The demand for a cost effective site investigation method has resulted in the introduction of various advanced in-situ testing techniques. These techniques utilise modern electronics instrumentation to monitor various soil parameters during site investigation. The data is then processed using high speed, low cost digital computers which allow an accurate and rapid assessment of the conditions of the foundation soil under a proposed construction site. In this thesis, a site investigation tool that drives a coring tube into the ground under a combination of vibration and impact is considered. This machine, called a vibro-impact corer, is fully instrumented to provide penetrometer-type information and a core sample for further inspection in the laboratory. The self-adjusting mechanism inherent in this machine delivers the minimum level of energy required to overcome soil resistance which thereby allows continuous penetration of the coring tube. This mechanism is also results in minimal induced disturbance during the coring process. This thesis investigates use of the vibro-impact corer as a soil classification tool. It involves the design of data analysis software to perform the soil classification procedure. Due to the nature of the system, the resistance monitored through the annular load cell fitted at the tip of the coring tube consists of the dynamic end resistance waveform and the peak magnitude of these waveforms over a sampling period. The vibro-impact soil classification system is based on the distinct self-adjusting mechanism of the machine. The self-adjustment mechanism imparts a different level of impact and vibration as soil conditions change which produces distinct dynamic soil resistance waveforms. In addition, the penetration rate and the magnitude of the soil resistance encountered also varies according to the material being penetrated. These two features are used to form the basis of the soil classification system in this software. The software also includes options for empirical correlation of the results obtained from the vibro-impact penetrometer with the CPT and SPT tests to allow comparison. The vibro-impact soil classification software is designed to be user-friendly. It reads the data files from a Biodata Transient Capture System for the classification process. The output devices such as plotter and printer are used to produce hardcopy records for various data. All the options are menu driven. A two degree freedom simulation of the operational responses of the vibro-impact machine is also included in this thesis. The main objective of this simulation is to study the soil response during vibro-impact mode of driving. This allows a comparison of the simulation soil responses to the model test results to provide an understanding of the soil behaviour under a combination of both vibratory and impact loadings. This thesis presents the results of several laboratory model and full scale vibro-impact penetrometer tests. It concentrates on the main subject of soil classification during the discussions although in some occasions the operational mechanism of the machine is mentioned. The results justify the approaches adopted for the soil classification system using a vibro-impact machine.

A força de radiação acústica tem sido utilizada como o método de examinar propriedades físicas de materiais em diversas áreas. A vibro-acustografia é uma das técnicas que emprega este tipo de força para realizar análises de propriedades mecânicas de materiais. Esta técnica consiste na aplicação de força acústica modulada e focalizada na região de interesse. O alvo excitado vibra na frequência de modulação e o som emitido é característico da impedância mecânica do meio. Este som é detectado usando um hidrofone dedicado. Neste trabalho, propomos uma modificação nesta técnica de vibro-acustografia (VAG) e aplicando a técnica denominada vibro-acustomagnetografia (VAMG) substituindo o hidrofone por um sensor magnético de alta sensibilidade. A radiação acústica modulada será aplicada sobre um alvo magnetizado imerso no fluido em estudo. Com este procedimento, poder-se-á medir o deslocamento estático e dinâmico do alvo magnético (esfera) quando acusticamente excitado. Neste trabalho, foi usado um sensor magnetorresistivo com resolução da ordem de 1 nT para a montagem do transdutor de detecção de deslocamento do alvo magnético. A vibração do alvo foi induzida por uma força sem contato, usando a força acústica produzida por dois feixes concêntricos gerado por elementos piezelétricos confocais de mesma área e com foco comum a 7 cm. O alvo usado foi uma esfera magnética com um raio de 2,36 mm. O aparato foi avaliado por meio de medidas em água e em óleo. Os parâmetros viscoelásticos foram estimados a partir de ajustes não lineares da resposta do transdutor magnético em função da freqüência de modulação. / The acoustic radiation force has been used as the method to examine some materials physical properties in various areas. The vibro-acoustography is a technique that is being used to perform analysis of mechanical properties of materials. This technique involves the application of a focused acoustic modulated force. The excited target will vibrate at the frequency of modulation and the emitted sound is characteristic of the medium mechanical impedance. This sound is detected using a dedicated hydrophone. In this paper, we propose a modification of this technique vibro-acoustography (VAG) and applying a technique called vibro-acustomagnetography (VAMG) replacing the hydrophone by a magnetic sensor with high sensitivity. In this case, the modulated acoustic radiation will be applied on a magnetized target immersed in the fluid under study. With this procedure, static and dynamic displacement of the magnetic target (ball) will be measured when acoustically excited. In this study, we used a magnetoresistive sensor with resolution of about 1 nT for mounting the transducer to detect displacement of the magnetic target. The vibration of the target was induced by a non-contact force, using an ultrasonic beam modulated by two concentric beams generated by two piezoelectric elements confocal of the same area and common focus to 7 cm. The target used was a magnetic sphere with a radius of 2.36 mm. The apparatus was evaluated through of measurements in water and oil. Viscoelastic parameters were estimated fitting the nonlinear response of the magnetic transducer function of frequency modulation.

