This thesis concerns three-dimensional finite element modelling of Biot's equations for elasto-acoustic modelling of wave propagation in layered media including porous elastic materials. The concept of hierarchical (p-version) finite elements are combined with various weak forms of Biot's equations. Computationally efficient methods providing accurate solutions of sound propagation in layered porous media are discussed. The research falls within the areas linear acoustics and numerical acoustics. Important applications of the developed methods may be found within vehicle interior acoustics, e.g. engineering design of damping treatment based on multiple layers of porous materials. / QC 20100618

New modelling tools intended to contribute to the development of components for quieter vehicles are developed. The tools are based on continuum models for wave propagation in poro– and visco–elastic media. By using geometric attributes of the studied components, the computational cost may be radically decreased compared to traditional methods. By assigning known analytical functions for one or two of the spatial directions, the spatial dimension of the remaining numerical problem is reduced. This reduction of spatial dimensions is performed in two di↵erent ways. The first one treats wave propagation in infinitely extended homogeneous and hollowed cylindrical rods, or wave guides, consisting of visco–elastic media. The wave solutions obtained are then used to model rubber vibration isolators of finite length by mode–matching the fields to the radial boundary conditions of interest. The second one is a method for modelling rotationally symmetric multilayered structures consisting of poro–elastic, elastic and fluid domains. By using a harmonic expansion for the azimuthal spatial dependence, the original three–dimensional problem is split up into several, much smaller, two– dimensional ones, radically decreasing the computational load. Moreover, using a mixed measurement/modelling approach, the audible frequency range characteristics of a viscous damper from a truck is studied, illustrating the influence of the rubber bushings by which it is attached to surrounding structures. The modelling approaches presented in this thesis are intended as tools aiding the design process of new vehicles, enabling new technology striving for more sustainable vehicle concepts. More specifically, the tools aim to improve the modelling of sound and vibration properties which are often penalised when seeking new, more sustainable vehicle designs. / <p>QC 20120522</p> / Centre for Eco2 Vehicle Design

Ce document rapporte une étude qui s'inscrit dans une démarche visant à diminuer les nuisances sonores produites par l'aspirateur électroménager. La première partie est une étude perceptive du son de neuf aspirateurs commercialisés. Des enregistrements binauraux ont été proposés à une population d'auditeurs constituée suivant des critères commerciaux définis par le constructeur. Lors d'une comparaison par paires chaque auditeur jugeait de l'agrément et de l'impression d'efficacité ressentie. Les résultats obtenus mettent en avant la difficulté de juger par l'écoute de cette dernière et permettent de définir les points sur lequel l'industriel doit travailler pour améliorer l'agrément du produit. Une deuxième étape applique la méthode des plans d'expériences aux tests d'écoutes perceptives. Un enregistrement binaural a été réalisé sur un aspirateur prototype du constructeur. Le son de celui-ci a été modifié selon trois paramètres identifiés comme important dans l'agrément. Ces modifications suivent une table de plan d'expérience fractionnaire. Les réponses d'agrément des auditeurs ont permis de quantifier les contributions relatives de ces différents paramètres. La seconde partie du document expose la fabrication d'un prototype de banc de comparaison et de caractérisation d'une source solidienne à liaison symétrique de révolution. Pour caractériser cette source, la connaissance de sa mobilité et des efforts qu'elle introduit dans une structure réceptrice sont nécessaires. La géométrie et les matériaux de la source ne permettent cependant pas de mesure directe. Une identification indirecte de force sur structure réceptrice est ici nécessaire. Celle-ci fait l'objet du plus important développement de cette seconde partie. Une coque cylindrique fait office de structure réceptrice académique. L'opérateur différentiel de Donnell nous permet d'utiliser une forme discrétisée de l'équation de mouvement et d'exprimer les efforts à partir des déplacements. Une difficulté technique majeure lors d'une identification de force sur coque est qu'elle nécessite un grand nombre de mesures tridimensionnelles des déplacements. En effet le couplage entre les directions de déplacements peut être important. Nous nous affranchissons ici de ce problème en proposant un développement particulier d'une discrétisation de l'équation de mouvement de la coque permettant de déterminer un effort tournant appliqué par la source au cylindre. S'il s'agit d'un effort tournant radial, la mesure des déplacements radiaux de la structure réceptrice en un nombre limité de génératrices est suffisant pour son identification.

