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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

[pt] MODELAGEM NUMÉRICA DE EVAPORITOS PARA FINS DE BARREIRA NATURAL NO ABANDONO DE POÇOS DE PETRÓLEO / [en] NUMERICAL MODELLING OF EVAPORITES AS A NATURAL BARRIER FOR THE ABANDONMENT OF OIL WELLS

ALESSANDRA LIDIA MAZON 07 June 2022 (has links)
[pt] A construção de poços através de formações salinas continua sendo um grande desafio na engenharia de perfuração em muitas províncias petrolíferas ao redor do mundo, notadamente offshore no Brasil, devido às suas propriedades mecânicas únicas, em particular, sua alta mobilidade de fluência sob condições de fundo de poço. Inicialmente, é necessário controlar o fechamento do poço durante a perfuração para permitir a instalação do revestimento. Mais tarde, o carregamento do revestimento nas seções cimentadas e não cimentadas é motivo de preocupação para evitar problemas de integridade do poço a longo prazo. No entanto, ocontato do sal com o revestimento pode fornecer uma barreira natural necessária e economicamente benéfica. Este trabalho consiste em extratos do projeto de pesquisa Avaliação do potencial de formações argilosas e evaporíticas atuarem como barreira externa ao revestimento para o abandono de poços, realizado pelo Grupo de Tecnologia e Engenharia de Petróleo (GTEP) da Pontifícia Universidade Católica do Rio de Janeiro, Brasil. O objetivo deste trabalho é modelar o fechamento de um poço em sal ao longo de zonas de revestimento não cimentadas considerando anular aberto. Para isso, foi desenvolvida uma metodologia computacional, utilizando o código comercial de elementos finitos ABAQUS. Na primeira etapa, a fim de validar o protocolo de simulação, apresenta-se a reprodução de estudos sobre a formação de barreiras naturais em sal, reportados na literatura, considerando os modos de pequena e grande deformação do ABAQUS. A comparação entre os resultados obtidos demonstra uma diferença de tempo para o fechamento anular variando de alguns meses a alguns anos, dependendo da profundidade e do tipo de sal. Discussões sobre aspectos específicos da simulação de fluência em rochas salinas também são feitas nesta etapa. Na segunda etapa, é apresentada uma análise para estimar o tempo de fechamento do poço em condições de campo representativas das bacias brasileiras, acoplando os ajustes realizados na etapa anterior. O comportamento constitutivo do sal utilizado para simular a fluência em regime permanente foi o modelo de mecanismo duplo e os parâmetros são representativos do cenário offshore brasileiro. Como resultado, observa-se o potencial de formação de barreiras naturais em camadas salinas para operações de tampão permanente e abandono. Em ambas as simulações, o fechamento anular é feito utilizando modelos 2D de estado plano de deformação e axissimétrico, representando a seção transversal e longitudinal, respectivamente. As etapas de simulação são divididas em campo de tensão de equilíbrio inicial (geostática) seguido de perfuração e fluência simulada como um material viscoelástico. / [en] Wellbore construction through salt formation remains a great challenge in drilling engineering in many oil provinces around the world, notably offshore Brazil, due to its unique mechanical properties, in particular, its high creep mobility under downhole conditions. Initially, it is necessary to control wellbore closure during drilling in order to allow casing installation. Later, the loading of the casing in both the cemented and uncemented sections is cause of concerns to prevent issues of long-term wellbore integrity. However, the contact between the salt and the casing can provide a necessary and economically beneficial natural barrier. This work consists of extracts of the research project Evaluation of the potential of clayey and evaporitic formations to act as an external barrier to the casing for the abandonment of wells, carried out by the Group of Technology and Petroleum Engineering (GTEP) at the Pontifical Catholic University of Rio de Janeiro, Brazil. The aim of this work is to model wellbore closure in salt throughout uncemented casing zones considering open annular. For this, a computational methodology was developed, using the commercial finite element code ABAQUS. As the first stage of the study, in order to validate the simulation protocol, the reproduction of studies about the formation of natural barriers in salt, reported in the literature, is presented, considering the small and large deformation modes of the ABAQUS. The comparison between the results obtained demonstrates a time difference for annular closure ranging from a few months to a few years, depending of depth and type of salt. Discussions on specific aspects of creep simulation in salt rocks are also made at this stage. In the second stage of the work, is presented an analysis to estimate the wellbore closure time under field conditions representative of the Brazilian basins, coupling the adjustments made in the previous stage. The salt constitutive behavior used to simulate the steady-state creep was double mechanism model and the parameters are representative of the Brazilian offshore scenario. As a result, it is observed the potential for the formation of natural barriers in saline layers for permanent plug and abandonment operations. In both simulations, annular closure is performed using 2D models of plane strain and axisymmetric, representing the cross section and longitudinal section, respectively. The simulation steps are divided into initial equilibrium stress field (geostatics) followed by drilling and simulated creep as a viscoelastic material.
82

