Diplomová práce se zabývá modifikací stávající pozemní verze letounu EV-55 pro možnost přistání na vodní hladině. Snahou je najít takovou variantu, která nepovede k výrazným konstrukčním zásahům do draku letounu a bude vyhovovat stavebnímu předpisu CS 23, zejména požadavkům týkající se plovatelnosti a stability na vodě. Je proveden hmotový rozbor modifikované verze a s tím související omezení hmotové obálky a rozsahu centráží. Zatížení od vody je spočítáno v souladu s CS 23. Pro toto zatížení je následně navrhnuto konstrukční řešení uchycení plováků k trupu a provedena pevnostní kontrola jednotlivých prvků a spojovacích uzlů. Tyto hodnoty jsou dále porovnány s pozemními případy zatížení a stanoveny součinitele rezerv. V závěru jsou spočítány letové výkony: maximální horizontální rychlost, stoupavost, dolet a vytrvalost.

It is often needed to predict the behavior of structures. With the helpof an FE model, it is possible to see the motion of the structure. Inthis, Master thesis work time domain analyses were carried out on afinite element model representing a window attached by click-ins. Theaim was to establish an FE model which gives a good correlation withtest data. The finite element modelling was carried out in MSC Apex.MSC Nastran was utilised to analyze the FEA model and the resultwas post-processed in Simxpert. Different vibrational tests were made. A crane was used to exciteand support the wall together with the window and the responseswere recorded with tri-axial accelerometers. During the thesis, it wasfound that the FE model requires more work and accurate boundaryconditions to provide better resemblance with the test data.The results deviate from the measured. This opens future possibilities tocarry on the project.

The structural design of flight vehicles is a balancing act between maximizing loading capability while minimizing weight. An engineer must consider not only the classical static structural yielding failure of a vehicle, but a variety of ways in which structural deformations can in turn, affect the loading conditions driving those deformations. Lift redistribution, divergence, and flutter are exactly such dynamic aeroelastic phenomena that must be properly characterized during the design of a vehicle; to do otherwise is to risk catastrophe. Relevant within the university context is the design of small-scale aircraft for student projects and of particular consideration, the DBF competition hosted by AIAA. This work implements a variety of aeroelastic analysis methods: K and PK with Theodorsen aerodynamics via Matlab, NASA EZASE, and the FEMAP NX NASTRAN Aeroelasticity Package. These techniques are applied to a number of baseline test cases in addition to two representative DBF wings. Both wings considered ultimately indicated stability within reasonable flight conditions, although each for a different reason. Analysis results for the Cal Poly 2020 wing, a spar-rib construction emblematic of the collocation design approach, showed that the wing was stable within expected flight regions. The USC 2020 wing model, a composite top spar construction, exhibited unstable behavior, however this was well outside the scope of expected flight conditions. The codebase developed as a part of this work will serve as a foundation for future student teams to perform aeroelastic analyses of their own and support continued aeroelastic research at Cal Poly - SLO.

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This thesis presents a novel method for the correlation of FEM results to experimental test results known as the "Load updating method." Specifically, the load updating method uses the math model from the FEM and the strains measured from experimental or flight test data as inputs and then predicts the loads in the FEM which would result in strains that would correlate best to the measured strains in the least squared sense. In this research, the load updating method is applied to the analysis of a complex frame structure whose validation is challenging due to the complex nature of its structural behavior, load distributions, and error derived from residual strains. A FEM created for this structure is used to generate strain data for thirty-two different load cases. These same thirty-two load cases are replicated in an experimental setup consisting of the frame, supporting structure, and thirty actuators which are used to load the frame according to the specifications for each of the thirty-two load conditions. A force-strain matrix is created from the math model in NASTRAN using unit loads which are separately applied to each load point in order to extract strain results for each of the locations of the seventy-four strain gages. The strain data from the structural test and the force-strain matrix is then input into a Matlab code which is created to perform the load updating method. This algorithm delivers a set of coefficients which in turn gives the updated loads. These loads are applied to the FEM and the strain values extracted for correlation to the strains from test data. It is found that the load updating method applied to this structure produces strains which correlate well to the experimental strain data. Although the loads found using the load updating method do not perfectly match those which are applied during the test, this error is primarily attributed to residual strains within the structure. In summary, the load updating method provides a way to predict loads which, when applied to the FEM, would result in strains that correlate best to the experimental strains. Ultimately, this method could prove especially useful for predicting loads in experimental and flight test structures and could aid greatly in the Federal Aviation Administration (FAA) certification process. / Master of Science / The research presented in this thesis provides a new way for correlating data obtained during structural testing with results obtained from computer analysis known as the finite element method (FEM). During the process of certifying an aircraft structure with the FAA, it is important to be able to demonstrate that the results obtained for a given structure with a computer model matches the results produced by a real world experiment within a reasonable tolerance. Traditionally, differences between these two results have been accounted for by adjusting the model within the computer until its results match those from the test. However, in this research the loads which are applied on the computer model are changed instead until loads are found which produce results in the computer models that match those from testing. This method, known as the load updating method, therefore provides a way to predict loads on a structure where the loads are unknown such as a flight test article. Here, the ability of the load updating method to predict loads on a complex three dimensional frame structure is explored and the accuracy of the results studied by comparing the results to those from a structural test whose loads are known. It was found that the load updating method does indeed predict unknown loads to a reasonable accuracy and could aid future design efforts immensely.

