By reason of the topography of the land, Utah is and probably will remain a livestock grazing state. As far as agriculture is concerned over 90 percent of the area is suitable for grazing only. This grazing range is used by cattle and sheep.

abstract: This thesis intends to cover the experimental investigation of the propagation of laser-generated optoacoustic waves in structural materials and how they can be utilized for damage detection. Firstly, a system for scanning a rectangular patch on the sample is designed. This is achieved with the help of xy stages which are connected to the laser head and allow it to move on a plane. Next, a parametric study was designed to determine the optimum testing parameters of the laser. The parameters so selected were then used in a series of tests which helped in discerning how the Ultrasound Waves behave when damage is induced in the sample (in the form of addition of masses). The first test was of increasing the mases in the sample. The second test was a scan of a rectangular area of the sample with and without damage to find the effect of the added masses. Finally, the data collected in such a manner is processed with the help of the Hilbert-Huang transform to determine the time of arrival. The major benefits from this study are the fact that this is a Non-Destructive imaging technique and thus can be used as a new method for detection of defects and is fairly cheap as well. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019

Bonding composite structures using adhesives offers several advantages over mechanical fastening such as better flow stress, weight saving, improved fatigue resistance and the ability to join dissimilar structures. The hesitation to adopt adhesively bonded composite joints stems from the lack of knowledge regarding damage initiation and propagation mechanisms within the joint. A means of overcoming this hesitation is to continuously monitor damage in the joint. This study proposes a methodology to conduct structural health monitoring (SHM) of an adhesively bonded composite lap joint using acoustic, guided Lamb waves by detecting, locating and predicting the size of damage. Finite element modeling of a joint in both 2D and 3D is used to test the feasibility of the proposed damage triangulation technique. Experimental validation of the methodology is conducted by detecting the presence, location and size of inflicted damage with the use of tuned guided Lamb waves.

Fifty-nine mature "Western" (Suffolk x Rambouillet) and 71 mature ¼ - Finn (Suffolk x Finn-Rambouillet) ewes were bred to Suffolk-Hampshire rams to lamb in either spring (March) or fall (September). Effects of ewe breed type and lambing season on ewe fertility (ewes lambing/ewes exposed), prolificacy (lambs born/ewe lambing) and lambing date, and on lamb birth weight, 30-d survival, and average daily gain (ADG) to 55 d and to weaning were evaluated. Fertility was higher in spring than in fall (94 vs 64%, P<.01). Use of %-Finn ewes tended to increase fertility in fall lambing (69 vs 59%, P<.25) but not in spring (94 vs 93%). Use of ¼ -Finn increased prolificacy by .36 lambs; fall lambing reduced prolificacy by .49 lambs. Lambs of Western ewes were born 5 d later (P<.01) and .6 Ib heavier (P<.001) than lambs of ¼ -Finn ewes. Lamb survival and ADG to 55 d and to weaning were not affected by ewe breed. Season affected ADG: fallborn lambs grew faster to 55 d (P< .05) and to weaning (P< .001) than spring-born lambs, attributable to differences in environmental factors. Effect of weaning on growth of spring-born lambs grazing summer pasture was analyzed. Spring lambs weaned at 90 d of age to graze independently grew more slowly and were older at market weight than lambs remaining with their dams on native perennial pastures (.24 vs .42 lb/d, P<.001; 201 vs 186 d of age, P<.001). Use of millet (Pennisetum americanum [L.] Leeke) as annual mid-summer forage and turnip (Brassica rapa L.) as annual late-fall forage were investigated. Dry ewes grazing millet lost weight in one yr, but averaged .23 Ib/d gain in a second yr; weaned lambs grazing pearl millet averaged .32 lb/d gain over 2 yr. Lactating and dry ewes grazing turnip had average weight changes of -.37 and +.11 lb/d, respectively. Budgets for production systems were constructed. Variable revenues and expenses for all combinations of ewe breed type, lambing season, weaning treatment, and annual forage use were integrated into an annual production system. The most profitable production systems were those that exhibited the greatest reproductive efficiency, required the least drylot time to finish lambs, and maximized use of perennial pastures. / Master of Science

