This work presents a study and implementation of the simulation of residual stresses in castings. The objects of study are a cast iron truck Hub part (provided by the company Volvo 3P) and an optimized version of the Hub resulting from the application of a topology optimization process. The models are solved through an uncoupled thermo-mechanical solidification analysis, performed both in the FE commercial software Abaqus and the FD commercial software Magmasoft and the results are compared. First, a thermal analysis is carried out where the casting is cooled down from a super-heated temperature to room temperature. The thermal history obtained, is then used as an external force to calculate the residual stresses by means of a quasi-static mechanical analysis, using a J2-plasticity model. The simulation procedures are explained through a simplified model of the Hub and then applied to the geometries of interest. A results comparison between the original Hub and its optimized version is also presented. The theoretical base is given in this work as well as detailed implementation procedures. The results shows that the part subjected to the topology optimization process develop less residual stresses than its original version.

Many studies with Thermoelastic Stress Analysis (TSA) and Infrared Thermography, in Fiber Reinforced Polymeric materials (FRPs), are concerned with surface detection of "hot spots" in order to locate and infer damage. Such experimental analyses usually yield qualitative relations where correlations between stress state and damage severity cannot be obtained. This study introduces quantitative experimental methodologies for TSA and Digital Image Correlation to expand the use of remote sensing technologies for static behavior, static damage initiation detection, and fatigue damage in FRPs. Three major experimental studies are conducted and coupled with nonlinear anisotropic material modeling: static and TSA of hybrid bio-composite material systems, a new stochastic model for fatigue damage of FRPs, and fracture analysis for FRP single-lap joints. Experimental calibration techniques are developed to validate the proposed macromechanical and micromechanical nonlinear anisotropic modeling frameworks under multi-axial states of stress. The High Fidelity Generalized Method of Cells (HFGMC) is a sophisticated micromechanical model developed for analysis of multi-phase composites with nonlinear elastic and elastoplastic constituents is employed in this study to analyze hybrid bio-composites. Macro-mechanical nonlinear anisotropic models and a linear orthotropic model for fracture behavior using the Extended Finite Element method (XFEM) are also considered and compared with the HFGMC method. While micromechanical and FE results provide helpful results for correlating with quasi-static behavior, analyzing damage progression after damage initiation is not straightforward and involves severe energy dissipation, especially with increasing damage progression. This is especially true for fatigue damage evolution, such as that of composite joints as it is associated with uncertainty and randomness. Towards that goal, stochastic Markov Chain fatigue damage models are used to predict cumulative damage with the new damage indices proposed using full-field TSA image analysis algorithms developed for continuously acquired measurements during fatigue loading of S2-Glass/E733FR unidirectional single-lap joints. Static damage initiation is also investigated experimentally with TSA in single-lap joints with thick adherends providing for new design limitations. The computational modeling, stochastic and experimental methods developed in this study have a wide range of applications for static, fracture and fatigue damage of different FRP material and structural systems.