FEM-simulering av defekter från klippning av varmvalsad stång. / FEM simulation of defects from shearing of hot-rolled steel rods

Sipinen, Izak, Brostedt Dehlin, Martin January 2022 (has links)
Den världsledande stålproducenten Ovako Group AB tillverkar valsade stålstänger i sin produktion i Hällefors. De färdigvalsade stängerna klipps efter nedkylning i luft enligt kundlängd, vilket i vissa fall har visat sig resultera i defekter vid ändarna. Mindre och övergripande statiska analyser av klipprocessen tyder på att dessa uppstår för vissa typer av stålsorter vid för höga och för låga temperaturer. De defekta ändarna behöver justeras genom räddningsuppdrag som kräver extra resurser och tid. Eftersom Ovako har upprättat långsiktiga klimatmål i form av reducerat klimatavtryck, vilket kan uppnås genom besparingar av resurser, inleder de nu ett arbete mot att optimera klipprocessen och minimera antalet defekter.Denna studie avser undersöka om det går att simulera klipprocessen för en av Ovakos stålstänger med hjälp av den finita elementmetoden och mjukvaran Abaqus. Det långsiktiga syftet med detta är att genom vidare arbeten, om detta visar sig vara möjligt, hitta optimala klipptemperaturer för olika typer av stålstänger med målet att reducera resursanvändningen och därtill Ovakos klimatavtryck. De frågeställningar som studien ämnar besvara är därmed; Kan verkliga defekter från kallklippning av stålstänger vid olika temperaturer simuleras? och Inom vilket temperaturintervall går det att klippa en stålstång utan defekter?Studien tyder på att det går att göra verklighetstrogna simuleringar för klipp av upphettade stålstänger i Abaqus då godtyckliga materialparametrar införs. Det fastställdes även att kompletterande primärdata behövs för att öka validiteten av resultaten från experimenten, speciellt vid undersökningar av en specifik stålsort. Denna slutsats kan tillämpas i vidare arbeten för att i kombination med utökad mekanisk data hitta optimala klipptemperaturer för flera typer av stålstänger. / The world-leading steel producer Ovako Group AB manufactures rolled steel bars at their production in Hällefors. The rolled rods are cut after cooling in air according to customer length, which in some cases has been shown to result in defects at the ends. Scarce and comprehensive static analyzes of the cutting process indicate that these occur for certain types of steels at too high and low temperatures. The defect ends need to be adjusted through rescue missions that require extra resources and time. Since Ovako has set long-term climate goals in the form of a reduced climate footprint, which can be achieved through savings in resources, they are now initiating work towards optimizing the cutting process and minimizing the number of defects.This study aims to investigate whether it is possible to simulate the cutting process for one of Ovakos steel rods using the finite element method and the Abaqus software. The long-term purpose of this is to, through further work and if it proves to be possible, find optimal cutting temperatures for different types of steel bars with the aim of reducing resource use and, in addition, Ovako's climate footprint. The questions that the study intends to answer are thus; Can real defects from cold cutting of steel bars at different temperatures be simulated? and Within what temperature range is it possible to shear cut a steel rod without defects?The study indicates that it is possible to make realistic simulations for cutting heated steel rods in Abaqus when arbitrary material parameter values  are introduced. It was also determined that additional primary data are needed to increase the validity of the results from the experiments, especially in studies of a specific type of steel. This conclusion can be applied in further work to find optimal cutting temperatures for several types of steel bars in combination with extended mechanical data.
83

