An��lise de modelos de escoamento aplicados a ��guas superficiais e subterr��neas

Disserta����o de mest., Recursos H��dricos, 2007, Faculdade de Engenharia de Recursos Naturais, Universidade do Algarve

A influ��ncia da viscosidade dos solos argilosos na consolida����o do dique n�� 3 da Represa de Lebrija

Disserta����o de mestrado, Engenharia Civil (Constru����o), Instituto Superior de Engenharia, Universidade do Algarve, 2014

Higher order model for analysis of magneto-electro-elastic plates

In this paper is presented an higher-order model for static and free vibration analyses of magneto-electro-elastic plates, wich allows the analysis of thin and thick plates, which allows the analysis of thin and thick plates. The finite element model is a single layer triangular plate/shell element with 24 degrees of fredom for the generalized mechanical displacements. Two degrees on freedom are introduced per each element layer, one corresponding to the electrical potential and the other for magnetic potential. Solutions are obtained for different laminations of the magneto-electro-elastic plate, as well as for the purely elastic plate as a special case.

Controle activo de estruturas adaptativas com sensores e actuadores piezoel��ctricos

Nos ��ltimos anos o estudo de estruturas inteligentes tem atra��do v��rios investigadores devido ��s suas potenciais vantagens numa larga gama de aplica����es, tais como controle de forma, supress��o de vibra����es, atenua����o de ru��do e detec����o de dano. O uso de materiais ���inteligentes��� tal como os materiais piezoel��ctricos na forma de l��minas ou ���patches���, embebidas ou coladas na superf��cie de estruturas constru��das de materiais comp��sitos, permite assim obter estruturas que por um lado s��o adaptativas e por outro revelam excelentes propriedades mec��nicas, aumentando assim bastante o desempenho e a fiabilidade de sistemas estruturais. Os materiais piezoel��ctricos t��m a propriedade de gerar uma carga el��ctrica sob a ac����o duma carga mec��nica e o reverso, isto ��, aplicando um campo el��ctrico nos elementos piezoel��ctricos da estrutura, esta deforma-se. Neste trabalho, �� apresentado um modelo de elementos finitos, baseado na teoria cl��ssica de placas, desenvolvido para a an��lise do controle activo em est��tica e din��mica lineares de estruturas integrando sensores e actuadores piezoel��ctrico na forma de l��minas, os quais introduzem um grau de liberdade referente ao potencial el��ctrico, por cada camada piezoel��ctrica do elemento finito. �� utilizado m��todo de Newmark para a solu����o iterativa das equa����es de equil��brio. Apresentam-se os resultados obtidos em tr��s exemplos ilustrativos.

Resonance control of piezolaminated structures

This paper deals with a third order shear deformation finite element model wich is applied on the active resonance control thin plate/shell laminated structures with integrated piezoelectric layers of patches, acting as sensors and actuators. The finite element model is a single layer tringular nonconforming plate/shell element with 24 degrees of freedom for he generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, wich are surface bonded on the laminated. The newwork method is considered to calculate the dynamic response of the laminated sructures forced to vibrate in the first natural frequency. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers. The model is applied to the solution of one illustrative case, and the results are presented and discussed.

Optimiza����o de estruturas laminadas adaptativas com controlo activo

Neste trabalho apresenta-se um modelo de elementos finitos, baseados na teoria cl��ssica das placas, desenvolvido para a an��lise de controlo activo em din��mica de estruturas de tipo placa/casca integrando sensores e actuadores piezoel��ctricos. O controlo �� iniciado atrav��s de uma optimiza����o pr��via do n��cleo laminado de modo a diminuir a amplitude da vibra����o. �� usado um algoritmo de controlo baseado na liga����o entre as l��minas piezoel��ctricas sensoras e actuadoras para obter um mecanismo de controlo da resposta din��mica da estrutura. A resolu����o por elementos finitos usa um elemento placa/casca triangular plano de 3 n��s, e em cuja formula����o se introduz um grau de liberdade referente ao potencial el��ctrico, por cada camada piezoel��ctrica do elemento finito. Apresentam-se os resultados obtidos em dois exemplos ilustrativos.

An��lise geometricamente n��o-linear de estruturas adaptativas piezolaminadas

Neste trabalho apresenta-se um modelo de elementos finitos, baseado na teoria cl��ssica de placas, para a an��lise linear e n��o-linear de estruturas do tipo placa/casca integrando sensores e actuadores piezoel��ctricos. �� usado um simples e eficiente elemento placa/casca triangular plano de 3 n��s, e em cuja formula����o se introduz um grau de liberdade referente ao potencial el��ctrico, por cada camada piezoel��ctrica do elemento finito. �� utilizada a formula����o Lagrangeana actualizada associada �� tecnica de Newton - Raphson para a solu����o iterativa das equa����es de equilibrio .O modelo pode ser aplicado a cascas piezolaminadas com geometria e carregamento arbitr��rios. Apresentam-se v��rios exemplos ilustrativos cujos resultados mostram a eficiencia do modelo proposto.

