Tesis: "Dynamic Vibration Absorber"

1

Park, Jeong Gyu. "Vibration suppression of ropeway carrier by dynamic vibration absorber". 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149772.

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要旨には「Vibration Suppression of Ropeway Carrier by Optimally Tuned Passive Devices」とあり
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第9529号
工博第2115号
新制||工||1230(附属図書館)
UT51-2002-G287
京都大学大学院工学研究科精密工学専攻
(主査)教授松久寛, 教授久保愛三, 教授吉村允孝
学位規則第4条第1項該当

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2

Ting-Kong, Christopher. "Design of an adaptive dynamic vibration absorber". Title page, contents and abstract only, 1998. http://thesis.library.adelaide.edu.au/adt-SUA/public/adt-SUA20010220.212153.

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3

Brötz, Nicolas, Manuel Rexer y Peter F. Pelz. "Fluid dynamic vibration absorber for cabin suspension". Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71227.

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Truck drivers spend all day moving goods. They are exposed to vibrations every time they drive. Modern cabin suspension and an air-suspended seat already offer a high level of comfort. This, however, is designed for vertical dynamics and you can observe the cab of a truck performs large pitching vibrations during acceleration. These are examined here. A pitch model of the cabin is set up for this purpose. On the basis of this model it is examined which reduction of the vibration can be achieved by the use of a hydraulically translated vibration absorber. The advantage of this absorber is the use of the hydraulic transmission to reduce the heavy mass at high absorber inertia. 4 kg of fluid mass act as 131 kg absorber mass reducing vibrations by more than 10%. The conventional vibration absorber is inacceptable due to the additional load. The investigation based on VDI 2057 Part 1 shows that driving comfort can be increased.

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4

Heilmann, John. "A dual reaction-mass dynamic vibration absorber for active vibration control". Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063315/.

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5

Hsu, Yungsheng. "The performance of a nonlinear dynamic vibration absorber". Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/364273/.

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This project investigated the physical behaviour and the effectiveness of a nonlinear dynamic vibration absorber (NDVA), which was designed to possess hardening stiffness characteristics. Two types of external force excitation were considered (harmonic and random input) applied to a primary system, with attached NDVA, and the response compared. For harmonic excitation, the governing equations of motion for the entire vibrating system and the expressions for the solution were derived using the Harmonic Balance Method (HBM). Mathematical expressions for the frequency response curves of the structural system were subsequently determined. The bifurcation and stability characteristics of the identified periodic steady state solutions were obtained. The effect of the NDVA parameters (e.g., nonlinear stiffness, damping ratio, mass ratio and frequency ratio) on the vibration reduction were studied. From the numerical results it was observed that the NDVA had a much wider effective vibration reduction bandwidth compared to a linear absorber. The frequency response curve of the NDVA had the effect of moving the second resonance peak to a higher frequency away from the tuned frequency, so that the device is robust to mistuning. For random excitation, time and frequency domain techniques were used and the effect of the nonlinear absorber parameters on the vibration reduction have been determined. The experimental validation, for the nonlinear absorber considered, involved a nonlinear hardening spring supporting a mass which was designed and attached to a cantilever beam excited by a shaker. The absorber nonlinearity that occurred was due to large geometric displacement and in-plane effects. The cantilever beam, at low frequencies, acted as a linear single degree-of-freedom system. The nonlinear absorber was designed to behave as a hardening Duffing oscillator. Validation is presented for both harmonic and random excitation, supporting the previously produced analytical and numerical results.

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6

Cambou, Pierre E. "A Distributed Active Vibration Absorber (DAVA) for Active-Passive Vibration and Sound Radiation Control". Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/10105.

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This thesis presents a new active-passive treatment developed to reduce structural vibrations and their associated radiated sound. It is a contribution to the research of efficient and low cost devices that implement the advantages of active and passive noise control techniques. A theoretical model has been developed to investigate the potential of this new "active-passive distributed absorber". The model integrates new functions that make it extremely stable numerically. Using this model, a genetic algorithm has been used to optimize the shape of the active-passive distributed absorber. Prototypes have been designed and their potential investigated. The device subsequently developed can be described as a skin that can be mechanically and electrically tuned to reduce unwanted vibration and/or sound. It is constructed from the piezoelectric material polyvinylidene fluoride (PVDF) and thin layers of lead. The tested device is designed to weight less than 10% of the main structure and has a resonance frequency around 1000 Hz. Experiments have been conducted on a simply supported steal beam (24"x2"x1/4"). Preliminary results show that the new treatment out-performs active-passive point absorbers and conventional constrained layer damping material. The compact design and its efficiency make it suitable for many applications especially in the transportation industry. This new type of distributed absorber is totally original and represent a potential breakthrough in the field of acoustics and vibration control.
Master of Science

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7

Muluka, Venu. "Optimal suspension damping and axle vibration absorber for reduction of dynamic tire loads". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0005/MQ39479.pdf.