A força de radiação acústica tem sido utilizada como o método de examinar propriedades físicas de materiais em diversas áreas. A vibro-acustografia é uma das técnicas que emprega este tipo de força para realizar análises de propriedades mecânicas de materiais. Esta técnica consiste na aplicação de força acústica modulada e focalizada na região de interesse. O alvo excitado vibra na frequência de modulação e o som emitido é característico da impedância mecânica do meio. Este som é detectado usando um hidrofone dedicado. Neste trabalho, propomos uma modificação nesta técnica de vibro-acustografia (VAG) e aplicando a técnica denominada vibro-acustomagnetografia (VAMG) substituindo o hidrofone por um sensor magnético de alta sensibilidade. A radiação acústica modulada será aplicada sobre um alvo magnetizado imerso no fluido em estudo. Com este procedimento, poder-se-á medir o deslocamento estático e dinâmico do alvo magnético (esfera) quando acusticamente excitado. Neste trabalho, foi usado um sensor magnetorresistivo com resolução da ordem de 1 nT para a montagem do transdutor de detecção de deslocamento do alvo magnético. A vibração do alvo foi induzida por uma força sem contato, usando a força acústica produzida por dois feixes concêntricos gerado por elementos piezelétricos confocais de mesma área e com foco comum a 7 cm. O alvo usado foi uma esfera magnética com um raio de 2,36 mm. O aparato foi avaliado por meio de medidas em água e em óleo. Os parâmetros viscoelásticos foram estimados a partir de ajustes não lineares da resposta do transdutor magnético em função da freqüência de modulação. / The acoustic radiation force has been used as the method to examine some materials physical properties in various areas. The vibro-acoustography is a technique that is being used to perform analysis of mechanical properties of materials. This technique involves the application of a focused acoustic modulated force. The excited target will vibrate at the frequency of modulation and the emitted sound is characteristic of the medium mechanical impedance. This sound is detected using a dedicated hydrophone. In this paper, we propose a modification of this technique vibro-acoustography (VAG) and applying a technique called vibro-acustomagnetography (VAMG) replacing the hydrophone by a magnetic sensor with high sensitivity. In this case, the modulated acoustic radiation will be applied on a magnetized target immersed in the fluid under study. With this procedure, static and dynamic displacement of the magnetic target (ball) will be measured when acoustically excited. In this study, we used a magnetoresistive sensor with resolution of about 1 nT for mounting the transducer to detect displacement of the magnetic target. The vibration of the target was induced by a non-contact force, using an ultrasonic beam modulated by two concentric beams generated by two piezoelectric elements confocal of the same area and common focus to 7 cm. The target used was a magnetic sphere with a radius of 2.36 mm. The apparatus was evaluated through of measurements in water and oil. Viscoelastic parameters were estimated fitting the nonlinear response of the magnetic transducer function of frequency modulation.

