with 5, 10 and 20-. The maximum ethanol productivity, 2,44 ± 0,26g.L-1.h- 1 was obtained for the highest cell concentration and the highest selectivity ethanol/xylitol, 2,57 ± 0.4 and 2,42 ± 0,01 for the highest enzyme concentrations (10 and 20% with 10% yeast). These results indicated that the highest concentration of xylulose favored more selectivity to ethanol. Fermentation was then performed using no enzyme in biocatalyst with a prior isomerized syrup concentrated in xylulose containing 58g.L-1 xylulose and 9g.L-1 xylose and another with xylose only. At first, xylulose was completely assimilated in 5 hours, xylose was barely consumed in both assays, and ethanol selectivity was lower than that obtained in the SIF tests. Xylitol show thus to be produced mainly from xylulose and selectivity contrary to expectations did not directly increase with increasing xylulose concentration, indicating that the formation of ethanol/xylitol depends not only on external xylulose, and it is probably finely regulated in yeast. The concentrations of enzyme and yeast 20 and 10% (equivalent to 100gderived.L-1 reactor and 50gwd.L-1 reactor) were selected as the best, which were used to study the influence of pH and temperature, and also different strains. The increase of initial pH from 5.6 to 6.5 did not improve the productivity, yield, neither selectivity in ethanol. Temperatures tested for Itaiquara ® were 32, 35 and 37 ° C, and for industrial strains CAT-1 and BG-1: 32, 37 and 40 ° C. Viability remained above 90% for all assays at 24 hours. All three strains showed increased selectivity in ethanol with temperature reduction, obtaining the maximum selectivity for industrial strains (3,06 ± 0,24 - CAT-1 and 3,19 ± 0,11 BG-1) with yield and productivity equal or greater than those obtained in higher temperatures. At 32 ° C and pH 5.6, Itaiquara ® showed lower conversion time, but lower selectivity, while the BG-1, demonstrated the highest selectivity, but low conversion and productivity. The strain CAT-1 combines high productivity, 2,17 ± 0,17 g.L-1.h-1, and selectivity, 3,06 ± 0,24, with 90% conversion in 9 hours, 32 ° C, which is apparently the best performance among the tested yeasts. The results were very promising, indicating the technical feasibility of producing ethanol from xylose with the biocatalyst developed. / Neste trabalho foi estudada a simultânea isomerização e fermentação de xilose a etanol (SIF) usando xilose isomerase (XI) e S. cerevisiae coimobilizadas em gel de alginato de cálcio. XI foi imobilizada em gel de quitosana ativado com glutaraldeido (IXI-Ch).. Foram estudadas as influências das concentrações de enzima/levedura no reator, do pH, da temperatura e da linhagem de levedura na produtividade e na seletividade em etanol. As concentrações de enzima e levedura no reator foram variadas mudando-se a massa de IXI-Ch e levedura por grama de solução de alginato, mantendo-se fixas as proporções 1:1 massa de biocatalisador:volume de meio no reator. As SIFs foram realizadas em