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8

Du, Yu. "Internal Resonances in Vibration Isolators and Their Control Using Passive and Hybrid Dynamic Vibration Absorbers". Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/27493.

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Conventional isolation models deal with massless isolators, which tend to overestimate the isolator performance because they neglect the internal resonances (IRs) due to the inertia of the isolator. Previous researches on the IR problem is not adequate because they only discussed this problem in terms of vibration based on single degree-of-freedom (SDOF) models. These studies did not reveal the importance of the IRs, especially from the perspective of the noise radiation. This dissertation is novel compared to previous studies in the following ways: (a) a three-DOF (3DOF) model, which better represents practical vibration systems, is employed to investigate the importance of the IRs; (b) the IR problem is studied considering both vibration and noise radiation; and (c) passive and hybrid control approaches using dynamic vibration absorbers (DVAs) to suppress the IRs are investigated and their potential demonstrated. The 3DOF analytical model consists of a rigid primary mass connected to a flexible foundation through three isolators. To include the IRs, the isolator is modeled as a continuous rod with longitudinal motion. The force transmissibility through each isolator and the radiated sound power of the foundation are two criteria used to show the effects and significance of the IRs on isolator performance. Passive and hybrid DVAs embedded in the isolator are investigated to suppress the IRs. In the passive approach, two DVAs are implemented and their parameters are selected so that the IRs can be effectively attenuated without significantly degrading the isolator performance at some other frequencies that are also of interest. It is demonstrated that the passive DVA enhanced isolator performs much better than the conventional isolator in the high frequency range where the IRs occur. The isolator performance is further enhanced by inserting an active force pair between the two passive DVA masses, forming the hybrid control approach. The effectiveness and the practical potential of the hybrid system are demonstrated using a feedforward control algorithm. It is shown that this hybrid control approach not only is able to maintain the performance of the passive approach, but also significantly improve the isolator performance at low frequencies.
Ph. D.

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9

Rodriguez, John Israel 1972. "A multi-frequency induction heating system for a thermally triggered gel polymer dynamic vibration absorber". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87905.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.
Includes bibliographical references (p. 277-280).
Since its invention in the early part of the twentieth century, the dynamic vibration absorber (DVA) has played an important role in vibration suppression. In its simplest form, a dynamic vibration absorber is a mechanical network consisting of a spring, a mass and sometimes a damping element. These networks have been used to successfully reduce vibrations in buildings, bridges and imbalances in rotating machinery. Because these absorbers are most effective at attenuating disturbance near or at their self-resonant frequency, there is on-going research to develop semi-active DVA's capable of adjusting their natural frequency in real time. A new semi-active DVA is described that can modify its moment of inertia, and therefore its natural frequency, by using a collection of thermo-responsive gel polymers. This thesis develops an induction heating system that is suitable for noncontact heating of these gel polymers. The proposed heating system addresses the more general problem of controllable power delivery to multiple induction targets driven by a single induction coil. The focus of this work divides neatly between the design of the induction heating targets and the necessary power electronics. Targets that have preferential heating characteristics at particular frequencies are developed and analyzed. These targets include both resonant RLC circuits as well as conductors whose critical dimensions are much smaller than their associated skin depth. Extensive modeling of these targets is carried out and experimental results are presented. The ability to "selectively" heat these induction targets requires a power supply that can generate a sinewave with enough purity to not excessively heat unwanted targets.
(cont.) A 1 kW multilevel inverter topology is presented as an excellent compromise between total harmonic distortion and efficiency for this application. Referred to as the Marx inverter, this circuit can maintain its multilevel nature during real power transfer without the need for an external voltage balancing circuit or complicated control- unlike more traditional multilevel topologies. In addition to the gel vibration damper, portions of this work stand to benefit both medical and industrial venues where a desired temperature profile must be generated in a noncontact manner.
by John Israel Rodriguez.
Ph.D.

