Master of Science / Department of Mechanical and Nuclear Engineering / B. Terry Beck / The objective of this project was to first evaluate the feasibility of developing a viscous damping device that used a Non-Newtonian Shear Thickening Fluid (STF) and incorporating it as a door latch into an existing commercial dryer unit. The device would keep the door closed during sudden large magnitude impact loads while still allowing the door to open normally when force is applied gradually at the door handle. The first phase of the project involved performing background research on the subject and performing preliminary analysis in order to determine if the concept was feasible enough to be worth constructing a physical prototype. This preliminary analysis consisted of a literature review of existing damping mechanisms and shear thickening fluids, rheometer testing of shear thickening suspensions to obtain viscosity data, and performing numerical simulations to determine if a damper that fit the size requirements could produce enough resistance force. The focus for the second phase of the project was to demonstrate a proof of concept in the form of a working model prototype. This prototype did not need be of identical shape and proportions as the finalized design, but would be developed to facilitate experimental testing and evaluation of performance under the desired operating conditions. It was also necessary to design and construct the test setup for the dynamic testing of the dryer door opening so that the opening displacement as well as the force applied to the door could be recorded as a function of time. The final phase of the project consisted of improving upon the original prototype in order to prove the validity of a viscous latch beyond the proof of concept phase in a form closer to what is desired for the commercial product. This required reducing the physical size of the new prototype latch so as to fit within the space available in a particular dryer, incorporate a one-way ratcheting device into the latch to allow unrestricted closing of the door, and increase the operational temperature range of the damper.

Atualmente é bem conhecido que o uso de dispositivos passivos de dissipação de energia, tais como amortecedores por atrito, reduzem consideravelmente a resposta dinâmica de estruturas. Entretanto, os melhores parâmetros de cada amortecedor e também a melhor posição para instalá-los dentro da estrutura permanecem difíceis de serem estabelecidas. Assim, a otimização de amortecedores é uma área que vem sendo estudada de forma crescente nos últimos anos, tendo grande impacto no projeto ótimo de dispositivos para o controle de vibrações de estruturas, possibilitando obter soluções seguras e ao mesmo tempo econômicas. Contudo, apesar dos amortecedores de vibração por atrito possuírem algumas vantagens em relação a outros dispositivos passivos, poucos trabalhos são encontrados sobre a otimização de seus parâmetros ou sobre a sua melhor posição dentro de uma estrutura, devido à maior dificuldade de se calcular sistemas que envolvem atrito, por este ser não-linear. Entretanto, é interessante se levar em conta as incertezas presentes nas propriedades estruturais e/ou na excitação dinâmica no processo de otimização, o que leva a um problema de otimização sob incerteza, como otimização robusta e otimização baseada em confiabilidade. Assim, nesta Tese é proposta uma metodologia para a otimização simultânea dos parâmetros e das posições de amortecedores de vibração por atrito a serem instalados em edifícios submetidos à excitação sísmica levando em conta as incertezas presentes tanto nas propriedades estruturais quanto no carregamento sísmico, assim como nas forças de atrito dos amortecedores. A fim de ilustrar a metodologia, dois exemplos de aplicação são apresentados, sendo o primeiro sobre otimização robusta e o segundo sobre otimização baseada em confiabilidade. Os resultados mostraram, em ambos os exemplos, que o método proposto obteve sucesso, melhorando consideravelmente o comportamento dinâmico dos edifícios estudados, mesmo para um número limitado de dispositivos instalados. Portanto, acredita-se que a metodologia de otimização desenvolvida constitui uma ferramenta eficaz para o projeto ótimo de amortecedores por atrito. / Nowadays it is well known that the use of passive energy dissipation devices, such as friction dampers, considerably reduces the dynamic response of structures. However, the best parameters of each damper and also the best position to install them within the structure remain difficult to be determined. Thus, optimization of dampers is an area that has been increasingly studied in recent years, having a big impact in the optimal design of devices for the vibration control of structures, allowing to obtain safe and at the same time economic solutions. However, although friction dampers have some advantages over other passive devices, few contributions are found on optimization of their parameters or on their optimal position within a structure. This fact can be explained due to the greater difficulty in determining the response of systems involving friction, because their nonlinear behavior. In addition to the lack of studies on optimization of friction dampers, the few studies found in the literature consider the problem in a deterministic way. However, the uncertainties present in the structural properties and/or in the dynamic excitation can alter the optimal solution. Thus, it is important to take into account these uncertainties in the optimization process, which leads to an optimization problem under uncertainty, such as robust optimization and reliability-based optimization. Thus, in this Thesis, a methodology is proposed for the simultaneous optimization of parameters and positions of friction dampers to be installed in buildings subjected to seismic excitation taking into account uncertainties present in both the structural properties and the seismic load, as well as in the friction forces of the dampers. In order to illustrate the approach, two examples are presented, the first one on robust optimization and the second on reliabilitybased optimization. The results show, in both examples, that the proposed method considerably improves the dynamic behavior of the studied buildings, even for a limited number of installed devices. Therefore, it was shown that the proposed procedure is an effective tool for the optimum design of friction dampers.