<p>This work presents a study and implementation of the simulation of residual stresses in castings. The objects of study are a cast iron truck Hub part (provided by the company Volvo 3P) and an optimized version of the Hub resulting from the application of a topology optimization process. The models are solved through an uncoupled thermo-mechanical solidification analysis, performed both in the FE commercial software Abaqus and the FD commercial software Magmasoft and the results are compared. First, a thermal analysis is carried out where the casting is cooled down from a super-heated temperature to room temperature. The thermal history obtained, is then used as an external force to calculate the residual stresses by means of a quasi-static mechanical analysis, using a J2-plasticity model. The simulation procedures are explained through a simplified model of the Hub and then applied to the geometries of interest. A results comparison between the original Hub and its optimized version is also presented. The theoretical base is given in this work as well as detailed implementation procedures. The results shows that the part subjected to the topology optimization process develop less residual stresses than its original version.</p>

Carbon fiber-reinforced silicon carbide matrix (C/SiC) composite is a ceramic matrixcomposite (CMC) that has considerable promise for use in high-temperature structuralapplications. In this thesis, systematic numerical studies including the prediction of elasticand thermal properties, analysis and optimization of stresses and simulation ofhigh-temperature oxidations are presented for the investigation of C/SiC composites.A strain energy method is firstly proposed for the prediction of the effective elastic constantsand coefficients of thermal expansion (CTEs) of 3D orthotropic composite materials. Thismethod derives the effective elastic tensors and CTEs by analyzing the relationship betweenthe strain energy of the microstructure and that of the homogenized equivalent model underspecific thermo-elastic boundary conditions. Different kinds of composites are tested tovalidate the model.Geometrical configurations of the representative volume cell (RVC) of 2-D woven and 3-Dbraided C/SiC composites are analyzed in details. The finite element models of 2-D wovenand 3-D braided C/SiC composites are then established and combined with the stain energymethod to evaluate the effective elastic constants and CTEs of these composites. Numericalresults obtained by the proposed model are then compared with the results measuredexperimentally.A global/local analysis strategy is developed for the determination of the detailed stresses inthe 2-D woven C/SiC composite structures. On the basis of the finite element analysis, theprocedure is carried out sequentially from the homogenized composite structure of themacro-scale (global model) to the parameterized detailed fiber tow model of the micro-scale(local model). The bridge between two scales is realized by mapping the global analysisresult as the boundary conditions of the local tow model. The stress results by global/localmethod are finally compared to those by conventional finite element analyses.Optimal design for minimizing thermal residual stress (TRS) in 1-D unidirectional C/SiCcomposites is studied. The finite element models of RVC of 1-D unidirectional C/SiCIIcomposites with multi-layer interfaces are generated and finite element analysis is realized todetermine the TRS distributions. An optimization scheme which combines a modifiedParticle Swarm Optimization (PSO) algorithm and the finite element analysis is used toreduce the TRS in the C/SiC composites by controlling the multi-layer interfaces thicknesses.A numerical model is finally developed to study the microstructure oxidation process and thedegradation of elastic properties of 2-D woven C/SiC composites exposed to air oxidizingenvironments at intermediate temperature (T<900°C). The oxidized RVC microstructure ismodeled based on the oxidation kinetics analysis. The strain energy method is then combinedwith the finite element model of oxidized RVC to predict the elastic properties of composites.The environmental parameters, i.e., temperature and pressure are studied to show theirinfluences upon the oxidation behavior of C/SiC composites.

No description available.

