Aplicação da computação simbólica na resolução de problemas de condução de calor em cilindros vazados com condições de contorno convectivas

Pós-graduação em Engenharia Mecânica - FEG

Técnica para dedução do modelo algébrico PTT, aplicações e análises numéricas em escoamentos bidimensionais

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Contribuições na modelagem dinâmica e no controle neural de um braço robótico com elos flexíveis

Em geral, estruturas espaciais e manipuladores robóticos leves têm uma característica similar e inerente que é a flexibilidade. Esta característica torna a dinâmica do sistema muito mais complexa e com maiores dificuldades para a análise de estabilidade e controle. Então, braços robóticos bastantes leves, com velocidade elevada e potencia limitada devem considerar o controle de vibração causada pela flexibilidade. Por este motivo, uma estratégia de controle é desejada não somente para o controle do modo rígido mas também que seja capaz de controlar os modos de vibração do braço robótico flexível. Também, redes neurais artificiais (RNA) são identificadas como uma subespecialidade de inteligência artificial. Constituem atualmente uma teoria para o estudo de fenômenos complexos e representam uma nova ferramenta na tecnologia de processamento de informação, por possuírem características como processamento paralelo, capacidade de aprendizagem, mapeamento não-linear e capacidade de generalização. Assim, neste estudo utilizam-se RNA na identificação e controle do braço robótico com elos flexíveis. Esta tese apresenta a modelagem dinâmica de braços robóticos com elos flexíveis, 1D no plano horizontal e 2D no plano vertical com ação da gravidade, respectivamente. Modelos dinâmicos reduzidos são obtidos pelo formalismo de Newton-Euler, e utiliza-se o método dos elementos finitos (MEF) na discretização dos deslocamentos elásticos baseado na teoria elementar da viga. Além disso, duas estratégias de controle têm sido desenvolvidas com a finalidade de eliminar as vibrações devido à flexibilidade do braço robótico com elos flexíveis. Primeiro, utilizase um controlador neural feedforward (NFF) na obtenção da dinâmica inversa do braço robótico flexível e o calculo do torque da junta. E segundo, para obter precisão no posicionamento... (Resumo completo, clicar acesso eletrônico abaixo)

Avaliação das condições de contorno da teoria de Hertz, comparando os resultados analíticos e numéricos a partir de simulações em software de elementos finitos

The objective of this study was to present the comparison between analytical and numerical results trying to identify the differences and behaviors of the variation of the principal stresses and the maximum contact pressure for different model configurations. The analytical equations of the theory of Hertz from the boundary conditions adopted by him were differences are shown. A step-by-step of developing the model indicating the geometric dimensions, surface contact, type of contact, the formulation used by the software, type of mesh, as well as the boundary conditions and load was presented. In the results, the stresses calculated analytically and compared with the stresses obtained by the finite element simulation software indicating the changes have been made

Otimização do braço inferior da suspensão dianteira do veículo Baja utilizando o método dos elementos finitos

Mass reduction coupled with the mechanical performance in service has been the goal of many projects related to the transport area, considering the advantages that mass reduction can bring. However, make a simple material substitution without design a new geometry to corroborate for the best component performance, often makes the replacement unviable. In this study, it was investigated the advantages of replacing the prototype BAJA SAE front suspension lower arm of Equipe Piratas do Vale de BAJA SAE - Universidade Paulista, Campus Guaratinguetá, actually produced with steel, for a new component made of carbon fiber composite. The new geometry has been developed to provide the best possible performance for this component and your easy manufacturing. The study was done using the 3D modeling tools and computer simulations via finite element method. The first stage of this work consisted on calculation of the estimated maximum contact force tire / soil in a prototype landing after jump at one meter high, drop test in the laboratory with the current vehicle, current front suspension lower arm 3D modeling, finite element simulation and analysis of critical regions. After all current component analysis, a new geometry for the part in study was designed and simulated in order to reduce the component mass and provide a technological innovation using composite materials. With this work it was possible to obtain a theoretical component mass reduction of 25,15% maintaining the mechanical strength necessary for the appropriated component performance when incited

Modelagem em 3D de uma patela humana e análise de esforços utilizando o método dos elementos finitos

Throughout the history of medicine surgeons realized the importance of the patella to the functioning of the knee. The main function of the patella is to increase the mechanical efficiency of the quadriceps tendon and knee extensor mechanism. It was found that 50% to 80% of the fractures without deviation of the patella have the transversal pattern, possibly due to excessive tensile forces applied to the extensor mechanism. The purpose of this study is to analyze the loads to which a patella is submitted during a normal extension movement of knee. This analysis will be done by modeling a 3D patella and subsequent load simulation as, described in medical literature, using the finite element method

