O emprego das estruturas de membrana é cada dia mais frequente em edificações de relevância civil e arquitetônica, em especial para a cobertura de grandes vãos. Sua aplicabilidade, contudo, vai além da construção civil, sendo igualmente importante nas indústrias das engenharias mecânica, naval, oceânica, aeroespacial e biomédica: aeronaves, satélites, paraquedas, airbags, velas de embarcações, moinhos de vento e até aplicações biomecânicas com tecidos humanos ou artificiais utilizam a tecnologia das estruturas de membrana. O comportamento mecânico de grande parte das membranas estruturais pode ser idealizado como uma casca isótropa de pequena espessura reforçada por uma membrana ortótropa. O objetivo desta pesquisa de mestrado é dar continuidade aos estudos referentes às teorias de casca geometricamente exatas desenvolvidas por [1], [2], [3] e [4], e sua generalização para o âmbito das membranas iniciada em [5]. Pretende-se contribuir, principalmente, para o desenvolvimento de equações constitutivas ortótropas consistentes para grandes deformações, apresentar uma metodologia para calibração dos parâmetros materiais destas equações constitutivas e para a análise de estabilidade com vistas ao estudo do fenômeno do enrugamento. / The use of membrane structures is becoming increasingly common in buildings of architectural and civil engineering importance, especially to cover large spans. Its applicability, however, goes beyond the construction industry being equally important in the industries of mechanical, naval, ocean, aerospace and biomedical engineering: aircraft, satellites, parachutes, airbags, sails of boats, windmills and even biomechanical applications with human and artificial tissues use the technology of membrane structures. The mechanical behavior of most structural membranes can be idealized as an isotropic thin shell reinforced by an orthotropic membrane. The objective of this work is to continue the studies on the geometrically exact shell theories developed by [1], [2] , [3] and [4] and its generalization to the scope of the membranes initially studied by [5]. It aims intended to contribute mainly to the development of consistent orthotropic constitutive equations for large deformations, to present a methodology for the calibration of the material parameters in those constitutive relations and for the stability analysis in order to study the phenomenon of wrinkling.

Orientador: Leandro Palermo Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-25T11:44:30Z (GMT). No. of bitstreams: 1 Reis_LuizAntonio_M.pdf: 3239468 bytes, checksum: 6e32be621db949f69c865def857a4bc9 (MD5) Previous issue date: 2014 / Resumo: O presente trabalho está divido em quatro partes. Na primeira parte, utilizando o método dos elementos de contorno (MEC), se fez a análise de problemas bidimensionais com aproximação linear. Foi considerada a possibilidade de se aplicar a técnica de sub-regiões para se levar em conta a diversidade de materiais, bem como a suavização do contorno por mínimos quadrados para evitar a possíveis perturbações. Foi considerado a possibilidade de colocação de uma linha de carga no domínio. Na segunda parte, utilizando o método dos elementos finitos (MEF), se fez a análise linear de pórticos planos. Para este estudo foram utilizadas barras com dois nós e esses com três graus de liberdade. Na terceira parte, a análise elástica linear de meios contínuos (Estado Plano de Tensão Generalizado) enrijecidos com elementos lineares (barras) é estudada fazendo-se um acoplamento entre elementos modelados com o MEC e com o MEF. As fibras são modeladas pelo MEF com elementos lineares de três graus de liberdade por nó e quatro nós por barra. Os elementos planos são modelados pelo MEC com elementos isoparamétricos lineares no perímetro. É permitido o uso de sub-regiões com objetivo de generalizar o tratamento do meio elástico. Na quarta parte, utilizando o acoplamento MEF/MEF, se fez a análise linear de pórticos planos sobre base elástica. O acoplamento se dá entre as barras do pórtico e as barras introduzidas como enriquecedor no problema elástico bidimensional. Tendo em conta estes aspectos da formulação desenvolvida, alguns exemplos são apresentados para avaliação de seu desempenho nos problemas de engenharia / Abstract: This paper is divided into four parts . In the first part , using the boundary element method (BEM) , we did the analysis of two-dimensional problems with linear approximation . We considered the possibility of applying the technique of sub - regions to take into account different materials, as well as smoothing the contour by least squares to avoid possible disturbances . We considered the possibility of placing a load line in the field. In the second part, the linear analysis for plane frames was carried out with the finite element method (FEM). Bars with two nodes and three degrees of freedom were used in this study . In the third part, the linear elastic analysis of continuous media (Generalized Plane Stress problems) stiffened with one-dimensional elements (bars) is studied through between elements of the BEM and the FEM. The fibers are modeled by FEM with three degrees of freedom linear elements and using four-nodes. The plane domain is modeled with the BEM and using isoparametric elements. The use of sub - regions in order to generalize the treatment of the elastic medium is allowed. In the fourth part , using the FEM / FEM coupling , a linear analysis of plane frames on elastic foundation is carried out. Some examples are presented to evaluate the formulation behavior engineering problems / Mestrado / Estruturas / Mestre em Engenharia Civil