Une méthode systématique permettant d'identifier et de hiérarchiser les sources sonores soit la méthode d'analyse des chemins de transfert en condition opérationnelle (OTPA) d'un véhicule récréatif a été investiguée. Elle a permis d'identifier et d'hiérarchiser les sources et les chemins de transfert dominants selon un critère de moyenne du niveau global avec pondération C des contributions sur tous les régimes d'opération. Des solutions basées sur les règles de l'art du domaine de la vibro-acoustique ont ensuite été appliquées sur ces sources et chemins de transfert dominants. Une validation expérimentale sur les composants individuels a été accomplie afin de quantifier le niveau d'amélioration. La mise en oeuvre de ces composants modifiés et installés sur le véhicule a permis de réduire de façon majeure le niveau sonore perçu pour le conducteur et le passager du véhicule en plus d'en augmenter la qualité subjective. Avec la même méthodologie, la hiérarchisation de ces sources a permis de confirmer la diminution importante du contenu fréquentiel en moyenne et haute fréquence. Cependant, le niveau global à l'opérateur n'a pas toujours diminué, conséquence d'une augmentation du niveau selon les ordres moteur 1 et 2. Cette hausse de niveau n'est toutefois pas perceptible pour l'utilisateur. Un indice amélioré, tenant compte non seulement du niveau sonore mais aussi de la "perception de qualité sonore" sur lequel la hiérarchisation des sources devrait reposer, doit être développé.

No description available.

With the development of manufacturing techniques such as the Electron Beam Free Form Fabrication (EBF3), a metal deposition technique which deposits metal in complex shapes on a metallic base plate, it has become easy to manufacture complex shapes such as panels with curvilinear stiffeners. Designing and optimizing stiffened panels with predefined structural and acoustic response is the focus of this dissertation. Researchers have dealt with sizing optimization of panels with straight/curvilinear stiffeners for many years and it has been proven that in some cases the mass of a panel with curvilinear stiffeners is lesser than the mass of a panel with straight stiffeners for a complex loading such as bi-axial compression with shear and transverse pressure. The research work in this dissertation addresses the sizing as well as placement optimization of panel with straight and curvilinear stiffeners for desired structural as well as acoustic response. For acoustic optimization, point-excited stiffened panels are designed for minimal sound radiation given the constraint on total mass of the structure. To reduce the computational expense of structural-acoustic optimization, a new methodology for the objective function evaluation is also proposed and optimal design for minimum radiated acoustic power is discussed. The developed framework, named EBF3PanelOpt for structural acoustic optimization of point excited stiffened panels is extended to multi point excitation to capture the realistic excitations such as turbulent boundary layer (TBL) pressure fluctuations. The Corcos model of representing TBL is used to capture correlation of TBL pressure excitation. Validation of the approach using Corcos TBL model, implemented in EBF3PanelOpt is performed using fast multi-pole boundary element method in FastBEM and a conventional boundary element code, HELM3D. The optimal designs are obtained for a panel with two and four stiffeners, respectively. The minimization of both, the mass and the acoustic response during structural-acoustic optimization is conflicting in nature. Therefore, a multi-objective design optimization using non-dominated sorting genetic algorithm-II (NSGA-II) is performed. The Pareto optimal designs, obtained using multi-objective design optimization approach has reduced the acoustic response significantly with a minor mass penalty of the structure when compared to a baseline design while meeting all the constraints such as buckling eigenvalue, von Mises, and crippling stresses. A multi-objective design optimization framework is also developed for design optimization of diffuse field excited panels with straight and curvilinear stiffeners. The Pareto optimal designs of panel with six stiffeners are obtained using developed framework and a comparative study is performed with a baseline design with six straight stiffeners. The developed framework is also extended to perform multi-objective design optimization of point excited complex structures such as curved panels with straight or curvilinear stiffeners. A fast multi-pole boundary element method is used to calculate the acoustic response of the curved panel with stiffeners and design optimization results of a curved panel with two and four stiffeners are discussed. Experiments are also performed at Sound and Acoustic Load Transmission (SALT) facility of Langley Research Center to measure the sound radiation and transmission loss for two panels with straight and curvilinear stiffeners, respectively. The stiffened test panels with six stiffeners have been designed using multi-objective design optimization framework for TBL excitation. / Ph. D.