batelada com xilose (~65g.L-1), antibiótico e outros sais. O primeiro experimento realizado, biocatalisador com 16% levedura Itaiquara® e 5% enzima (% menzima ou levedura/mbiocatalisador), mostrou que ocorria queda de pH durante o ensaio, impedindo conversão total da xilose, devido à redução da atividade enzimática. Foi incluído carbonato de cálcio 0,5-1,0% no biocatalisador, o que manteve o pH entre 5,2-5,6, permitindo total conversão do açúcar, em todas as concentrações testadas (%Levedura-Enzima no biocatalisador): 5-20, 17-5 e 10 levedura (Itaiquara®)com 5, 10 e 20% enzima. A máxima produtividade em etanol, 2,44 ± 0,26g.L-1.h-1, foi obtida para a mais alta concentração celular e a mais alta seletividade etanol/xilitol, 2,57± 0,4 e 2,42± 0,01, para as mais altas concentrações de enzima (10 e 20% com 10% levedura). Esses resultados indicavam que quanto mais alta a concentração de xilulose, mais favorecida a seletividade em etanol. Foi então realizada uma fermentação usando o biocatalisador sem enzima, com um xarope previamente isomerizado e concentrado em xilulose contendo 58g/L de xilulose e 9g/L xilose e outro apenas com xilose. No primeiro, xilulose foi totalmente assimilada em 5 horas, xilose foi pouco consumida nos dois ensaios, e a seletividade em etanol foi menor que a obtida nos ensaios SIF. Xilitol mostrou, assim, ser produzido majoritariamente a partir de xilulose e contrariamente ao esperado a seletividade não aumenta diretamente com o aumento da concentração de xilulose, indicando que o metabolismo etanol/xilitol não depende apenas da concentração externa de xilulose, devendo ser finamente regulado dentro da levedura. Selecionaram-se as concentrações de enzima e levedura de 20 e 10% (equivalente a 100gderivado.L-1 reator e 50gms.L-1 reator) como as melhores, as quais foram utilizadas para estudo da influência do pH e da temperatura e ainda de diferentes linhagens. O aumento do pH inicial do meio de 5,6 para 6,5 não favoreceu a produtividade, rendimento e nem a seletividade em etanol. As temperaturas testadas para Itaiquara® foram: 32, 35 e 37°C; e para as linhagens industriais CAT-1 e BG-1: 32, 37 e 40°C. A viabilidade manteve-se acima de 90% para todos os ensaios em 24 horas. As três linhagens mostraram aumento da seletividade em etanol com a redução da temperatura, obtendo-se a máxima seletividade para as linhagens industriais (3,06± 0,24- CAT-1 e 3,19± 0,11 BG-1), com rendimento e produtividade iguais ou maiores que os obtidos nas temperaturas maiores. A 32°C e pH 5,6, Itaiquara® apresentou menor tempo de conversão, mas a menor seletividade, já a BG-1, obteve maior seletividade, mas baixa conversão, rendimento e produtividade. A linhagem CAT-1 alia alta produtividade, 2,17 ± 0,17 (g.L-1.h-1), e seletividade, 3,06 ± 0,24, com 90% de conversão em 9 horas, 32°C, sendo aparentemente a de melhor desempenho dentre as testadas. Os resultados foram muito promissores, indicando viabilidade técnica de produção de etanol a partir de xilose com o biocatalisador desenvolvido.