[pt] O presente estudo descreve uma correlação entre o desempenho obtido por brocas de perfuração e o estado de tensões atuante na formação rochosa localizada imediatamente abaixo do fundo do poço. Os dados de desempenho de brocas de seis poços perfurados na costa marítima brasileira foram coletados e analisados. Tendo em vista reduzir o empirismo associado com este tipo de análise, é implementado um estudo que considera o perfil geomecânico do poço. O perfil geomecânico de uma dada formação rochosa é composto de suas propriedades mecânicas (módulo de Young, relação de Poisson, resistência à compressão simples, ângulo de atrito interno etc.), das pressões dos fluidos das formações e das tensões totais in situ. A dissertação mostra a sistemática utilizada para avaliar as tensões no fundo do poço através de um programa de elementos finitos 3D. Através destas tensões é possível definir um índice de plastificação à frente da broca de perfuração e o rendimento da mesma é avaliado levando este índice em conta. Alguns dos poços analisados foram perfurados em águas profundas, sendo que os resultados obtidos até o momento mostraram um grande potencial para a melhor compreensão de altos e baixos rendimentos com respeito à taxa de penetração da broca, de uma maneira racional. Baseados nesta análise novos estudos para avaliação de brocas poderão ser implementados indicando que reduções significativas de custo de perfuração poderão ser obtidas. / [en] The present dissertation describes a correlation between the bit performance and the state of stress acting upon the rock formation located immediately beneath the bottom of the wellbore. Bit performance data from 6 wells drilled offshore Brazil were collected and anlyzed. In order to reduce the empiricism associated with this type of data analysis, a study is being put forward that considers the geomechanical log along the drilled wellbore. The geomechanical log of a given rock formation is composed of its mechanical properties (Young's modulus, Poisson's Ratio, unconfined compressive strength, internal friction angle, etc.) as well as formation fluid pressure and in situ total stresses. The dissertation shows the metodology to evaluate the stresses at the bottom of the wellbore through a 3D finite element program. Trough these stresses it is possible to define an index of plastification ahead of the drill bit, and bit performance is rated taking this index into account. Some of the wells analyzed were drilled in deep water locations, and the initial results obtained herein, showed a great potential for better understanding for the good and bad performances, regarding the rate of penetration of the drill bit evaluation will be put forward with the great potential for drilling cost savings. / [es] El presente estudio describe la correlación entre el desempeño obtenido por brocas de perforación y las tensiones actuantes en la formación rocosa localizada debajo del fondo del pozo. Se colectaron y analizaron datos sobre el desempeño de brocas de seis pozos perforados en la costa marítima brasileira. Teniendo como objetivo reducir el empirismo asociado a este tipo de análisis, se implementa un estudio que considera el perfil geomecánico del pozo. El perfil geomecánico de una formación rocosa está compuesto de suas propriedades mecánicas (módulo de Young, relación de Pueson, resistencia a la compresión simple, etc.), de las presiones de los fluidos de las formaciones y de las tensiones totales in situ. La disertación muestra la sistemática utilizada para evaluar las tensiones en el fondo del pozo a través de un programa de elementos finitos 3D. A través de estas tensiones es posible definir un índice de plastificación al frente de la broca de perfuración y se evalúa su rendimiento llevando este índice en consideración. Algunos pozos analizados fueron perforados en aguas profundas, los resultados obtenidos hasta el momento mostraron un gran potencial para la mejor comprensión de altos y bajos rendimentos con respecto a la tasa de penetración de la broca, de una manera racional. Sobre este análisis nuevos estudios para evaluación de brocas pueden ser implementados indicando que pueden obtenerse reducciones significativas del costo de perforación.

This Diploma Thesis is dedicated to a proposal of a carrier swap bodies hooked up to a agrotruck 6x6 with a maximum technical weight 38000 kg and has been worked out in corporation with ZDT Nové Veselí company. The first section of the Thesis is occupied with legislation and then especially with a description of available agrotrucks and similar constuction solutions not just of the carrier swap bodies. In the following part of the Thesis the own carrier swap bodies construction proposal has been described, based on which the stress analysis has been done in the final part of the Thesis. Also the technical drawing forms an integral part of the Thesis.