Thesis (M.S.)--University of Wisconsin--Madison, 1949. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves i-iii).

Made available in DSpace on 2016-08-29T15:32:50Z (GMT). No. of bitstreams: 1 tese_3570_Danilo.pdf: 1685252 bytes, checksum: 346a7ccf40715ccb36eea052368a46ff (MD5) Previous issue date: 2009-10-16 / À medida que os sistemas mecânicos tornam-se mais flexíveis novos fenômenos da dinâmica de sistemas, antes menos importantes por causa da baixa probabilidade de sua ocorrência, ganham relevância. Entre estes estão os sistemas com vibro-impactos. É que os sistemas mais flexíveis terminam por amplificar os fenômenos que ocorrem nos impactos e há participação destes fenômenos na dinâmica global dos sistema. O trabalho apresenta um estudo sobre sistemas com vibroimpacto, tomando como objeto de estudo particular um sistema massa-mola-amortecedor com excitação pela base cujo movimento é limitado lateralmente por obstáculos contra os quais a massa em movimento colide. O sistema é analisado na sua forma adimensional onde nossa pesquisa se concentra na busca de condições de existência e estabilidade de certos tipos de movimento. A busca exaustiva da existência e estabilidade de muitos padrões de movimento não é o objetivo do trabalho. Por ora estamos buscando apenas à descrição detalhada da técnica e à estruturação de ferramentas computacionais que facilitem este trabalho. Vencida esta etapa, apresentam-se algumas análises para os padrões de movimento mais comuns com resultados satisfatórios que podem nos trazer interessantes questionamentos para expansão deste, o que na verdade aparece como sugestão para trabalhos futuros. Palavras-Chave: Oscilações, vibrações, vibro-Impacto, balanço harmônico

La caractérisation expérimentale de la réponse vibro-acoustique de panneaux excités par des champs de pression aléatoires est d'un grand intérêt autant en recherche que pour des applications industrielles. Deux excitations sont particulièrement étudiées: le champ acoustique diffus les pressions fluctuantes induites par une couche limite turbulente. Les moyens d’essais associés à ces excitations (chambre réverbérante, soufflerie, essais in situ) peuvent être très coûteux, difficilement contrôlables et rarement comparables entre laboratoires ou centre d’essais (installations de différentes dimensions ou mises en œuvres). La reproductibilité des mesures peut alors être remise en cause, ce qui rend difficile la comparaison entre différentes solutions technologiques. Il y a donc un fort intérêt à disposer d'un outil de laboratoire permettant de reproduire l’effet de ces excitations aléatoires dans un environnement contrôlé. Dans ce contexte, cette thèse propose de développer une méthode expérimentale permettant de caractériser le comportement vibro-acoustique de panneaux sous un champ de pression aléatoire en s’affranchissant des moyens d’essais usuels. Les approches que l’on étudie se basent sur la formulation mathématique du problème dans le domaine des nombres d'onde. Celle-ci met en évidence une séparation explicite des contributions de l'excitation (via l’interspectre de pression pariétale), de celles du comportement vibro-acoustique du panneau (via les fonctions de sensibilité). A partir de la connaissance de l'interspectre de pression pariétale, il suffit alors de déterminer expérimentalement les fonctions de sensibilité du panneau afin de déterminer par post-traitement sa réponse à l'excitation considérée. Deux méthodes permettant de déterminer les fonctions de sensibilité sont étudiées numériquement et validées expérimentalement : la méthode dite de l’antenne synthétique et une méthode basée sur des principes de réciprocité. Pour étudier la validité de ces méthodes, on compare leurs résultats à ceux obtenus par des moyens standards pour deux types de panneaux et les deux types d’excitations évoqués précédemment. / Abstract: The experimental vibro-acoustic characterization of panels submitted to random pressure fields is of great interest in the industry as well as in research laboratories. For the transport sector, this type of excitation can be found when a turbulent flow develops at the wall of a moving vehicle for example. The pressure fluctuations induced by the turbulent boundary layer excite the panels which radiate a noise inside the cabin. The experimental reproduction of those pressure fluctuations requires test means which can be very costly (i.e., wind tunnel, in situ tests) and whose physical parameters can hardly be controlled. The repeatability of measurements can thereby be questioned which makes it hard to compare different technological solutions. A second example of random pressure field is the diffuse acoustic field. This latter is usually reproduced in a reverberant room which is often coupled with an anechoic chamber by means of the panel whose acoustic insulation is to be tested. A pressure field is assumed to be diffuse if the acoustic energy comes from every direction with an equiprobable intensity of the incident waves. This assumption is never fully reached in practice (lack of grazing incident waves, strong modal behavior of the room at low frequencies, etc.). A laboratory tool which allows reproducing the effect of those random excitations in a controlled environment is therefore of great interest. In this context, this thesis aims at developing an experimental method to characterize the vibro-acoustic behavior of panels under random pressure fields without using the common test means (wind tunnel, reverberant room, in situ tests, etc.). For relevance sake, this approach must compensate for the previously stated issues. The approaches studied in this work are based on the mathematical formulation of the problem in the wavenumber domain. This latter allows an explicit separation of the contributions of the excitation via the wall-pressure cross-spectrum, from those of the vibro-acoustic behavior of the panel via so-called ‘sensitivity functions’. Assuming the wall-pressure cross-spectrum of the excitation is known, it is only required to experimentally determine those sensitivity functions, on the panel or in the acoustic medium, to determine the response of the panel to the considered excitation by post-processing. Two methods aiming at determining the sensitivity functions will be numerically and experimentally studied: the source scanning technique and the method based on the reciprocity principle. Results obtained with those method are compared to measurements using standard test means to attest the validity of those methods. Several vibro-acoustic indicators will be confronted while considering the two previously mentioned excitations and for two types of panels: an academic panel and a ‘complex’ from the aeronautic sector. This latter shows the applicability of the method in an industrial context.