La présente étude se propose de donner une traduction abondamment annotée de la seconde série des essais d’Élia qui paraissent dans les revues périodiques anglaises, entre 1820 et 1833. Dans un souci d’exactitude, cette traduction restitue les passages supprimés par l’auteur avant leur parution sous forme de recueil. Une attention toute particulière a été portée sur les traductions en français de certains essais d’Élia publiés séparément dans les revues du milieu du dix-neuvième siècle et sur les traductions plus modernes des Essais d’Elia, réunis en recueil, jusqu’à l’époque présente. Les Last Essays of Elia sont la dernière œuvre publiée par Lamb. La tentation était grande de chercher une continuité depuis les premiers écrits jusqu’aux LEE. Dans l’introduction critique, nous nous sommes efforcé de voir les différents aspects de l’oeuvre de Lamb qui est à la fois poète, journaliste, dramaturge, critique de théâtre et épistolier et qui connaît la notoriété dans le genre de l’essai, genre auquel il donne un souffle nouveau, grâce à la persona d’Élia. Le fait que Lamb ait été l’ami des premiers poètes romantiques anglais de l’époque, le fait que sa vie ait été marquée et bouleversée par le meurtre de sa propre mère de la main de sa sœur bien-aimée, confèrent à son œuvre un vif intérêt. Personnalité inclassable du Romantisme anglais, dont il est une figure mineure, humoriste amoureux des livres et de la langue du passé, Lamb n’en reste pas moins un chaînon indispensable pour comprendre la scène littéraire anglaise du début du XIXe siècle. / The present study aims to provide a carefully annotated translation of the second series of the Essays of Elia which appeared in English periodical magazines between 1820 and 1833. In order to be as complete as possible, this translation includes the passages removed by the author when they were published in book form in 1833. Particular attention has been paid to French translations of individual Elia essays scattered in mid-nineteenth century French magazines as well as to more modern translations of the collected Essays, up to the present day. The Last Essays of Elia was Lamb’s final published work. It was very tempting to look for threads running through his work from the early writings to the LEE. In the critical introduction, we have sought to consider the various aspects of the work of Lamb, who was at the same time a poet, a journalist, a playwright, a theatre critic and a letter-writer before making his name as an essay-writer, breathing new life into the genre, thanks to the Elia persona. The fact that Lamb was a friend of the first English Romantic poets and that his life was blighted by his mother’s murder at the hands of his beloved sister, brings a vivid interest to his work. An isolated figure of Romanticism, a "very reasonable Romantic" himself, a humourist in love with the books and language of the past, Lamb, though a relatively minor author, remains a key link to understanding the early nineteenth-century English literary scene.

The effect of stress on Lamb wave propagation is relevant to both nondestructive evaluation and structural health monitoring because of changes in received signals due to both the associated strain and the acoustoelastic effect. A homogeneous plate that is initially isotropic becomes anisotropic under biaxial stress, and dispersion of propagating waves becomes directionally dependent. The problem is similar to Lamb wave propagation in an anisotropic plate, except the fourth order tensor in the resulting wave equation does not have the same symmetry as that for the unstressed anisotropic plate, and the constitutive equation relating incremental stress to incremental strain is more complicated. Here we review the theory of acoustoelastic and develop theory for acoustoelastic Lamb wave propagation and show how dispersion curves shift anisotropically for an aluminum plate under biaxial tension. We also develop an approximate method using the effective elastic constants (EECs) and show that existing commercial tools to generate dispersion curves can be used under restricted conditions to describe wave propagation in biaxially stressed plates. Predictions of changes in phase velocity as a function of propagation direction using theory and the EEC method are compared to experimental results for a single wave mode.