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10

Valo, Lukáš. "Simulační analýza vibrací turbodmychadla". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401530.

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The master thesis deals with computational modeling of a turbocharger vibrations and and assessment of influnce of passive dynamic vibration absorber on vibrations of actuator bracket. The use of dynamic vibration absorber was summarized in the research study. The analysis were performed using finite element method in ANSYS. Several computational models of turbocharger were created with different ways of modeling bolted joints between turbocharger parts. Modal analysis of each model was performed and the results were compared. For the selected model, the response to the kinematic excitation from the internal combustion engine for two load conditions was calculated using harmonic analysis. A simple model of vibration dynamic absorber was applied to the turbocharger model with reduced degrees of freedom and its influnce on vibrations of actuator bracket was investigated. Significant decrease of the maximum acceleration amplitude was achieved in a given frequency range when absorber parameters were optimized.

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11

Tran, Thang Quang. "DYNAMIC RESPONSE OF AND POWER HARVESTED BY ROTATING PIEZOELECTRIC VIBRATION ENERGY HARVESTERS THAT EXPERIENCE GYROSCOPIC EFFECTS". OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2157.

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This study investigates energy harvesting characteristics from a spinning device that consists of a proof mass that is supported by two orthogonal elastic structures with the piezoelectric material. Deformation in the piezoelectric structures due to vibration of the proof mass generates voltages to power electrical loads. The governing equations for this electromechanically coupled device are derived using Newtonian mechanics and Kirchhoff's voltage law. The case where the device rotates at a constant speed and is subjected to sinusoidal base excitation is examined in detail. The energy harvesting behavior is investigated for devices with identical piezoelectric support structures (called tuned devices). Closed-form expressions are derived for the steady state response and power harvested. For nonzero rotation speeds, these devices have multifrequency dynamic response and power harvested due to the combined vibration and rotation of the host system. The average power harvested for one oscillation cycle is calculated for a wide range of operating conditions to quantify the devices' performance. Resonances do not occur for cases when the base excitation frequency is fixed and the rotation speed varies. For cases of fixed rotation speed and varying base excitation frequency, however, resonances do occur. The number and location of these resonances depend on the electrical circuit resistances and rotation speed. Resonances do not occur at speeds or frequencies predicted by resonance diagrams, which are commonly used in the study of rotating system vibration. These devices have broadband speed energy harvesting ability. They perform equally well at high and low speeds; high speeds are not necessary for their optimal performance. The impact of the chosen damping model on energy harvesting characteristics for tuned devices is investigated. Two common damping models are considered: viscous damping and structural (hysteretic) damping. Closed-form expressions for steady state dynamic response and power harvested are derived for models with viscous and structural damping. The average power harvested using the model with structural damping behaves similarly at high speeds and low speeds, and at high resistances and low resistances. For the viscous damping model, however, the average power harvested is meaningfully different at high speeds compared to low speeds, and at high resistances compared to low resistances. The characteristics of devices with nonidentical piezoelectric support structures (called mistuned devices) are investigated numerically. Similar to spinning tuned devices, mistuned devices have multifrequency dynamic response and power harvested. In contrast to tuned devices, high amplitude average power harvested occurs near speeds and base excitation frequencies predicted by resonance diagram.

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12

井上, 剛志, Tsuyoshi INOUE, 幸男石田, Yukio ISHIDA, 正貴角 y Masaki SUMI. "電磁共振ダンパによる振動制御". 日本機械学会, 2004. http://hdl.handle.net/2237/8977.

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13

Scheidler, Justin Jon. "Static and Dynamic Delta E Effect in Magnetostrictive Materials with Application to Electrically-Tunable Vibration Control Devices". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437647571.

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14

石田, 幸男, Yukio ISHIDA, 剛志井上 y Tsuyoshi INOUE. "動吸振器を用いた非線形回転軸系の制振". 日本機械学会, 2002. http://hdl.handle.net/2237/9050.

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15

YUOKA, Teruaki, Keiji TAGATANI, Yoshikazu HAYAKAWA, Akira NAKASHIMA, Daiyu INAGAKI y Kazuhiko OSHIMA. "A Hybrid Damper Composed of Elastomer and Piezo Ceramic for Multi-Mode Vibration Control". 日本機械学会, 2010. http://hdl.handle.net/2237/20764.

