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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Otimiza??o Topol?gica com Termo-elasticidade Utilizando Elementos Tri3

Silva, Paulo S?rgio Ramos da 28 September 2007 (has links)
Made available in DSpace on 2014-12-17T14:57:44Z (GMT). No. of bitstreams: 1 PauloSRS.pdf: 2327143 bytes, checksum: d0c547e333b52ab17a25cc8e23e265c2 (MD5) Previous issue date: 2007-09-28 / This work proposes a formulation for optimization of 2D-structure layouts submitted to mechanic and thermal shipments and applied an h-adaptive filter process which conduced to computational low spend and high definition structural layouts. The main goal of the formulation is to minimize the structure mass submitted to an effective state of stress of von Mises, with stability and lateral restriction variants. A criterion of global measurement was used for intents a parametric condition of stress fields. To avoid singularity problems was considerate a release on the stress restriction. On the optimization was used a material approach where the homogenized constructive equation was function of the material relative density. The intermediary density effective properties were represented for a SIMP-type artificial model. The problem was simplified by use of the method of finite elements of Galerkin using triangles with linear Lagrangian basis. On the solution of the optimization problem, was applied the augmented Lagrangian Method, that consists on minimum problem sequence solution with box-type restrictions, resolved by a 2nd orderprojection method which uses the method of the quasi-Newton without memory, during the problem process solution. This process reduces computational expends showing be more effective and solid. The results materialize more refined layouts with accurate topologic and shape of structure definitions. On the other hand formulation of mass minimization with global stress criterion provides to modeling ready structural layouts, with violation of the criterion of homogeneous distributed stress / Este trabalho ? uma combina??o dos trabalhos de Costa Jr. & Alves (2002) e Cho & Choi (2005), em que prop?e uma formula??o para otimiza??o de leiautes estruturais bidimensionais, submetidos aos carregamentos t?rmicos e mec?nicos. Ainda sob a formula??o, ser? aplicado um processo de refino do tipo h-adaptativo, de maneira a obter leiautes estruturais de alta defini??o e com baixo custo computacional. A id?ia b?sica da formula??o de ?timo do problema ? minimizar a massa da estrutura sujeita a um efetivo estado de tens?o de von Mises, com restri??es laterais e de estabilidade nas vari?veis de projeto. Um crit?rio de medida global ? utilizado para atender a condi??o param?trica do campo de tens?es. Para contornar o problema de singularidade, considera-se uma relaxa??o na restri??o de tens?o. Na otimiza??o ? utilizada uma abordagem material, onde a equa??o constitutiva homogeneizada ? fun??o apenas da densidade relativa do material. As propriedades efetivas das densidades intermedi?rias s?o representadas por um modelo artificial do tipo SIMP. O problema ? aproximado com a aplica??o do M?todo dos Elementos Finitos de Galerkin, utilizando elementos finitos triangulares de base Lagrangiana linear. Na solu??o do problema de otimiza??o, ser? aplicado o M?todo do Lagrangiano Aumentado, que consiste na solu??o de uma seq??ncia de problemas de m?nimo com restri??es do tipo caixa, o qual ? resolvido por um m?todo de proje??o de segunda ordem que usa o m?todo de quasi-Newton sem mem?ria, durante o processo de solu??o do problema. A abordagem reduz consideravelmente o custo computacional, mostrando ser muito efetiva e robusta. Os resultados proporcionaram leiautes refinados com n?tida defini??o da topologia e da forma da estrutura. Al?m disso, a formula??o de minimiza??o da massa com crit?rio global de tens?o, proporcionou leiautes estruturais prontos para a manufatura, com viola??o do crit?rio de tens?o distribu?da de maneira homog?nea

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