Submitted by João Rafael Alves null (joao.rafa.alves@gmail.com) on 2017-03-21T02:27:39Z No. of bitstreams: 1 Dissertação_15mar2017_Final.pdf: 12263333 bytes, checksum: d28726f4d986b72238323c581149a148 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2017-03-22T14:09:27Z (GMT) No. of bitstreams: 1 alves_jr_me_bauru.pdf: 12263333 bytes, checksum: d28726f4d986b72238323c581149a148 (MD5) / Made available in DSpace on 2017-03-22T14:09:27Z (GMT). No. of bitstreams: 1 alves_jr_me_bauru.pdf: 12263333 bytes, checksum: d28726f4d986b72238323c581149a148 (MD5) Previous issue date: 2017-01-31 / Quatro configurações de circuito elétrico são estudadas como opções de ligação em dispositivos eletromecânicos: puramente resistivo, RL em série, RLC em série e RLC em série com indutância de variação não linear. Respostas em frequência, diagramas de bifurcação, históricos no tempo, planos de fase, mapas de Poincaré e espectros de frequência são utilizados nas análises. Os três circuitos lineares explorados na dissertação revelam algumas diferenças em termos da transmissibilidade de deslocamento. O sistema com circuito puramente resistivo tem as mesmas características de um sistema puramente mecânico e viscosamente amortecido, mas a resistência elétrica e o fator de amortecimento viscoso se relacionam de forma inversamente proporcional. As respostas dos circuitos RL e RLC, ambos em série, apresentam aspectos mais comportados. A principal diferença entre os sistemas com circuitos RL e RLC em série está principalmente na transmissibilidade para baixas frequências. Embora com uma pequena diferença, a transmissibilidade do sistema com circuito RLC é menor do que a do sistema com circuito RL, para baixas frequências. Para o sistema não linear, nas respostas em frequência e diagramas de bifurcação percebem-se regiões de resposta desordenada para valores baixos de resistência elétrica em determinadas faixas de frequência. Com a análise das respostas, notam-se as presenças dos comportamentos dinâmicos periódico, quasi-periódico e caótico. Para valores baixos de resistência elétrica, a escolha do valor da capacitância é de suma importância para a classificação do tipo de comportamento dinâmico do sistema. Pequenas variações do valor da capacitância representam saltos enormes da dinâmica do sistema. Muitas vezes, mesmo dentro do campo de tolerância especificado pelos fornecedores de componentes elétricos, o valor da capacitância pode resultar em comportamentos caóticos indesejados. / Four configurations of electrical circuit are studied as options of electromechanical devices: purely resistive, RL in series, RLC in series e RLC in series with nonlinear inductance. Frequency responses, bifurcation diagrams, time series, phase plane, Poincaré maps and frequency spectrum are used in analysis. The three linear circuits explored in this dissertation reveal some differences in terms of displacement transmissibility. The system with purely resistive circuit has the same characteristics of a purely viscous damped, but the electrical resistance and the damping factor are inversely proportional. Responses of circuits RL and RLC, both in series, present behaving aspects. The main difference between the systems with RL and RLC circuits is related to the transmissibility for low frequencies. Although with a small difference, the transmissibility of RLC circuit system is smaller than the RL circuit system, for low frequencies. For the nonlinear system, it is possible to perceive disordered response regions for small values of electrical resistance on certain frequency bands. After response analisys, it is noted the presence of periodic, quasi-periodic and chaotic behaviors. For small values of electrical resistance, the choice of capacitance value is very important to determine the type of the dynamic behavior. Small differences of the capacitance values mean significant changes in the system dynamics. It is not rare that even inside the tolerance of electrical components, the capacitance value can result in chaotic behaviors.