Modelos dinâmicos simplificados, para verificação do comportamento de rede de satélites amarrados por cabos flexíveis, usando-se o método explícito das diferenças finitas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise estática de um guindaste de torre, utilizando o método dos elementos finitos

The finite element method is of great importance for the development and analysis of a new product being designed or already on the market, and that requires some specific request or special application. The tower crane, being an essential equipment for modern construction to increase productivity and safety on construction sites, is required for many types of special applications day after day, in many kinds of work. Paying attention to this growing need for handling special projects for the tower crane, faced with the importance and necessity of development and improvement of knowledge in more accurate and practical calculation methods such as the finite element method , for greater agility and precision in the response to a new project. The tower crane is defined by the maximum load moment that it can act with a certain amount of load. The tower crane which will be analyzed in this work , for example, is a tower crane with a resulting capacity of 85 Metric Tons which are considered basic dimensions data of a fisical tower crane of a crane company Liebherr in Guaratinguetá . Thus, the project analysis will begin with the threedimensional representation of the crane lines with AutoCAD software , conversion of this model to the format accepted ANSYS Workbench and completion of 3D modeling of structural components in Design module ANSYS software. After structural modeling is completed, the simulation is performed in static simulation of ANSYS Workbench software mode. The standards will be adopted to DIN (Deutsches Institut für Normung) and EN 14439 (Europäische Normung 14439) and some NR 's related to specific security class of tower cranes, which will be referred throughout the work

Análise de falhas por fadiga num rotor de hidrogerador vertical via método dos elementos finitos

Pós-graduação em Engenharia Mecânica - FEG

Simulação numérica de fluxo de águas subterrâneas do aquífero Rio Claro, na região do campus da UNESP - Rio Claro, SP

The water management in any area is highly important to the success of many business and also of life and the understanding of your relationship with the environment brings better control to its demand. I.e. hydrogeological studies are needed under better understanding of the behavior of an aquifer, so that its management is done so as not to deplete or harm it. The objective of this work is the numerical modeling in transient regime of a portion of the Rio Claro aquifer formation in order to get answers about its hydrogeological parameters, its main flow direction and also its most sensitive parameters. A literature review and conceptual characterization of the aquifer, combined with field campaigns and monitoring of local water level (NA), enabled the subsequent construction of the mathematical model by finite elements method, using the FEFLOW 6.1 ® computational algorithm. The study site includes the campus of UNESP and residential and industrial areas of Rio Claro city. Its area of 9.73 km ² was divided into 318040 triangular elements spread over six layers, totaling a volume of 0.25 km³. The local topography and geological contacts were obtained from previous geological and geophysical studies as well as profiles of campus wells and SIAGAS / CPRM system. The seven monitoring wells on campus were set up as observation points for calibration and checking of the simulation results. Sampling and characterization of Rio Claro sandstones shows up a high hydrological and lithological heterogeneity for the aquifer formation. The simulation results indicate values of hydraulic conductivity between 10-6 and 10-4 m / s, getting the Recharge/Rainfall simulation in transient ratio at 13%. Even with the simplifications imposed on the model, it was able to represent the fluctuations of local NA over a year of monitoring. The result was the exit of 3774770 m³ of water and the consequently NA fall. The model is considered representative for the...

Análise da influência de variantes do método de solução de escoamentos utilizando os métodos de elementos finitos com compressibilidade artificial e pseudo-características

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Numerical simulation of drop impact and jet buckling problems using the eXtended Pom-Pom model

This work presents numerical simulations of two fluid flow problems involving moving free surfaces: the impacting drop and fluid jet buckling. The viscoelastic model used in these simulations is the eXtended Pom-Pom (XPP) model. To validate the code, numerical predictions of the drop impact problem for Newtonian and Oldroyd-B fluids are presented and compared with other methods. In particular, a benchmark on numerical simulations for a XPP drop impacting on a rigid plate is performed for a wide range of the relevant parameters. Finally, to provide an additional application of free surface flows of XPP fluids, the viscous jet buckling problem is simulated and discussed. (C) 2011 Elsevier B.V. All rights reserved.

