Thesis (Ph.D.)--University of Alberta, 2009. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Orthodontics and Medical Sciences, Department of Dentistry. Title from pdf file main screen (viewed on August 1, 2009). Includes bibliographical references.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Seyed M. Ghiaasiaan; Committee Member: Dr. Marc K. Smith; Committee Member: Dr. Sheldon M. Jeter

Thesis (M.S.)--University of North Texas, Dec., 2008. / Title from title page display. Includes bibliographical references.

Thesis (M. Eng.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 169-176.

Η μελέτη αυτή αποσκοπεί να εμβαθύνει εμπεριστατωμένα στο ζήτημα του ελέγχου βλαβών αυτοκινήτου με την χρήση πιεζοκρυστάλλων. Οι κρύσταλλοι αυτοί είναι τοποθετημένοι στο σώμα της μηχανής και λαμβάνουν δονήσεις από το περιβάλλον τους τις οποίες μετατρέπουν σε ηλεκτρικά σήματα. Τα σήματα αυτά επεξεργάζονται κατόπιν από ένα μικροελεγκτή και συγκεκριμένα το AduC 7026 της Analog Devices. Η διάταξη μας δηλαδή είναι ικανή να ανιχνεύσει οποιαδήποτε βλάβη υπάρχει στο αυτοκίνητο η οποία επηρεάζει συστήματα εντός της εμβέλειας των πιεζοηλεκτρικών αισθητήρων οι οποίοι βρίσκονται πάνω στο σώμα της μηχανής. Η μελέτη χωρίζεται σε έξι μέρη. Στο πρώτο αναλύεται εξαρχής η κατασκευή , η λέιτουργία και τα μέρη της μηχανής του αυτοκινήτου. Στο δεύτερο αναλύεται η φύση , η λειτουργία των πιεζοκρυστάλλων και οι σχέσεις που διέπουν τη λειτουργία τους. Στο τρίτο μέρος ακολουθεί η μέθοδος με την οποία αναλύονται οι δονήσεις και εκμαιεύεται συμπέρασμα για την ορθή ή εσφαλμένη λειτουργία της μηχανής. Στο τέταρτο εξετάζεται η δομή και η λειτουργία του μικροελεγκτή, καθώς και παρουσιάζεται το λογισμικό Keil-Uvision. Στο πέμπτο παρατίθενται τμήματα του κώδικα που αναπτύχθηκε και εξηγείται η λειτουργία τους. Στο έκτο γίνεται η προσομοίωση του κώδικα. Ο κώδικας γράφτηκε σε γλώσσα προγραμματισμού C. / This thesis aims to investigate the subject of fault detection of automobile vehicles by the use of piezoelectric transducers that are placed upon the engine of the vehicle. The transducers receive the vibrations and turn them into electric signals. These signals are being processed by a microcontroller and specifically the Aduc7026 built by Analog Devices. The ordinance is capable of detecting faults in the vehicle affecting systems within the range of vibration receiving capability of piezoelectric transducers The thesis is devided into 6 parts. The 1st section deals with the construction and the operation of the internal combustion engine. In the 2nd section the nature, the operation and the mathematical formulations that define the operation of piezoelectric transducers are being analyzed. The 3rd part deals with the method by which the vibrations are analyzed so as to decide whether the engine operates normally. The 4th section deals with the structure and operation of the microcontroller and with the Keil-Uvision software. In the 5th part sections of the code are referenced and their operation is being explained. In the 6th and final part the code is being simulated. The code is written in C programming language.

Electromagnetic acoustic transducers (EMATs) are increasingly used in industries due to their attractive features of being non-contact, cost-effective and the fact that a variety of wave modes can be generated, etc. There are two major EMATs coupling mechanisms: the Lorentz force mechanism for conductive materials and the magnetostriction mechanism for ferromagnetic materials; EMATs operated on Lorentz force mechanism are the focus of this study. This work aims to investigate novel efficient modelling techniques for EMATs, in order to gain further knowledge and understanding of EMATs wave pattern, how design parameters affect its wave pattern and based on above propose and optimise novel sensor structures. In this study, two novel modelling methods were proposed: one is the method combining the analytical method for EM simulation and the finite-difference time-domain (FDTD) method for US simulation for studying the Rayleigh waves' properties on the vertical plane of the material; the other one is the method utilizing a wholly analytical model to explore the directivity of surface waves. Both simulations models have been validated experimentally. The wholly analytical model generates the radiation pattern of surface waves, which lays a solid foundation for the optimum design of such sensors. The beam directivity of surface waves was investigated experimentally, and results showed the length of wires has a significant effect on the beam directivity of Rayleigh waves. A novel configuration of EMATs, variable-length meander-line-coil (VLMLC), was proposed and designed. The beam directivity of surface waves generated by such novel EMATs were analytically investigated. Experiments were conducted to validate such novel EMATs models, and results indicated that such EMATs are capable of supressing side lobes, and therefore resulting in a more concentrated surface waves in the desired direction. Further, another two novel configuration of EMATs, the four-directional meander-line-coil (FDMLC) and the six-directional meander-line-coil (SDMLC), were proposed and designed; results showed these EMATs are capable of generating Rayleigh waves in multiple directions and at the same time suppressing side lobes.

