Página 1 dos resultados de 57 itens digitais encontrados em 0.027 segundos

Using of model updating considering damped frequency response function

Pereira, J. A.; Borges, A. S.; SPIE
Fonte: Soc Experimental Mechanics Inc Publicador: Soc Experimental Mechanics Inc
Tipo: Conferência ou Objeto de Conferência Formato: 1478-1484
ENG
Relevância na Pesquisa
66.05%
The search for better performance in the structural systems has been taken to more refined models, involving the analysis of a growing number of details, which should be correctly formulated aiming at defining a representative model of the real system. Representative models demand a great detailing of the project and search for new techniques of evaluation and analysis. Model updating is one of this technologies, it can be used to improve the predictive capabilities of computer-based models. This paper presents a FRF-based finite element model updating procedure whose the updating variables are physical parameters of the model. It includes the damping effects in the updating procedure assuming proportional and none proportional damping mechanism. The updating parameters are defined at an element level or macro regions of the model. So, the parameters are adjusted locally, facilitating the physical interpretation of the adjusting of the model. Different tests for simulated and experimental data are discussed aiming at defining the characteristics and potentialities of the methodology.

Ajuste de modelos estruturais aplicado em problema de contato

Garcia, André Mendes
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 113 f. : il.
POR
Relevância na Pesquisa
86.12%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Engenharia Mecânica - FEIS; O presente trabalho propõe uma metodologia de ajuste de modelos de elementos finitos aplicado a problemas de contato. O ajuste do modelo é realizado através da atualização dos parâmetros físicos e/ou geométricos do modelo bem como dos parâmetros dos elementos de contato. O método utilizado é baseado nas FRF(s) e é formulado a partir de um resíduo de entrada, dado pelo balanço de força do sistema. Um software é implementado para fazer a comparação e correlação dos modelos analítico e experimental, e se necessário, ajustar os parâmetros do modelo analítico. O modelo analítico é gerado pelo software comercial ANSYSâ, e os dados experimentais são obtidos em testes experimentais de análise modal. A metodologia foi avaliada com exemplos numéricos e testes experimentais buscando identificar as potencialidades e limitações do método. Dois testes experimentais foram realizados. O primeiro teste consiste em obter os parâmetros modais de uma estrutura simples do tipo viga. No segundo teste, os parâmetros modais são obtidos de uma estrutura composta por duas peças em contato. O objetivo do primeiro teste é avaliar a potencialidade da metodologia proposta utilizando uma base de dados experimental confiável...

Ajuste de modelos numericos de elementos finitos usando metodos de otimização; Finite element model updating using optimization methods

Aldecir Alves de Araujo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/07/2007 PT
Relevância na Pesquisa
86.08%
Predições de respostas dinâmicas de estruturas baseadas em técnicas numéricas ou experimentais estão sujeitas a erros e incertezas. Geralmente os modelos numéricos são idealizados e não levam em consideração certos fatores existentes na prática. A atualização de modelos numéricos a partir de medidas experimentais consiste em uma adequação matemática dos resultados obtidos nas técnicas de predição. Neste trabalho realizam-se ajustes de estruturas mecânicas modeladas pelo Método dos Elementos Finitos baseado em dados modais experimentais (freqüências naturais e formas dos modos), através dos métodos de otimização conhecidos como Método da Função Objetivo (MFO) e Método da Aproximação por Subproblema (MAS). Os resultados do MFO foram obtidos através de programas computacionais em MatLab, enquanto no MAS os mesmos foram obtidos utilizando o módulo de otimização de projetos (design optimization) do programa ANSYS. Um exemplo de uma viga engastada-livre foi realizado com ambos os métodos a partir de dados experimentais simulados. Um segundo exemplo de uma treliça espacial foi também avaliado por ambos os métodos com base em dados experimentais medidos. Um modelo simplificado de uma aeronave usando apenas o método MAS foi avaliado usando dados experimentais medidos. Os resultados são apresentados e as vantagens e desvantagens encontradas em cada método são apontadas e discutidas; Prediction of structural dynamic responses basecÍ on numerical or experimental techniques are subj.ects to errors and uncertainties. Usually numerical models are idealized and do not take into account certain factors found in real structures. A numerical mo dei updating based on experimental measurements are basically a mathematical adjustment of the results obtained from prediction techniques. In this work model updating of mechanical structures modeled by the Finite Element Method based on experimental modal data (natural frequencies and modal shapes) are done. These are based on optimization methods know as Objective Function Method (OFM) and Subproblem Approximation Method (SAM). OFM results were obtained through MatLab computational codes...