Reduced-order modelling, circuit-level design and SOI fabrication of microelectromechanical resonators

This thesis deals with two important research aspects concerning radio frequency (RF) microresonators and switches. First, a new approach for compact modeling and simulation of these devices is presented. Then, a combined process flow for their simultaneous fabrication on a SOI substrate is proposed. Compact models for microresonators and switches are extracted by applying mathematical model order reduction (MOR) to the devices finite element (FE) description in ANSYS c° . The behaviour of these devices includes forms of nonlinearities. However, an approximation in the creation of the FE model is introduced, which enables the use of linear model order reduction. Microresonators are modeled with the introduction of transducer elements, which allow for direct coupling of the electrical and mechanical domain. The coupled system element matrices are linearized around an operating point and reduced. The resulting macromodel is valid for small signal analysis around the bias point, such as harmonic pre-stressed analysis. This is extremely useful for characterizing the frequency response of resonators. Compact modelling of switches preserves the nonlinearity of the device behaviour. Nonlinear reduced order models are obtained by reducing the number of nonlinearities in the system and handling them as input to the system. In this way, the system can be reduced using linear MOR techniques and nonlinearities are introduced directly in the reduced order model. The reduction of the number of system nonlinearities implies the approximation of all distributed forces in the model with lumped forces. Both for microresonators and switches, a procedure for matrices extraction has been developed so that reduced order models include the effects of electrical and mechanical pre-stress. The extraction process is fast and can be done automatically from ANSYS binary files. The method has been applied for the simulation of several devices both at devices and circuit level. Simulation results have been compared with full model simulations, and, when available, experimental data. Reduced order models have proven to conserve the accuracy of finite element method and to give a good description of the overall device behaviour, despite the introduced approximations. In addition, simulation is very fast, both at device and circuit level. A combined process-flow for the integrated fabrication of microresonators and switches has been defined. For this purpose, two processes that are optimized for the independent fabrication of these devices are merged. The major advantage of this process is the possibility to create on-chip circuit blocks that include both microresonators and switches. An application is, for example, aswitched filter bank for wireless transceiver. The process for microresonators fabrication is characterized by the use of silicon on insulator (SOI) wafers and on a deep reactive ion etching (DRIE) step for the creation of the vibrating structures in single-crystal silicon and the use of a sacrificial oxide layer for the definition of resonator to electrode distance. The fabrication of switches is characterized by the use of two different conductive layers for the definition of the actuation electrodes and by the use of a photoresist as a sacrificial layer for the creation of the suspended structure. Both processes have a gold electroplating step, for the creation of the resonators electrodes, transmission lines and suspended structures. The combined process flow is designed such that it conserves the basic properties of the original processes. Neither the performance of the resonators nor the performance of the switches results affected by the simultaneous fabrication. Moreover, common fabrication steps are shared, which allows for cheaper and faster fabrication.

Three-dimensional finite element modelling of stack pollutant emissions

[EN]In this paper we propose a finite element method approach for modelling the air quality in a local scale over complex terrain. The area of interest is up to tens of kilometres and it includes pollutant sources. The proposed methodology involves the generation of an adaptive tetrahedral mesh, the computation of an ambient wind field, the inclusion of the plume rise effect in the wind field, and the simulation of transport and reaction of pollutants. The methodology is used to simulate a fictitious pollution episode in La Palma island (Canary Island, Spain)…

Finite-element discretization of 3D energy-transport equations for semiconductors

In this thesis a mathematical model was derived that describes the charge and energy transport in semiconductor devices like transistors. Moreover, numerical simulations of these physical processes are performed. In order to accomplish this, methods of theoretical physics, functional analysis, numerical mathematics and computer programming are applied. After an introduction to the status quo of semiconductor device simulation methods and a brief review of historical facts up to now, the attention is shifted to the construction of a model, which serves as the basis of the subsequent derivations in the thesis. Thereby the starting point is an important equation of the theory of dilute gases. From this equation the model equations are derived and specified by means of a series expansion method. This is done in a multi-stage derivation process, which is mainly taken from a scientific paper and which does not constitute the focus of this thesis. In the following phase we specify the mathematical setting and make precise the model assumptions. Thereby we make use of methods of functional analysis. Since the equations we deal with are coupled, we are concerned with a nonstandard problem. In contrary, the theory of scalar elliptic equations is established meanwhile. Subsequently, we are preoccupied with the numerical discretization of the equations. A special finite-element method is used for the discretization. This special approach has to be done in order to make the numerical results appropriate for practical application. By a series of transformations from the discrete model we derive a system of algebraic equations that are eligible for numerical evaluation. Using self-made computer programs we solve the equations to get approximate solutions. These programs are based on new and specialized iteration procedures that are developed and thoroughly tested within the frame of this research work. Due to their importance and their novel status, they are explained and demonstrated in detail. We compare these new iterations with a standard method that is complemented by a feature to fit in the current context. A further innovation is the computation of solutions in three-dimensional domains, which are still rare. Special attention is paid to applicability of the 3D simulation tools. The programs are designed to have justifiable working complexity. The simulation results of some models of contemporary semiconductor devices are shown and detailed comments on the results are given. Eventually, we make a prospect on future development and enhancements of the models and of the algorithms that we used.