Mestrado em Engenharia de Produção

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https://repositorio.ufcat.edu.br/handle/tede/84

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Navegando Mestrado em Engenharia de Produção por Autor "Duarte, Carlos Antônio Ribeiro"

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    Uma abordagem não linear ao estudo de modelos de deformação via elementos finitos para viga 2d de concreto protendido com cordoalha aderente
    (Universidade Federal de Goiás, 2020-12-16) Silva, Werley Rafael da; Rabelo, Marcos Napoleão; http://lattes.cnpq.br/0067281135180613; Rabelo, Marcos Napoleão; Silva, Wellington Andrade da; Duarte, Carlos Antônio Ribeiro
    The purpose of this work is to develop the nonlinear analysis of prestressed beams and obtain their load/displacement curves, the formulation of a finite element of the bar type will be presented for non-linear physical and geometric analysis based on the method of forces. Geometric nonlinearity is considered using the Euler-Bernoulli beam strain theory, with simplification for moderate rotations. In physical non-linearity, non-linear stress / strain relationships provided by the models constituting the materials are allowed. The contribution to concrete in compression uses the model developed by Hognestad (1951), and when subjected to traction the model developed by Bergan and Holand (1973), for the steel of active reinforcement, the model developed by Menegotto and Pinto (1973) and for the passive reinforcement the bi-linear model with perfect elastoplastic behavior is considered. In the coupling between the constituent materials of the structure, perfect adherence between its elements is considered, that is, there is no relative movement between them. The problem is formulated through the balance of nodal forces. For this, the forces and moments are calculated as a function of the stress/strain relationship. To solve the equations, the finite element method is employed. The methodology presented here proposes to achieve the balance of forces directly at the nodal points of the structure using differential equations instead of integral equations. The concept of generalized forces and moments at nodal points is introduced. Finally, numerical simulations are used to compare the results obtained with experimental results. The novelty in the present work resides in the fact that the modeling is done through the coupling between three elements, namely: the displacement of the concrete, the prestressing strand and passive reinforcement. It is also observed that prestressing is responsible for applying axial and shear forces; while the passive reinforcement only contributes to axial displacement. The incorporation of axial displacements is necessary, since the prestressing force is considered to be external, causing, in addition to axial forces, moment reactions due to the eccentricity between the position of the strand and the neutral line of the structure. Using appropriates theory of strain to, concrete, prestressing and reinforcement steel the stiffness matrix is obtained.
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    Avaliação de aspectos operacionais do processo de soldagem TIG-MIG/MAG
    (Universidade Federal de Goiás, 2019-03-12) Azevedo, Sarah Cristina; Resende, André Alves de; http://lattes.cnpq.br/3492793149542286; Resende, André Alves de; Duarte, Carlos Antônio Ribeiro; Reis, Ruham Pablo
    In the search for productivity gains and cost reduction, the optimization of welding processes has been presented as an opportunity for the industries of the metal-mechanic sector. In this context, the so-called "Hybrid Welding Processes", in which two or more conventional processes are combined, have gained prominence. Among these, TIG-MIG / MAG has shown itself to be an alternative, mainly because it associates processes already traditionally known and used in the market. Thus, the general objective of the present work is to analyze the influence of the TIG-MIG / MAG process variables on the weld bead geometry obtained. For this purpose, welds of simple deposition on sheet were performed, varying the TIG current, the TIG torch angle, the MIG / MAG torch angle and the distance between the electrodes. Then, tests were performed by varying the current circuit of the TIG and MIG / MAG process. As main results, for the set of evaluated parameters, it was verified that it is possible to act on the weld bead geometry, varying the positioning parameters and the TIG and MIG / MAG current. Greater melt and penetration area achieved with TIG torch angle and MIG / MAG torch angle, maximum values and the distance between the electrodes in the minimum value. Inserting the current into the TIG circuit contributes to a greater melt area and greater penetration. A greater width is obtained by using the TIG torch angle and the MIG / MAG torch angle in the minimum values and the distance between electrodes, in the maximum values, in this sense, the insertion of the current in the TIG circuit increases the width. The greatest reinforcement is obtained by using the TIG torch angle and the MIG / MAG torch angle at the maximum values and the minimum electrode distance. Already when the current is inserted in the TIG circuit, there is a decrease in the values of the reinforcement. Finally, a greater angle of convexity was achieved by using the torch angles at the maximum values, and with the insertion of the current in the TIG circuit, there was a decrease in the convexity angle values.