Navegando por Autor "Telles, José Cláudio de Faria"

Agora exibindo 1 - 4 de 4

Análise via Método dos Elementos de Contorno (MEC) de elementos estruturais compósitos de seções genéricas e rigidez variável submetidos a torção não uniforme.
(2022) Hillesheim, Maicon José; Araújo, Francisco Célio de; Araújo, Francisco Célio de; Neves, Francisco de Assis das; Silva, Amilton Rodrigues da; Telles, José Cláudio de Faria; Wrobel, Luiz Carlos
Algoritmos capazes de simular com exatidão o comportamento de estruturas de materiais compósitos demandam grande esforço computacional, sobretudo em casos de sólidos tridimensionais com geometrias complexas. Nesse contexto, este trabalho se propõe a desenvolver um elemento finito unidimensional, fundamentado em teoria de vigas, capaz de reconstituir a resposta de sólido 3D para barras de seção heterogênea e variável submetidas a torção não uniforme. Nessa abordagem, dois modos de empenamento são considerados, o primeiro descrito pela equação diferencial de Laplace o segundo, pela equação de Poisson, as quais são resolvidas através de uma formulação bidimensional do MEC. Ao longo do comprimento, o problema é descrito por um sistema de equações diferenciais ordinárias cujas variáveis independentes são as parcelas primária e secundária do ângulo de torção. Nesta pesquisa, essas equações são solucionadas de maneira inédita através do Método dos Resíduos Ponderados (MRP). Em formulações do MEC, a heterogeneidade da seção transversal demanda o emprego de uma estratégia de decomposição de domínio. Para isso emprega-se uma técnica de subestruturação genérica de modelos de elementos de contorno (BE-SBS), que possibilita trabalhar com um número qualquer de subdomínios. Um aspecto relevante dessa técnica é o uso de solvers de Krylov, que possibilitam eliminar operações com grandes blocos de zeros, ocasionando grande otimização dos recursos computacionais. Além disso, a técnica conta com elementos descontínuos e algoritmos especiais de integração, viabilizando de forma unificada o tratamento de seções envolvendo domínios esbeltos ou espessos. Diversos exemplos são apresentados para demonstrar a acurácia, eficiência e robustez das formulações desenvolvidas.
Application of a generic domain-decomposition strategy to solve shell-like problems through 3D BE models.
(2007) Araújo, Francisco Célio de; Silva, Kátia Inácio da; Telles, José Cláudio de Faria
Efficient integration algorithms and solvers specially devised for boundary-element procedures have been established over the last two decades. A good deal of quadrature techniques for singular and quasisingular boundary-element integrals have been developed and reliable Krylov solvers have proven to be advantageous when compared to direct ones, also in case of non-Hermitian matrices. The former has implied in CPU-time reduction during the assembling of the system of equations and the latter in its faster solution. Here, a triangular polar co-ordinate transformation and the Telles co-ordinate transformation are employed separately and combined to develop the matrix-assembly routines (integration routines). In addition, the Jacobi-preconditioned Biconjugate Gradient solver (J-BiCG) is used along with a generic substructuring boundary element algorithm. Thus, solution CPU time and computer memory can be considerably reduced. Discontinuous boundary elements are also included to simplify the coupling of the BE models (substructures). Numerical experiments involving 3D thin-walled domains (shell-like structural elements) are carried out to show the performance of the computer code with respect to accuracy and efficiency of the system solution. Precision, CPU-time and potential applications of the BE code developed are commented upon.
Generic domain decomposition and iterative solvers for 3D BEM problems.
(2006) Araújo, Francisco Célio de; Silva, Kátia Inácio da; Telles, José Cláudio de Faria
In the past two decades, considerable improvements concerning integration algorithms and solvers involved in boundary-element formulations have been obtained. First, a great deal of efficient techniques for evaluating singular and quasi-singular boundary-element integrals have been, definitely, established, and second, iterative Krylov solvers have proven to be advantageous when compared to direct ones also including non-Hermitian matrices. The former fact has implied in CPU-time reduction during the assembling of the system of equations and the latter fact in its faster solution. In this paper, a triangle-polar-co-ordinate transformation and the Telles co-ordinate transformation, applied in previous works independently for evaluating singular and quasi-singular integrals, are combined to increase the efficiency of the integration algorithms, and so, to improve the performance of the matrixassembly routines. In addition, the Jacobi-preconditioned biconjugate gradient (J-BiCG) solver is used to develop a generic substructuring boundary-element algorithm. In this way, it is not only the system solution accelerated but also the computer memory optimized. Discontinuous boundary elements are implemented to simplify the coupling algorithm for a generic number of subregions. Several numerical experiments are carried out to show the performance of the computer code with regard to matrix assembly and the system solving. In the discussion of results, expressed in terms of accuracy and CPU time, advantages and potential applications of the BE code developed are highlighted.
Nonuniform torsion analysis in tapered composite bars by including higher-order warping modes.
(2022) Araújo, Francisco Célio de; Hillesheim, Maicon José; Renostro, Gabriel Viecelli; Telles, José Cláudio de Faria
This paper presents a generalized formulation to describe nonuniform torsion in composite bars with variable cross section including higher-order warping modes. In that, the boundary-element subregion-by-subregion (BE SBS) technique is applied to determine the warping modes for cross sections constituted of any number of different materials. The distribution of the nonuniform warping along the axis is taken into account by multiplying the warping modes by derivatives of the associated twist angle functions. A new process based on the weighted residual method is proposed to solve the resulting global equilibrium equations. One also makes generic comments on the solution of the local coupled boundary-value problems (BVPs), which encompasses preconditioned Krylov solvers (embedded in the BE SBS technique), discontinuous boundary elements, and efficient (low-order) quadratures for singular and nearly-singular integrals. Efficiency and robustness of the technique are verified by comparing the present results with highly accurate 3D responses.