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16

Kotinda, Giovanni Iamin. "Absorvedor dinâmico de vibração tipo lâmina vibrante". Universidade Federal de Uberlândia, 2005. https://repositorio.ufu.br/handle/123456789/14912.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
This work is dedicated to the design of a vibrating blade dynamic vibration absorber (ADVLV), which is composed by a blade that is subjected to an initial traction T , and contains a concentrated mass m that is fixed at a given position d along the blade. These three parameters can be adjusted so that the ADVLV is tuned. For this aim, a finite element model of the system was built, leading to a design methodology for the absorber. Also, design of experiment techniques were performed to obtain the most interesting configurations for the system, both for the computational and experimental models. Special care was taken with respect to the boundary conditions for the finite element model, so that the dynamic responses could correspond to the physical aspects of the problem, accordingly. Besides, an experimental prototype was constructed and tested under laboratory conditions. The experimental results were compared with those obtained from mathematical simulation. From this comparison, it was concluded that the finite element model had to be updated in such a way that experimental results could match. A vibrating string dynamic vibration absorber (ADVCV) was also studied. However, this DVA configuration presented two anti-resonant frequencies due to the coupling of the first vibration mode along the horizontal and vertical directions with a concentrated mass. Another phenomenon that was observed is the tridimensional motion of the vibrating string around its equilibrium position, leading to an ellipsoid-shape movement when a harmonic excitation whose frequency coincides with the primary system resonance frequency is applied to the system. This way, the ADVCV is not able to attenuate the vibration amplitude of the primary system satisfactorily. It is worth mentioning that the proposed ADVLV presents a good dynamic behavior besides a wide frequency range along which the DVA can be tuned. Besides, the present vibration absorbing device is simple and can be easily connected to the primary system both to mechanical and civil engineering structures.
Este trabalho aborda o projeto de um absorvedor dinâmico de vibrações do tipo lâmina vibrante (ADVLV), sendo este constituído por uma lâmina sujeita a uma tração inicial T com uma massa concentrada m que pode ser fixada em uma posição d da lâmina. Este três parâmetros podem ser alterados a fim de se obter a sintonia do ADVLV. Para realizar o estudo deste, foi elaborado um modelo de elementos finitos do sistema, permitindo assim obter a metodologia para seu projeto. Também foram usadas técnicas de planejamento de experimento para obter as melhores configurações, tanto para os ensaios computacionais como experimentais. Foram tomados cuidados na criação das condições de contorno do modelo de elementos finitos, a fim de se obter respostas que representem adequadamente os aspectos físicos do problema. Também foi construído um protótipo e este foi ensaiado no laboratório. Os resultados obtidos foram comparados com os obtidos através da simulação computacional. A partir desta comparação verificou-se a importância de realizar ajustes no modelo de elementos finitos para adequar este à realidade. Também foi estudado o absorvedor dinâmico de vibração do tipo corda vibrante. Entretanto este ultimo ADV apresentou duas freqüências de anti-ressonância devido ao acoplamento do primeiro modo de vibrar nas direções horizontal e vertical da corda vibrante com uma massa concentrada. Outro fenômeno observado foi o movimento tridimensional da corda vibrante em torno da sua posição de equilíbrio, resultando uma forma semelhante a um elipsóide de revolução quando uma excitação harmônica com freqüência igual à freqüência de ressonância do sistema primário é aplicada sobre o sistema. Desta forma, o ADVCV não consegue cumprir a sua função de atenuar a amplitude de vibração da estrutura primária, sendo, portanto, completamente ineficiente neste caso. O ADVLV, proposto neste trabalho, apresentou comportamento dinâmico satisfatório, além de uma grande faixa de freqüências na qual o ADV pode ser sintonizado. Este dispositivo é de fácil construção e acoplamento, tanto a sistemas mecânicos, como a estruturas de construção civil.
Mestre em Engenharia Mecânica

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17

Godoy, Willians Roberto Alves de. "Projeto, análise e otimização de um absorvedor dinâmico de vibrações não linear". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-06112017-140840/.