A utilização de ondas guiadas em técnicas de monitoramento de integridade estrutural tem se mostrado uma alternativa interessante para economia de tempo e de custos de operação. Técnicas com ondas guiadas apresentam a característica de monitorar trechos extensos de uma estrutura a partir de um único ponto de acesso, permitindo a inspeção de partes remotas e de difícil acesso. Entre os modos fundamentais de propagação de ondas guiadas em chapas, o modo SH0 possui a vantagem de não ser dispersivo, além de sofrer menores atenuações ao se propagar em superfícies em contato com fluidos. Neste trabalho é proposto um modelo de transdutor do modo SH0 de forma omnidirecional em uma chapa de aço utilizando um arranjo com cerâmicas piezoelétricas, que permita inspecionar determinada área de um componente através de um único modo de propagação. Para caracterizar e compreender o comportamento da resposta obtida foram realizadas simulações numéricas parametrizando características do modelo proposto, como o número de elementos piezoelétricos e dimensões geométricas dos componentes do transdutor. Para validação dos resultados do modelo numérico foram construídos modelos experimentais do transdutor, os quais foram instalados sobre uma chapa de aço de 2mm de espessura para verificação dos modos de propagação emitidos. Avaliando a relação entre intensidades de cada modo emitido e a qualidade da emissão de SH0 foi possível identificar as frequências que apresentaram resposta com a característica desejada. Também foi verificado o comportamento dos transdutores construídos ao serem excitados por ondas propagando na chapa, avaliando a sua utilização também como receptores. / The use of guided waves in structural health monitoring techniques has already proved to be an interesting alternative to reduce inspection time and overall operational costs. Guided waves techniques enable monitoring large structures from one single access point, allowing the inspection of distant and hard access parts. Among the fundamental propagation modes of guided waves in plates, the SH0 mode has the advantage of being non dispersive, as well as being subject to less attenuation when propagating through surfaces in contact with fluids. In this work, it is proposed one omnidirectional SH0 mode transducer in a steel plate using a piezoelectric ceramic array, which allows inspecting a component area through a single propagation mode. Numeric simulations parameterizating features of the transducer, such as the number of piezoelectric elements and the geometric dimensions of the transducer’s components, were developed to characterize and investigate the effect on the output response. To validate the numeric simulation results, experimental models of the transducer were built, which were installed on a 2mm thick steel plate to verify the generated propagation modes. The analysis of the relation between the intensity of each mode generated in the plate and the emission quality of the SH0 mode allowed the identification of frequencies that presented the most desirable response characteristics. The behavior of the built transducers was also studied when they were excited by waves propagating through the plate, evaluating the use of the transducers as signal receptors.