Modélisation géomécanique des réservoirs : méthodologies de mise en œuvre et d'analyse des incertitudes / Uncertainty Analysis in Geomechanical Modelling of Petroleum Reservoirs

Hu, Tianmeng 06 November 2008 (has links)
L’objectif de ce travail est double : d’une part, il s’agit de développer une méthodologie intégrée pour la construction d’un modèle géomécanique ainsi que la représentation des incertitudes associées aux propriétés poro-élastiques des roches constitutives, en exploitant l’ensemble des données disponibles et en s’appuyant de façon cohérente sur les modèles de réservoir statique et dynamique classiquement utilisés par les géologues et les ingénieurs réservoir ; d’autre part, il s’agit d’analyser quel est l’impact des hétérogénéités géologiques, souvent négligées, dans la réponse mécanique du réservoir sollicité par son exploitation, et d’aboutir à des incertitudes sur les champs de contraintes et de déplacements, issues des incertitudes sur ces hétérogénéités et leurs paramètres mécaniques. Pour ce faire, une méthodologie intégrée s’appuyant sur des simulations géostatistiques a été développée. Après la construction du cadre géométrique 3D, le remplissage des propriétés au sein du réservoir suit une démarche de simulations géostatistiques 3D emboîtées, dans laquelle la représentation des hétérogénéités lithologiques conditionne la génération des propriétés poro-élastiques. La démarche consiste ensuite à représenter les incertitudes sur le modèle géomécanique par des ensembles de réalisations géostatistiques dont la réponse mécanique est alors calculée avec un simulateur mécanique aux éléments finis. Les incertitudes sur les champs de contraintes et de déformations sont déduites ensuite des différentes réponses mécaniques obtenues. La démarche a été mise en œuvre sur un réservoir réel, dans un environnement fluvio-deltaïque, produisant en Mer du Nord. Dans ce cadre, il a été démontré que les hétérogénéités du réservoir et leurs incertitudes influencent significativement les calculs des champs de contraintes et de déformations, ainsi que les risques mécaniques de rupture. Des incertitudes sur les quantités mécaniques analysées (premier invariant du tenseur des contraintes et subsidence) ont été aussi estimées / This work has two main objectives. The first one is to develop an integrated methodology allowing to build a 3D geomechanical model and also to image the uncertainties attached to the poro-mechanical properties of the constitutive rocks. This geomechanical model should be based on all related available data and should be consistent with the static and dynamic models, currently built by reservoir geologists and engineers. The second objective is to analyse the impact of geological heterogeneities, which are often neglected, in the mechanical response of the reservoir induced by its exploitation, and furthermore to derive uncertainties on the stress and deformation fields related to the uncertainties on the input properties of the geomechanical model. An integrated methodology based on geostatistical simulations is developed. First, the geometric frame is built; then an approach of embedded stochastic simulations is carried out to infill the different reservoir properties, the lithological description constraining the petrophysical and poro-elastic descriptions. The next step is to generate the mechanical responses of the stochastic realisations, using a finite-element mechanical simulator. The uncertainties on the resulting stress and displacement fields are then deduced from the multiple mechanical responses which are computed. This approach is demonstrated on a real field case, a fluvio-deltaic reservoir in North Sea. It is shown on this example that the reservoir heterogeneities and their uncertainties significantly influence the calculations of stress and strain fields, and also the risks of mechanical failure. Uncertainties on the mechanical quantities under analysis (first invariant of the stress tensor and subsidence) are also derived
84

[en] NUMERICAL ANALYSIS OF THE STATIC AND SEISMIC BEHAVIOR OF POMACOCHA DAM - PERU / [pt] MODELAGEM DO COMPORTAMENTO ESTÁTICO E SÍSMICO DA BARRAGEM DE TERRA DE POMACOCHA - PERU