The numerical solution of the convection-diffusion-reaction problem is considered in two and three dimensions. A stabilized finite element method of Galerkin/Least squares type accomodates diffusion-dominated as well as convection- and/or reaction- dominated situations. The resolution of boundary layers occuring in the singularly perturbed case is accomplished using anisotropic mesh refinement in boundary layer regions. In this paper, the standard analysis of the stabilized Galerkin method on isotropic meshes is extended to more general meshes with boundary layer refinement. Simplicial Lagrangian elements of arbitrary order are used.

Orientador: Renato Pavanello / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-28T11:58:24Z (GMT). No. of bitstreams: 1 Calixto_TainanKhalilLeite_M.pdf: 15775150 bytes, checksum: e5e4d45becc32f922a1fd31b8f9bd3ab (MD5) Previous issue date: 2015 / Resumo: A utilização de materiais de alta performance se tornou uma realidade em diversos campos da engenharia, como na indústria automotiva e aeroespacial, devido aos avanços nas técnicas de manufatura aditiva. Por outro lado, sabe-se que a otimização topológica estrutural é uma ferramenta de desenvolvimento de estruturas com ampla aplicação industrial. Dentre os vários métodos de otimização topológica existentes, a otimização estrutural evolucionária tem se destacado pela sua versatilidade, podendo ser utilizada em diversos tipos de problemas de engenharia. Na tentativa de combinar esses campos, este trabalho consiste no estudo do método de otimização evolucionária BESO (Bi-directional Evolutionary Structural Optimization) aplicado a sistemas bidimensionais multiescala a fim de se projetar as topologias ótimas, em ambas as escalas, de uma estrutura. A análise do modelo multiescala é feita através do método da homogeneização, onde o padrão do material microestrutural é considerado periódico. O algoritmo implementado pode buscar dois objetivos distintos: a minimização da flexibilidade média, que resulta na maximização da rigidez global; ou a maximização da frequência fundamental. Resultados numéricos do algoritmo são apresentados para o projeto de materiais, onde apenas a microestrutura é otimizada, e de estruturas, na qual otimiza-se as topologias nas duas escalas. Para a análise do desempenho do método de otimização multiescala, são propostos um índice de eficiência estrutural e uma metodologia de fabricação de estruturas periódicas / Abstract: High-performance materials utilization became a reality in many fields of actual engineering, such as in automotive and aerospace industries, due to advances in additive manufacturing techniques. In the other hand, structural topology optimization is a powerful tool for the structure development with wide industrial application. Among the various optimization methods, evolutionary structural optimization stands out for its versatility and it can be used in many engineering problems. As an attempt to combine these fields, this work intends to study the Bi-directional evolutionary Structural Optimization method applied to two-dimensional multi-scale systems in order to design the optimal topologies of structures in both scales. The analysis of multi-scale model is made using the homogenization method, where the pattern of the micro-structural material is considered periodic. The implemented algorithm can use two different objective function: mean compliance minimization, which results in maximizing the global stiffness; or fundamental frequency maximization. Numerical results are presented for material design, where only the micro structure is optimized, and for structural design, in which the topologies in both scales are optimized. Deepening the study in multiscale optimization, it is proposed an index to analyse the structural efficiency and also a manufacturing methodology of periodic structures / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

The thesis builds on the project FSI-S-14-2394, in which the biaxial state of tension of longitudinally welded tubes made from material 17 240 was investigated. The experiment was carried out under dynamic conditions on an impact tester, which was designed with structural simplicity and ease of observation of the experiment in mind. Deformation was recorded by high-speed cameras and a dynamometer. Results of the experiment were processed by measuring devices and subsequently used in a simulation created using a software utilizing the finite element method. Simulations were created for samples DA8 and DB9. These samples were selected because they did not crack and were fully stamped. Results of the simulation correspond to the values measured by high-speed cameras and a dynamometer with a small variance. Based on comparison of the results, it can be states that the simulation is technically acceptable.