Submitted by Marcelo Marchi (marcelo.marchi@outlook.com) on 2016-02-01T14:54:11Z No. of bitstreams: 1 MARCHI_M.pdf: 2521553 bytes, checksum: bbdd16180ad3fd8085e045a41549b236 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-02-02T13:31:26Z (GMT) No. of bitstreams: 1 marchi_m_dr_bauru_pdf.pdf: 2521553 bytes, checksum: bbdd16180ad3fd8085e045a41549b236 (MD5) / Made available in DSpace on 2016-02-02T13:31:26Z (GMT). No. of bitstreams: 1 marchi_m_dr_bauru_pdf.pdf: 2521553 bytes, checksum: bbdd16180ad3fd8085e045a41549b236 (MD5) Previous issue date: 2015-12-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O processo de retificação é considerado um dos últimos na cadeia de produção de peças de precisão, sendo, portanto, essencial ter um sistema de monitoramento confiável para avaliar a condição da superfície da peça. Neste trabalho é proposto o uso do método da impedância eletromecânica (EMI) para monitorar, em tempo real, o processo de retificação plana, especialmente no que diz respeito à condição da peça retificada. O método EMI se destaca por sua simplicidade e por utilizar componentes de baixo custo, tais como os transdutores piezelétricos de PZT (Pb-Lead Zirconate Titanate). A fim de avaliar a viabilidade do método EMI no processo de retificação, ensaios experimentais foram realizados numa máquina retificadora plana empregando-se rebolo CBN e peça de aço SAE 1020, com transdutores de PZT instalados na peça e no seu suporte. Durante o processo de retificação, a impedância elétrica do transdutor foi medida e índices de dano foram calculados e comparados com o desgaste da peça. Os resultados experimentais indicam que o método EMI pode ser uma alternativa eficiente e de baixo custo para o monitoramento de peças de precisão no processo de retificação plana. / Grinding is considered one of the last processes in precision parts manufacturing, which makes it indispensable to have a reliable monitoring system to evaluate workpiece surface integrity. This paper proposes the use of the electromechanical impedance (EMI) method to monitor the surface grinding operation in real time, particularly the surface integrity of the ground workpiece. The EMI method stands out for its simplicity and for using low-cost components such as PZT (lead zirconate titanate) piezoelectric transducers. In order to assess the feasibility of applying the EMI method to the grinding process, experimental tests were performed on a surface grinder using a CBN grinding wheel and a SAE 1020 steel workpiece, with PZT transducers mounted on the workpiece and its holder. During the grinding process, the electrical impedance of the transducers was measured and damage indices were calculated and compared with workpiece wear. The experimental results indicate that the EMI method can be an efficient and cost effective alternative for monitoring precision workpieces during the surface grinding process. / CAPES: 118227-2

Made available in DSpace on 2014-12-02T11:16:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-09-15Bitstream added on 2014-12-02T11:20:51Z : No. of bitstreams: 1 000799830.pdf: 4517190 bytes, checksum: 4566f2d205fed1f4cb035a7c44ec4214 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Esta tese apresenta o estudo e implementação de técnicas de inspeção de estruturas delgadas tipo placa utilizando arrays de transdutores piezelétricos e ondas acústicas guiadas, associados a métodos de formação e composição de imagens. A detecção de danos em estruturas através de ondas guiadas e arrays de transdutores é um campo de pesquisa de grande importância, principalmente em áreas como a aeroespacial e de geração de energia, que utilizam estruturas delgadas e que exigem inspeção eficaz e completa, visando confiabilidade e segurança. O emprego de ondas acústicas guiadas permite inspecionar grandes áreas utilizando sensores sem a necessidade de realizar varreduras pela peça, de maneira não-destrutiva. Além disso, apresenta sensibilidade a diversos tipos de defeitos, como furos, corrosão, variação de espessura e defeitos superficiais. São estudados aspectos de propagação de ondas, diferentes modos de propagação e dispersão, assim como as principais características dos arrays e a formação de imagens. Os estudos teóricos são acompanhados por simulações usando os softwares MATLAB e PZFlex para obtenção dos modos de propagação das ondas, interação com defeitos e diagramas de radiação dos transdutores, cujos resultados são validados por meio da análise experimental em placas de materiais isotrópicos (alumínio). Montou-se um array linear de transdutores piezelétricos com 16 elementos na borda de uma placa de alumínio com defeitos artificiais. Os sinais provenientes de todas as possíveis combinações dos pares transmissor-receptor foram adquiridos para a utilização de técnicas de abertura sintética. A primeira contribuição deste trabalho é um método para detecção dos defeitos baseado na fase instantânea dos sinais. Substituindo-se a informação de amplitude dos sinais pela fase instantânea (IP) no método de formação de imagem, ... / This thesis presents the study and implementation of non-destructive testing techniques of platelike structures using piezoelectric array transducers and guided acoustic waves, associated with beamforming techniques and image compounding methods. Damage detection in structures using guided waves and arrays is a promising research area, especially in the aerospace and energy fields, where the use of plate-like structures demands thorough inspection due to the high safety levels of operation. Guided acoustic waves techniques can be used to inspect relatively large areas without the necessity of moving the transducers, in a non-destructive way. There are different propagation modes that can be coupled to the plate, and each mode is sensitive to specific types of defects, like notches, delamination and surface defects. Wave propagation, different propagation modes and dispersion characteristics, as well as arrays characteristics and imaging algorithms, are studied. MATLAB and PZFlex simulations are used to get further insight in the theoretical aspects, to obtain dispersion curves, interaction with defects and array response. Experimental results validate the simulations with isotropic materials (aluminum). A 16-elements piezoelectric linear array is mounted at the border of an aluminum plate with artificial defects. The signals related to all combinations of transmit-receive pairs are obtained with burst excitation, for use with synthetic aperture (SA) techniques. The first contribution of this work is a method for defect detection based on the instantaneous phase of the aperture data. The instantaneous phase (IP) image is obtained by replacing the amplitude information by the instantaneous phase in the conventional SA beamforming. From the analysis of the IP image, a threshold level is proposed in terms of the number of signals used for imaging. This threshold is applied to the IP image, resulting ... / FAPESP: 10/02240-0 / FAPESP: 10/16400-0 / FAPESP: 13/00330-0

