EE - Escola de Engenharia
URI permanente desta comunidadehttps://rihomolog.furg.br/handle/1/512
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6 resultados
Resultados da Pesquisa
- ItemNumerical simulation and constructal theory applied for geometric optimization of thin perforated plates subject to elastic buckling(2013) Correia, Anderson Luis Garcia; Helbig, Daniel; Real, Mauro de Vasconcellos; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréMany elements in engineering are formed by thin plates. Hulls and decks of ships are examples of application. These elements can have holes that serve as inspection port, access or even to weight reduction. The presence of holes causes a redistribution of the membrane stresses in the plate, significantly altering their stability. In this paper the Bejan’s Constructal Theory was employed to discover the best geometry of thin perforated plates submitted to elastic buckling phenomenon. To study this behavior simply supported rectangular plates with a centered elliptical perforation were analyzed. The purpose was to obtain the optimal geometry which maximizes the critical buckling load. For this, the degrees of freedom H/L (ratio between width and length of the plate) and H0/L0 (ratio between the characteristic dimensions of the hole) were varied. Moreover, different values of hole volume fraction ϕ (ratio between the perforation volume and the massive plate volume) were also investigated. A computational modeling, based on the Finite Element Method (FEM), was used for assessing the plate buckling load. The results showed that Constructal Design can be employed not only in the heat transfer and fluid flow problems, but also to define the best shapes in solid mechanics problems.
- ItemConstructal design of perforated steel plates subject to linear elastic and nonlinear elastoplastic buckling(2013) Helbig, Daniel; Real, Mauro de Vasconcellos; Correia, Anderson Luis Garcia; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréSteel plates are used in a great variety of engineering applications, such as deck and bottom of ship structures, and platforms of offshore structures. Cutouts are often provided in plate elements for inspection, maintenance, and service purposes. So, the design of shape and size of these holes is significant. Usually these plates are subjected to axial compressive forces which make them prone to instability or buckling. If the plate is slender, the buckling is elastic. However, if the plate is sturdy, it buckles in the plastic range causing the so-called inelastic (or elasto-plastic) buckling.Therefore, the goal of this work is to obtain the optimal geometry which maximizes the buckling load for steel plates with a centered elliptical perforation when subjected to linear and nonlinear buckling phenomenon by means of Constructal Design. To do so, numerical models were developed in ANSYS software to evaluate the elastic and elasto-plastic buckling loads of simply supported and uniaxially loaded rectangular plates with elliptical cutouts. The results indicated that the optimal shapes were obtained in accordance with the Constructal Principle of "Optimal Distribution of Imperfections", showing that the Constructal Design method can be satisfactorily employed in mechanic of materials problems.
- ItemOtimização geométrica de placas com enrijecedores submetidas à flexão(2012) Silveira, Thiago da; Correia, Anderson Luis Garcia; Silva, Caio César de Castro da; Rocha, Luiz Alberto de Oliveira; Real, Mauro de Vasconcellos; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréAs placas enrijecidas são muito utilizadas em estruturas navais. Quando estas estruturas estão sob forte ação de cargas de flexão, é necessário que os reforços contribuam para a redução da deflexão da placa. O Método de Elementos Finitos (MEF) pode ser utilizado para obter os valores da deflexão resultante de cargas de flexão sobre a placa. Para otimizar a geometria da placa enrijecida faz-se uso da Teoria Constructal desenvolvida por Adrian Bejan. Com as geometrias otimizadas, é possível a obtenção de deflexões que apresentam melhoria de aproximadamente 84% em relação às placas sem enrijecedores.