SERGIO LEON MONTOYA CASTILLO 22 August 2003 (has links)
[pt] Construção de barragens de terra é uma atividade milenar, empregada com o objetivo de atender às mais diversas necessidades humanas como o armazenamento de água, irrigação, regularização de cursos d água, geração de enregia elétrica, etc. Ao longo da história, o projeto destas obras de terra passou de conceito simples, baseados em técnicas empíricas e regras intuitivas, para as análises modernas que consideram o comportamento da barragem em suas diversas fases de vidas (construção, enchimento do reservatório, regime de plena operação), sob carregados estáticos e sísmicos, condições de contorno complexas e sofisticadas relações constitutivas dos materiais da estrutura e do maciço de fundação. Nesta trabalho a construção, primeiro enchimento do reservatório e a resposta sísmica da barragem de terra de Pomacocha, Peru, são analisados pelo método dos elementos finitos, utilizando o software ABAQUS (versus 6.3). Os campos de tensão e de deslocamentos para diversos estágios de aplicação dos carregamentos estático e sísmico são apresentados, incluindo-se histórias de deformação e de tensão para determinados pontos do corpo da barragem e do solo de fundação. / [en] Dam construction is a millenary activity, carried out with the objective of fulfilling human necessities as water supply, land irrigation, water flow regularization, electric power generation, etc. Along the history, the design of these earthworks evolved from simple concepts, based on empirical techniques and rules of thumb, to modern analyses that consider all phases of a dam s life (construction, first reservoir filling, full operation) understatic and seismic loads, as well as complex boundary conditions and sophisticated constitutive relationships for the structure itself and the foundation mass. In this work, the construction, first reservoir filling and the seismic response of the Pomacocha Dam, located in Peru, are analyzed by the finite element method using the software ABAQUS (version 6.2). At several loading stages the corresponding stress and displacement are presented as well as, for some specific points in the dam body and in the foundation soil, the characteristic stress and strain histories during the static and seismic loads.
85

Análise numérica de vigas mistas de madeira e concreto em situação de incêndio / Numerical analysis of timber-concrete composite beams in fire situation

Fernandes, Felipi Pablo Damasceno 10 May 2018 (has links)
As vigas mistas de madeira e concreto são formadas pela união de vigas de madeira a lajes de concreto armado por meio de conectores de cisalhamento. Quando os pisos mistos de madeira e concreto são comparados aos pisos construídos unicamente em madeira ou àqueles confeccionados somente em concreto armado é possível destacar algumas vantagens, incluindo o bom desempenho em situações de incêndio. Os elementos estruturais quando submetidos a ações térmicas sofrem redução de resistência e rigidez, sendo, desta forma, necessário conhecer as modificações sofridas por cada um de seus componentes, que para o caso estudado são: a madeira, o concreto e os conectores de cisalhamento. Desta forma, foi elaborada uma estratégia de modelagem numérica para o estudo de vigas mistas de madeira e concreto em situação de incêndio, utilizando o programa computacional ABAQUS, o qual é baseado no método dos elementos finitos. Em uma primeira etapa da pesquisa foram realizadas modelagens numéricas de vigas de madeira e mistas de madeira e concreto em temperatura ambiente, encontrando-se boa correlação entre as curvas força versus deslocamento no meio do vão obtida numericamente e por meio de ensaios disponíveis na literatura. Em seguida procedeu-se a calibração das propriedades térmicas e mecânicas da madeira brasileira, alcançando-se resultados numéricos próximos aos experimentais, seja em relação às temperaturas do elemento analisado seja em relação à curva de deslocamento vertical em função do tempo de incêndio. Por fim, a estratégia de modelagem termoestrutural desenvolvida para a viga mista de madeira e concreto forneceu curva de deslocamento vertical em função do tempo de incêndio semelhante à curva obtida por meio de modelo analítico disponível na literatura. Por meio do modelo elaborado foi possível observar que a elevação do nível de carregamento reduz o tempo de resistência do elemento estrutural e que a proteção térmica do concreto é essencial para aumentar o tempo até a ruptura da viga. / Timber-concrete composite beams are formed by the union of timber beams to reinforced concrete slabs through of shear connectors. When timber-concrete composite floors are compared to timber floors or reinforced concrete floors it is possible to highlight some advantages, including good performance in fire situations. When subjected to thermal actions, structural elements suffer strength and stiffness reductions, being, therefore, necessary to know the modifications suffered by each of its components, which for the case studied are: timber, concrete and shear connectors. Thus, it is developed a numerical modeling strategy using the computational program ABAQUS, which is based on the finite element method, for the study of timber-concrete composite beams in fire situation. In the first stage of the research it was carried out a numerical modeling of timber beam and timber-concrete composite beam at room temperature, finding good correlation between the force versus displacement curves in the middle of the span obtained numerically and through tests available in the literature. Then, it was carried out the calibration of the thermal and mechanical properties of the Brazilian wood, reaching numerical results close to the experimental ones, either in relation to the temperatures of the analyzed element or in relation to the vertical displacement curve as a function of the fire time. Finally, the thermo-structural modeling strategy developed for the timber-concrete composite beam provided a vertical displacement curve as a function of the fire time similar to the curve obtained through an analytical model available in the literature. Through of the elaborated model it was possible to observe that the load level increase reduces the resistance fire time of the structural element and that the thermal protection of the concrete is essential to increase the rupture time of the beam.
86