Submitted by MARLON RODRIGUES GARCIA null (marlon92319@aluno.feis.unesp.br) on 2016-04-18T18:04:02Z No. of bitstreams: 1 Dissertação Final - Marlon.pdf: 6766003 bytes, checksum: 4849566caadd0c8935bb400de40fb690 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-04-19T14:54:06Z (GMT) No. of bitstreams: 1 garcia_mr_me_ilha.pdf: 6766003 bytes, checksum: 4849566caadd0c8935bb400de40fb690 (MD5) / Made available in DSpace on 2016-04-19T14:54:06Z (GMT). No. of bitstreams: 1 garcia_mr_me_ilha.pdf: 6766003 bytes, checksum: 4849566caadd0c8935bb400de40fb690 (MD5) Previous issue date: 2016-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho aborda-se a utilização de um sensor de deslocamento angular em fibra óptica para a caracterização de líquidos utilizando-se ondas de Lamb e o modo quase Scholte (QSCH) propagados em placa metálica. O sensor reflexivo compreende duas fibras ópticas, uma emissora e outra receptora, uma lente positiva, uma superfície reflexiva, um laser e um fotodetector. Primeiramente, realiza-se um breve estudo sobre a propagação de ondas mecânicas guiadas em placas metálicas imersas em fluidos. Nesse estudo, são obtidas as curvas de dispersão para a velocidade de fase e para a velocidade grupo em função do produto frequência-semiespessura da placa, tanto para as ondas de Lamb quanto para o modo QSCH, considerando diferentes fluidos. Posteriormente, aborda-se o modelamento matemático do sensor reflexivo, obtendo-se as curvas características estáticas para quatro diferentes configurações. Em seguida, descreve-se o processo de montagem do sensor reflexivo, com todos os seus detalhes construtivos. Já na parte experimental, aplicando-se um pulso senoidal de envoltória gaussiana em um transdutor, investiga-se primeiramente a excitação do modo fundamental simétrico da onda de Lamb, S0. Captando-se simultaneamente os sinais da onda propagada na placa pelo sensor reflexivo e por uma piezocerâmica em modo de recepção, obtêm-se os valores experimentais da velocidade de grupo. Comparando-se os valores experimentais com os valores teóricos previstos pelas curvas de dispersão, percebe-se que o sensor reflexivo pode ser utilizado para se medir modos simétricos da onda de Lamb.Visando-se a caracterização de líquidos, imerge-se parcialmente uma placa de alumínio em um fluido sob teste, e excita-se o modo fundamental antissimétrico da onda de Lamb, A0. O modo A0 converte-se em modo QSCH na interface ar-fluido, o qual sofre reflexão na borda da placa e se reconverte em modo A0 na interface fluido-ar. Utilizando-se o sensor reflexivo, pode-se medir a velocidade de propagação do modo QSCH. Sabendo-se que a velocidade do modo QSCH é diferente para diferentes fluido, verifica-se que o sensor pode ser utilizado para medir porcentagens de misturas de fluidos. Adicionalmente, medem-se também os deslocamentos lineares gerados pelo modo A0 na placa de alumínio na direção out-of-plane, comparando-se os resultados com as medições realizadas por um interferômetro de Michelson. / In this work one approaches the use of an angular displacement optical fiber sensor for characterization of liquids using Lamb waves and quasi-Scholte waves (QSCH) propagated in a metal plate. The reflective sensor comprises two optical fibers, one emitting and another receiving, a reflective surface, a laser and a photodetector. Firstly, one develops a brief study about the propagation of mechanical waves in metal plates imbibed in fluids. In this study, one obtains the dispersion curves for the phase velocity and the group velocity as a function of the frequency-halfwidth product for both Lamb waves and QSCH mode, considering different fluids. Subsequently, it one approaches the mathematical modeling of the reflective sensor, obtaining the static characteristic curves for four different configurations. Next, one describes the assembly process of the reflective sensor, with all the construction details. In the experimental part, one investigates the excitement of the symmetrical fundamental mode of the Lamb wave applying a sinusoidal pulse of gaussian envelope. Catching up simultaneously the wave propagated signals by the reflective sensor and by a piezoceramic, one obtains the experimental values of the group velocity. Comparing the experimental values with the values proposed by the dispersion curves, one notices that the reflective sensor can be used to measure the symmetric modes of the Lamb waves. Aimed at the characterization of liquids, one immerges partially an aluminum plate in a fliud under test, and one excites the fundamental antisymmetric mode of the Lamb wave, A0. The A0 mode becomes QSCH in the air-fluid interface, which reflects in the edge of the plate and is reconverted into A0 mode in the fluid-air interface. Using the reflective sensor, one can measure the QSCH mode propagation velocity. Knowing that the QSCH velocity is different for different fluids, one verifies that the sensor can be used to measure percentages of fluid mixtures. One measures also the linear displacements generated by the A0 mode in the aluminum plate in the out-of-plane direction, comparing the results with the measurements made by a Michelson interferometer.

