Numerical model usage has substantially increased in many industries. It is the aerospace industry that numerical models play possibly the most important role for development of optimum design. However, numerical models need experimental verification. This experimental verification is used not only for validation, but also updating numerical model parameters. Verified and updated models are used to analyze a vast amount of cases that structure is anticipated to face in real life. In this thesis, structural finite element model updating of a utility helicopter fuselage was performed as a case study. Initially, experimental modal analyses were performed using modal shakers. Modal analysis of test results was carried out using LMS Test.lab software. At the same time, finite element analysis of the helicopter fuselage was performed by MSC.Patran &amp / Nastran software. v Initial updating was processed first for the whole helicopter fuselage then, tail of the helicopter was tried to be updated. Furthermore, a new method was proposed for the optimum node removal location for getting better Modal Assurance Criterion (MAC) matrix. This routine was tried on the helicopter case study and it showed better performance than the Coordinate Modal Assurance Criterion (coMAC) that is often used in such analyses.

This study investigated the vibration serviceability of timber structures with dowel-type connections. It addressed the use of such connections in cutting-edge timber structures such as multi-storey buildings and long-span bridges, in which the light weight and flexibility of the structure make it possible that vibration induced by dynamic forces such as wind or footfall may cause discomfort to occupants or users of the structure, or otherwise impair its intended use. The nature of the oscillating force imposed on connections by this form of vibration was defined based on literature review and the use of established mathematical models. This allowed the appropriate cyclic load to be applied in experimental work on the most basic component of a dowel-type connection: a steel dowel embedding into a block of timber. A model for the stiffness of the timber in embedment under this cyclic load was developed based on an elastic stress function, which could then be used as the basis of a model for a complete connector. Nonlinear and time-dependent behaviour was also observed in embedment, and a simple rheological model incorporating elastic, viscoelastic and plastic elements was fitted to the measured response to cyclic load. Observations of the embedment response of the timber were then used to explain features of the behaviour of complete single- and multiple-dowel connections under cyclic load representative of in-service vibration. Complete portal frames and cantilever beams were tested under cyclic load, and a design method was derived for predicting the stiffness of such structures, using analytical equations based on the model for embedment behaviour. In each cyclic load test the energy dissipation in the specimen, which contributes to the damping in a complete structure, was measured. The analytical model was used to predict frictional energy dissipation in embedment, which was shown to make a significant contribution to damping in single-dowel connections. Based on the experimental results and analysis, several defining aspects of the dynamic response of the complete structures, such as a reduction of natural frequency with increased amplitude of applied load, were related to the observed and modelled embedment behaviour of the connections.

Modal parameter identification of a structure is done through modal testing and modal analysis using various system identification methods. These methods employ linear input-output relationships to extract the modes of a structure. There are cases where laboratory testing of a structure is not possible or information about the structure under operating conditions is seeked. A set of techniques called Operational Modal Analysis have been developed for modal parameter identification in operating conditions of a structure. These techniques use only response measurements to extract the modes. The aim of this study is to investigate the applicability and use of three selected time-domain methods adapted to operational modal analysis. The algorithms are programmed in Matlab&copy / environment, and various cases are evaluated using computer simulations for each method. Two of the selected methods are evaluated on a laboratory scale test setup.

Vibration is an inherent phenomenon in dynamic mechanical systems. The work undertaken in this thesis is to identify natural frequencies of a variable length blade. Therefore designers can ensure that natural frequencies will not be close to the frequency (or integer multiples) of the main excitation forces in order to avoid resonance. For a wind turbine blade, the frequency range between 0.5 Hz and 30 Hz is relevant. The turbine blade is approximated by a cantilever, therefore, it is fully constrained where attached to a turbine shaft/hub. Flap-wise, edge-wise and torsional natural frequencies are calculated. The MATLAB program “BEAMANALYSIS.m” has been developed for the finite element analysis of a one dimensional model of the beam. Similarly, a three dimensional model of the beam has been developed in a finite element program Unigraphics NX5. The results found using the MATLAB program are compared with those found with NX5. Satisfactory agreement between the results is found for frequencies up to almost 500 Hz. Additionally, the frequencies one might expect in an experiment are identified. Experimental modal analysis has been performed on a uniform and stepped beam made of mild steel to extract the first five flap-wise natural frequencies. The results found have been compared to numerical results and the exact solution of an Euler-Bernoulli beam. Concurrence is found for the frequency range of interest. Although, some discrepancies exist at higher frequencies (above 500 Hz), finite element analysis proves to be reliable for calculating natural frequencies. Finally, the fixed portion and moveable portion of the variable length blade are approximated respectively by a hollow and a solid beam which can be slid in and out. Ten different configurations of the variable length blade, representing ten different positions of the moveable portion are investigated. A MATLAB program named VARIBLADEANALYSIS.m was developed to predict natural frequencies. Similarly three dimensional models of the variable length blade have been developed in the finite element program Unigraphics NX5. / This work was supported by the Research office of CPUT.

