Orientador : Renato Pavanello / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-31T21:52:13Z (GMT). No. of bitstreams: 1 Nunes_Alexandre_M.pdf: 10234250 bytes, checksum: b23f996b5cfd8fd277d5617e0bb9956c (MD5) Previous issue date: 2001 / Mestrado

Orientador: Hans Ingo Weber / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-19T16:11:32Z (GMT). No. of bitstreams: 1 DiasJunior_Milton_D.pdf: 26891221 bytes, checksum: 68d180280b5bb56ce35d64070234444f (MD5) Previous issue date: 1994 / Resumo: Uma das causas mais importantes de geração de ruído sonoro e vibração em máquinas elétricas é a excitação do estator pelas forças magnéticas harmônicas existentes dentro de motores ou geradores. Durante o projeto destas máquinas, deve-se cuidar para que as freqüências das forças de excitação não coincidam com as freqüências naturais do estator/carcaça, o que elevaria significativamente os níveis de ruído sonoro e vibração. Este trabalho apresenta um estudo do comportamento dinâmico de estruturas segmentadas que serve de base para a determinação das freqüências naturais de estruturas como os estatores. O interesse maior se concentra no estudo dos modos longitudinais de cascas cilíndricas segmentadas onde o efeito da descontinuidade do material é mais acentuado. Assim, faz-se uma comparação entre as diversas propostas de modelagem de estatores e os resultados da análise modal experimental de um pacote de chapas, prensadas com tirantes e com pressão de empacotamento controlada através de extensômetros. É apresentado também um estudo de modelagem destas estruturas tratando-as como sendo ortotrópicas e não mais isotrópicas, como tem sido feito até hoje. A fim de verificar a influência da segmentação, desenvolveu-se um programa de elementos finitos contendo os elementos de viga, massa, mola e interface. Este último simula as condições do contato entre dois segmentos, utilizando um modelo linear, desprezando o efeito do atrito e dependente da força de empacotamento. A proposta de modelagem de estruturas segmentadas foi verificada através de protótipos constituídos de várias vigas, cada uma com um número diferente de segmentos / Abstract: One of the main reasons for the acoustical noise and vibrations in electrical machines is the excitation of the stator due to the presence of magnetic harmonics in motors and generators. During the design of these machines one must care that the frequencies of the excitation forces do not coincide with the natural frequencies of the stator, which would increase considerably the acoustic noise levels and the vibrations. This work concerns the study of dynamic behavior of segmented (laminated) structures that will define the natural frequency of stators. Our main interest consists in the longitudinal modes of cilindrical segmented shells where the effect of discontinuous layers is more concentrated. A comparison of proposals for modelling of stators is done with the results of experimental modal analysis of a stack of metal sheets, clamped with tie rods and with the clamping pressure controled through strain gages. A study of these structures considered orthotropic (and not isotropic as one normaly assumes) is done. To obtain the effect of the segmentation, there was developed a finite element approach with beam, mass, stiffness and interface elements. This last one simulates the contact conditions between two segments, using a linear model, neglecting the da:rp.ping effect but considering the clamping force. The proposed model for segmented structures was checked in a prototype consisting of several beams, each one with a different number oí segments / Doutorado / Projeto Mecanico / Doutor em Engenharia Mecânica

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21611号 / 理博第4518号 / 新制||理||1648(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 正高 信男, 准教授 後藤 幸織, 教授 髙井 正成 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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Magíster en Ciencias de la ingeniería, Mención Ingeniería Estructural, Sísmica y Geotécnica. Ingeniero Civil / La identificación operacional en estructuras civiles tienen como fin el monitoreo continuo de estas. Sin embargo, al estar apoyada en algoritmos de identificación que suponen parámetros constantes del sistema a lo largo de toda la ventana de análisis, es incapaz de controlar la evolución del sistema en el tiempo. Las metodologías de seguimiento modal tienen como fin el control automático de la evolución temporal de los modos físicos. Una parte importante de la variación de los parámetros del sistema puede explicarse a partir de las variables meteorológicas, sobre todo de la temperatura. Esto es especialmente cierto para la frecuencia modal. En cambio, la forma modal puede considerarse constante, al menos ante variaciones moderadas del ambiente. El objetivo de este trabajo es evaluar las metodologías existentes de seguimiento modal y, al mismo tiempo, evaluar la pertinencia de incorporar el efecto de las variables meteorológicas a estas, recogido a través de modelos estadísticos. La evaluación se hace sobre la identificación del edificio de la Torre Central de la Facultad de Ciencias Físicas y Matemáticas de la Universidad de Chile, que ha estado siendo monitoreado de manera continua desde el año 2009 a la fecha. También se cuenta con los registros de la estación meteorológica del Departamento de Geofísica de la Universidad de Chile, aledaña a la estructura a estudiar. Los resultados obtenidos indican que la incorporación de modelos de frecuencia modal en función de variables meteorológicas al seguimiento modal permite capturar la evolución de los modos físicos, sin embargo la metodología puede verse muy afectada por los altos niveles de ruido en los registros o la identificación. También muestran que, si bien la forma modal permanece virtualmente constante, esta no puede ser usada como parámetro exclusivo de seguimiento si la cantidad de sensores es muy baja. Adicionalmente, se comprueba que la temperatura y la dirección de incidencia de los rayos solares son las variables meteorológicas a considerar para predecir con precisión la frecuencia modal.