In-vehicle warning systems are today mainly using the visual and auditory channels for presentation. As cars get more and more sophisticated the demand on new ways of presenting information increases. This report investigates if the sense of touch, in form of a vibro-tactile seat is a prospective channel for warning information. To achieve the objectives the tactile seat was developed, implemented and tested in a simulator environment. The final result is a complete tactile seat with a set of warnings which correspond with different critical situations. The tactile seat made it possible to conduct a simulator-based experiment including comparison with a visual head-up warning presentation. The experiment proved significant difference in discovery distance in the comparison between the no system and the tactile warning system. The overall conclusion is that a vibro-tactile warning display in the driver’s seat is an excellent way of presenting certain warning information. The tactile channel is especially favorable when fast reaction time is essential. Further work could include designing and testing a combined tactile and visual system.

Low frequency noise caused by vibrating panels can pose problems for vehicles from noise, vibration and harshness (NVH) standpoint. In order to reduce interior noise levels in cars, some structural modifications are required on the car body. Structural modifications studied in this work are stiffeners welded on the walls of enclosed structure to change vibration characteristics. In this thesis, interaction between acoustic domain inside closed structures and their vibrating enclosing boundaries are analyzed. Analysis of vibro-acoustic behavior includes frequency response analysis of structure by Finite Element Method (FEM) and sound pressure level (SPL) prediction of the cabin interior by Boundary Element Method (BEM). The standard parts of the analyses are performed using available CAE (Computer Aided Engineering) software. It is demonstrated that the structural modification technique integrated with the vibro-acoustic model of the system reduces the computational effort considerably. The frequency response functions of a structure for each modification can easily be obtained in a fast and efficient way by using the structural modification technique. Thus, effects of design changes in the structure body on noise levels due to vibration of the structure can be very handily and efficiently studied. In the case studies presented, the effects of various different stiffeners applied on a simple closed structure are studied in detail.

<p>In-vehicle warning systems are today mainly using the visual and auditory channels for presentation. As cars get more and more sophisticated the demand on new ways of presenting information increases. This report investigates if the sense of touch, in form of a vibro-tactile seat is a prospective channel for warning information. To achieve the objectives the tactile seat was developed, implemented and tested in a simulator environment. The final result is a complete tactile seat with a set of warnings which correspond with different critical situations.</p><p>The tactile seat made it possible to conduct a simulator-based experiment including comparison with a visual head-up warning presentation. The experiment proved significant difference in discovery distance in the comparison between the no system and the tactile warning system.</p><p>The overall conclusion is that a vibro-tactile warning display in the driver’s seat is an excellent way of presenting certain warning information. The tactile channel is especially favorable when fast reaction time is essential. Further work could include designing and testing a combined tactile and visual system.</p>