Orientador: José Manoel Balthazar / Banca: Bento Rodrigues de Pontes Junior / Banca: Vicente Lopes Junior / Resumo: Nesta dissertação faz-se a análise da dinâmica não-linear de um sistema que possui preso a ele um motor de corrente contínua com potência limitada, onde são acoplados uma mola não linear e um amortecedor do tipo magneto-reológico (dispositivo que tem como fluído interno o fluído magneto-reológico). Com o objetivo de estudar e analisar a influência deste dispositivo na dinâmica do oscilador. Inicialmente apresenta-se uma breve descrição do tipo de problema estudado (sistemas não ideais) e uma revisão dos principais trabalhos que têm sido feitos tendo este dispositivo como foco de estudos. Apresentam-se os modelos utilizados para prever o comportamento destes dispositivos e também uma síntese de alguns modelos (mecânicos e matemáticos) mais elaborados e completos utilizados também para prever este comportamento. A partir daí é feita a apresentação do modelo que prevê o comportamento do amortecedor MR utilizado (modelo Bingham) e de uma suavização do mesmo, utilizada com o objetivo de melhorar o comportamento computacional do modelo inicial, junto a isso, apresenta-se a modelagem matemática do problema visando à obtenção das equações governantes do sistema. Faz-se então a análise do sistema durante a passagem pela ressonância (onde a freqüência de rotação do motor CC se aproxima numericamente e passa pela freqüência natural do sistema), analisando o efeito deste amortecedor durante esta passagem, analisa-se também a influência do dispositivo na evolução do Efeito Sommerfeld, um dos fenômenos intrínsecos desta classe de sistemas e também é feita uma analise do sistema em condições de movimento caótico também com o objetivo de prever o comportamento deste dispositivo, tudo isso é executado através da integração numérica das equações governantes do sistema. Para efeito de ilustração apresenta-se, também, uma pequena amostra do comportamento do sistema ideal paralelo ao estudado ... / Abstract: In this dissertation it made the analysis of the nonlinear dynamics of a system that possess to fixed it a direct-current motor with limited power, where is connected a damper of the type Magnetorheological (device that has as fluid intern the fluid Magnetorheological), with the objective to study and to analyze the influence of this device in the dynamics of the oscillator. Initially one brief description of the type of studied problem is presented (nonideal systems) and a revision of the main works that have been made having this device as focus of studies. The used models are presented to predict the behavior of these devices and also a synthesis of some models (mechanics and mathematicians) more elaborated and complete also used to predict this behavior. To continue this work, we present the model that predict the behavior of used MR damper (the Bingham Model) and a smoothing of the same, used with the objective to improve the computational behavior of the initial model and the mathematical modeling of the problem, together this, we show mathematical modeling of this problem aiming at to the attainment of the governing equations of the system. The analysis of the system it is made then during the passage for the resonance (where the frequency of DC motor it approaches numerically and crosses the natural frequency of the system), analyzing the effect of this damper during this passage, the influence of the device in the evolution of Sommerfeld Effect is also analyzed, one of the intrinsic phenomena of this classroom of systems and also is made a analyzes of the system in conditions of chaotic motions also with the objective to predict the behavior of this device, everything this is executed through the numerical integration of the governing equations of the system. For illustration effect it is presented, also, a small sample of the behavior of the parallel ideal system to the studied one, also with the presence of shock absorber MR, in the.. / Mestre