Sabe-se que à inevitÃvel a ocorrÃncia de acidentes de trÃnsito em rodovias, onde centenas de milhares de veÃculos transitam a cada dia e que, alÃm de gerarem fatalidades, geram danos materiais, fÃsicos e morais Ãs pessoas envolvidas. Quando os acidentes envolvem colisÃes com um poste de distribuiÃÃo de energia elÃtrica, estes sÃo responsÃveis por deixar, em mÃdia, cinco mil residÃncias sem fornecimento de energia de forma imediata. Nestes casos, essa interrupÃÃo no fornecimento pode durar atà quatro horas para os moradores prÃximos ao local da colisÃo devido ao trabalho de substituiÃÃo, bem como gerar altos custos com a reposiÃÃo dos postes. Portanto, faz-se necessÃrio o estudo de um sistema de defensa de postes visando à proteÃÃo destes, bem como salvaguardar os motoristas de veÃculos em caso de colisÃo. O objetivo deste trabalho consiste em avaliar o comportamento do poste e do sistema poste-defensa devido ao choque de veÃculos. Para tanto, sÃo realizadas duas anÃlises paramÃtricas. A primeira consiste na anÃlise modal numÃrica a fim de se determinar a influÃncia de componentes tais como cabos e defensas nos parÃmetros naturais do poste. A segunda consiste na anÃlise transiente paramÃtrica do poste e do conjunto poste-defensa. Neste caso, sÃo variadas a massa do veÃculo, sua velocidade e o tempo de impacto. Estas anÃlises sÃo realizadas no programa comercial, baseado no MÃtodo dos Elementos Finitos, SAP2000 V.14.0. A histÃria no tempo do deslocamento da extremidade livre do poste à comparada entre os diversos modelos, bem como com os resultados das amplitudes das cargas dinÃmicas aplicadas de forma estÃtica. Dos resultados observa-se que a defensa cumpre seu papel diminuindo a possibilidade de colapso devido aumentar as frequÃncias naturais e afastando-as das frequÃncias de excitaÃÃo das cargas de impacto. Da anÃlise transiente conclui-se que a defensa aumenta a rigidez do sistema reduzindo os deslocamentos. / It is known that is inevitable the incidence of traffic accidents in highways, where hundreds of thousands of vehicles pass daily. These accidents can cause material damages, physical and moral injuries to involved persons, besides fatalities. When collisions are into an electric distribution pole, these are responsible by five thousand residences without electric power immediately. In this case, the stop in supplying can take four hours to residents who live close to accident site due to replacement work, as well as to generating high costs to replace the poles. So, it is necessary to study a system that protects the pole, as well as safeguards the vehicles drivers in case of collision. The objective of this work is to evaluate the behavior of pole and of system pole-defence due to the vehicles shock. Two parametric analyses are carried out. The first one is the numerical modal analysis in order to determine the influence of components like cables and defence in the pole natural parameters. The second one is the transient parametric analysis of pole and of pole-defence system. In this case, the vehicle mass and his impact time are varied. These analyses are executed in the commercial program based on the Finite Elements Method, SAP2000 V.14.0. The displacement history of pole free end is compared between the several models, as well as with the results obtained when the dynamic load maximum value is applied statically. From results it is noticed that defence carries out his paper reducing the possibility of collapse due to increasing the natural frequencies and making away from excitation frequencies of impact loads. From transient analysis it is concluded that defence raises the rigidity of the system by reducing the displacements.

Nonlinear response history analysis is accepted as the most accurate analytical tool for seismic response determination. However, accurate estimation of displacement responses using conceptually simple, approximate analysis procedures is preferable, since there are shortcomings in the application of nonlinear response history analysis resulting from its complexity. An equivalent linearization procedure, which utilizes the familiar response spectrum analysis as the analysis tool and benefits from the capacity principles, is developed in this thesis study as an approximate method for predicting the inelastic seismic displacement response of MDOF systems under earthquake excitations. The procedure mainly consists of the construction of an equivalent linear system by reducing the stiffness of structural members which are expected to respond in the inelastic range. Different from similar studies in literature, equivalent damping is not explicitly employed in this study. Instead, predetermined spectral displacement demands are utilized in each mode of the equivalent linear system for the determination of global displacement demands. Response predictions of the equivalent linearization procedure are comparatively evaluated by using the benchmark nonlinear response history analysis results and other approximate methods including conventional pushover analysis and modal pushover analysis (MPA). It is observed that the proposed procedure results in similar accuracy with approximate methods which employ nonlinear analysis. Considering the conceptual simplicity of the procedure and the conventional analysis tools used in its application, presented equivalent linearization procedure can be suggested as a practically applicable method for the prediction of inelastic seismic displacement response parameters with sufficient accuracy.

