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Doctoral Thesis
DOI
10.11606/T.18.2008.tde-19012011-142931
Document
Author
Full name
Thiago Rodrigo Cicogna
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2008
Supervisor
Committee
Varoto, Paulo Sergio (President)
Balthazar, Jose Manoel
Lopes Júnior, Vicente
Marques, Flavio Donizeti
Trindade, Marcelo Areias
Title in Portuguese
Identificação de matrizes de função de resposta em freqüência multidirecionais em estruturas complexas
Keywords in Portuguese
Bimorph
FRF angular
Material piezelétrico
Movimentos angulares
Abstract in Portuguese
Este trabalho apresenta o desenvolvimento de uma metodologia para a estimativa de funções de resposta em freqüência angulares (FRFAs). Trata-se de uma técnica que utiliza transdutores piezelétricos (PZT) do tipo bimorph para a medição da curvatura local da estrutura através do potencial elétrico induzido pela extensão e compressão do sensor. A partir da estimativa da curvatura, a rotação pode ser obtida diretamente através de várias técnicas de interpolação (polinomial, formas modais, etc). Apresenta-se a modelagem téorica da qual se deriva as equações que governam a dinâmica de estruturas uni-dimensionais, do tipo viga, e estruturas bidimensionais, do tipo placa, ambas isotrópicas, onde se incorpora o sensor bimorph. Modelos em elementos finitos foram propostos no intuito de avaliar a utilização destes sensores (bimorphs) aplicados à estimativa das FRFAs. Apresentam-se também resultados numéricos e experimentais considerando-se uma viga engastada-livre (cantilever) e resultados numéricos considerando-se uma placa simplesmente apoiada. Um algoritmo genético foi ainda desenvolvido no intuito de determinar a posição e dimensão ótimas dos bimorphs em estruturas do tipo viga.
Title in English
Multidirectional frequency response functions matrices assessment in complex structures
Keywords in English
Angular FRF
Angular motions
Bimorph
Piezoelectric material
Abstract in English
The present work aims to perform the development of an attractive approach for accurate measurement of angular frequency response functions (AFRFs). It uses bimorph piezoceramic patches to measure the structure's local curvature through the measurement of the electric potential induced by the extension and compression of the patch's top and bottom stripes, respectively. From this curvature, rotation can be obtained directly by several interpolation techniques (single polynomial, modes basis). Theoretical modeling of the vibration incorporating piezoelectric bimorph sensor is presented and equations governing the dynamics for one-dimensional structures, like a beam, and for two-dimensional structures, like a plate, are derived for isotropic structures. Finite element model for the dynamic analysis were proposed to evaluate bimorphs patches applied to the measurement of angular FRFs. Numerical and experimental results are presented considering a cantilever beam and numerical results for a simply supported plate as tested structured. Also, in this work, a genetic algorithm was used as an adaptive heuristic search algorithm for optimal placement and sizing of the bimorph sensor into beam like structures.
 
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TRCicognatese.pdf (6.94 Mbytes)
Publishing Date
2011-02-07
 
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