Este trabalho apresenta um modelo matemático linear para um sistema hidráulico proposto para funcionar como um amortecedor para pequenas amplitudes de deslocamento, da ordem de décimos de milímetros. As dimensões para o sistema hidráulico foram adotadas e parâmetros foram determinados. Foram escolhidos dois conjuntos de parâmetros dimensionais e dois valores para o bulk modulus equivalente, o que permitiu fazer o estudo de quatro situações. A verificação das características dinâmicas do sistema foi efetuada utilizando o conceito de função descritiva. Um programa em Matlab/Simulink com um filtro de Fourier foi implementado para obtenção das curvas da resposta em freqüência. A eficiência deste programa computacional foi comprovada através de sua aplicação a sistemas cujas respostas em freqüência são conhecidas. As curvas das respostas em freqüência do sistema hidráulico e do amortecedor ideal foram comparadas. Considerando tolerância de \'+ OU -\' 1 grau para a fase e de \'+ OU -\' 1 db para magnitude, o sistema hidráulico simulado, com bulk modulus equivalente de 100000 psi teve comportamento similar ao amortecedor ideal na faixa de freqüência de 0,1 a 150 rad/seg. No caso do bulk modulus de 30000 psi, a faixa foi estendida, isto é, de 0,1 a 200 rad/seg. / This work presents a linear mathematical model for a proposed hydraulic system intended to work as a damper for small displacement, of the order of decimals of millimeters. The dimensions of the hydraulic system were adopted and parameters were determined. Two sets of the dimensions and two values for the equivalent bulk modulus were chosen and that allowed the study of four situations. The system dynamic properties were verified using the concept of describing function. A Matlab/Simulink program applying the concept of a Fourier filter was carried out in order to obtain the frequency response curves. The efficiency of this program was verified through its application in systems which frequency responses are known. The systems and the ideal damper frequency response curves were compared. Considering tolerance of \'+ OU -\' 1 degree for the phase and \'+ OU -\' 1 db for magnitude, the simulated hydraulic system with an equivalent bulk modulus of 100000 psi showed to be similar to an ideal damper, for the frequency range from 0.1 to 150 rad/sec. For the equivalent bulk modulus of 30000 psi, the frequency range was extended from 0.1 to 200 rad/sec.

This thesis presents numerical predictions for the leakage and direct stiffness coefficients of pocket damper seals. Modifications made to earlier flow-prediction models are discussed. Leakage and static pressure measurements on straight-through and diverging configurations of eight-bladed and twelve-bladed seals were used for code validation and for calculation of seal discharge coefficients. Higher than expected leakage rates were measured in the case of the twelve-bladed seal, while the leakage rates for the eight-bladed seals were predicted reasonably accurately. Results are presented for shake tests conducted on the seals at pressures of up to 1000 Psi (6.90 MPa). Test variables included pressure drop across the seals and rotor speed. The experimentally obtained stiffness coefficients are compared to results of a rotordynamic damper seal code, which uses the corrected mass flow-rate calculation method. Results show that the code under-predicts the magnitude of the seal's stiffness for most test cases. However, general trends in the frequency dependency of the direct stiffness are more accurately predicted. The expectation of high values of negative stiffness in diverging seals is confirmed by the results, but the frequency at which the sign of the stiffness becomes positive is considerably lower than is predicted. In addition to presenting high-pressure test data, this thesis also attempts to provide some insight into how seal parameters can be modified to obtain desired changes in seal stiffness.

A new damping technology, the Viscoelastic Coupling Damper (VCD), has been developed at the University of Toronto for reinforced concrete (RC) coupled wall high-rise buildings. These dampers are introduced in place of coupling beams to provide distributed supplemental damping in all lateral modes of vibration. This thesis presents an analytical investigation of the application of VCDs in a high-rise case study building located in a region of high seismicity. A parametric study has been conducted to determine the optimal number and placement of the dampers to achieve enhanced seismic performance without compromising the wind response of the structure. Nonlinear time history analyses have been carried out in order to compare the seismic performance of a conventional coupled wall building to alternative designs incorporating VCDs. Results highlight the improved performance of VCDs over RC coupling beams at all levels of seismic hazard. A design procedure for seismic-critical buildings is proposed.

The objective of this thesis is to describe the design, construction, implementation and performance of a prototype adaptive pendulum tuned mass damper (APTMD). Furthermore the thesis aims at demonstrating the performance improvements obtained when the tuned mass damper (TMD) parameters are optimized. The study considers the effect of adjusting the APTMD tuned frequency and damping ratio on a two storey test structure subjected to broadband and narrowband excitation. An analytical model of the APTMD for a single-degree-of-freedom (SDOF) structure is used to demonstrate the performance improvements when the APTMD parameters are optimized. The optimized model considers the effects of adjusting the frequency ratio, damping ratio, and mass ratio of the combined system to reduce the maximum deflection when the structure is subjected to a harmonic excitation force. The analytical model is used to simulate the optimal performance of the APTMD system. The experimental APTMD is capable of identifying the structural vibration modes in real time and tuning to the desired mode. The structural vibration modes are identified by calculating the windowed power spectral density of the structure’s acceleration, followed by peak-picking algorithm to identify the modal frequencies. Tuning is performed by moving the pivot location of the pendulum arm via a tuning frame along a set of rails. The design also allows for changes in the external dampening force. An adjustable damper is attached to the pendulum mass to allow for control of the APTMD damping ratio. A prototype of the APTMD is built and tested in a modal testing setup. The test structure is a two-storey model of a building structure. The structure is excited using a shaker fixed to the lower storey of the structure. The performance of the APTMD under broadband and narrowband excitation is examined for various tuning and damping parameters. The performance of the APTMD system under optimally tuned and detuned conditions is investigated. The results of the experimental studies demonstrate the importance of optimizing the TMD tuned frequency and damping ratio to reduce structural vibrations. Since the APTMD is designed to autonomously update both parameters, it is an effective tool in mitigating structural vibrations where user interaction is either difficult or expensive. Further study on the performance of a prototype APTMD applied to a large scale structure is required before implementation on full-scale structures.