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Absorvedores de vibração são comumente usados em aplicações com intuito de reduzir indesejadas amplitudes de vibração de estruturas e maquinas vibrantes. O conceito de um absorvedor de vibração linear consiste na ideia de projetar um subsistema com frequência de ressonância coincidente com uma dada frequência de interesse, tal que a amplitude de vibração do sistema primário e significativamente reduzida quando comparada a situação original, sem o absorvedor de vibração. Porem, uma deficiência dos absorvedores de vibração lineares típicos e sua estreita faixa de frequência de operação. Para superar essa deficiência, muitas tentativas de solução usando subsistemas não lineares tem sido propostas na literatura, ja que se apropriadamente projetados, eles podem aumentar a faixa de frequência de absorção de vibração e/ou melhorar a redução das amplitudes de vibração do sistema primário. Contudo, a síntese e o projeto de tais absorvedores não lineares não e tão simples e direta como no caso linear. Baseado na geometria de uma topologia proposta e encontrada na literatura, que compreende a inclusão de uma montagem do tipo snap through truss no lugar da mola linear do absorvedor de vibração, este trabalho tem intenção de apresentar um estudo sobre o projeto e otimização de um absorvedor dinâmico de vibrações não linear. Portanto, o efeito dos parâmetros do absorvedor e analisado quanto as perspectivas de redução das amplitudes de vibração do sistema principal como também de aumento da faixa de frequência de operação. A analise paramétrica do absorvedor foi promovida para responder questões sobre as variáveis de projeto, tanto físicas como geométricas. Realizou-se otimização do absorvedor com objetivo de sintoniza-lo a frequência de trabalho desejada, através de busca extensiva e algoritmos genéticos. Os resultados mostram que o absorvedor não linear proposto pode ser mais efetivo que seu correspondente linear em ambos os aspectos, na redução da máxima amplitude de vibração e no aumento da faixa de frequência de absorção. Portanto, apesar da dificuldade inicial de projeto, esse tipo de absorvedor representa uma alternativa interessante na atenuação das amplitudes de vibração ao longo de uma extensa faixa de frequência.
Dynamic vibration absorbers are commonly used in several applications in order to reduce undesired vibration amplitudes of vibrating machinery and structures. The concept of a linear vibration absorber is based on the idea of designing a subsystem with a resonance frequency coincident with a given frequency of interest such that the vibration amplitude of the primary system is significantly reduced when compared to the original situation (without the vibration absorber). But one of the known handicaps of typical linear vibration absorbers is their narrow frequency range of operation. To overcome this handicap, a number of tentative solutions have been proposed in the literature using nonlinear subsystems. If properly designed, they could enlarge the frequency range of vibration absorption and/or improve vibration reduction of the primary system. However, the synthesis and design of such nonlinear absorbers are not as straightforward as for their linear counterpart. A proposed design found in the open literature consists of replacing the linear spring of the vibration absorber by a nonlinear snap-through truss. This work aims to present a study on the design and optimization of a nonlinear dynamic vibration absorber based on snap-through absorber geometry. The effect of the absorber parameters was analyzed on both, the primary system vibration amplitude reduction and the frequency range of operation. Parametric analyses of the absorber were carried out to answer questions about the physical and geometric design variables. The absorber optimization was performed in two different ways, by extensive search and genetic algorithms, in order to tune it in the desired working frequency. The results show that the proposed nonlinear vibration absorber may be more effective than its linear counterpart both in terms of maximum vibration amplitude reduction and absorption frequency-range. Therefore, despite the increased design complexities such an absorber is an interesting alterna- tive in attenuating vibration amplitudes over a wide frequency range.

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18

Collette, Christophe. "Usure ondulatoire en transport ferroviaire: mécanismes et réduction". Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210701.

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L'usure ondulatoire des rails associée aux vibrations de torsion des essieux de métro a été mise en évidence il y a près d'un demi siècle. L'utilisation d'absorbeurs dynamiques comme solution potentielle à ce problème a été suggérée pour la première fois dans le projet américain du TCRP "Rail Corrugation Mitigation in Transit" en 1998. Cette thèse, réalisée dans le cadre du projet européén "Wheel-rail CORRUGATION in Urban transport", a pour objectif de concevoir un absorbeur dynamique et d'étudier son influence sur la réduction de l'usure ondulatoire liée aux vibrations de torsion. Dans le cadre de ce travail, d'autres types d'usure ondulatoire ont également été traités par des absorbeurs dynamiques.