Made available in DSpace on 2014-06-11T19:35:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-11Bitstream added on 2014-06-13T19:44:51Z : No. of bitstreams: 1 verri_fr_dr_araca.pdf: 1853726 bytes, checksum: 578403c1602d78c980bb821e076ea43c (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A colocação de PPR de extremidade livre no arco inferior é uma das mais complexas dentro da área protética. A associação desta com implantes na região distal tem melhorado biomecanicamente seu funcionamento. Porém, existem poucos estudos a respeito desta associação levando em consideração o nível de inserção óssea do dente suporte. Assim, o objetivo desta pesquisa foi avaliar, por meio do método dos elementos finitos bidimensional, a distribuição de tensão nas estruturas de suporte de uma PPREL, associada a um implante osseointegrado de 10,0 x 3,75 mm (Sistema Branemark), próximo ao dente suporte, com diferentes níveis de inserção óssea (íntegro e 1/2 da raiz) e com diferentes tipos de conexão entre a PPR e o dente suporte (apoio incisal e placa distal). Para o estudo, foram confeccionados 8 modelos mandibulares, de extremo livre, com a presença apenas do dente 33, sendo: MA - PPREL convencional, apoio incisal distal, inserção íntegra; MB - idem ao MA, mas utilizando placa distal; MC - idem ao MA, com implante de 3,75 x 10,0 mm e sistema ERA associado; MD - idem ao MC, mas utilizando placa distal; ME - idem ao MA, mas com perda de inserção de 1/2 da raiz; MF - idem ao MB, mas com perda de inserção de 1/2 da raiz; MG - idem ao MC, mas com perda de inserção de 1/2 da raiz; MH - idem ao MD, mas com perda de inserção de 1/2 da raiz. Com o auxilio do programa ANSYS 9.0, os modelos foram carregados com forças verticais de 50 N em cada ponta de cúspide. Os resultados foram obtidos pelos mapas de deslocamento e de tensão de von Mises e mostraram que o implante favorece a associação da forma descrita, que a placa possibilita um maior alívio e menor deslocamento do dente suporte, e que a perda do periodonto de suporte prejudica o prognóstico da prótese. / The rehabilitation with distal extension RPDA is very complex in the prosthetic area and the association with implants had improving its work biomechanical. However, there is little studies about this type of association and no study about the lost of insertion was encountered by FEA. So, the aim of this study was to evaluate, by FEA 2-D, the tension distribution in support structures of a DERPD associated with a osseointegrated implant of 10,0 x 3,75 mm (Branemark System), near to support tooth, with different levels of bone insertion (no lost and 1/2 of root) and with different type of connection between the DERPD and de support tooth (incisal rest and distal plate). For the study, 8 distal extension mandibular models were made, with the presence of tooth 33, presenting: MA - conventional DERPD, incisal rest, no bone lost; MB - like MA, but with distal plate; MC - like MA, but with implanto of 3,75 x 10,0 mm and ERA system associated; MD - like MC, but with distal plate; ME - like MA, but with bone lost of 1/2 of root; MF - like MB, but with bone lost of 1/2 of root; MG - like MC, but with bone lost of 1/2 of root; MH - like MD, but with bone lost of 1/2 of root. By mean of program of FEA ANSYS 9.0, the models were carried with axial forces of 50 N in each cusp tip. The results were obtained by dislodgement maps and von Mises tension maps and shown that the implant was benefit to association by the study, and the plate decreased the tension and the dislodgement of the support tooth, and the bone lost was prejudicial to prognostic of this type of prosthesis. By this methodology, was possible to conclude that: the introduction of an osseointegrated implant with ERA system used like this study decrease the dislodgement of above structures in all models.

O surgimento dos implantes osseointegrados melhorou a qualidade de vida de pacientes edêntulos. Seu uso favorece retenção e estabilidade, gerando maior eficiência mastigatória e conforto. O objetivo deste estudo foi avaliar manutenção da força de retenção e padrões de tensões gerados na mandíbula em overdentures confeccionadas com dois sistemas de retenção retidas por 2 ou 3 implantes. Teste de carga cíclica e análise fotoelástica de tensões foram realizados. Para o teste de carga cíclica foram utilizados modelos representativos de mandíbulas desdentadas e os grupos analisados foram: A) 2 implantes com barra clipe; B) 3 implantes com barra clipe; C) 2 implantes com barra clipe e bola/o\'ring nas extremidades; D) 3 implantes com barra clipe e bola/o\'ring nas extremidades. Cinco espécimes por grupo foram submetidos à ciclagem e 5 permaneceram imersos na máquina