Made available in DSpace on 2014-06-11T19:27:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-24Bitstream added on 2014-06-13T18:55:43Z : No. of bitstreams: 1 franco_vr_me_ilha.pdf: 5148348 bytes, checksum: 722b347f89e5e9a0aa5c379afe0dadba (MD5) / Financiadora de Estudos e Projetos (FINEP) / Este trabalho apresenta o estudo e desenvolvimento de uma técnica de monitoramento da integridade estrutural, para identificação e caracterização de falhas estruturais através da metodologia das ondas de Lamb utilizando materiais piezelétricos como sensores e atuadores. Ondas de Lamb são uma forma de perturbação elástica que se propaga guiada entre duas superfícies paralelas livres. Ondas de Lamb são formadas quando o atuador excita a superfície da estrutura com um pulso depois de receber um sinal. Quando uma onda propaga na superfície de uma placa, ela chega em um PZT sensor por diferentes caminhos. Um caminho é quando a onda atinge o sensor diretamente, ou seja, sem obstáculos no caminho em que ela se propaga. Outro caminho possível é quando a onda chega ao sensor após se propagar sobre descontinuidades existentes na superfície da estrutura. Com as várias características dos sinais recebidos, e com o uso de certas técnicas de processamento de sinais, essas falhas podem ser identificadas, realizando-se a ação correta tentando evitar a total falha da estrutura. Nesse contexto, diferentes testes experimentais foram realizados em diferentes tipos de estruturas. Redes de sensores e atuadores piezelétricos foram acopladas na superfície dessas estruturas, a fim de se fazer a configuração das ondas de Lamb. Os PZTs atuadores excitaram a estrutura em altas faixas de frequência. Diferentes tipos de falhas estruturais foram simuladas, através do aumento de massa, alteração de rigidez e através de cortes na borda das estruturas. Quatro índices de falha foram utilizados para detectar a presença da falha na estrutura, são eles: Root- Means-Square Deviation (RMSD), Índice de Falha Métrica (IFM), Norma H2 e Correlation Coefficient Deviation Mean (CCDM). Estes índices foram computados através dos sinais de entrada e de saída no domínio da frequência... / This work presents the study and development of a Structural Health Monitoring technique for identification and characterization of structural damages based on Lamb waves methodology using piezoelectric materials as actuators and sensors. Lamb waves are a form of elastic perturbation that remains guided between two parallel free surfaces. Lamb waves are formed when the actuator excites the structure’s surface with a pulse after receiving a signal. When the wave propagates on the structure, it comes in a PZT sensor from different paths. One path is when the wave reaches the sensor directly, i.e. without obstacles in the path in which it propagated. Another possible path is when the wave reaches the sensor after spreads on discontinuities in the structure’s surface. Damages can be detected and located through several features of the received signals and with the use of certain techniques of signal processing. In this context, several experimental tests were performed on different kinds of structures. Piezoelectric actuators and sensors networks were attached on the surface of these structures in order to make the Lamb waves configuration. The PZTs actuators excited the structure in high frequency ranges. Different kinds of structural damages were simulated by increasing mass, reduction of stiffness and cuts through the edge of the structures. Four damage-sensitive indexes were used to detect the presence of the damage in the structure: Root-Means-Square Deviation (RMSD), Metric Damage Index (MDI), H2 Norm and Correlation Coefficient Deviation (CCDM). These indices were computed in the frequency domain. The results showed the viability of the Lamb waves methodology for Structural Health Monitoring system using smart materials as actuators and sensors

Orientador: Cláudio Kitano / Resumo: Neste trabalho aborda-se a utilização de um sensor de deslocamento angular em fibra óptica para a caracterização de líquidos utilizando-se ondas de Lamb e o modo quase Scholte (QSCH) propagados em placa metálica. O sensor reflexivo compreende duas fibras ópticas, uma emissora e outra receptora, uma lente positiva, uma superfície reflexiva, um laser e um fotodetector. Primeiramente, realiza-se um breve estudo sobre a propagação de ondas mecânicas guiadas em placas metálicas imersas em fluidos. Nesse estudo, são obtidas as curvas de dispersão para a velocidade de fase e para a velocidade grupo em função do produto frequência-semiespessura da placa, tanto para as ondas de Lamb quanto para o modo QSCH, considerando diferentes fluidos. Posteriormente, aborda-se o modelamento matemático do sensor reflexivo, obtendo-se as curvas características estáticas para quatro diferentes configurações. Em seguida, descreve-se o processo de montagem do sensor reflexivo, com todos os seus detalhes construtivos. Já na parte experimental, aplicando-se um pulso senoidal de envoltória gaussiana em um transdutor, investiga-se primeiramente a excitação do modo fundamental simétrico da onda de Lamb, S0. Captando-se simultaneamente os sinais da onda propagada na placa pelo sensor reflexivo e por uma piezocerâmica em modo de recepção, obtêm-se os valores experimentais da velocidade de grupo. Comparando-se os valores experimentais com os valores teóricos previstos pelas curvas de dispersão, percebe-se que... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work one approaches the use of an angular displacement optical fiber sensor for characterization of liquids using Lamb waves and quasi-Scholte waves (QSCH) propagated in a metal plate. The reflective sensor comprises two optical fibers, one emitting and another receiving, a reflective surface, a laser and a photodetector. Firstly, one develops a brief study about the propagation of mechanical waves in metal plates imbibed in fluids. In this study, one obtains the dispersion curves for the phase velocity and the group velocity as a function of the frequency-halfwidth product for both Lamb waves and QSCH mode, considering different fluids. Subsequently, it one approaches the mathematical modeling of the reflective sensor, obtaining the static characteristic curves for four different configurations. Next, one describes the assembly process of the reflective sensor, with all the construction details. In the experimental part, one investigates the excitement of the symmetrical fundamental mode of the Lamb wave applying a sinusoidal pulse of gaussian envelope. Catching up simultaneously the wave propagated signals by the reflective sensor and by a piezoceramic, one obtains the experimental values of the group velocity. Comparing the experimental values with the values proposed by the dispersion curves, one notices that the reflective sensor can be used to measure the symmetric modes of the Lamb waves. Aimed at the characterization of liquids, one immerges partially an alumi... (Complete abstract click electronic access below) / Mestre