Les trois premiers chapitres de cette thèse sont dédiés à la description des différents types d'usure ondulatoire et à la présentation des méthodes de prédiction. La méthode de dimensionnement des absorbeurs dynamiques est présentée au chapitre 4, ainsi que quelques perspectives de leur efficacité à réduire l'usure ondulatoire. Dans le chapitre 5, un tronçon réel du RER parisien a été étudié. D'une part les prédictions obtenues par différentes méthodes ont été comparées aux mesures sur site. D'autre part, le bénéfice résultant de l'utilisation d'un absorbeur dynamique a été étudié numériquement. Dans le chapitre 6, le cas de l'usure ondulatoire liée aux vibrations de torsion a été étudié spécifiquement. Un absorbeur dynamique a été développé pour réduire ce type d'usure ondulatoire. Son efficacité a été évaluée théoriquement et numériquement, avec un modèle multi-corps flexible du véhicule et de la voie. Dans le chapitre 7, un absorbeur dynamique visant à réduire les vibrations de torsion d'un essieu de métro à échelle réduite a été construit au laboratoire. Son efficacité a été validée expérimentalement en reproduisant les conditions d'apparition des vibrations de torsion de l'essieu sur le banc d'essais du Laboratoire des Technologies Nouvelles de l'INRETS. La correspondance entre les prédictions d'usure à échelle réduite et à échelle réelle a été établie. Une demande de brevet a été déposée par le Laboratoire des Structures Actives pour ce système (N° 06120344.4).
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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19

Red, Wing Rodney D. "Adaptive tuned vibration absorber". Thesis, This resource online, 1997. http://scholar.lib.vt.edu/theses/available/etd-08252008-162250/.

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Silva, Rafael de Oliveira [UNESP]. "Atenuação de vibrações em sistemas que utilizam molas de liga de memória de forma". Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/150444.

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Diversos estudos relacionados à atenuação de vibrações utilizando materiais inteligentes vem sendo amplamente explorados no meio acadêmico. Neste âmbito, as Ligas de Memória de Forma (LMF) se destacam por apresentarem dissipação de energia vibratória devido ao seu comportamento histerético promovido pelo efeito pseudoelástico. No presente trabalho, dois sistemas com um e dois graus de liberdade, contendo mola helicoidal de LMF como elemento resiliente, são implementados numericamente para demonstrar a atenuação de vibrações ocasionada pelas transformações de fase presentes no material. Para cada um dos sistemas mecânicos investigados, dois modelos termomecânicos são confrontados numericamente visando a obtenção das características de cada modelo em representar a atenuação de vibrações dos sistemas submetidos à carregamentos termo-mecânicos. O trabalho termina comentando as potencialidades da proposta apresentada, discutindo as facilidades e dificuldades encontradas na sua implementação e apontando para o desenvolvimento de futuros estudos.
Several studies regarding the vibration attenuation using intelligent materials have been widely explored in the academic world in engineering. In this context, the shape memory alloys (SMAs) exhibit vibratory energy dissipation due to their hysteretic behavior caused by the pseudoelastic effect. In the present work, two systems with one and two degrees of freedom, containing a SMA helical spring as a resilient element, are numerically implemented to demonstrate the vibration attenuation of the system caused by the phase transformations present in the SMA spring. For each considered mechanical systems, two thermomechanical models are numerically confronted in order to obtain the characteristics of each model in representing the vibration attenuation of the systems submitted to thermo-mechanical loads. This work is concluded presenting the potentialities of the design methodology proposed and future developments to be implemented.

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Silva, Rafael de Oliveira. "Atenuação de vibrações em sistemas que utilizam molas de liga de memória de forma /". Ilha Solteira, 2017. http://hdl.handle.net/11449/150444.

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Orientador: Gustavo Luiz Chagas Manhães de Abreu
Resumo: Diversos estudos relacionados à atenuação de vibrações utilizando materiais inteligentes vem sendo amplamente explorados no meio acadêmico. Neste âmbito, as Ligas de Memória de Forma (LMF) se destacam por apresentarem dissipação de energia vibratória devido ao seu comportamento histerético promovido pelo efeito pseudoelástico. No presente trabalho, dois sistemas com um e dois graus de liberdade, contendo mola helicoidal de LMF como elemento resiliente, são implementados numericamente para demonstrar a atenuação de vibrações ocasionada pelas transformações de fase presentes no material. Para cada um dos sistemas mecânicos investigados, dois modelos termomecânicos são confrontados numericamente visando a obtenção das características de cada modelo em representar a atenuação de vibrações dos sistemas submetidos à carregamentos termo-mecânicos. O trabalho termina comentando as potencialidades da proposta apresentada, discutindo as facilidades e dificuldades encontradas na sua implementação e apontando para o desenvolvimento de futuros estudos.
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22

Schottmüller, Martin [Verfasser] y A. [Akademischer Betreuer] Albers. "Ein Ansatz zur dynamischen Charakterisierung und Bewertung von nichtlinearen Schwingungssystemen anhand des Beispiels Fliehkraftpendel = An approach for dynamic characterization and evaluation of nonlinear vibration systems using the example of a centrifugal pendulum absorber / Martin Schottmüller ; Betreuer: A. Albers". Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1240314515/34.