A heliostat is a device that reflects the sun’s rays to a stationary object. There are two different types of heliostat serial and parallel type. The most used is the serial type of heliostat with Azimuthal-Elevation(Az-El) drive. The parallel heliostat includes two or more actuators to accommodate for the movement, one such design is heliostat with Hydraulic Infinite Linear Actuator (HILA). In this design, the mirror assembly is supported by two HILA’s and a universal joint. The mirror thus has three support points making it a parallel heliostat. This thesis work includes setting up the geometry of the new concept for160 m2reflector area and formulating kinematics and optics equations for calculating the lengths of the actuators and rotations at the universal joint. For structural analysis, the application of wind loads on the structure in the form of pressure is calculated and the structure is designed to satisfy the deflection requirements of 2 mRads at a maximum allowable wind speed of 22 m/s. The symmetric structure is modelled and checked for deflection requirements in Ansys Workbench. The reaction forces are calculated which are then used for topology optimization of the base structure, which is performed Trinitas. When there is an established design for the heliostat with HILA benchmarking is done by designing a scaled-down model for 25 m2 and comparing it with pre-existing results for Az-El type heliostats in literature.

No description available.

We computationally explore the dynamics of superconductivity near the superheating field in two ways. First, we use a finite element method to solve the time-dependent Ginzburg-Landau equations of superconductivity. We present a novel way to evaluate the superheating field Hsh and the critical mode that leads to vortex nucleation using saddle-node bifurcation theory. We simulate how surface roughness, grain boundaries, and islands of deficient Sn change those results in 2 and 3 spatial dimensions. We study how AC magnetic fields and heat waves impact vortex movement. Second, we use automatic differentiation to abstract away the details of deriving the equations of motion and stability for Ginzburg-Landau and Eilenberger theory. We present calculations of Hsh and the critical wavenumber using linear stability analysis.

The work in this thesis focuses on the use of explicit finite element analysis (FEA) in the modelling of fluid-structure interaction of panel-water impacts. Paper A, considers modelling of a two-dimensional rigid wedge impacting a calm water surface. From analytical methods and results of a systematic parameter study a generalised approach for determination of fluid discretization and contact parameters in the modelling of arbitrary hull-water impact situations is developed and presented. In paper B the finite element modelling methodology suggested in paper A is evaluated for elastic structures by a convergence study of structural response and hydrodynamic load. The structural hydroelastic response is systematically studied by a number of FE-simulations of different impact situations concerning panel deadrise, impact velocity and boundary conditions. In paper B a tentative method for dynamic characterization is also derived. The results are compared with other published results concerning hydroelasticity in panel water impacts. The long-term goal of this work is to develop design criteria, by which it can be determined whether the loading situation of a certain vessel type should be regarded as quasi-static or dynamic, and which consequence on the design a dynamic loading has. / QC 20101126

The Flex Representation Method (FRM) leverages unique computational advantages of splines to address limitations in the process of building CAE simulation models from CAD geometric models. Central to the approach is the envelope CAD domain that encapsulates a CAD model. An envelope CAD domain can be of arbitrary topological and geometric complexity. Envelope domains are constructed from spline representations, like U-splines, that are analysis-suitable. The envelope CAD domain can be used to approximate none, some, or all of the features in a CAD model. This yields additional simulation modeling options that simplify the model-building process while leveraging the properties of splines to control the accuracy and robustness of computed solutions. Modern integration techniques are adapted to envelope domains to maintain accurate solutions regardless of the CAD envelope chosen. The potential of the method is illustrated through several carefully selected benchmark problems.