Análise numérica de vigas mistas de madeira e concreto em situação de incêndio / Numerical analysis of timber-concrete composite beams in fire situation

Felipi Pablo Damasceno Fernandes 10 May 2018 (has links)
As vigas mistas de madeira e concreto são formadas pela união de vigas de madeira a lajes de concreto armado por meio de conectores de cisalhamento. Quando os pisos mistos de madeira e concreto são comparados aos pisos construídos unicamente em madeira ou àqueles confeccionados somente em concreto armado é possível destacar algumas vantagens, incluindo o bom desempenho em situações de incêndio. Os elementos estruturais quando submetidos a ações térmicas sofrem redução de resistência e rigidez, sendo, desta forma, necessário conhecer as modificações sofridas por cada um de seus componentes, que para o caso estudado são: a madeira, o concreto e os conectores de cisalhamento. Desta forma, foi elaborada uma estratégia de modelagem numérica para o estudo de vigas mistas de madeira e concreto em situação de incêndio, utilizando o programa computacional ABAQUS, o qual é baseado no método dos elementos finitos. Em uma primeira etapa da pesquisa foram realizadas modelagens numéricas de vigas de madeira e mistas de madeira e concreto em temperatura ambiente, encontrando-se boa correlação entre as curvas força versus deslocamento no meio do vão obtida numericamente e por meio de ensaios disponíveis na literatura. Em seguida procedeu-se a calibração das propriedades térmicas e mecânicas da madeira brasileira, alcançando-se resultados numéricos próximos aos experimentais, seja em relação às temperaturas do elemento analisado seja em relação à curva de deslocamento vertical em função do tempo de incêndio. Por fim, a estratégia de modelagem termoestrutural desenvolvida para a viga mista de madeira e concreto forneceu curva de deslocamento vertical em função do tempo de incêndio semelhante à curva obtida por meio de modelo analítico disponível na literatura. Por meio do modelo elaborado foi possível observar que a elevação do nível de carregamento reduz o tempo de resistência do elemento estrutural e que a proteção térmica do concreto é essencial para aumentar o tempo até a ruptura da viga. / Timber-concrete composite beams are formed by the union of timber beams to reinforced concrete slabs through of shear connectors. When timber-concrete composite floors are compared to timber floors or reinforced concrete floors it is possible to highlight some advantages, including good performance in fire situations. When subjected to thermal actions, structural elements suffer strength and stiffness reductions, being, therefore, necessary to know the modifications suffered by each of its components, which for the case studied are: timber, concrete and shear connectors. Thus, it is developed a numerical modeling strategy using the computational program ABAQUS, which is based on the finite element method, for the study of timber-concrete composite beams in fire situation. In the first stage of the research it was carried out a numerical modeling of timber beam and timber-concrete composite beam at room temperature, finding good correlation between the force versus displacement curves in the middle of the span obtained numerically and through tests available in the literature. Then, it was carried out the calibration of the thermal and mechanical properties of the Brazilian wood, reaching numerical results close to the experimental ones, either in relation to the temperatures of the analyzed element or in relation to the vertical displacement curve as a function of the fire time. Finally, the thermo-structural modeling strategy developed for the timber-concrete composite beam provided a vertical displacement curve as a function of the fire time similar to the curve obtained through an analytical model available in the literature. Through of the elaborated model it was possible to observe that the load level increase reduces the resistance fire time of the structural element and that the thermal protection of the concrete is essential to increase the rupture time of the beam.
87