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23

Tatera, James E. "Vibration reduction of marine cable systems using dynamic absorbers". Thesis, Monterey, California. Naval Postgraduate School, 1996. http://hdl.handle.net/10945/9141.

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24

Agnes, Gregory Stephen. "Performance of Nonlinear Mechanical, Resonant-Shunted Piezoelectric, and Electronic Vibration Absorbers for Multi-Degree-of-Freedom Structures". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30740.

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Linear vibration absorbers are a valuable tool used to suppress vibrations due to harmonic excitation in structural systems. Limited evaluation of the performance of nonlinear vibration absorbers for nonlinear structures exists in the current literature. The state of the art is extended in this work to vibration absorbers in their three major physical implementations: the mechanical vibration absorber, the inductive-resistive shunted piezoelectric vibration absorber, and the electronic vibration absorber (also denoted a positive position feedback controller). A single, consistent, physically similar model capable of examining the response of all three devices is developed. The performance of vibration absorbers attached to single-degree-of-freedom structures is next examined for performance, robustness, and stability. Perturbation techniques and numerical analysis combine to yield insight into the tuning of nonlinear vibration absorbers for both linear and nonlinear structures. The results both clarify and validate the existing literature on mechanical vibration absorbers. Several new results, including an analytical expression for the suppression region's location and bandwidth and requirements for its robust performance, are derived. Nonlinear multiple-degree-of-freedom structures are next evaluated. The theory of Nonlinear Normal Modes is extended to include consideration of modal damping, excitation, and small linear coupling, allowing estimation of vibration absorber performance. The dynamics of the N+1-degree-of-freedom system reduce to those of a two-degree-of-freedom system on a four-dimensional nonlinear modal manifold, thereby simplifying the analysis. Quantitative agreement is shown to require a higher order model which is recommended for future investigation. Finally, experimental investigation on both single and multi-degree-of-freedom systems is performed since few experiments on this topic are reported in the literature. The experimental results qualitatively verify the analytical models derived in this work. The dissertation concludes with a discussion of future work which remains to allow nonlinear vibration absorbers, in all three physical implementations, to enter the engineer's toolbox.
Ph. D.

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25

Noori, Behshad. "Application of dynamic vibration absorbers on double-deck circular railway tunnels to mitigate railway-induced ground-borne vibration". Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667305.