La harpe de concert est un instrument à cordes dont les propriétés acoustiques et vibratoires ont fait l'objet de peu d'études. L'objectif visé au cours de ce travail de thèse est de comprendre et de modéliser le comportement vibro-acoustique de cet instrument.<br />Dans une première partie, une description générale de l'instrument est proposée, de ses origines à sa constitution actuelle. Une attention particulière est ensuite portée à l'interaction entre le doigt et la corde au moment du pincement : l'analyse d'images obtenues avec une caméra rapide permet d'obtenir les paramètres d'un modèle d'interaction. <br />Dans une deuxième partie, le rayonnement acoustique du corps sonore de l'instrument est étudié. Ce rayonnement met en jeu des couplages entre la table d'harmonie et la caisse de résonance. Une analyse modale, complétée par des mesures de vitesse particulaire acoustique en sortie d'évents permet d'identier deux modes couplés caractéristiques du comportement vibro-acoustique de l'instrument en basses fréquences. Un modèle discret 2 degrés de liberté décrivant la réponse de la harpe autour des fréquences de ces deux modes est développé. Du fait de la particularité des mécanismes d'amortissement présents dans le système, l'estimation des paramètres du modèle n'est possible que grâce à l'utilisation d'une méthode non standard d'analyse modale : l'appropriation par le calcul. Par ailleurs, le rayonnement acoustique en champ lointain est étudié à l'aide d'une antenne de microphones. La méthode dite des sources équivalentes est appliquée an d'identier une distribution de monopoles acoustiques rendant compte du rayonnement acoustique de l'instrument. Finalement, en basses fréquences, la harpe de concert est modélisée par 2 sources acoustiques élémentaires, l'une placée sur la table d'harmonie et l'autre au niveau des évents.<br />La troisième partie est consacrée à l'étude des couplages entre les cordes et la table d'harmonie qui donnent lieu à des phénomènes de résonance par sympathie. Ces couplages sont étudiés au moyen d'un modèle d'instrument à cordes générique constitué d'une poutre encastrée à ses extrémités sur laquelle des cordes sont xées à leurs extrémités. Le formalisme du vecteur d'état et la méthode des matrices de transfert sont utilisés pour décrire la propagation des ondes de exion et de compression dans chaque sous-structure (cordes et poutre). A partir des conditions de couplage entre les sous-structures, les modes de l'assemblage sont déterminés et ceux responsables du phénomène de vibration par sympathie sont identiés. Appliqués au cas de la harpe de concert, ces modes, dit sympathiques, sont également extraits expérimentalement. Les multiples couplages entre les cordes, occasionnés par ces modes, donnent lieu à des signaux musicaux présentant un grand nombre de composantes spectrales, dont les fréquences sont parfois très proches et non résolues dans un même partiel. L'identication de ces composantes est alors eectuée par l'emploi de méthodes spéciques du traitement du signal : des méthodes à haute résolution.<br />Des résultats issus de ces travaux sont mis en perspective pour des applications possibles en facture instrumentale.

New modelling tools intended to contribute to the development of components for quieter vehicles are developed. The tools are based on continuum models for wave propagation in poro- and visco-elastic media. By using geometric attributes of the studied components, the computational cost may be radically decreased compared to traditional methods. By assigning known analytical functions for one or two of the spatial directions, the spatial dimension of the remaining numerical problem is reduced. This reduction of spatial dimensions is performed in two di↵erent ways. The first one treats wave propagation in infinitely extended homogeneous and hollowed cylindrical rods, or wave guides, consisting of visco-elastic media. The wave solutions obtained are then used to model rubber vibration isolators of finite length by mode-matching the fields to the radial boundary conditions of interest. The second one is a method for modelling rotationally symmetric multilayered structures consisting of poro-elastic, elastic and fluid domains. By using a harmonic expansion for the azimuthal spatial dependence, the original three-dimensional problem is split up into several, much smaller, two- dimensional ones, radically decreasing the computational load.Moreover, using a mixed measurement/modelling approach, the audible frequency range characteristics of a viscous damper from a truck is studied, illustrating the influence of the rubber bushings by which it is attached to surrounding structures.The modelling approaches presented in this thesis are intended as tools aiding the design process of new vehicles, enabling new technology striving for more sustainable vehicle concepts. More specifically, the tools aim to improve the modelling of sound and vibration properties which are often penalised when seeking new, more sustainable vehicle designs.