Submitted by Caio Cesar Policelli Amalfi (c_amalfi@hotmail.com) on 2017-12-06T19:19:26Z No. of bitstreams: 1 amalfi_ccp_me_eng_int.pdf: 2459316 bytes, checksum: 945ef161efa25c84f202bbd2b7a8fd7b (MD5) / Approved for entry into archive by Minervina Teixeira Lopes null (vina_lopes@bauru.unesp.br) on 2017-12-07T12:24:46Z (GMT) No. of bitstreams: 1 amalfi_ccp_me_bauru.pdf: 2459324 bytes, checksum: 6c5471ff71b8b95a377f4453ebaa4162 (MD5) / Made available in DSpace on 2017-12-07T12:24:46Z (GMT). No. of bitstreams: 1 amalfi_ccp_me_bauru.pdf: 2459324 bytes, checksum: 6c5471ff71b8b95a377f4453ebaa4162 (MD5) Previous issue date: 2017-10-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A alta complexidade atrelada às necessidades de segurança e confiabilidade dos processos industriais têm demandado a implantação de sistemas automáticos de segurança. Esse sistema, conhecido como Sistema Instrumentado de Segurança (SIS), é responsável pela segurança operacional do processo dentro de limites seguros através da monitoração de valores e parâmetros quando houver condições de risco. Os SISs são concebidos com diferentes Níveis de Integridade de Segurança (SIL) de acordo com o risco do processo. O desafio na implantação de um SIS é que seu procedimento de projeto é complexo e pouco difundido, além de existirem diversos métodos de cálculo e análise de riscos aceitos pelas normas de segurança. A motivação para este trabalho foi automatizar e auxiliar o projeto de SIS no que diz respeito à redução da quantidade de pessoas envolvidas e de tarefas manuais que podem causar erros, à padronização e simplificação dos procedimentos e cálculos necessários e também à diminuição do tempo de projeto, promovendo um aumento na eficiência e redução dos custos envolvidos. O objetivo é desenvolver uma ferramenta de análise e projeto de SIS, com programação voltada para Web, capaz realizar um estudo de riscos e falhas de um processo industrial e calcular um valor adequado para a seleção do SIL requerido para implantação de um sistema de segurança. A ferramenta é composta de quatro módulos: o Estudo de riscos e falhas usando a técnica HAZOP, a Quantificação dos riscos e criação de árvores de falhas; a Obtenção do SIL através da Análise da Árvores de Falhas (AAF) e a Definição de uma Função Instrumentada de Segurança (SIF) apropriada para o SIL calculado. A ferramenta desenvolvida é inovadora ao automatizar e combinar no mesmo ambiente todos os procedimentos necessários para a análise e projeto de SIS. Diversos casos de estudo de projeto de SIS, sendo um caso industrial real e outros da literatura, são utilizados para teste e validação dos módulos da ferramenta afim de demonstrar sua eficiência, flexibilidade de uso e exatidão dos resultados obtidos com a sua aplicação. / The high complexity tied to the reliability and security requirements of industrial processes has demanded the deployment of automatic safety systems. This system is known as Safety Instrumented Systems (SIS) and is responsible for the process operational safety within safe limits through the monitoring of values and parameters when there are conditions of risk. The SIS is designed with different Safety Integrity Levels (SIL) according to the process risk. The challenge in the deployment of SIS is that the design procedure is complex and not well known, and there are many calculation and risk analysis methods accepted by the safety standards. The motivation was automating and assisting in the design of SIS with regard to the reduction of people involved and manual tasks that may cause errors, the standardization and simplification of procedures and calculations needed and the reduction in project time, promoting an increase in efficiency and reducing the costs. The objective was developing an analysis and design tool for SIS, with web-based programming, capable of performing a study of the risks and failures of an industrial process and calculating an adequate value for the selection of the Safety Integrity Level (SIL) required for the implementation of the safety system. The tool is comprised of four modules: the Study of risks and failures using the HAZOP technique, the Quantification of risks and creation of fault trees; the SIL calculation through the Fault Tree Analysis (FTA) and the Definition of a Safety Instrumented Function (SIF) suitable for SIL calculated. The developed tool is innovative by systemizing and combining in the same environment all the procedures required for the analysis and design of SIS. Several case studies of SIS design are used for testing and validation of the tool modules, considering a real industrial case and others cases in the literature, in order to demonstrate the efficiency, flexibility of use, and accuracy of the results obtained with the tool application. / 1649039