Increasing Damping Capacity of Shear Walls with Glued-Nail Joints / Ökning av dämpningen hos skjuvväggar med limmade spikförband

Karlsson, Fredrik, Ramic, Zlatan, Tartes, Karl January 2012 (has links)
The purpose of this master thesis has been to investigate the possibility to increase the damping capacity of shear walls with the use of glue in combination with nails. It has been done with experiment and with FE-simulations.   The first experimental part is tensile tests of four different glue types which have been analyzed to get material data. The second experimental part is analysis of glued-nail joint in shear test. FE-simulations of glued-nail joints are finally done in Abaqus/CAE.   The experiments in shear tests of glued-nail joints showed that two glues failed and could not be used for further analysis. The two other glues had an increase in damping capacity compared with results from nail joint.   Further FE-simulations of glued-nailed joints have to be done in order to calibrate the FE-model with the results of glued-nailed joints in shear tests. The uncertainty is found in the material properties of the glue, experimental test data was not adequate. The conclusion is that glued-nail joints can increase the damping capacity in shear walls. / Damping capacity, shear wall, hysteresis, shear test, finite element method, Abaqus/CAE
88

A numerical platform for the identification of dynamic non-linear constitutive laws using multiple impact tests : application to metal forming and machining / Une plate-forme numérique pour l'identification des lois de comportement dynamiques non linéaires à l'aide d'essais d'impact multiples

Ming, Lu 28 March 2018 (has links)
Le travail principal de cette thèse consiste à proposer une nouvelle procédure d'identification inverse appliquée aux situations de mise en forme et d'usinage des métaux, qui peut fournir un ensemble de paramètres appropriés pour toute loi constitutive elastoplastique suivant le modèle de plasticité de type J_{2} avec écrouissage isotrope, en évaluant la corrélation entre les réponses expérimentales et numériques. En premier lieu, un programme d'identification a été développé, en combinant l'algorithme de Levenberg-Marquardt et des méthodes de traitement de données pour identifier les paramètres constitutifs. En termes d'expérimentation, des essais de compression et de traction dynamiques ont été effectués. La forme finale déformée des spécimens, qui repose sur une analyse post-mortem, a été choisie comme quantité d'observation. Comme pour la simulation numérique, des modèles numériques de ces mêmes procédures expérimentales ont été construits en utilisant le code éléments finis Abaqus/Explicit afin de fournir des réponses numériques. Un algorithme numérique a été proposé pour l'implémentation de lois constitutives elastoplastiques définies par l'utilisateur dans Abaqus/Explicit. / The main concern of this thesis is to propose a new inverse identification procedure applied to metal forming and machining situations, which can provide an appropriate parameters set for any elastoplastic constitutive law following J_{2} plasticity and isotropic hardening, by evaluating the correlation between the experimental and numerical responses. Firstly the identification program has been developed, which combines the Levenberg-Marquardt algorithm and the Data processing methods to optimize the constitutive parameters. In terms of experimentation, dynamic compression and tensile tests have been conducted. The final deformed shape of specimens, which relies on a post-mortem analysis, has been selected as the observation quantity. As for the numerical simulation, the numerical models of the same experimental procedure have been built with the finite element software Abaqus/Explicit in order to provide numerical responses. A numerical algorithm has been proposed for the implementation of user defined elastoplastic constitutive laws in Abaqus/Explicit.
89