Tato diplomová práce se zabývá modifikací původního tvaru součásti za účelem co nejlepšího splnění provozních podmínek daného zatížení a omezujících podmínek v programech M.S.C. NASTRAN, M.S.C. PATRAN a FUSION 360. Součást je připevněna na ortotropní desce (sendvičovém panelu). Cílem této práce je zjištění efektu elastického podkladu na výsledky optimalizace. Součást bude optimalizována za použití různých cílových funkcí a omezení. Elastický podklad změní tuhost, což může změnit napěťový stav součásti. Únosnost původního a modifikovaného tvaru bude srovnána pomocí programu M.S.C NASTRAN/PATRAN. Po tvarové optimalizaci má být 3D model připravený pro výrobní proces, který bude cenově nejefektivnější.

Neste trabalho foi realizado o cálculo das cargas aerodinâmicas e o pré-projeto estrutural de asa de uma aeronave de 50 passageiros durante o Mestrado Profissionalizante em Engenharia Aeronáutica e Mecânica, ministrado pelo ITA em parceria com a EMBRAER, através do seu Programa de Especialização em Engenharia. Primeiramente, o modelo estrutural foi desenvolvido baseando-se nas características aerodinâmicas iniciais da aeronave, possibilitando que o programa de análise aerodinâmica BLWF fosse utilizado para a geração numérica das distribuições de pressão na asa. Estas foram transferidas para o modelo estrutural através do método de interpolação linear bidimensional. Comparativamente, a diferença entre os totais de cisalhamento e de momento fletor obtidos pelo BLWF e pelo NASTRAN apresentou-se menor que 10%. Após isto, foi realizada uma análise estrutural estática de dois casos de carregamento da pressão aerodinâmica em um modelo de elementos finitos construído no MSC.Nastran a partir da geometria do programa CATIA. Através da comparação com aeronave da EMBRAER de porte semelhante, os resultados obtidos nas análises aerodinâmica e estrutural mostraram-se coerentes, necessitando de mais iterações do projeto para a otimização do modelo. A validação da primeira foi realizada através de gráficos de distribuição de sustentação, de esforço cortante, momento fletor e momento torçor. E a segunda através da análise dos valores de tensão obtidos.

This thesis presents a finite element method based comparative study of linear and geometrically non-linear progressive failure analysis of thin walled composite aerospace structures, which are typically subjected to combined in-plane and out-of-plane loadings. Different ply and constituent based failure criteria and material property degradation schemes have been included in a PCL code to be executed in MSC Nastran. As case studies, progressive failure analyses of sample composite laminates with cut-outs under combined loading are executed to study the effect of geometric non-linearity on the first ply failure and progression of failure. Ply and constituent based failure criteria and different material property degradation schemes are also compared in terms of predicting the first ply failure and failure progression. For mode independent failure criteria, a method is proposed for the determination of separate material property degradation factors for fiber and matrix failures which are assumed to occur simultaneously. The results of the present study show that under combined out-of-plane and in-plane loading, linear analysis can significantly underestimate or overestimate the failure progression compared to geometrically non-linear analysis even at low levels of out-of-plane loading.

Volvos trucks are used to carry boulders of varying sizes from different mining sites or construction sites. These boulders are loaded onto the dumper of the truck by a wheel-loader which drops the boulders from various heights causing an impulse like force which distributes throughout the frame and to the rest of the truck. Depending on the size and what height the boulders are being dropped from, the distributed forces can cause damage to important parts of the truck. An experiment done by Volvo has shown that a two-ton weight dropped from 3.5 meters caused some truck components to crack, such as flywheel housing. Since this is alerting and it is costly to do the experiment on all trucks that Volvo manufactures it is our objective to come up with a method based on Finite Element which would evaluate the rock loading case. By using ANSA as the pre-processor which helps set up the model before running a simulation, and Nastran and LS-DYNA as the FEM solvers, a result was obtained that is somewhat comparable with the measurements. In the Nastran model, no non-linearities such as contact were considered, while in LS-DYNA nonlinear contact between the weight and the dumper body was defined, which improved the results considerably. The key conclusion from the two results was that the contact definition used in LS-DYNA is necessary if accurate results are important. Since LS-DYNA uses an explicit numerical method the model can be made more complicated by including more nonlinearities in the model and it would not affect the computation to much or at all. Hence the method would be future proof.

This project is centered around the use of finite element analysis for developing a beam for a new type of motor used in a screening machine. Essentially the main purpose of the developed beam is to transfer vibrations to the screen machine that it will be attached to. Since the machine operates on vibrations from the motor, the beam was to be designed with material fatigue in mind, which demanded examination of stresses in the welded joints of the beam. Concepts were generated with a specification of requirements as a basis, and the concepts were then analysed with finite element analysis. The results from this analysis were compared and a final design choice was selected. Since the beam will be subjected to varying fatigue loads, an S-N curve was needed to gain information of the material’s cyclic stress versus life. Most S-N curves are accessible through literature or databases, however, there are some materials that do not have an S-N curve available. If that is the case then the designer has the option to estimate one using ultimatetensile strength and the material’s fatigue limit. Hence, an S-N curve was estimated in this project.