Resumo: Este trabalho apresenta o estudo e desenvolvimento de uma técnica de monitoramento da integridade estrutural, para identificação e caracterização de falhas estruturais através da metodologia das ondas de Lamb utilizando materiais piezelétricos como sensores e atuadores. Ondas de Lamb são uma forma de perturbação elástica que se propaga guiada entre duas superfícies paralelas livres. Ondas de Lamb são formadas quando o atuador excita a superfície da estrutura com um pulso depois de receber um sinal. Quando uma onda propaga na superfície de uma placa, ela chega em um PZT sensor por diferentes caminhos. Um caminho é quando a onda atinge o sensor diretamente, ou seja, sem obstáculos no caminho em que ela se propaga. Outro caminho possível é quando a onda chega ao sensor após se propagar sobre descontinuidades existentes na superfície da estrutura. Com as várias características dos sinais recebidos, e com o uso de certas técnicas de processamento de sinais, essas falhas podem ser identificadas, realizando-se a ação correta tentando evitar a total falha da estrutura. Nesse contexto, diferentes testes experimentais foram realizados em diferentes tipos de estruturas. Redes de sensores e atuadores piezelétricos foram acopladas na superfície dessas estruturas, a fim de se fazer a configuração das ondas de Lamb. Os PZTs atuadores excitaram a estrutura em altas faixas de frequência. Diferentes tipos de falhas estruturais foram simuladas, através do aumento de massa, alteração de rigidez e através de cortes na borda das estruturas. Quatro índices de falha foram utilizados para detectar a presença da falha na estrutura, são eles: Root- Means-Square Deviation (RMSD), Índice de Falha Métrica (IFM), Norma H2 e Correlation Coefficient Deviation Mean (CCDM). Estes índices foram computados através dos sinais de entrada e de saída no domínio da frequência... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work presents the study and development of a Structural Health Monitoring technique for identification and characterization of structural damages based on Lamb waves methodology using piezoelectric materials as actuators and sensors. Lamb waves are a form of elastic perturbation that remains guided between two parallel free surfaces. Lamb waves are formed when the actuator excites the structure's surface with a pulse after receiving a signal. When the wave propagates on the structure, it comes in a PZT sensor from different paths. One path is when the wave reaches the sensor directly, i.e. without obstacles in the path in which it propagated. Another possible path is when the wave reaches the sensor after spreads on discontinuities in the structure's surface. Damages can be detected and located through several features of the received signals and with the use of certain techniques of signal processing. In this context, several experimental tests were performed on different kinds of structures. Piezoelectric actuators and sensors networks were attached on the surface of these structures in order to make the Lamb waves configuration. The PZTs actuators excited the structure in high frequency ranges. Different kinds of structural damages were simulated by increasing mass, reduction of stiffness and cuts through the edge of the structures. Four damage-sensitive indexes were used to detect the presence of the damage in the structure: Root-Means-Square Deviation (RMSD), Metric Damage Index (MDI), H2 Norm and Correlation Coefficient Deviation (CCDM). These indices were computed in the frequency domain. The results showed the viability of the Lamb waves methodology for Structural Health Monitoring system using smart materials as actuators and sensors / Orientador: Vicente Lopes Junior / Coorientador: Michael J. Brennan / Banca: Gilberto Pechoto de Melo / Banca: José Roberto de França Arruda / Mestre