Placas elasto-electro-magn��ticas

Neste trabalho apresenta-se um modelo de elementos finitos, baseado na teoria cl��ssica de placas, para a an��lise linear e n��o-linear de estruturas do tipo placa/casca integrando sensores e actuadores piezoel��ctricos. �� usado um simples e eficiente elemento placa/casca triangular plano de 3 n��s, e em cuja formula����o se introduz um grau de liberdade referente ao potencial el��ctrico, por cada camada piezoel��ctrica do elemento finito. �� utilizada a formula����o Lagrangeana actualizada associada �� tecnica de Newton - Raphson para a solu����o iterativa das equa����es de equilibrio .O modelo pode ser aplicado a cascas piezolaminadas com geometria e carregamento arbitr��rios. Apresentam-se v��rios exemplos ilustrativos cujos resultados mostram a eficiencia do modelo proposto.

Non-linear finite element analysis of thin composite structures

A non-conforming three-node triangular finite element with 18 degree of freedom, is used in conjugation with the Kirchhoff theory for the non-linear analysis of thin composite plate-shell structure. The formulation of the geometrically non-linear analysis is based on an updated Lagrangian formulation associated with the Newton-Raphson iterative technique, which incorporates an automatic arc-length control procedure.

Shape control of laminated panels using piezoelectric actuators

This paper presents a finite element formulation based on the classical laminated plate theory for laminated structures with integrated piezoelectric layers or patches, acting as actuators.The finite element model is a single layer trinaguular nonconforming plate/shell element with 18 degrees of fredom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element elemenet layer or patch. An optimization of the patches position is perfomed to maximize the piezoelectric actuators efficiency as well as,the electric potential distribution is serach to reach the specified strusctura transverse displacement distribution is search to reach the specified structures trsnsverse displacement distribution (shape control). A gradient based algorithm is used for this purpose.Results are presented and discussed.

Optimal dynamic control of laminated adaptive structures using a higher order model and a genetic algorithm

This paper deals with a finite element formulation based on the classical laminated plate theory, for active control of thin plate laminated structures with integrated piezoelectric layers, acting as sensors and actuators. The control is initialized through a previous optimization of the core of the laminated structure, in order to minimize the vibration amplitude. Also the optimization of the patches position is performed to maximize the piezoelectric actuator efficiency. The genetic algorithm is used for these purposes. The finite element model is a single layer triangular plate/shell element with 24 degrees of freedom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, which can be surface bonded or embedded on the laminate. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers. To calculate the dynamic response of the laminated structures the Newmark method is considered. The model is applied in the solution of an illustrative case and the results are presented and discussed.

Non-linear analysis of composite structures with integrated piezoelectric sensors and actuators

This paper deals with the geometrically non linear analysis of thin plate/shell laminated structures with embedded integrated piezoelectric actuors or sensors layers and/or patches.The model is based on the Kirchhoff classical laminated theory and can be applied to plate and shell adaptive structures with arbitrary shape, general mechanical and electrical loadings. the finite element model is a nonconforming single layer triangular plate/shell element with 18 degrees of fredom for the generalized displacements and one e��lectrical potential degree of freedom for each piezoelectric layer or patch. An updated Lagrangian formulation associated to Newton-Raphson technique is used to solve incrementally and iteratively the equilibrium equation.The model is applied in the solution of four illustrative cases, and the results are compared and discussedwith alternative solutions when available.

Design of laminated structures using piezoelectric materials

Composite structures incorporating piezoelectric sensors and actuators are increasingly becoming important due to the offer of potential benefits in a wide range of engineering applications such as vibration and noise supression, shape control and precisition positioning. This paper presents a finit element formulation based on classical laminated plate theory for laminated structures with integrated piezoelectric layers or patches, acting as actuators. The finite element model is a single layer triangular nonconforming plate/shell element with 18 degrees of freedom for the generalized displacements, and one electrical potential degree of freedom for each piezsoelectric elementlayer or patch, witch are surface bonded on the laminate. An optimization of the patches position is performed to maximize the piezoelectric actuators efficiency as well as, the electric potential distribuition is search to reach the specified structure transverse displacement distribuition (shape control). A gradient based algorithm is used for this purpose. The model is applied in the optimization of illustrative laminated plate cases, and the results are presented and discussed.

Finit element model for active control of adaptive laminated structures

A finite element formulation for active vibration control of thin plate laminated structures with integrated piezoelectric layers, acting as sensors and actuators in presented. The finite element model is a nonconforming single layer triangular plate/shell element with 18 degrees of freedom for the generalized displacements and one electrical potential degree of freedom for each piezoelectric element layer, and is based on the kirchhoff classical laminated theory. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorithm is used, coupling the sensor and active piezoelectric layers, and Newmark method is used to calculate yhe dynamic response of the laminated structures. The model is applied in the solution of several illustrative cases, and the results are presented and discussed.

Core and patch position optimizations for vibration control of piezolaminated structures

This paper deals with a finite formulation baserd on the classical laminated plate tehory, for active control of thin late laminated structures with integrated piezoelectric layers, acting as sensors and actuators. The control is initialized through a previuos optimization of the core of the laminated structure, in order to minimize the vibration amplitude. Also the optimization of the patches position in performed to maximize the piezoelectric actuator efficiency. the simulating annealing mthod is used for these purposes. The finite element model is a single layer triangular nonconforming plate/shell element with 18 degrees of fredom for the generalized displacements, and one electrical potential degree of freedom for each piezoelectric element layer, wich can be surface bonded or imbedded on the laminate. To achieve a mechanism of active control of the structure dynamic response, a feedback control algorirhm is used, coupling the sensor and active piezoelectric layers. To calculate the dynamic response of the laminated structures the Newmark method is considered. The model is applied in the solution of an illustrative case and the results are presented and discussed.