Optimização do comportamento dinâmico de um componente estrutural de um auto-rádio

Martins, Jorge Filipe Sá
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2011 POR
Relevância na Pesquisa
66.13%
Dissertação de mestrado integrado em Engenharia Mecânica; A presente dissertação tem como principal objectivo a “Optimização do comportamento dinâmico de um componente estrutural de um Auto-Rádio” através de uma metodologia desenvolvida anteriormente, “updating” (melhoramento) do comportamento dinâmico do componente. O componente estrutural é o painel traseiro de um Auto-Rádio, que tem como função fazer o suporte e ligação da consola à caixa de componentes. O seu comportamento dinâmico é caracterizado pelos modos de vibração e frequências naturas, procura-se melhorar a geometria da peça para aperfeiçoar o seu comportamento na aplicação em que está previsto e se possível reduzir o seu custo. A ferramenta numérica de apoio para “updating” desenvolvida por Meireles em 2007, executa a optimização de um modelo numérico por minimização de uma função objectivo, de forma a melhorar o comportamento dinâmico de estruturas; esta técnica utiliza um modelo de referência e um modelo numérico do componente, por alterações de parâmetros definidos, que variam ao longo da optimização. Os parâmetros a variar estão relacionados com a geometria ou com o material do qual o componente estrutural é fabricado. O algoritmo utilizado recorre ao MAC (“Modal Assurance Criterion”) afectado do ASMAC (“Alternated Modal Search Assurance Criteria”)...

Determination of material/geometry of the section most adequate for a static loaded beam subjected to a combination of bending and torsion

Silva, Hugo Miguel; Meireles, José F.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
86.05%
The acceleration of industrial machines mobile parts has been increasing over the last few years, due to the need of higher production in a short period of time. The machines were dimensioned for a lower value of acceleration, which means there is not enough rigidity for the correct operation at much higher accelerations. Nowadays, the accelerations can be near 12 times the acceleration of gravity. There is the need of improving rigidity to make possible the correct machine operation without undesired vibrations that can ultimately lead to failure. The main applications of this work are plotters and laser cutting machines. To improve rigidity, one must improve the relevant material properties, and the relevant geometric variables of the model.[1] A novel Finite Element Model Updating methodology is presented in this paper. The considered models were : a ribbed plate and a tubular beam. The models were built by means of the Finite Element Method (FEM), and MATLAB was used to control the optimization process, using a programming code. Both material properties and geometric parameters were optimized. The main aim of the materials modeling is to know how the value of the objective function changes with the value of the material properties. Materials selection was performed...

Determination of the material/geometry of the section most adequate for a static loaded beam subjected to a combination of bending and torsion

Silva, Hugo Miguel
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2011 ENG
Relevância na Pesquisa
86.13%
Dissertação de mestrado integrado em Engenharia de Materiais; The Finite Element Method (FEM) is widely used to solve structural analysis problems. In this work, a novel Finite Element Model Updating methodology for static analysis is presented. The aim of the work is to improve the quality of the results using the Finite Element Updating techniques, by optimizing geometric parameters of the models and material properties in order to minimize deflection. Deflection can be minimized by increasing the Inertia moment of the section and/or Young modulus of the material. The Young modulus can be optimized by selecting an adequate material. In this work, material selection charts were used to determine the most reliable material. The selected material was then tested by tensile and extensometry tests to obtain Young modulus, Yield stress, and Poisson coefficient. The Inertia moment can be maximized by improving the geometry of the section, such as adding ribs or webs. A substantial improvement of the deflection can be achieved, but, in order to obtain the best results, optimization must be used. A MATLAB program was used to optimize the ANSYS models using a programming code. In order to know if the results are getting worse or better in relation to the previous iterations...

