Mestrado em Modelagem e Otimização - PPGMO

URI Permanente para esta coleção

https://repositorio.ufcat.edu.br/handle/tede/40

O Mestrado em Modelagem e Otimização tem um papel essencial no desenvolvimento de novas tecnologias. Atualmente, se faz muito intensamente o uso de modelos matemáticos, simulações avançadas e sofisticados desenvolvimentos computacionais na pesquisa científica em geral.

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Agora exibindo 1 - 8 de 8

Abordagem estocástica de máquinas rotativas utilizando os métodos hipercubo latino e caos polinomial
(Universidade Federal de Goiás, 2017-09-15) Queiroz, Layane Rodrigues de Souza; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Santee, Donald Mark; Cavallini Junior, Aldemir Aparecido
Mechanical systems may suffer with uncertainties that can appear from non-precise data and due the dynamic nature of the problem. Different methods have been used to deal with uncertainty propagation, such as the Latin Hypercube sampling and Polynomial Chaos. Latin hypercube allows to obtain the solution of the random process, from sampling using some probability distribution, over the process domain data. In its turn, the polynomial chaos expansion allows to separate the stochastic components from the deterministic ones of the random solution by using orthogonal polynomials in conformity with the probability distribution of the random variables representing uncertainties. In this work, we apply the Latin hypercube and the polynomial chaos in the quantification of uncertainties. In the beginning some simple mechanical systems were considered, for the purpose to validate the methodology and, then, we studied the effects of uncertainties on a rotor supported by hydrodynamic bearings.
Análise analítica e numérica de vigas casteladas com diferentes padrões geométricos
(Universidade Federal de Goiás, 2018-10-22) Melo, Pedro Henrique Pedrosa de; Silva, Wellington Andrade da; http://buscatextual.cnpq.br/buscatextual/ visualizacv.do?id=K4750483A1; Silva, Wellington Andrade da; Borges, Romes Antonio; Ferreira, Maurício Pina
The present paper deals with the main subjects related to castellated steel beams, initially showing a brief review of the history of emergence and use of the world, highlighting the characteristics that favored the growth of use and the difficulties of its use. The main failure modes are characterized, highlighting the analytical procedures available in the literature to circumvent them, in order to propose a calculation procedure for the design. The proposed procedure is evaluated through the experimental result of four surveys. The work also presents numerical modeling, using Finite Element Method (FEM), for beams available in the technical literature, in order to complement the analysis of beam behavior during loading and to verify the validity of the proposed numerical model, mainly in relation to the analysis criteria adopted in the numerical model, such as von Mises stress distribution, isotropic hardening and tensile stress behavior of the steel using the multilinear graph, also available in the technical literature. The validity allows the proposed beams, with Anglo-Saxon geometry, Litzka and Peiner, to have reliability of analysis of the model, and for the proposed loading the Anglo-Saxon beam obtained greater resistance, mainly due to the small distance between the holes and also the lowest overall width of the aperture. The results of the numerical models, via MEF, showed good precision when compared to the experimental results, showing that MEF is an extremely useful tool for nonlinear analysis, provided the model is properly calibrated. Another important result is the resistance values presented by the proposed analytical procedure, which presents a good approximation to the actual values of the experiment and also the resistance values obtained in the proposed numerical models, and can be adopted for the practical dimensioning of these beams.
Análise de estabilidade em sistemas mecânicos não lineares com vistas a atenuação de vibrações
(Universidade Federal de Goiás, 2016-03-09) Purcina, Alcione Borges; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Lima, Antônio Marcos Gonçalves de; Abud, Celso Vieira
In the last years, there is a growing interest in the study of nonlinear phenomena that because with the modernization of the structures and employment of innovative and more flexible materials, the nonlinearities become more evident. In that sense, this work aims to study the behavior of a mechanical system with two degrees of freedom with non-linear characteristics in primary resonance. The structure consists of the main system connected to a secondary system to act as a Nonlinear Dynamic Vibration Absorber, which partially or fully absorbs the vibrational energy of the system. The numerical solutions of the problem are obtained using the Runge-Kutta methods of 4th order and approximate analytical solutions are obtained using the Multiple Scales Method, and then it turns out how close can be closer to the numerical solutions. Through the mentioned disturbance method, too, it is determined the answers for the ordinary differential equations of the first order, which describe the modulation amplitudes and phases. Thus, the solution in steady state and the stability are studied using the frequency response. Furthermore, the behavior of the main system and the absorber are investigated through numerical simulations, such as responses in the time domain, phase planes and Poincaré map; which show that the system displays periodic movements, quasi-periodic and chaotic.
Avaliação numérica e computacional do efeito de incertezas inerentes a sistemas mecânicos
(Universidade Federal de Goiás, 2016-08-25) Costa, Tatiane Nunes da; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; Cavallini Junior, Aldemir Aparecido; Rabelo, Marcos Napoleão
Most of the time, modern problems of engineering are nonlinear and, may also be subject to certain types of uncertainty that can directly influence in the answers of a particular system. In this sense, the stochastic methods have been thoroughly studied in order to get the best settings for a given project. Out of the stochastic techniques, the Method of Monte Carlo stands out and, especially the Latin Hypercube Sampling (LHS) which is a simpler version of the same. For this type of modeling, the Stochastic Finite Elements Method (SFEM) is becoming more frequently used, given that, an important tool for the discretization of stochastic fields can be given by the Karhunèn-Loève (KL) expansion. In this work, the following three case studies will be used: A discrete system of 2 g.d.l., a continuous system of a coupled beam type both in linear and nonlinear springs and a rotor consisting of axis, bearings and disks. In this sense, the influence of uncertainties in the systems studied will be checked, using for this, the LHS, SFEM and the KL expansion. The stochastic study in question will be used in the construction of the great project for the rotor problem already presented.