Modelos computacionais para análise da influência de parâmetros estatísticos de textura superficial no contato dentário humano

Oliveira, Evelyn Aparecida de 01 April 2016 (has links)
Submitted by isabela.moljf@hotmail.com (isabela.moljf@hotmail.com) on 2017-02-13T14:23:53Z No. of bitstreams: 1 evelynaparecidadeoliveira.pdf: 4026204 bytes, checksum: c1b720f3501ffcd12b38f9d4c877dfa9 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-02-13T16:49:50Z (GMT) No. of bitstreams: 1 evelynaparecidadeoliveira.pdf: 4026204 bytes, checksum: c1b720f3501ffcd12b38f9d4c877dfa9 (MD5) / Made available in DSpace on 2017-02-13T16:49:50Z (GMT). No. of bitstreams: 1 evelynaparecidadeoliveira.pdf: 4026204 bytes, checksum: c1b720f3501ffcd12b38f9d4c877dfa9 (MD5) Previous issue date: 2016-04-01 / O desgaste do dente, que se manifesta com uma grande variedade de graus ou níveis, é uma das anomalias dentárias comumente encontradas em diversas populações. A modelagem computacional do problema de contato oclusal pode ajudar na compreensão das interações entre os dentes, que gera concentrações de tensões. A abordagem utilizada para simular o contato entre as superfícies ásperas, dadas as funções de densidade de probabilidade das alturas das asperezas, consiste em discretizá-las em vários intervalos, de modo que cada um deles represente uma aspereza principal. As deformações das asperezas principais são analisadas e, utilizando técnicas de homogeneização, é possível estabelecer a relação entre as respostas que ocorrem em microescala e as respostas esperadas na macroescala. Neste trabalho, foi criada uma rotina para geração numérica de superfícies, um script acoplado ao programa de elementos finitos, Abaqus, para análise dos microcontatos, e, finalmente, um código para o procedimento de homogeneização e análise paramétrica das medidas de rugosidade. Na estimativa da dureza superficial, verificou-se que a curvatura média das asperezas exerce maior influência. Os parâmetros que mais influenciam nas forças e áreas de contato são o coeficiente de achatamento (kurtosis), cujo aumento leva ao decaimento dessas grandezas, seguido da rugosidade média quadrática, que, por sua vez, tem uma relação diretamente proporcional com a carga e consequentemente com a área de contato. / Tooth wear, which manifests with a great variety of degrees or levels, is one of the dental abnormalities commonly found in different populations. The computational modelling of the occlusal contact problem can help the comprehension of any interaction between teeth generating stress concentration. The approach used in this work to simulate contact between rough surfaces, given the probability density functions of asperities, consists in discretizing them in several intervals, so that each one represents a main asperity. The deformations of the main asperities are analyzed and, using homogenization techniques, it is possible to developed the relationship among the responses occurred in micro-scale and the predicted responses in macro-scale. In this work a routine has been established for numerical generation of surfaces, a script as well as has been coupled to the finite element program Abaqus, for analysis of the micro-contacts, and, finally, a code for homogenization and parametric analysis of the roughness measure. In the estimate of the surface hardness it was found that the mean curvature of the asperities exerts the largest influence. The parameters that influence the forces and contact areas are the flattening coefficient (kurtosis), which when increases leads to decay of these greatness, followed by the mean square roughness, which, in turn, has a direct proportional relationship with the strength and consequently with the contact area.
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Deformationsanalys av klämvillkor av en vevaxel / Deformation Analysis Of Clamping Conditions Of A Crankshaft

