Vita. / Digitized by Kansas Correctional Industries

To visualize vibrations in mechanical systems, e.g., machine tools, their movements are measured by means of suitable sensors. The signals from these sensors are processed and displayed as animated pictures on a computer screen. Accelerometers have been chosen as the most suitable sensors for this purpose. Their main advantages include small size, wide sensitivity range and frequency bandwidth. In addition, accelerometers measure signals with reference to the Earth, so they do not require stable fixtures such as used with cameras or lasers. The visualization methodology involves nine accelerometers attached to a mechanical component, e.g., a dynamometer's platform. Vibration signals were acquired using a data acquisition (DAQ) system which is controlled by a LabVIEW��-based program. These signals are processed to suppress errors and convert acceleration into generalized coordinate that describes motion of the visualized component as a rigid plate's movement in 3-D space. The animation is accomplished by displaying a time series of pictures representing instantaneous position of the plate. The animation program employs homogenous coordinate transformation to draw 3-D 'wireframe' pictures. Since various errors distort the measured signals, the animated movement may be inaccurate. The knowledge of a mathematical model of the system whose vibrations are animated allows detection and suppression of distortions. For this purpose, the signals measured from the actual dynamic system are compared with the signals simulated by the system's model subjected to the same excitation as the actual system. Discrepancies between the actual and simulated signals are detected. They are analyzed to identify possible sources and forms of distorting signals. As the next step, the measured (actual) signals are corrected by removing estimated distortions. A methodology and software package capable of performing all functions necessary to implement the visualization of vibration have been developed in this research using LabVIEW�� programming environment. As compared with commercial software for experimental modal analysis, the most distinctive feature of the developed package is improved accuracy achieved by applying concepts utilized in control theory, such as modeling of multi-input-multi-output (MIMO) systems and on-line system identification for the model development and correction of signals. / Graduation date: 1998

No description available.

Typescript (photocopy) / 106 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Mechanical Engineering, University of Adelaide, 1984

Typescript (photocopy) / 106 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Mechanical Engineering, University of Adelaide, 1984

Made available in DSpace on 2016-03-07T19:20:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-31. Added 1 bitstream(s) on 2016-03-07T19:24:28Z : No. of bitstreams: 1 000859664.pdf: 6049739 bytes, checksum: cb41e6f436b277c94769bb46555828ed (MD5) / Este trabalho integrou duas técnicas de manutenção preditiva: Análise de vibrações e análise de lubrificantes para identificar e monitorar o desgaste severo na superfície do dentado. Engrenagens são as partes mais propensas a apresentar falhas em redutores, devido às suas características dinâmicas (cargas cíclicas aplicadas nos dentes). As principais falhas são de contato por fadiga conhecido como pitting e dados gerados pelo desgaste devido ao contato deslizante conhecido como scuffing. O aparecimento destes defeitos altera o perfil do dente que geralmente possui a forma de involuta, Desta maneira, o contato entre as engrenagens é afetado causando uma variação na razão de engrenamento (não uniforme), diminuição da eficiência, aumento dos efeitos dinâmicos que podem levar a uma grave falha no dente. Técnicas de processamento de sinais têm sido desenvolvidas para auxiliar na detecção de falhas em engrenagens em seus estágios iniciais. Como o comportamento dinâmico de um sistema mecânico altera devido à presença de um defeito, a resposta do sistema pode ser utilizada para detectar falhas nas suas fases iniciais. No entanto, para investigar e desenvolver tais técnicas é fundamental o entendimento físico do problema, que por ser feito utilizando um modelo analítico de um par engrenado. Desta forma simulações controladas podem ser obtidas auxiliando o desenvolvimento de novas técnicas de monitoramento. Neste trabalho, utiliza-se a técnica baseada na função densidade de probabilidade Beta juntamente com sinais de vibrações de pares engrenados, na localização da falha no dentado, bem como, o acompanhamento da evolução de tal falha. A utilização da técnica de lubrificantes mostrou ser muito eficiente para detecção de desgaste severo desde o início do experimento. Para este trabalho foi construída uma bancada experimental com o propósito de se verificar e... / This work investigates the use together of two techniques to detect faults in toothed gears. These techniques are based on the vibration monitoring and the oil lubricant analysis. Gears are the parts more likely to present faults in many mechanical systems due to its dynamic characteristics, such as the cyclic load applied to the meshing teeth. The main faults in gears are the so-called pitting and scuffing, where the tooth profile (involute) is heavily affected. Moreover, such change in the tooth profile lead to non-uniform angular speed ratio, decrease the efficiency of the system (gear pairs) and increase the dynamic effects which may lead to severe damages in the tooth. Hence, signal processing techniques have been developed to aid in the detection of gear faults at their early stages. It is already known that the dynamic behaviour of a mechanical system changes when its characteristics are affected, such as the presence of fault. As result, the response of such system can be used to detect a fault at its early stage. This is where the vibration monitoring is based on. However, in order to investigate and develop techniques based on the vibration analysis, the physical understanding of the system, in here a gear pair, is required. In this work a technique based on the beta probability density function is investigate to detect in which tooth of a meshing gear the fault is occurring, and also monitoring its evolution along time. Furthermore, the analysis of debris in the lubricant oil (tribology) is also used to reinforce the presence of a fault in the system. Although the later show that the lubricant analysis is quite efficient in detecting faults at its early stages, this technique does not pinpoint in which tooth the fault is occurring. In this case, the beta function complements the lubricant analysis being one of the objectives of this work. A special test rig has been designed and ...