Estudo de vibrações induzidas por linhas férreas
(Universidade Federal de Goiás, 2017-03-13) Silva, Gabriel Gomes; Borges, Romes Antônio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; Silva, Alice Rosa da; Silva, Wellington Andrade da
Vibrations in the soil, induced by the passage of trains on railways, can cause countless effects in the areas bordering the railroads. In most problems, resort to simplified models of the system of interaction between rails foundation and trains for predicting responses that meet certain expectations, especially in order to avoid damaging nearby structures and also avoid discomfort of the people residing in areas surrounding the railway lines. Several soil-foundation interaction models have been developed seeking to get the answer to a foundation when subjected to static and dynamic actions, however, this response depends on multiple factors such as the nature and the mechanical characteristics of the terrain, the geometry of the elements involved, the rigidity of the foundation and the nature of his own excitement. Also of great importance in this type of analysis is the use of optimization techniques in order to obtain projects that are more realistic and safe from an engineering point of view. In this paper, was proposed a study of the effect of vibrations on railway lines, where it aims to model a system coupled between foundations and rails, subject to dynamic actions, in order to simulate the displacement in the time domain and in the domain of the frequency, using optimization for the construction of an optimum design that can attenuate the amplitudes of vibration of the system.
Introdução aos métodos de redução de modelos adaptados a sistemas mecânicos com características não lineares
(Universidade Federal de Goiás, 2016-03-11) Gonçalves, Daniel Ferreira; Lima, Antônio Marcos Gonçalves de; http://lattes.cnpq.br/0632660969306570; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Rade., Domingos Alves; Moura Júnior, José dos Reis V. de
Studies focused on modeling and mechanical system behavior prediction are relevant to the avoidance of excessive deflections and structural failures. Most of these systems are discretized by finite element models which are constituted by a large number of degrees of freedom, making it quite expensive computationally. In this context, the application of models reduction methods becomes particularly prominent because it provides a greater saving in time, keeping the solution quality. This work aims to study methods of reducing models applied to nonlinear dynamical systems. Among the methods aimed at reducing models, there is the Guyan method, Improved Reduction System (IRS), Iterative Improved Reduction System (IIRS) System Equivalent Reduction Expansion Process (SEREP), Component Mode Synthesis (CMS) and method of modal projection. In order to verify the efficiency of the models reduction methods when applied to nonlinear systems is presented in this paper a study where the system responses are analyzed by checking the computational cost and quality of the reduced solution of the problem for each of the mentioned methods.
Projeto ótimo de um sistema automotivo utilizando materiais viscoelásticos
(Universidade Federal de Goiás, 2017-03-10) Andrade, Guilherme de Oliveira; Borges, Romes Antonio; http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4737737P7; Diniz, Alberto Carlos Guimarães Castro; Rabelo, Marcos Napoleão; Borges, Romes Antonio
In order to attenuate unwanted vibrations, coming from mechanical systems, are increasing research in developing efficient products in the vibrant energy dissipation, being carried out in this line, full characterization of viscoelastic materials for the identification of its main phenomena and effectiveness check, reliability and security. The non-linear behavior of viscoelastic materials, when subjected to cyclic loading, is due to their microstructural characteristics, where it is possible that an effective vibration attenuation occurs. However, the complexity of the proposed problem suggests the implementation of numerical-computational procedures, the So that the deformation rates can be evaluated through harmonic analysis, so that the temperature variations can be defined and the phenomena associated with the material can be analyzed. With this, based on the dissipative characteristics of the material, the present work aims at the application of the same in the automotive area, being applied on the vehicular structure of utility vehicles aiming at the attenuation of the vibrations that arrive to the passenger compartment. To prove the efficacy of the material, the structural modeling of the viscoelastic was carried out in a computer environment (MatLab®) and then the material was inserted into the vehicle structure in the finite element software (Ansys®), where the structural and modal harmonic analysis , Thus verifying attenuations of the order of 8.746% for the second vibrating mode of the structure. However, due to the safety involved in automotive projects, it was necessary to analyze the computational effectiveness of these materials on the wide range of operational and environmental factors in which utility vehicles are submitted, thus guaranteeing the necessary reliability to the project.
Técnica de redução de modelos improved reduced system enriched aplicada ao estudo do comportamento de sistemas mecânicos não lineares
(Universidade Federal de Goiás, 2016-03-08) Fonseca Júnior, Lázaro Antônio da; Lima, Antônio Marcos Gonçalves de; http://lattes.cnpq.br/0632660969306570; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Borges, Romes Antonio; http://lattes.cnpq.br/3888145024042412; Steffen Junior, Valder; Stoppa, Marcelo Henrique
Currently, the structures are increasingly diverse and complex. In many cases, these structures are model by numerical approximations methods because, due to its complexity, the analytical model does not exist or is not feasible. The finite element method is a numerical approximation methods most used. Thus, the model generated by the finite element method is in most cases considerably too large, and the time taken to perform computer simulations is high. In this context, models reduction methods, it has been studied to meet the need of accurate results while maintaining the dynamic properties of the structure with less processing time. A comparative study of three reduction methods will be presented, the Improved Reduced System (IRS) and the Iterative Improved Reduced System method (IIRS). The third reduction method, it is an enrichment of the IRS method proposed by the author, which provided great improvement in time savings during simulations. This method was called Improved Reduced System Enriched (IRSE). Such reduction methods were applied in non-linear systems with non-localized linear and geometric nonlinearity due to large displacements. Keywords: Finite element method, nonlinear modeling, not linearity located and geometric, reduced models.

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