O presente trabalho tem por objetivo a avaliação das características aeroelásticas referentes a flutter de uma aeronave militar de treinamento em sua fase inicial de projeto. Para a execução da análise ée elaborado um modelo aeroelástico da aeronave, composto de dois modelos distintos: um em elementos finitos representativo das características dinâmicas da aeronave e um modelo aerodinâmico não-estacionário baseado na teoria Doublet Lattice. Correções para ajuste do comportamento aerodinâmico estacionário do modelo são feitas com base em resultados obtidos junto ao grupo de aerodinâmica do Projeto Treinador Avançado. A ocorrência do fenômeno de flutter colocará restrições ao projeto. Os detalhes do modelamento dinâmico e aerodinâmico, bem como ajuste aerodinâmico adotado, são também apresentados. O software utilizado na solução dos problemas dinâmico e aeroelástico ée o MSC.Nastran V.70.7. Um estudo paramétrico ée realizado para analisar o comportamento do modelo aeroelástico após alteração de parâmetros relacionados com as superfícies de controle (canard, aileron, leme e empenagem horizontal). Os resultados são apresentados em forma gráfica através dos gráficos V-g-f que mostram a tendência do comportamento do amortecimento e freqüência de cada modo com a variação da velocidade do escoamento.

O crescente interesse do Exército Brasileiro no desenvolvimento de veículos aéreos não tripulados (VANT) é a motivação para a redação de uma proposta de requisitos técnicos que atendam às necessidades da Força Terrestre, para o estudo de projetos aeronáuticos de VANTs e para a análise de estruturas de material composto, enfatizando painéis sanduíche com núcleo de honeycomb NOMEX. Este trabalho apresenta o projeto preliminar da asa de uma aeronave não tripulada de reconhecimento tático, tendo como base as metodologias aplicadas para aviões tripulados, porém adaptadas aos dados de veículos aéreos não tripulados. Além disso, são apresentados modos de obtenção das propriedades mecânicas de honeycombs, traçando-se comparações entre os métodos, identificando a melhor opção para cada constante elástica. Finalmente, propõe-se duas maneiras de realizar a análise estrutural, pelo método de elementos finitos, de estruturas aeronáuticas composta por sanduíches de fibra de vidro como face e honeycomb como núcleo. A fim de comparar resultados teóricos com os obtidos experimentalmente, realizou-se ensaios em uma empenagem horizontal do alvo aéreo Harpia, construído com o mesmo tipo de estrutura. Buscou-se com este trabalho o aprofundamento do conhecimento de análise de estruturas de material composto empregando tanto desenvolvimentos analíticos, como o método de elementos finitos, permitindo aplicá-los em futuros projetos de engenharia a serem desenvolvidos pelo Exército Brasileiro.

The acoustic environment generated during launch is the most demanding structural load case for large, lightweight satellite reflector antennas. The reflector is exposed to extremely high sound pressure levels originating from the structural excitation of the rocket engines and exterior air flow turbulence. This thesis aims to predict the structural responses in the reflector due to the acoustic pressure load with a model based on Finite Element Modelling (FEM). The FE-model is validated against a previously performed Boundary Element Method (BEM) analysis. An approach called Split Loading together with a combination of BEM and FEM will be utilized to handle the surrounding air mass and the applied sound pressures. The idea of Split Loading is to divide the structure into several patches and apply a unit pressure load to each patch separately. In the last step the unit pressure is scaled and correlated by a power spectral density calculated from the acoustic pressures. Split Loading will be implemented in software packages MSC.NASTRAN/PATRAN. The model developed in this thesis handles both the added mass of the surrounding air and the sound pressure applied to the reflector. The model can qualitatively well reproduce the results of the BEM-analysis and the test data. However, the model tends to overestimate responses at low frequencies and underestimate them at high frequencies. The end results is that the model becomes too conservative at low frequencies to be used without further development.

Tato práce zkoumá možností řešení kritické síly vzpěrné stability laminátových kompozitních válcových skořepin jak analytickým tak MKP přístupem. Analytické řešení je prezentováno detailně a je zpracován Matlab program pro jeho výpočet. MKP řešení je prováděno ve dvou řešičích softwaru MSC.Nastran, jsou zjišťována vhodná nastavení těchto řešičů a jejich chování. Všechny způsoby řešení jsou na závěr porovnány a je navrženo několik závěrů.

This master thesis describes design of frame construction of Formula Student car. The objective was to reduce weight and increase the torsional stiffness against to last version of the car. Next objective was to prove advantages of alternative frame. This had been achieved by gradual transformation of standard design of frame to alternative with the usage of FSAE alternative frame rules. The weight was reduced by 20% and torsional stiffness was increased by 34% thanks to FEM simulation and sophisticated changes of alternative frame design.

At Saab Aerostructures they are manufacturing a lot of parts for Airbus and Boeing. When these components are investigated using finite element analysis four-node Kirchhoff shell elements and a very fine mesh is often used. In order to make the pre-processing easier Saab would like to offset the shell mid surface from the nodal plane (the modeling surface) rather than to extract mid surfaces for the entire component. This would also make it easier to model a component which needs a thickness change later on, this since the original modeling surface could be used but with an offset of the elements in order to represent the new geometry. When offset is used in Nastran multi point constraints are created between the nodes and the shell mid surface points. All loads, which are applied in the nodal plane, are then transformed to the mid surface where the stiffness matrices, displacements and stresses are calculated. In order to be able to use this method more knowledge about its effects are needed, which is the reason for this thesis work. The offset is studied for two simpler cases, thickness variation and a 90°corner, as well as fora more complicated component called a C-bar. This is a hinge connecting the flaps to the wings of an airplane. The simpler cases are modeled using both mid surface and offset models subject to either a transverse load, an in-plane load or a bending moment. These are compared to a solid model in order to determine which is the most accurate. When mid surface modeling is used fort he thickness variation the surfaces are connected using rigid links. The conclusion made from these simulations is that using offset may give different results if the load is an in-plane load. This kind of load leads to the creation of a bending moment, which is linearly dependent on the amount of offset. The severity of this depends on the overall geometry and how this load is applied.