abstract: The world’s population is currently 9% visually impaired. Medical sciences do not have a biological fix that can cure this visual impairment. Visually impaired people are currently being assisted with biological fixes or assistive devices. The current assistive devices are limited in size as well as resolution. This thesis presents the development and experimental validation of a control system for a new vibrotactile haptic display that is currently in development. In order to allow the vibrotactile haptic display to be used to represent motion, the control system must be able to change the image displayed at a rate of at least 30 frames/second. In order to achieve this, this thesis introduces and investigates the use of three improvements: threading, change filtering, and wave libraries. Through these methods, it is determined that an average of 40 frames/second can be achieved. / Dissertation/Thesis / Masters Thesis Engineering 2018

Made available in DSpace on 2016-06-02T19:55:35Z (GMT). No. of bitstreams: 1 5078.pdf: 4584807 bytes, checksum: 70e2c15d24d5960f2013d1c5b90260f9 (MD5) Previous issue date: 2013-03-19 / Universidade Federal de Sao Carlos / Convective drying of leaves involves heat and mass transfer in packed-beds of deformable material, since the leaves shrink significantly when the moisture is removed. Therefore, the packing structure changes over time, and the transfer properties alter as well. An additional drawback is the challenge to obtain reproducible packings, given the random nature of packing for such an irregular type of material. In this work, an experimental investigation was conducted to analyze how basil leaves (Ocimum basilicum L.) behave during drying focusing in the challenging characteristics of this particulate phase. A full characterization of the leaves as a particulate solid was conducted by measuring their dimensions, specific density, initial moisture content and equilibrium moisture content. Loose and compacted bulk densities were measured for beds of leaves under different moisture content. Results indicate that the basil leaves have a low sphericity (&#61546;=0.160), a high projected area (Aproj=4.55 cm2) and density equal to 0.874 g.cm-3. Bulk density of fresh leaves was 0.089 g.cm-3 in loosely packed-beds, and 0.198 g.cm-3 in compacted packed-beds. Drying experiments were performed in a range of 30 to 60oC under different air-particle contact modes, including fixed and moving beds. Drying cells 10 cm in diameter with heights of either 1 or 12 cm (corresponding to thin-layer and deep-layer beds respectively) were tested with air flowing perpendicular to the samples. In moving beds, a rectangular chamber of dimensions 20 cm x 11 cm was used, also with air flowing perpendicular to the samples. In the conditions tested, problems were observed regarding reproducibility of data of moisture content versus time, bed shrinking, channeling and non-homogeneous drying. It was demonstrated that these problems appear due to the inherent characteristics of the leaves (low density, high ratios of surface area to volume, rough surface, etc.), and also due to their biological variability, which made it difficult to obtain packed-beds with reproducible characteristics in different assays. Homogeneous drying was obtained only for moving beds with vertical vibration, under dimensionless vibration parameter equal to 1.0 and an amplitude of vibration of 0.5 cm. The effect of the cell diameter to mean leaf size ratio (D/dm) on the bulk densities and drying rates was also investigated. For that, the size of leaves was reduced by cutting them in two parts widthways (half-sized particles), and also in four parts, width- and lengthways (quarter-sized particles), resulting in D/dm= 4.2 (whole leaves), 5.3 and 7.8 (half- and quarter-sized leaves respectively). It was observed that loose and compacted bulk densities did not vary significantly for beds of half-sized particles, but increased approximately 20% in beds of quarter-sized leaves. Regarding the drying rates, a tendency of an increase as D/dm was raised to 7.8 was observed, but the variation remained within the range of standard deviation of experimental data. Axial shrinking of the beds throughout drying was measured in deep packed-beds. The initial bed height was reduced by approximately 47% after 100 minutes of drying at 60 oC. The pressure drop through the bed decreased drastically