A global optimization approach applied to structural dynamic updating

Dourado, Marco; Meireles, José F.; Rocha, Ana Maria A. C.
Fonte: Springer International Publishing Publicador: Springer International Publishing
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
96.07%
In this paper, the application of stochastic global optimization tech- niques, in particular the GlobalSearch and MultiStart solvers from MatLab®, to improve the updating of a structural dynamic model, are presented. For com- parative purposes, the efficiency of these global methods relatively to the local search method previously used in a Finite Element Model Updating program is evaluated. The obtained solutions showed that the GlobalSearch and MultiStart solvers are able to achieve a better solution than the local solver previously used, in the updating of a structural dynamic model. The results show also that the GlobalSearch solver is more efficient than the MultiStart, since requires less computational effort to obtain the global solution.; Fundação para a Ciência e a Tecnologia (FCT)

Detection of Earthquake-Induced Damage in a Framed Structure Using a Finite Element Model Updating Procedure

Yu, Eunjong; Kim, Seung-Nam; Park, Taewon; Lee, Sang-Hyun
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 16/01/2014 EN
Relevância na Pesquisa
66.1%
Damage of a 5-story framed structure was identified from two types of measured data, which are frequency response functions (FRF) and natural frequencies, using a finite element (FE) model updating procedure. In this study, a procedure to determine the appropriate weightings for different groups of observations was proposed. In addition, a modified frame element which included rotational springs was used to construct the FE model for updating to represent concentrated damage at the member ends (a formulation for plastic hinges in framed structures subjected to strong earthquakes). The results of the model updating and subsequent damage detection when the rotational springs (RS model) were used were compared with those obtained using the conventional frame elements (FS model). Comparisons indicated that the RS model gave more accurate results than the FS model. That is, the errors in the natural frequencies of the updated models were smaller, and the identified damage showed clearer distinctions between damaged and undamaged members and was more consistent with observed damage.

Artificial boundary conditions in sensitivity based finite element model updating and structural damage detection

Fernandez, Constance R. S.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado
Relevância na Pesquisa
65.97%
A finite element (FE) model is a computational representation of a given structure. In order for the FE model to accurately predict structure response, the model is "updated" or improved. This thesis investigates the use of artificial boundary conditions in sensitivity-based model updating and damage detection. A comparative analysis was conducted on the accuracy of error identification and location with respect to the artificial boundary conditions imposed and the number of modes retained. Results are demonstrated with actual test data from a simple structure.

Finite element model updating and damage detection using artificial boundary conditions

DeGregory, Christopher P.
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
75.95%
An experimental test of a structure results in a database of frequency response functions from which natural frequencies and mode shapes are identified for the given boundary conditions of the test. The natural frequencies of a system under a variety of boundary conditions can be identified by applying artificial boundary conditions (ABCs) at measurement locations and obtaining the frequency response function for the unrestrained degrees of freedom. These frequencies are found without any physical alterations of the test boundary conditions. Use of the ABCs in sensitivity-based model updating and damage detection in conjunction with baseline data provides improved error localization and results in a more accurate finite element model.

Development, correlation and updating of a finite element model of the OH-6A helicopter.

Pampalone, Michael R.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
66.04%
Approved for public release; distribution is unlimited; This thesis is part of the helicopter research program established at The Naval Postgraduate School (NPS). NPS currently has two OH-6A light observation helicopters which were obtained from the U.S. Army. One of these is dedicated to ground vibration testing and dynamics research. Previous research on the OH-6A at NPS established baseline vibration test data. The data includes natural frequencies, principal mode shapes and damping characteristics. This thesis continues previous research of the OH-6A and develops a detailed finite element model to be used in future helicopter dynamics research at NPS. The model is based on an MSC/NASTRAN finite element model of a similar aircraft obtained from the McDonnell Douglas Helicopter Company. Both the nose and empennage were modified to represent the structural characteristics of the test article. Due to lack of structural design data, model mass updating was performed using previously obtained test data and a design sensitivity approach. The updated model natural frequencies agree well with the test data

Optimal solution selection for sensitivity-based finite element model updating and structural damage detection