- ItemGeometric optimization based on the constructal design of perforated thin plates subject to buckling(2012) Rocha, Luiz Alberto Oliveira; Real, Mauro de Vasconcellos; Correia, Anderson Luis Garcia; Vaz, Joaquim; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréElastic buckling is an instability phenomenon that can occur if a slender and thin-walled plate is subjected to axial compressive load. It is well known that the presence of holes in structural plate elements is almost inevitable in inspection, maintenance, and service purposes, or to reduce the structural weight. In this paper constructal design was employed to optimize the geometry of thin perforated plates submitted to elastic buckling. Simply supported rectangular perforated plates were analyzed with three different shapes of centered holes: elliptical, rectangular, and diamond. The purpose was to obtain the optimal geometry that maximizes the critical buckling load. The ratio between the height and length of the plate was kept constant, while the ratio between the characteristic dimensions of the holes was optimized for several hole volume fractions (φ). A finite-element model was used to assess the plate buckling load, and the Lanczos method was applied to the solution of the corresponding eigenvalue problem. When φ ≤ 0.20 the optimum geometry is the diamond hole, reaching maximum buckling loads around 80.0,21.5, and 17.4% higher than a plate without perforation and plates with elliptical and rectangular holes, respectively. For intermediate and higher values of φ, the elliptical and rectangular holes, respectively, led to the best performance. The optimal shapes were obtained according to the constructal principle of minimization of distribution of imperfections, showing that the constructal design also can be employed to define the optimized geometries in the mechanics of material problems.
- ItemConstructal design applied to the elastic buckling of thin plates with holes(2013) Rocha, Luiz Alberto Oliveira; Isoldi, Liércio André; Real, Mauro de Vasconcellos; Santos, Elizaldo Domingues dos; Correia, Anderson Luis Garcia; Lorenzini, Giulio; Biserni, CesareElastic buckling is an instability phenomenon that can occur if a slender and thin plate is subjected to axial compression. An important characteristic of the buckling is that the instability may occur at a stress level that is substantially lower than the material yield strength. Besides, the presence of holes in structural plate elements is common. However these perforations cause a redistribution in plate membrane stresses, significantly altering their stability. In this paper the Bejan’s Constructal Design was employed to optimize the geometry of simply supported, rectangular, thin perforated plates subjected to the elastic buckling. Three different centered hole shapes were considered: elliptical, rectangular and diamond. The objective function was to maximize the critical buckling load. The degree of freedom H/L (ratio between width and length of the plate) was kept constant, while H0/L0 (ratio between the characteristic dimensions of the holes) was optimized for several hole volume fractions (φ). A numerical model employing the Lanczos method and based on the finite element method was used. The results showed that, for lower values of φ the optimum geometry is the diamond hole. For intermediate and higher values of φ, the elliptical and rectangular hole, respectively, led to the best performance.
- ItemConstructal design aplicado a placas com furos elípticos sob flambagem.(2013) Correia, Anderson Luis Garcia; Silveira, Thiago da; Silva, Caio César de Castro da; Rocha, Luiz Alberto Oliveira; Real, Mauro de Vasconcellos; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréPlacas são elementos amplamente empregados na engenharia estrutural. Em muitas situações é necessária a existência de perfurações nestas placas. Sabe-se ainda que elementos estruturais esbeltos submetidos a cargas de compressão axial podem falhar de maneira súbita, com uma tensão inferior à tensão de escoamento do material, devido a um fenômeno de instabilidade conhecido como flambagem. Nesse artigo, a Teoria Constructal será utilizada para otimizar geometricamente placas finas perfuradas, submetidas a compressão uniaxial, tendo como objetivo obter a dimensão ótima do furo que maximize a carga crítica de flambagem. Para isso diversas simulações numéricas foram realizadas, utilizando um modelo computacional baseado no Método dos Elementos Finitos (MEF). Observou-se que para todos os valores de Ø (relação entre o volume do furo e o volume da placa) analisados, a placa que apresenta melhor desempenho sob compressão uniaxial é a que possui a maior relação H/L (relação entre a altura e o comprimento da placa). No que diz respeito à análise individual de cada placa, a que obteve o maior acréscimo percentual no valor de carga crítica de flambagem em relação a uma placa sem furo foi a placa 1 (H/L = 1.00), chegando a 198.98%. A placa que apresentou o menor acréscimo percentual foi a placa 4 (H/L = 0.25), com 7.72%. Ao realizar uma comparação global entre as placas, a que obteve o melhor desempenho foi a placa 1 (H/L = 1.00), apresentando uma carga crítica máxima de flambagem 176.85% maior que a carga crítica máxima na placa de pior desempenho, placa 4 (H/L = 0.25).