when the leaves were dried, resulting in an increase by 141 times in the bed permeability for drying at a temperature of 60°C. The results obtained show that the packed-bed structure strongly affects the heat and mass transfer during convective drying of leaves. / A secagem convectiva de folhas envolve os processos de transferência de calor e massa em leitos empacotados de materiais deformáveis, uma vez que as folhas apresentam um elevado encolhimento com a redução da umidade. Desta forma, a estrutura do pacote de folhas muda ao longo do tempo de secagem, e as propriedades de transferência também se alteram. Um inconveniente adicional é a dificuldade de se obter pacotes reprodutíveis, devido à natureza aleatória dos empacotamentos constituídos por este tipo de material, que tem formatos irregulares. Neste trabalho, uma investigação experimental foi realizada com o intuito de avaliar como as folhas de manjericão (Ocimum basilicum L.) comportam-se durante o processo de secagem, levando em consideração as características desta fase particulada. Uma caracterização completa das folhas enquanto um sólido particulado foi realizada medindo-se suas dimensões características, massa específica, teor de umidade inicial e teor de umidade de equilíbrio. As densidades bulk solta e compactada foram medidas para leitos de folhas com diferentes teores de umidade. Os resultados indicam que as folhas de manjericão possuem baixa esfericidade (&#61546;=0,160), elevada área projetada (Aproj=4,55 cm2) e massa específica igual a 0,874 g.cm-3. As densidades bulk obtidas para as folhas in-natura foram iguais a 0,089 g.cm-3 e 0,198 g.cm-3, para os leitos com empacotamento solto e compactado, respectivamente. Experimentos de secagem foram realizados para temperaturas do ar de secagem entre 30 e 60°C, e com os leitos de folhas sendo submetidos a diferentes formas de contato sólido-fluido, incluindo leitos fixos e móveis. Células de secagem com 10,0 cm de diâmetro e com alturas de 1,0 ou 12,0 cm (correspondendo às alturas de leitos com camada fina e espessa, respectivamente) foram testadas com escoamento de ar perpendicular ao material. Nos ensaios de secagem em leitos móveis, uma câmara retangular com área de seção transversal de 20,0 cm x 11,0 cm foi usada, também com escoamento de ar perpendicular às amostras. Nas condições investigadas, problemas com relação à reprodutibilidade das curvas de cinética de secagem, encolhimento do leito, canalização do ar nas proximidades das paredes da célula e secagem não homogênea foram observados. Foi demonstrado que estes problemas aparecem como consequência das características inerentes às folhas (baixa massa específica, elevada relação Ap/Vp, rugosidade superficial, etc.), e também devido à variabilidade biológica, que dificulta a obtenção de pacotes de folhas com características similares entre diferentes ensaios. Um produto final seco de forma homogênea foi obtido somente para os ensaios realizados em leitos móveis com vibração vertical, utilizando adimensional de vibração igual a 1,0 e amplitude vibracional de 0,5 cm. O efeito da razão D/dm (diâmetro da célula/dimensão média da folha) sobre as densidades bulk e taxas de secagem foi também avaliado. Para isto, as folhas inteiras (D/dm=4,2) foram cortadas em duas e em quatro partes (valores de D/dm=5,3 e 7,8, respectivamente). Verificou-se que as densidades bulk médias solta e compactada não variaram significativamente para os leitos de folhas cortadas em duas partes, mas aumentaram em 20% para as folhas cortadas em quatro partes em relação às folhas inteiras. Em relação às taxas de secagem, uma tendência de aumento foi observada quando D/dm passou de 4,2 para 7,8, mas as diferenças mantiveram-se dentro da faixa de desvios padrão dos dados experimentais. O encolhimento axial dos leitos foi medido durante ensaios de secagem utilizando camadas espessas de folhas. A altura inicial dos leitos de folhas foi reduzida em aproximadamente 47% após cerca de 100 minutos de secagem para os ensaios de secagem realizados a 60°C. Os valores de queda de pressão através do leito diminuíram bastante quando as folhas foram secas, resultando em um aumento de 141 vezes na permeabilidade do leito para a secagem com o uso de T=60°C. Os resultados experimentais obtidos neste trabalho mostram que a estrutura dos leitos de folhas afetam fortemente as transferências de calor e massa que ocorrem durante a secagem das folhas.