Automotive turbochargers (TCs) increase internal combustion engine power and efficiency in passenger and commercial vehicles. TC rotors are usually supported on floating ring bearings (FRBs) or semi-floating ring bearings (SFRBs), both of which are inexpensive to manufacture. However, fluid film bearings are highly nonlinear components of TC units and contribute to the complex behavior (i.e. bifurcations and frequency jumps between a first whirl frequency and a second whirl frequency) of the entire rotor-bearing system (RBS). The frequency jump phenomenon concerns the TC manufacturing industry due to increased levels of noise generation. This thesis presents progress on assessing the effects of some bearing parameters and operating conditions on the RBS dynamic forced performance and the frequency jump phenomenon. A fluid film bearing model is integrated into a finite element rotordynamics computational model for numerical prediction of the TC linear and nonlinear (time transient) forced response. Since automotive TCs operate with variable rotational speed, predictions are conducted with shaft acceleration/deceleration. Over most of its operating speed range, TC rotor nonlinear response predictions display two subsynchronous whirl frequencies w1 and w 2 representing a conical mode and a cylindrical bending mode, respectively. At low shaft speeds w1 is present up to a shaft speed (Omega bifurcation), where there is a frequency jump from w1 to w 2. The second whirl frequency may persist up to the highest shaft speeds (depending on operating conditions). Results show during rotor deceleration the Omega bifurcation may be different from the one during rotor acceleration (hysteresis). Predictions show the following factors delay the Omega bifurcation: increasing oil supply pressure, decreasing oil supply temperature, and increasing shaft acceleration. Also, rotor imbalance distribution greatly affects Omega bifurcation and the shaft amplitude of total motion. Overall, this study shows the sensitivity of bifurcations and frequency jump phenomenon in TC nonlinear response due to various bearing parameters and operating conditions. Further analysis is required to generalize these findings and to assess the effect of other bearing parameters (i.e. clearances, outer film length, ring rotation, etc.) on this phenomenon. In addition further validation of the predictions against test data is required for refinement of the predictive tool.

Tests are performed on a flexure-pivot-pad tilting-pad bearing with a series integral squeeze film damper in load-between-pads configuration, with both active and locked damper. The damper effects are negated when locked, resulting in a flexure-pivot-pad bearing only. Experimental tests provide static performance data and dynamic stiffnesses from which rotordynamic coefficients are extracted. The following two excitation schemes are implemented: (1) multi-frequency, single direction excitation and (2) single-frequency, rotating load excitation (or "circular excitation"). The XLTRC2 Rotordynamics Software Suite provides stiffness and damping coefficient, eccentricity, and power loss predictions for the locked damper bearing. Test conditions include the rotor-speed range of 4000-12000 rpm and the unit-load range of 0-862 kPa (0-125 psi). Dynamic tests utilizing the multi-frequency excitation for the locked and active damper bearing configurations both show that the real portion of the dynamic stiffness is well modeled by a quadratic curve fit, and the imaginary portion representing the damping is a linear function of excitation frequency. This means that frequency independent coefficients can be obtained when an added mass term is included. While stiffness coefficients are lower for the active damper bearing, damping coefficients remain almost constant between the locked and active damper configurations. A simulation shows that, although the damping coefficients do not change significantly, the reduced stiffness provided by the damper results in greater effective damping. Static performance tests for the locked and active damper bearing indicate low cross-coupling, as shown by the eccentricity and low attitude angle measurements. Pad metal temperature measurements show a smaller temperature differential along the pad arcs for the active damper bearing, than observed for the locked damper case. Frictional power loss is estimated based on lubricant temperature rise and does not differ significantly for the two bearing configurations.