Eliasson, Fredrik, Todorovic, Ilija January 2017 (has links)
Vevaxeldeformation studeras i samband med uppspänning i en virvelfräsmaskin inför en skärande process. Syftet är att öka förståelse om deformationsbeteendet av vevaxelns viktiga funktionsytor genom analysering med Finita elementmetoden (FEM). Volvo Cars i Skövde hanterar i dagsläget oönskad vevaxeldeformation genom tidskrävande fysiska tester. Därför önskar företaget ta stöd av virtuell analysering. Detta arbete leder även till ett fastställande om FEM är ett tillämpbart verktyg att utgå ifrån för att upprätthålla snäva vevaxeltoleranser. Användning av virtuell analysering istället för fysiska tester skulle medföra tidsbesparing och ha positiv inverkan på miljön.  Programvaran Abaqus används för genomförande av deformationsanalyser vilka också utvärderas mot fysiska mätningar i en dragprovmaskin (Instron) för att därigenom säkerställa pålitligheten av använd FE modell.  Analyser genomförs huvudsakligen för deformationsuppkomst av vevaxeln i samband med uppspänning. Två olika typer av vevaxlar analyseras. Till respektive vevaxel skapas en FE modell med ansatta randvillkor och belastningsförhållanden utgående från en genomförd mekanisk analys av vevaxeln. Erhållna resultat visar att bricksidorna av vevaxeln deformeras med i storleksordningen <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?10%5E%7B-2%7D" /> mm då vevaxeln belastas i samband med uppspänning med en hoptryckning på 0,2 mm. Denna deformation anses medföra risk att ett bearbetningsfel kan förorsakas. Analyserna visar även vilka ytor som deformeras mest/minst. Utvärdering mot dragprovning indikerar att riktning på vevaxeldeformation stämmer överens med analyserna, men att avvikelser på deformationsstorleken förekommer. Skillnaden kan möjligen förklaras med att E-modulen varierar inom den testade vevaxeln medan den definierade E-modulen i Abaqus antar ett konstant värde. Dessutom kan eventuella felkällor från dragprovningen ha inverkan på resultatutfallet av de fysiska mätningarna.  Genomförda analyser tyder på att FEM är tillämpbar för analysering av vevaxeldeformation och rekommendationer om en lämplig FE modell tillhandahålls. En potentiell lösning till deformationsproblemet anses vara beräkning av optimal klämkraft vid uppspänning. / Crankshaft deformation is studied in connection with clamping conditions in a whirl milling machine before a cutting process. The purpose of the project is to increase knowledge about the deformation behaviour of the crankshaft and its important functional surfaces by performing analyses using the finite element method (FEM). Volvo Cars in Skövde, Sweden is currently managing unwanted crankshaft deformation occurrence by using time consuming physical testing methods. Therefore, the company wish to use virtual analyses instead of physical tests. This work also leads to a determination if FEM is an applicable tool in order to maintain narrow tolerances of the crankshaft. Using virtual analyses instead of physical tests would be time saving and would also have a positive impact on the environment. The computer software Abaqus is used to implement the deformation analyses that are also evaluated against physical measurements done with a tensile testing machine (Instron) and thereby be able to ensure the reliability of the used FE model. FE analyses are mainly performed to evaluate the deformation of the crankshaft associated with clamping. Two different crankshaft types are being analysed. A FE model is created for each crankshaft along with applied boundary and load conditions according to performed mechanical analysis of the crankshaft. Obtained results show that the thrust bearing sides of the crank pins on the crankshaft deform in the range of <img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?10%5E%7B-2%7D" /> mm when the crankshaft is compressed during clamping with 0.2 mm. This deformation is considered to entail a risk for a processing error to occur. At the same time the analyses show which surfaces are most/least deformed. Evaluation according to the tensile testing indicates that the direction of the crankshaft deformation corresponds to the analysis but slight deviation of the deformation magnitude is present. The deviations can be explained by variations of the E-module within the crankshaft while the defined E-module in Abaqus has a constant value. Furthermore, there is a possibility that sources of error from the tensile tests can have an influence on the obtained results from the physical measurements. Conducted analyses indicates that FEM is applicable for crankshaft deformation analyses and recommendations of a suitable FE model are provided. A potential solution of the deformation problem is considered to be the calculation of optimal clamping force.

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