Orientador: Aparecido Carlos Gonçalves / Co-orientador: Fabrício César Lobato de Almeida / Banca: Marcio Antonio Bazini / Banca: Gilberto de Magalhães Bento Gonçalves / Resumo: Este trabalho integrou duas técnicas de manutenção preditiva: Análise de vibrações e análise de lubrificantes para identificar e monitorar o desgaste severo na superfície do dentado. Engrenagens são as partes mais propensas a apresentar falhas em redutores, devido às suas características dinâmicas (cargas cíclicas aplicadas nos dentes). As principais falhas são de contato por fadiga conhecido como "pitting" e dados gerados pelo desgaste devido ao contato deslizante conhecido como "scuffing". O aparecimento destes defeitos altera o perfil do dente que geralmente possui a forma de involuta, Desta maneira, o contato entre as engrenagens é afetado causando uma variação na razão de engrenamento (não uniforme), diminuição da eficiência, aumento dos efeitos dinâmicos que podem levar a uma grave falha no dente. Técnicas de processamento de sinais têm sido desenvolvidas para auxiliar na detecção de falhas em engrenagens em seus estágios iniciais. Como o comportamento dinâmico de um sistema mecânico altera devido à presença de um defeito, a resposta do sistema pode ser utilizada para detectar falhas nas suas fases iniciais. No entanto, para investigar e desenvolver tais técnicas é fundamental o entendimento físico do problema, que por ser feito utilizando um modelo analítico de um par engrenado. Desta forma simulações controladas podem ser obtidas auxiliando o desenvolvimento de novas técnicas de monitoramento. Neste trabalho, utiliza-se a técnica baseada na função densidade de probabilidade Beta juntamente com sinais de vibrações de pares engrenados, na localização da falha no dentado, bem como, o acompanhamento da evolução de tal falha. A utilização da técnica de lubrificantes mostrou ser muito eficiente para detecção de desgaste severo desde o início do experimento. Para este trabalho foi construída uma bancada experimental com o propósito de se verificar e... / Abstract: This work investigates the use together of two techniques to detect faults in toothed gears. These techniques are based on the vibration monitoring and the oil lubricant analysis. Gears are the parts more likely to present faults in many mechanical systems due to its dynamic characteristics, such as the cyclic load applied to the meshing teeth. The main faults in gears are the so-called pitting and scuffing, where the tooth profile (involute) is heavily affected. Moreover, such change in the tooth profile lead to non-uniform angular speed ratio, decrease the efficiency of the system (gear pairs) and increase the dynamic effects which may lead to severe damages in the tooth. Hence, signal processing techniques have been developed to aid in the detection of gear faults at their early stages. It is already known that the dynamic behaviour of a mechanical system changes when its characteristics are affected, such as the presence of fault. As result, the response of such system can be used to detect a fault at its early stage. This is where the vibration monitoring is based on. However, in order to investigate and develop techniques based on the vibration analysis, the physical understanding of the system, in here a gear pair, is required. In this work a technique based on the beta probability density function is investigate to detect in which tooth of a meshing gear the fault is occurring, and also monitoring its evolution along time. Furthermore, the analysis of debris in the lubricant oil (tribology) is also used to reinforce the presence of a fault in the system. Although the later show that the lubricant analysis is quite efficient in detecting faults at its early stages, this technique does not pinpoint in which tooth the fault is occurring. In this case, the beta function complements the lubricant analysis being one of the objectives of this work. A special test rig has been designed and ... / Mestre

In this thesis a mathematical model for the combined effects of vortex-induced oscillation and galloping of a square section cylinder in cross flow is examined. The model equations are obtained by simply combining Parkinson and Smith's Quasi-Steady Model for galloping with the Hartlen-Currie model for vortex-induced vibration, which is essentially the same model used by Bouclin in the hydrodynamic case. The semi-empirical model is solved using three popular approximate analytical methods, and the methods of solution are evaluated. The solution of the model is compared with recent experimental data. The methods of solution used are the Method of Van Der Pol, (also called the method of Harmonic Balance), the Method of Multiple Scales, and some results from the Hopf Bifurcation Theory. The Method of Multiple Scales provides the most useful solutions, getting good results even with just the ༠(1) terms, although the next-order terms are necessary for the solution in the resonance regions. The phenomenon of subharmonic resonance, observed in recent experiments, is also observed in the solution of the model equations. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The application of laser Doppler vibrometry to high speed rotating structures has been hampered by technical limitations. Whereas full-field three-dimensional velocity measurements can be made on stationary structures, the capability on rotating structures is limited to low speed, one-dimensional, steady state operation. This work describes the implementation of a self-tracking laser vibrometry system which overcomes many of the limitations of current techniques for vibration measurements on rotating structures. A model of the self-tracker is developed and used to predict the effects of static misalignments on the position and velocity errors. These predictions are supported by experimental results and simplified models of the self-tracker. NOTE: (02/2011) An updated copy of this ETD was added after there were patron reports of problems with the file. / Ph. D.

No / This paper presents and compares the most important and often used methods to measure turbine blade vibrations: use of strain gauges and telemetry system which is an intrusive method or, on the other site. The Blade Tip Timing (BTT) method known as Non-Intrusive Stress Measurement (System) NSMS. Both methods have advantages and disadvantages which are described below. This paper focused on synchronous vibrations, which are more important in terms of turbine blades fatigue prediction and design optimization.