de ciclagem (controle). As leituras de força de retenção foram realizadas por ensaio de tração em máquina de ensaios universal antes da ciclagem e a cada 500 mil ciclos. A ciclagem foi realizada com frequência de 1,8 Hz, carga de 130 N, por 2 milhões de ciclos. Para a aplicação de carga, foram feitas pontas correspondentes à arcada antagonista unilateral posterior. Os dados obtidos foram analisados estatisticamente pelo modelo linear de efeitos mistos. Para a análise fotoelástica, foi feito um modelo mestre curvo em resina acrílica. O modelo foi preparado para conter cinco implantes, paralelos, distribuídos na região interforaminal. Grupo com 4 implantes com barra clipe e o\'rings nas extremidades foi incluído como controle. Prótese total foi confeccionada e usada em todos os grupos. A cada grupo, nova captura de retentores foi realizada. Para obtenção dos modelos fotoelásticos, foram confeccionados moldes em silicone do modelo mestre. A verificação das tensões em torno dos implantes foi realizada por meio de análise fotoelástica qualitativa de transmissão sob aplicação de carga cêntrica estática de 50 N. Diferentes tipos de pontas e locais de aplicação de carga foram usados. Os resultados demonstraram que carga cíclica influencia na perda de retenção overdentures mandibulares. Comparando grupos controle e teste, observou-se que os grupos com três implantes apresentaram maior influência da ciclagem na perda de retenção. Os sistemas de retenção estudados apresentaram comportamentos diferentes até um milhão de ciclos, após não houve diferença quanto à manutenção de retenção. Todos os grupos mantiveram retenção satisfatória ao final da ciclagem. Três implantes apresentaram maior tensão ao redor dos implantes e pouca ou nenhuma sobre o rebordo. Nos grupos com dois implantes, aplicação de carga posterior gerou tensões no rebordo alveolar e implantes. Grupos com extensões distais evidenciaram uma maior tensão ao redor dos implantes que os sem extensão. / The appearance of osseointegrated dental implants improved the quality of life of fully edentulous patients. Implants promote retention and stability, producing higher masticatory efficiency and comfort. The aim of this study was analyze the retention maintenance and the stress pattern generated by two or three implants-supported mandibular overdentures with two attachments systems. Cyclic loading test and photoelastic stress analysis were performed. For the cyclic loading test, edentulous mandibular models were used. The analyzed groups were: A) 2 implants with bar clip; B) 3 implants with bar clip; C) 2 implants with bar clip and balls/o\'rings in the extremity; D) 3 implants with bar clip and balls/o\'rings in the extremity. Five specimens per group were submitted to cyclic loading and five were kept immersed inside the test machine (control group). The measurements of retention force were performed by tensile test in a universal testing machine before cyclic loading and after each 500 thousands cycles. The cycling was performed with frequency of 1.8 Hz, loading of 130 N, up to two million cycles. For the load application, tips corresponding to posterior unilateral antagonist teeth were produced. Data were statistically analyzed by linear mixed-effects model. For the photoelastic analysis, a curved master model was produced in acrylic resin. The model contained five parallel implants, distributed in interforaminal area. A group with 4 implants splinted with bar clip and balls/o\'rings in the extremity was included as a control. Complete denture was made and used in all groups. In each group, incorporating of new attachments was performed. For the obtainment of photoelastic models, silicone impression of the master model was performed. The assessment of stress around implants was done through quantitative transmission photoelastic analysis under static centric load application of 50 N. Different sorts of tips and load application places were used. The results showed that cyclic load influences the retention loss of mandibular overdentures. Comparing test and control groups, it was observed that groups with three implants showed higher influence of cyclic loading in retention loss. The studied attachments systems showed different behaviors up to one million cycles, after that there was not difference in the maintenance of retention. All groups had satisfactory retention at the end of cycling. Groups with three implants showed higher stress around implants and lower or none on alveolar ridge. In groups with two implants, load application on posterior area caused stress on alveolar ridge and implants. Groups with distal extensions demonstrated higher stress around implants than groups without extension.