Indiana University-Purdue University Indianapolis (IUPUI) / In a multifidelity structural design process, depending on the required analysis, different levels of structural models are needed. Within the aerospace design, analysis and optimization community, there is an increasing demand for automatic generation of parametric feature tree (build recipe) attributed multidisciplinary models. Currently, this is mainly done by creating separate models for different disciplines such as mid-surface model for aeroelasticity, outer-mold line for aerodynamics and CFD, and built-up element model for structural analysis. Since all of these models are built independently, any changes in design parameters require updates on all the models which is inefficient, time-consuming and prone to deficiencies. In this research, Engineering Sketch Pad (ESP) is used to create attribution and maintain consistency between structural models with different fidelity levels. It provides the user with the ability to interact with a configuration by building and/or modifying the design parameters and feature tree that define the configuration. ESP is based an open-source constructive solid modeler, named OpenCSM, which is built upon the OpenCASCADE geometry kernel and the EGADS geometry generation system. The use of OpenCSM as part of the AFRL’s CAPS project on Computational Aircraft Prototype Syntheses for automatic commercial and fighter jet models is demonstrated. The rapid generation of parametric aircraft structural models proposed and developed in this work will benefit the aerospace industry with coming up with efficient, fast and robust multidisciplinary design standardization of aircraft structures. Metallic aircraft wings are usually not optimized to their fullest potential due to shortage of development time. With roughly \$1000 worth of potential fuel savings per pound of weight reduction over the operational life of an aircraft, airlines are trying to minimize the weight of aircraft structures. A stiffness based strategy is used to map the nodal data of the lower-order fidelity structural models onto the higher-order ones. A simple multi-fidelity analysis process for a parametric wing is used to demonstrate the advantage of the approach. The loads on the wing are applied from a stick model as is done in the industry. C program is created to connect the parametric design software ESP, analysis software Nastran, load file and design configuration file in CSV format. This problem gets compounded when it comes to optimization of composite wings. In this study, a multi-level optimization strategy to optimize the weight of a composite transport aircraft wing is proposed. The part is assumed to initially have some arbitrary number of composite super plies. Super plies are a concept consisting of a set of plies all arranged in the same direction. The thickness and orientation angles of the super plies are optimized. Then, each ply undergoes topometry optimization to obtain the areas of each super ply taking the least load so that it could be cut and removed. Each of the super plies are then optimized for the thickness and orientation angles of the sub plies. The work presented on this paper is part of a project done for Air Force Research Laboratory (AFRL) connecting the parametric geometry modeler (ESP) with the finite element solver (Nastran).

No description available.

The particular study case in this thesis is the shock test performed on the LISA Pathfinder satellite conducted in a laboratory environment on a dedicated test bed: Vega Shock Test Apparatus (VESTA). This test is considered fully representative to study shock levels produced by fairing jettisoning event at Vega Launcher Vehicle, which induces high shock loads towards the satellite. In the frame of this thesis, some transient response analyses have been conducted in MSC Nastran, and a shock simulation tool for the VESTA test configuration has been developed. The simulation tool is based on Nastran Direct Transient Response Analysis solver (SOL 109), and is representative of the upper composite of Vega with the LISA Pathfinder coupled to it. Post-processing routines of transient response signals were conducted in Dynaworks which served to calculate Shock Response Spectra (SRS). The simulation tool is a model of forcing function parameters for transient analysis which adequately correlates with the shock real test data, in order to understand how the effect of shock generated by the launcher is seen in the satellite and its sub-systems. Since available computation resources are limited the parameters for analysis were optimised for computation time, file size, memory capacity,  and model complexity. The forcing function represents a release of the HSS clamp band which is responsible for fairing jettisoning, thus the parameters which were studied are mostly concerning the modelling of this event. Among many investigated, those which visibly improved SRS correlation are radial forcing function shape, implementation of axial impulse, clamp band loading geometry and refined loading scheme. Integration time step duration and analysis duration were also studied and found to improve correlation.  From each analysis, the qualifying shock environment was then derived by linear scaling in proportion of the applied preload, and considering a qualification margin of 3dB. Consecutive tracking of structural responses along shock propagation path exposed gradual changes in responses pattern and revealed an important property that a breathing mode (n = 0) at the base of a conical Adapter translates into an axial input to the spacecraft. The parametrisation itself was based on responses registered at interfaces located in near-field (where the clamp band is located and forcing function is applied) and medium-field with respect to the shock event location. Following shock propagation path, the final step was the analysis of shock responses inside the satellite located in a far-field region, which still revealed a very good correlation of results. Thus, it can be said that parametrisation process was adequate, and the developed shock simulation tool can be qualified. However, due to the nature of shock, the tool cannot fully replace VESTA laboratory test, but can support shock assessment process and preparation to such test. In the last part of the thesis, the implementation of some finite element model improvements is investigated. Majority of the panels in spacecraft interior exhibited shock over-prediction due to finite element model limitation. Equipment units modelled as lump masses rigidly attached with RBE2 elements to the panel surface are a source of such local over-predictions. Thus, some of the units were remodelled and transient responses were reinvestigated. It was found that remodelling with either solid elements, or lump mass connected to RBE3 element and reinforced by RBE2 element, can significantly improve local transient responses. This conclusion is in line with conclusions found in ECSS Shock Handbook.