This study presents the investigation and the verification of the modal parameters of a plate-like structure by using different modal analysis methods. A fin-like structure which is generally used in aircraft is selected as a subcategory of a plate-like test structure. In the first part of the thesis, the natural frequencies and the corresponding mode shapes of the fin are extracted by Finite Element Analysis method. Classical Modal Analysis and Testing methods comprising both impact hammer and modal shaker applications are then applied in order to obtain the modal parameters such as / resonance frequencies, mode shapes and damping ratios. In the second part, a recent modal analysis technique, Operational Modal Analysis, is also applied in the laboratory environment. Since Operational Modal Analysis method does not require any information of input forcing, the fin structure is tested under both mechanical and acoustical types of excitations without measuring the given input forces. Finally, Operational Modal Analysis and Testing is also performed under various flow conditions generated in the wind tunnel which may simulate the real operating environment for the fin structure. The modal parameters extracted under these flow conditions are then compared with the previously obtained Finite Element, Classical and Operational Modal Analyses results.

In this study, experimental modal analysis was studied. Experimental modal analysis includes modal testing, modal parameter estimation and calibration. For this purpose a 4 span skewed steel frame was constructed in Structural Mechanics Laboratory of Civil Engineering Department of METU. The model was transported to Vibration and Acoustic Laboratory of Mechanical Engineering Department of METU. The tests were conducted by cooperation with Vibration and Acoustics Laboratory. Due to lack of experimental modal analysis software in Structural Mechanics Laboratory, modal parameter estimation and finite element updating softwares were written in Matlab platform. The written softwares were executed on the data obtained from modal testing. 15 reasonable modes are extracted from the FRFs that are obtained from modal testing. 59.23 percent consistency is found for the nominal modal comparison. At the end of calibration process 76.14 percent consistency is achieved between the experimental results and analytical results.

Orientador: Paulo Roberto Gardel Kurka / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T11:40:22Z (GMT). No. of bitstreams: 1 Izuka_JaimeHideo_D.pdf: 4550690 bytes, checksum: d283c500cecbc7a038784ba35f0f73df (MD5) Previous issue date: 2013 / Resumo: A utilização de braços manipuladores flexíveis em veículos de exploração foi o motivador deste trabalho. Estas estruturas têm como vantagens a sua massa reduzida e a capacidade de suportar grandes deformações sem que o limite de elasticidade seja excedido. O controle das vibrações de sua extremidade livre é essencial para uma aplicação prática. Neste contexto, este trabalho tem como objetivo a determinação de um modelo dinâmico para uma estrutura longa e flexível, visando o seu controle de vibração. A estrutura considerada possui seção variável, semelhante a uma viga telescópica. Considera-se ainda que a estrutura esteja sujeita a uma grande deformação causada pelas ações de tendão de tração, peso próprio e cargas concentradas. O modelo dinâmico consiste na adaptação de uma malha de elementos finitos de baixa ordem à configuração da linha de deformação estática da viga. A vibração a ser controlada consiste das pequenas oscilações que ocorrem em torno da posição de equilíbrio da viga deformada. O modelo dinâmico encontrado para a estrutura é utilizado no projeto de um controlador de vibrações, ativado por forças exercidas no tendão de tração, responsável pela deformação estática da própria viga. Comparações com a literatura, bem como resultados experimentais comprovam a validade do modelo empregado para a caracterização do sistema. Simulações numéricas mostram o sucesso de uso do modelo no projeto de um controlador ativo de vibrações / Abstract: The use of flexible manipulator arms in exploration vehicles was the motivation of this work. The advantages of such structures are their light weight and the capability to withstand large displacements without exceeding their specified elastic limit. The control of vibrations of its free end is essential for a practical application. In this context, the objective of this study is to determine a dynamic model for a long and flexible structure, aiming its vibration control. The structure has a variable section, similar to a telescopic beam. Large deformation behavior of the structure is considered. Concentrated loads, self-weight of the structure and tendon traction are the loads applied to the structure. The model dynamics is described by a low order finite element mesh, which is adapted to the geometry defined by the static deformation of the beam. The vibrations to be controlled are the small oscillations about the equilibrium position of the deformed beam. The dynamic model found for the structure is applied to design an active vibration controller. The controller forces are applied though the tendon traction cables, which is also responsible for the static deformation of the beam itself. Comparison with literature as well as experimental results prove the validity of the model used to characterize the system. Numerical simulations show the success of using the model in the design of an active vibration controller / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

This thesis deals with determination of effect of wing flexibility on load distribution. FSI analysis using modal superposition was used for determination of effect of wing flexibility. Analysis was verified by analytic calculation. Differences of load distribution, between rigid and flexible wing, was determined for the selected flight regimes. Change of the bending moment was up to 3,9 %. Thesis shows importance of including effect of wing flexibility for sailplane design.