Effective models of vibratory screens which can capture the true response characteristics are crucial in the understanding of faults and failures which occur in vibratory screens. However, the current available models are usually simplified and have limited validation to that of a physical screen. Much research has been conducted to optimise the screening efficiency of screens. The optimisation includes screen geometry, material processing of the screen and the dynamic response of the screen. These investigations have not been furthered to investigate the effects of different faults on the dynamic response of a vibratory screen. To model a vibratory screen which can replicate the dynamics of a physical vibratory screen it is important to create a model with enough complexity to capture the dynamics of the screen. The model of the screen was validated using both modal analysis and the transient response of the screen. The modal analysis was used to ensure that the physical characteristics of the model are consistent with that of the physical screen. Once this was completed, the second validation aimed to investigate if the model of the screen could capture transient faults which are measured experimentally. It was found that it was not possible to conclusively determine if the finite element methods model could Finally, an intelligent method was used to distinguishing between different faults and classifying them accordingly. The intelligent method was also trained using the FEM data and then used to classify the physical screen data. / Dissertation (MEng)--University of Pretoria, 2020. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

This thesis investigated the application of seismic analysis methods and the response of idealized shear frames subjected to seismic loading. To complete this research, a Design Basis Earthquake (DBE) for a project site in San Luis Obispo, CA, and five past earthquake records were considered. The DBE was produced per the American Society of Civil Engineers’ Minimum Design Loads for Buildings and Other Structures (ASCE 7-10) and used for application of the Equivalent Lateral Force Procedure (ELFP) and Response Spectrum Analysis (RSA). When applying RSA, the modal peak responses were combined using the Absolute Sum (ABS), Square-Root-of-the-Sum-of-Squares (SRSS), and Complete Quadratic Combination (CQC) method. MATLAB scripts were developed to produce several displacement, velocity, and acceleration spectrums for each earthquake. Moreover, MATLAB scripts were written to yield both analytical and numerical solutions for each system through application of Linear Time History Analysis (THA). To obtain analytical solutions, two implicit forms of the Newmark-beta Method were employed: the Average Acceleration Method and the Linear Acceleration Method. To generate a comparison, the ELFP, RSA, and THA methods were applied to shear frames up to ten stories in height. The system parameters that impacted the accuracy of each method and the response of the systems were analyzed, including the effects of classical damping and nonclassical damping models. In addition to varying levels of Rayleigh damping, non-linear hysteric friction spring dampers (FSDs) were implemented into the systems. The design of the FSDs was based on target stiffness values, which were defined as portions of the system’s lateral stiffness. To perform the required Nonlinear Time History Analysis (NTHA), a SAP2000 model was developed. The efficiencies of the FSDs at each target stiffness, with and without the addition of low levels of viscous modal damping are analyzed. It was concluded that the ELFP should be supplemented by RSA when performing seismic response analysis. Regardless of system parameters, the ELFP yielded system responses 30% to 50% higher than RSA when combing responses with the SRSS or CQC method. When applying RSA, the ABS method produced inconsistent and inaccurate results, whereas the SRSS and CQC results were similar for regular, symmetric systems. Generally, the SRSS and CQC results were within 5% of the analytical solution yielded through THA. On the contrary, for irregular structures, the SRSS method significantly underestimated the response, and the CQC method was four to five times more accurate. Additionally, both the Average Acceleration Method and Linear Acceleration Method yielded numerical solutions with errors typically below 1% when compared with the analytical solution. When implemented into the systems, the FSDs proved to be most efficient when designed to have stiffnesses that were 50% of the lateral stiffness of each story. The addition of 1% modal damping to the FSDs resulted in quicker energy dissipation without significantly reducing the peak response of the system. At a stiffness of 50%, the FSDs reduced the displacement response by 40% to 60% when compared with 5% modal damping. Additionally, the FSDs at low stiffnesses exhibited the effects of negative lateral stiffness due to P-delta effects when the earthquake ground motions were too weak to induce sliding in the ring assemblies.

京都大学 / 0048 / 新制・課程博士 / 博士(人間健康科学) / 甲第18203号 / 人健博第20号 / 新制||人健||2(附属図書館) / 31061 / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 三谷 章, 教授 精山 明敏, 教授 髙橋 良輔 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21082号 / 工博第4446号 / 新制||工||1691(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 KIM Chul-Woo, 教授 河野 広隆 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The dynamic characteristics of a part are highly dependent on geometric and material properties of the part. The identification and tracking of vibrational mode shapes within an iterative design process becomes difficult and time consuming due to the frequently changing part definition. Currently, visual inspection of analysis results is used as the means to identify the shape of each vibrational mode determined by the modal analysis. This thesis investigates the automation of the mode shape identification process through the use of parametric geometry and the Modal Assurance Criterion. Displacement results from finite element modal analysis are used to create parametric geometry templates which can be compared one to another irrespective of part geometry or finite element mesh density. Automation of the mode shape identification process using parametric geometry and the Modal Assurance Criterion allows for the mode shapes from a baseline design to be matched to modified part designs, giving the designer a more complete view of the part's dynamic properties. It also enables the identification process to be completed much more quickly than by visual inspection.