Orientador: Ricardo Tokio Higuti / Co-orientador: Oscar Martinez-Graullera / Banca: Claudio kitano / Banca: Samuel da Silva / Banca: Nicolas Leonardo Pérez Alvarez / Banca: Joaquim Miguel Maia / Resumo: Esta tese apresenta o estudo e implementação de técnicas de inspeção de estruturas delgadas tipo placa utilizando arrays de transdutores piezelétricos e ondas acústicas guiadas, associados a métodos de formação e composição de imagens. A detecção de danos em estruturas através de ondas guiadas e arrays de transdutores é um campo de pesquisa de grande importância, principalmente em áreas como a aeroespacial e de geração de energia, que utilizam estruturas delgadas e que exigem inspeção eficaz e completa, visando confiabilidade e segurança. O emprego de ondas acústicas guiadas permite inspecionar grandes áreas utilizando sensores sem a necessidade de realizar varreduras pela peça, de maneira não-destrutiva. Além disso, apresenta sensibilidade a diversos tipos de defeitos, como furos, corrosão, variação de espessura e defeitos superficiais. São estudados aspectos de propagação de ondas, diferentes modos de propagação e dispersão, assim como as principais características dos arrays e a formação de imagens. Os estudos teóricos são acompanhados por simulações usando os softwares MATLAB e PZFlex para obtenção dos modos de propagação das ondas, interação com defeitos e diagramas de radiação dos transdutores, cujos resultados são validados por meio da análise experimental em placas de materiais isotrópicos (alumínio). Montou-se um array linear de transdutores piezelétricos com 16 elementos na borda de uma placa de alumínio com defeitos artificiais. Os sinais provenientes de todas as possíveis combinações dos pares transmissor-receptor foram adquiridos para a utilização de técnicas de abertura sintética. A primeira contribuição deste trabalho é um método para detecção dos defeitos baseado na fase instantânea dos sinais. Substituindo-se a informação de amplitude dos sinais pela fase instantânea (IP) no método de formação de imagem, ... / Abstract: This thesis presents the study and implementation of non-destructive testing techniques of platelike structures using piezoelectric array transducers and guided acoustic waves, associated with beamforming techniques and image compounding methods. Damage detection in structures using guided waves and arrays is a promising research area, especially in the aerospace and energy fields, where the use of plate-like structures demands thorough inspection due to the high safety levels of operation. Guided acoustic waves techniques can be used to inspect relatively large areas without the necessity of moving the transducers, in a non-destructive way. There are different propagation modes that can be coupled to the plate, and each mode is sensitive to specific types of defects, like notches, delamination and surface defects. Wave propagation, different propagation modes and dispersion characteristics, as well as arrays characteristics and imaging algorithms, are studied. MATLAB and PZFlex simulations are used to get further insight in the theoretical aspects, to obtain dispersion curves, interaction with defects and array response. Experimental results validate the simulations with isotropic materials (aluminum). A 16-elements piezoelectric linear array is mounted at the border of an aluminum plate with artificial defects. The signals related to all combinations of transmit-receive pairs are obtained with burst excitation, for use with synthetic aperture (SA) techniques. The first contribution of this work is a method for defect detection based on the instantaneous phase of the aperture data. The instantaneous phase (IP) image is obtained by replacing the amplitude information by the instantaneous phase in the conventional SA beamforming. From the analysis of the IP image, a threshold level is proposed in terms of the number of signals used for imaging. This threshold is applied to the IP image, resulting ... / Doutor