Renken, Jay A.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
76.13%
The finite element model has become the standard way in which complex structural systems are modeled, analyzed, and the effects of loading simulated. A new method is developed for comparing the finite element simulation to experimental data, so the model can be validated, which is a critical step before a model can be used to simulate the system. An optimization process for finite element structural dynamic models utilizing sensitivity based updating is applied to the model updating and damage detection problems. Candidate solutions are generated for the comparison of experimental frequencies to analytical frequencies, with mode shape comparison used as the selection criteria for the optimal solution. The method is applied to spatially complete simulations and to spatially incomplete experimental data which includes the model validation of a simple airplane model, and the damage localization in composite and steel beams with known installed damage. (AN)

Application of artificial boundary conditions in sensitivity-based updating of finite element models

Mentzer, John R.
Fonte: Monterey California. Naval Postgraduate School Publicador: Monterey California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xiv, 95 p. ;
Relevância na Pesquisa
76.01%
In structural dynamics the ability of a finite element model, or (FEM), to accurately represent a structure's dynamic response (natural frequencies and mode shapes) determines its utility as a solution tool. Oftern the model needs to be updated or improved to better represent the structure it is modeling. An updated or improved model of an undamaged structure is often needed in order to identify damage in an in-service structure. A difficulty generally arises in trying to slove for this error because it is often represented by an underdetermined problem, as the number of parameters potentially in error in the FEM is typically much larger than the number of measured parameters. The method of Artifical Boundary Conditions (ABC) can help to resolve the problem and lead to an improved solution. The ABC systems provide the natural frequencies for the structure under test, under a variety of boundary conditions which are imposed computationally. Specifically, the use of ABC in sensitivity based updating will be investigated and its improvement on performance reviewed.; US Navy (USN) author.

Experimental modal identification of an existent earthen residential building

Aguilar, Rafael; Ramos, Luís F.; Torrealva, D.; Chácara, C.
Fonte: IOMAC'13 Publicador: IOMAC'13
Tipo: Conferência ou Objeto de Conferência
Publicado em 13/05/2013 POR
Relevância na Pesquisa
75.95%
The paper presents the preliminary round of in-situ experimental tests carried out at “Hotel Comercio”, a historical construction located at the historical centre of Lima (capital of Peru). The building is a three story republican-type construction built at 19th Century with composite structure of Adobe and “Quincha”. The experimental works consisted on Operational Modal Analysis (OMA) tests aiming at identifying the dynamic characteristics of the building using the environmental noise as source of excitation. The severe damage at the Hotel, as well as its complex boundary conditions made the dynamic identification process hard to carry out. The experimental results showed coupled global and local modes. The expected different behaviour of the Quincha panels and the Adobe in terms of flexibility was also verified. The Finite element model of the building was implemented and a preliminary numerical model updating was carried out. The modal comparison of the numerical and experimental results evidenced that few modes were accurately assessed by the analytical approach. An important contribution of the paper is the introduction of OMA as a tool for better understanding the structural behaviour which may also allow assessing the real damage condition of the buildings.

Finite Element Model Updating Using Fish School Search Optimization Method

Boulkabeit, I.; Mthembu, L.; Marwala, T.; Neto, F. De Lima
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/08/2013
Relevância na Pesquisa
75.99%
A recent nature inspired optimization algorithm, Fish School Search (FSS) is applied to the finite element model (FEM) updating problem. This method is tested on a GARTEUR SM-AG19 aeroplane structure. The results of this algorithm are compared with two other metaheuristic algorithms; Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). It is observed that on average, the FSS and PSO algorithms give more accurate results than the GA. A minor modification to the FSS is proposed. This modification improves the performance of FSS on the FEM updating problem which has a constrained search space.; Comment: To appear in the 1st BRICS Countries & 11th CBIC Brazilian Congress on Computational Intelligence