Orientador: Luis Roberto Marcondes Martins / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-13T11:40:25Z (GMT). No. of bitstreams: 1 SantosFilho_PauloCesardeFreitas_D.pdf: 10660151 bytes, checksum: bd3f67697b369623400074dcf22ec01c (MD5) Previous issue date: 2009 / Resumo: O objetivo deste estudo foi desenvolver protocolo de modelagem tridimensional para incisivo central superior com aplicabilidade ao método de elementos finitos e avaliar o comportamento biomecânico de incisivo superior tratado endodonticamente e restaurado com retentores e coroa cerâmica por meio de análise por elementos finitos comparado ao dente hígido. Para geração do modelo 3D foi selecionado incisivo central superior hígido. Esmalte e dentina foram degradados em diferentes fases com ácido clorídrico-10%, e mapeados com scanner de contato 3D (Modela, Roland). Para o mapeamento do volume pulpar, a dentina foi seccionada longitudinalmente no sentido mesio-distal e realizado o escaneamento do espaço negativo referente à polpa. Os arquivos *.STL foram exportados para programa Bio-CAD (Rhinoceros-3D). Volumes de cada estrutura dental e técnicas restauradoras foram gerados por meio da associação de superfícies NURBS. Os modelos foram exportados para o programa de elementos finitos (FEMAP-NeiNastran), onde foi realizado o processo de malhagem, inserção das propriedades mecânicas e condições de contorno. Foram gerados 17 modelos, sendo um do dente hígido e 16 modelos de acordo com os 4 fatores em estudo: tipo de retentor em dois níveis: pino de fibra de vidro (PFV) e núcleo moldado fundido (NMF), extensão do retentor em dois níveis: 7,0mm (7,0) e 12,0mm (12,0), remanescente coronário em dois níveis: remanescente de 2,0mm (RE) e ausência de remanescente (ARE), enfraquecimento do canal radicular em dois níveis: ausência de enfraquecimento (AENF) e presença de enfraquecimento (ENF). Foi simulada aplicação de pressão constante no valor de 100N perpendicularmente à superfície palatina do incisivo. Os resultados foram analisados pelo critério de von Mises e tensão máxima principal. Os resultados obtidos mostraram que o modelo geométrico 3D desenvolvido é adequado para a análise por elementos finitos. Concluiu-se que o PFV apresenta distribuição homogênea das tensões mais semelhante ao dente hígido, enquanto o NMF apresentou grande concentração de tensão no interior do canal radicular. O fator extensão do retentor intra-radicular influenciou isoladamente apenas a distribuição de tensões do NMF. A presença de remanescente coronário sempre melhorou a distribuição de tensões. O enfraquecimento do canal radicular teve maior impacto na distribuição de tensões. / Abstract: The aim of this study was develop 3D model generation protocol for upper anterior teeth for finite element analysis and evaluate biomechanical behavior of endodontically treated incisor with finite element analysis compared to sound teeth. It was selected intact upper central incisor. Enamel and dentin were treated in different steps with cloridric acid 2% and scanned with 3D-contact scanner. The stereolithographics archives were exported to Bio CAD program. The volums of each dental structure and restorative techniques were generated by association of NURBS surfaces. The models were exported for finite element software, where were realized the meshed process, mechanical properties insertion and bondary conditions. It were generated 17 models, one was a sound incisor model and 16 models according to 4 studied factors: post type: glass fiber post (GFP) and cast post and core (CPC), post length: 7,0mm (7,0) e 12,0mm (12,0), ferrule: 2,0mm ferrule (FE) and absence of ferrule (AFE), weakness of root canal: absence of weakness (AWR) and weakened root (WR). It was simulated 100N loading application on the palatal surface with 135° angulation. The results were analised by Von Mises criteria and principal maximum tension. Obtained results showed that geometric model developed is appropriated for finite element analysis. It can be concluded that GFP showed homogeneous stress distribution like the sound incisor, while CPC showed stress concentration into root canal. The post length influenced only the CPC stress distribution. The ferrule always showed better stress distribution. The weakness of root showed the highest impact in stress distribution. / Doutorado / Dentística / Doutor em Clínica Odontológica