Doutorado em Engenharia Mecânica

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Navegando Doutorado em Engenharia Mecânica por Autor "Bulcão, André"

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    Estudo de duas técnicas para a solução de problemas dinâmicos utilizando o método dos elementos de contorno: a superposição modal e a transformada de Laplace
    (Universidade Federal do Espírito Santo, 2024-12-20) Santos, Aquila de Jesus dos; Lara, Luciano de Oliveira Castro; Loeffler Neto, Carlos Friedrich; https://orcid.org/0000-0002-5754-6368; Saenz, Juan Sérgio Romero; Campos, Lucas Silveira; Bulcão, André; Albuquerque, Éder Lima de
    The search for a reliable and accurate method to convert domain integrals involving non-self-adjoint operators into boundary integrals, in accordance with the philosophy of the Boundary Element Method, remains a significant challenge. One of the most recent proposals to achieve this goal is the Direct Interpolation Technique of the Boundary Element Method (DIBEM). Already successfully employed in solving scalar problems governed by the Poisson, Helmholtz, and Advection-Diffusion equations, this work presents the results of using DIBEM in the analysis of wave propagation problems in homogeneous media. The main objective is to evaluate the integration of DIBEM with two distinct techniques for handling the time-dependent term: Modal Superposition and the Laplace Transform, two well-established strategies. In the first formulation, a modified modal superposition, which uses a correlated eigenvalue problem associated with the transpose of the dynamic matrix, is applied to decouple the dynamic equations. Time advancement is performed using the Houbolt algorithm, whose fictitious damping eliminates spurious modal contents, producing greater stability. In the second formulation, the Laplace transform is used to eliminate time dependence; DIBEM is used to solve the resulting stationary problem in terms of the transformation variable, and an inversion method is used to return to the time domain. Several typical wave propagation problems were solved using linear boundary elements.
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    O método dos elementos de contorno com interpolação direta aplicado aos problemas escalares de onda em meios homogêneos
    (Universidade Federal do Espírito Santo, 2024-12-16) Santos, Gyslane Aparecida Romano dos; Lara, Luciano de Oliveira Castro ; https://orcid.org/0000-0003-1329-2957; http://lattes.cnpq.br/1675675424615229; Loeffler Neto, Carlos Friedrich; https://orcid.org/0000-0002-5754-6368; http://lattes.cnpq.br/3102733972897061; https://orcid.org/0009-0008-0138-3556; http://lattes.cnpq.br/0314997680090929; Bulcão, André ; https://orcid.org/0000-0002-9871-9683; http://lattes.cnpq.br/2273897370773348; Chacaltana, Julio Tomás Aquije ; https://orcid.org/0000-0003-2488-6232; http://lattes.cnpq.br/9108224414966705; Campos, Lucas Silveira ; https://orcid.org/; http://lattes.cnpq.br/0275751616450131; Mansur, Webe João ; https://orcid.org/0000-0001-6033-9653; http://lattes.cnpq.br/9499429606822923
    The search for a consistent and accurate method for transforming domain integrals composed of non-self-adjoint operators into contour integrals, strictly following the philosophy of the Boundary Element Method, is still a challenge to be overcome. The Direct Interpolation of the Contour Element Method (DIBEM) technique is among the most recent proposals to achieve this goal. After being successful in solving scalar problems governed by the Poisson, Helmholtz and Advection Diffusion equations, this work presents the results of the DIBEM procedure in approaching acoustic wave propagation problems in homogeneous media. The main objective is to achieve greater stability of the discrete model, particularly examining the numerical characteristics of the mass matrix or acoustic inertia, which is generated approximately through a sequence of radial basis functions. Some of the best-known full support radial functions were tested, several matrix conditioning standards were verified, the degrees of positivity of the matrix related to the modal content were evaluated and the minimum time steps achieved with the refinement of the mesh were investigated. contouring and insertion of interpolating internal points. The time advance scheme used was the Houbolt algorithm, whose fictitious damping eliminates spurious modal contents, related to high frequencies, producing greater stability and accuracy. Several typical wave propagation problems in bars and membranes were solved, using linear boundary elements with DIBEM to compare with the analytical solutions of displacement and stresses in several cases