Bayesian evidence for finite element model updating

Mthembu, Linda; Marwala, Tshilidzi; Friswell, Michael I.; Adhikari, Sondipon
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/10/2008
Relevância na Pesquisa
86.19%
This paper considers the problem of model selection within the context of finite element model updating. Given that a number of FEM updating models, with different updating parameters, can be designed, this paper proposes using the Bayesian evidence statistic to assess the probability of each updating model. This makes it possible then to evaluate the need for alternative updating parameters in the updating of the initial FE model. The model evidences are compared using the Bayes factor, which is the ratio of evidences. The Jeffrey scale is used to determine the differences in the models. The Bayesian evidence is calculated by integrating the likelihood of the data given the model and its parameters over the a priori model parameter space using the new nested sampling algorithm. The nested algorithm samples this likelihood distribution by using a hard likelihood-value constraint on the sampling region while providing the posterior samples of the updating model parameters as a by-product. This method is used to calculate the evidence of a number of plausible finite element models.; Comment: 10 pages, to appear in the IMAC 2009

Finite Element Model Updating Using Bayesian Approach

Marwala, Tshilidzi; Mdlazi, Lungile; Sibisi, Sibusiso
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/05/2007
Relevância na Pesquisa
86.04%
This paper compares the Maximum-likelihood method and Bayesian method for finite element model updating. The Maximum-likelihood method was implemented using genetic algorithm while the Bayesian method was implemented using the Markov Chain Monte Carlo. These methods were tested on a simple beam and an unsymmetrical H-shaped structure. The results show that the Bayesian method gave updated finite element models that predicted more accurate modal properties than the updated finite element models obtained through the use of the Maximum-likelihood method. Furthermore, both these methods were found to require the same levels of computational loads.; Comment: 7 pages, IMAC2004

Sampling Techniques in Bayesian Finite Element Model Updating

Boulkaibet, I.; Marwala, T.; Mthembu, L.; Friswell, M. I.; Adhikari, S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 15/10/2011
Relevância na Pesquisa
76.09%
Recent papers in the field of Finite Element Model (FEM) updating have highlighted the benefits of Bayesian techniques. The Bayesian approaches are designed to deal with the uncertainties associated with complex systems, which is the main problem in the development and updating of FEMs. This paper highlights the complexities and challenges of implementing any Bayesian method when the analysis involves a complicated structural dynamic model. In such systems an analytical Bayesian formulation might not be available in an analytic form; therefore this leads to the use of numerical methods, i.e. sampling methods. The main challenge then is to determine an efficient sampling of the model parameter space. In this paper, three sampling techniques, the Metropolis-Hastings (MH) algorithm, Slice Sampling and the Hybrid Monte Carlo (HMC) technique, are tested by updating a structural beam model. The efficiency and limitations of each technique is investigated when the FEM updating problem is implemented using the Bayesian Approach. Both MH and HMC techniques are found to perform better than the Slice sampling when Young's modulus is chosen as the updating parameter. The HMC method gives better results than MH and Slice sampling techniques, when the area moment of inertias and section areas are updated.; Comment: Paper Accepted in the 25th International Modal Analysis Conference...

Finite Element Model Updating Using Response Surface Method

Marwala, Tshilidzi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/05/2007
Relevância na Pesquisa
86.19%
This paper proposes the response surface method for finite element model updating. The response surface method is implemented by approximating the finite element model surface response equation by a multi-layer perceptron. The updated parameters of the finite element model were calculated using genetic algorithm by optimizing the surface response equation. The proposed method was compared to the existing methods that use simulated annealing or genetic algorithm together with a full finite element model for finite element model updating. The proposed method was tested on an unsymmetri-cal H-shaped structure. It was observed that the proposed method gave the updated natural frequen-cies and mode shapes that were of the same order of accuracy as those given by simulated annealing and genetic algorithm. Furthermore, it was observed that the response surface method achieved these results at a computational speed that was more than 2.5 times as fast as the genetic algorithm and a full finite element model and 24 times faster than the simulated annealing.; Comment: 9 pages

Optimization of modal analysis and cross-orthogonality techniques to insure finite element model correlation to test data

Miller, Carlton W.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Relevância na Pesquisa
85.91%
This work summarizes the views of current authors on the multifaceted problems associated with updating a finite element model with vibration test data. It presents the practical optimization solutions for each step from pre-test analysis, through the actual vibration test, through post-test orthogonality checks and subsequent model correlation.