Les fuselages des avions sont généralement en aluminium ou en composite renforcés par des raidisseurs longitudinaux (lisses) et transversaux (cadres). Les raidisseurs peuvent être métalliques ou en composite. Durant leurs différentes phases de vol, les structures d'avions sont soumises à des excitations aériennes (couche limite turbulente : TBL, champs diffus : DAF) sur la peau extérieure dont l'énergie acoustique produite se transmet à l'intérieur de la cabine. Les moteurs, montés sur la structure, produisent une excitation solidienne significative. Ce projet à [i.e. a] pour objectifs de développer et de mettre en place des stratégies de modélisations des fuselages d'avions soumises à des excitations aériennes et solidiennes. Tous [i.e. Tout] d'abord, une mise à jour des modèles existants de la TBL apparaît dans le deuxième chapitre afin de mieux les classer. Les propriétés de la réponse vibro-acoustique des structures planes finies et infinies sont analysées. Dans le troisième chapitre, les hypothèses sur lesquelles sont basés les modèles existants concernant les structures métalliques orthogonalement raidies soumises à des excitations mécaniqués, DAF et TBL sont réexaminés en premier lieu. Ensuite, une modélisation fine et fiable de ces structures est développée. Le modèle est validé numériquement à l'aide des méthodes des éléments finis (FEM) et de frontière (BEM). Des tests de validations expérimentales sont réalisés sur des panneaux d'avions fournis par des sociétés aéronautiques. Au quatrième chapitre, une extension vers les structures composites renforcées par des raidisseurs aussi en composites et de formes complexes est établie. Un modèle analytique simple est également implémenté et validé numériquement. Au cinquième chapitre, la modélisation des structures raidies périodiques en composites est beaucoup plus raffinée par la prise en compte des effets de couplage des déplacements planes et transversaux. L'effet de taille des structures finies périodiques est également pris en compte. Les modèles développés ont permis de conduire plusieurs études paramétriques sur les propriétés vibro-acoustiques des structures d'avions facilitant ainsi la tâche des concepteurs. Dans le cadre de cette thèse, un article a été publié dans le Journal of Sound and Vibration et trois autres soumis, respectivement aux Journal of Acoustical Society of America, International Journal of Solid Mechanics et au Journal of Sound and Vibration.