Carbon Capture and Storage (CCS) is recognised as having a significant role to play in tackling climate change and reducing carbon dioxide (CO2) emissions. In CCS schemes, CO2 is captured from anthropogenic sources, and transported to suitable sites either for EOR (Enhanced Oil Recovery) or storage. The transport of such huge amount of CO2 causes new challenges. The main concern is in the difference between natural gas and CO2 transportation pipelines. CO2 phase behaviour during decompression, existence of different impurities and very high operating pressure are some of the new challenges for pipeline designer and operators. This PhD study has taken a systematic approach to understand the mechanics involved in the fracture of pipes containing high pressure flue-gas CO2. The work involved the development of a novel weight function stress intensity factor solution that can be used with complex stress fields induced by residual and/or thermal stresses in addition to applied pressure. In addition, the thesis reports a substantial experimented test programme which involved low temperature fracture toughness tests linked to a detailed finite element based stress analysis. Overall, the thesis presents an integrated engineering criticality means to assess the suitability or otherwise of a pipeline system to transport high pressure flue-gas CO2.

Nas plantas industriais dos setores químico e petroquímico observa-se uma grande quantidade de complexas redes de tubulações instaladas, o que se deve basicamente à necessidade de transferir e processar fluídos em diversas condições de pressão e temperatura em suas operações produtivas. Uma indústria petroquímica de médio porte possui entre 3.000 e 15.000 toneladas de tubulações de aço-carbono instaladas, fazendo com que o adequado dimensionamento desse sistema de tubulações adquira grande importância. Este trabalho caracteriza os principais componentes, materiais, condições de projeto e critérios normativos existentes, em especial sob temperaturas elevadas. Realiza uma avaliação comparativa dos métodos de solução estrutural dessas tubulações e analisa criticamente algumas das premissas originais que ainda orientam o seu dimensionamento, visando uma melhor adequação destas. Por fim, juntamente com um estudo de caso, apresenta uma proposta de metodologia de dimensionamento, aplicando o Método dos Elementos Finitos, com o objetivo de aliar mais segurança, otimizar a construção e permitir um projeto mais econômico, diante das grandes quantidades de material envolvidas nessas instalações. / In the chemical and petrochemical plants we can notice a big amount and complexity of pipings installeds, it happens due to the need to transfer and process fluids with differents pressures and temperatures and to get the operational requirements of production. A middle size petrochemical plant has among 3,000 to 15,000 tons of carbon steel pipings assembled so an adjusted sizing of these piping systems is very important. This study presents the main components, materials, design features and existing code procedures, especially under higher temperatures. It makes a comparative valuation about methods of structural solution to pipings and discussing previous concepts applied in the codes to improve these applications. In also, together a case study, presents a proposal of a methodology to sizing of pipings using Finity Element Analyse, with the goal to get a solution more safety, optimized and an economic project, in front of the large quantity of material involved in these installations.

No description available.

No description available.

Rivets are widely used as a means of fastening in airframe construction industry. There are various types of riveted joints on an aircraft fuselage or on a helicopter body. Among the other types of fasteners riveted joints are preferred in such applications due to / their permanence after installation and their economical advantages. In a riveted joint, it is known that residual stresses are present as a result of the installation process. Furthermore, during the flight of an aircraft, the fuselage is loaded in one cycle and such cycles are repeated throughout the service life. As a result, the panels and the rivets are subjected to fatigue type loading. The integrity of the joint must be maintained against this combination of service loads and the residual stresses. Hence, the riveting process parameters which influence the residual stresses are utmost critical in terms of fatigue life of the hole body. In this study it is aimed to obtain an accurate numerical model of a single-lap riveted joint which is widely used in airframes. 2-D axisymmetrical and 3-D numerical models are generated using commercial finite element code ABAQUS/CAE and subsequent parametric studies are carried out on these models. The Results of both models are compared with those found in the literature. Clearance between hole and rivet shank is selected as the primary parameter to be inspected. The effects of hole clearance on the final residual stress field are examined on 2-D and 3D models. Furthermore, a through the thickness, crack on the inner panel which is initiated after installation is modeled. The crack is perpendicular to the direction of loading. It is placed to the residual tensile stress zone that surrounds the rivet hole. Hence, the effects of residual stresses are also taken into account. For a riveted joint subjected to fatigue loading, such a macroscopic crack could eventually form. In this thesis, stress intensity factors (SIF&rsquo / s) for this crack are calculated for various parameters such as clearance and crack length. These can be utilized in a subsequent fatigue crack growth analysis as the initial values or they can be used in a fracture analysis, to predict unstable crack growth due to overload (i.e. crack linking).

In order to determine fracture parameters of the body and fracture conditions, stress and strain fields in the crack zone should be precisely calculated, especially near the crack tip. These goals can be achieved by performing experiments which are very complicated and expensive. More efficient numerical finite element and boundary element methods yielding the reliable data faster than experiments are usually used for practical calculations. A great number of classical analytical, experimental and numerical investigations are restricted to solving two-dimensional problems by making different assumptions. The results may be uncertain when three-dimensional state is simplified to two-dimensional one. Therefore, it is very important to study the effect of this simplification, in other words, to investigate the influence of three-dimensionality. The dissertation research belongs to the area of numerical fracture mechanics.