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This dissertation is concerned with investigating the efficiency of dynamic vibration absorbers (DVAs) as measures to mitigate ground-borne vibrations induced by railway traffic in double-deck tunnels. The main topics of the dissertation are the coupling of a set of longitudinal distributions of DVAs to the interior floor of a double-deck tunnel dynamic model, the computation of the response of this coupled system due to train traffic and obtaining the optimum design parameters of the DVAs to minimize this response. To address the first concern, a methodology for coupling a set of longitudinal distributions of DVAs to any railway subsystem in the context of a theoretical dynamic model of railway infrastructure is developed. The optimum design parameters of the DVAs are obtained using an optimization process based on a genetic algorithm. The effectiveness of the DVAs is assessed by two response parameters, which are used as objective functions to be minimized in the optimization process: the energy flow radiated upwards by the tunnel and the maximum transient vibration value (MTVV) in the building near the tunnel. The model used to compute the former is a two-and-a-half dimensional (2.5D) semi-analytical model of a train-track-tunnel-soil system that considers a full-space soil model, and the one used to compute the latter is a hybrid experimental-numerical model of a train-track-tunnel-soil-building system. In the hybrid model, a numerical model of the track-tunnel system based on 2.5D coupled finite element-boundary element formulation along with a dynamic rigid multi-body model of the vehicle is used to compute the response in the tunnel wall, and then, the response in the building is computed using experimentally obtained transfer functions between the tunnel wall and the building. The triaxial response in the building is used to compute the MTVV. An alternative option to evaluate the MTVV in a building is to use a fully theoretical model of the train-track-tunnel-soil-building system. In the context of this modeling strategy, a computationally efficient method to calculate the 2.5D Green's functions of a layered soil is also presented. The results show that the DVAs would be an effective mitigation measure for railway-induced vibrations in double-deck tunnels as reductions up to 6.6 dB in total radiated energy flow and up to 3.3 dB in the vibration inside a nearby building are achieved in the simulations presented in this work.
En esta tesis se estudia la eficiencia de los absorbedores de vibraciones dinámicos (DVAs) como medidas de mitigación de las vibraciones inducidas por infraestructuras ferroviarias aplicados a túneles ferroviarios de dos niveles. Los principales desarrollos de la tesis son el acoplamiento de un conjunto de distribuciones longitudinales de DVAs a la losa intermedia de un modelo dinámico de túnel de dos niveles, el cálculo de la respuesta de este sistema acoplado debido al paso del tren y la obtención de los parámetros óptimos de los DVAs para minimizar esta respuesta. Para abordar la primer punto, se ha desarrollado una metodología con el fin de acoplar un conjunto de distribuciones longitudinales de DVAs a cualquier subsistema ferroviario en el contexto de modelos teóricos de la dinámica de infraestructura ferroviarias. Los parámetros óptimos de los DVAs han sido obtenidos mediante un proceso de optimización basado en un algoritmo genético. La eficiencia de los DVAs se evalúa mediante dos quantificadores de la respuesta dinámica del sistema, los cuales se utilizan como funciones objetivo a minimizar en el proceso de optimización: el flujo de energía total radiado hacia arriba desde el túnel y el valor máximo de vibración transitoria (MTVV) en el forjada de un edificio cercano al túnel. El modelo utilizado para calcular el primero es un modelo semi-analítico del sistema vehículo-vía-túnel-terreno que considera un modelo de terreno de espacio completo, y el que se utiliza para calcular el segundo es un modelo híbrido experimental-numérico del sistema vehículo-vía-túnel-terreno-edificio. En el modelo híbrido, se utiliza un modelo numérico del sistema vía-túnel basado en la formulación acoplada de elementos finitos-elementos de contorno acoplados, formulada en el dominio del número de onda y la frecuencia, junto con un modelo dinámico multicuerpo del vehículo con el objetivo de calcular la respuesta en la pared del túnel. Luego, la respuesta en el edificio se calcula utilizando funciones de transferencia obtenidas experimentalmente entre la pared del túnel y el edificio. Para calcular el MTVV, se utiliza la respuesta triaxial en el edificio. Una opción alternativa para evaluar el MTVV en un edificio es utilizar un modelo totalmente teórico del sistema vehículo-vía-túnel-terreno-edificio. En el contexto de esta estrategia de modelado, también se presenta un método computacionalmente eficiente para calcular las funciones de Green de un terreno en capas en el dominio 2.5D. Los resultados muestran que los DVAs pueden ser una medida de mitigación efectiva para las vibraciones inducidas por infraestructuras ferroviarias en el marco de un túnel ferroviario de dos niveles, ya que en las simulaciones presentadas en esta tesis se alcanzan reducciones de hasta 6.6 dB en el flujo de energía total radiado y hasta 3.3 dB en la vibración dentro de un edificio cercano.

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26

Oueini, Shafic Sami. "Techniques for Controlling Structural Vibrations". Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/27176.

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We tackle the problem of suppressing high-amplitude vibrations of cantilever beams when subjected to either primary external or principal parametric resonances. Guided by results of previous investigations into the nonlinear dynamics of single- and multi-degree-of-freedom structures, we design mechatronic systems of sensors, actuators, and electronic devices and implement nonlinear active feedback control. In the case of external excitation, we devise two vibration absorbers based on either quadratic or cubic feedback. We conduct theoretical analyses and demonstrate that when a two-to-one (one-to-one) internal resonance condition is imposed between the plant and the quadratic (cubic) absorber, there exists a saturation phenomenon. When the plant is forced near its resonant frequency and the forcing amplitude exceeds a certain small threshold, the nonlinear coupling creates an energy-transfer mechanism that limits (saturates) the response of the plant. Our theoretical studies reveal that the cubic absorber creates regimes of high-amplitude quasiperiodic and chaotic responses, thereby limiting its utility. However, we show that superior results can be achieved when the natural frequency of the quadratic absorber is set equal to one-half the excitation frequency. Consequently, we apply the quadratic technique through a variety of linear and nonlinear actuators, sensors, and electronic devices. We design and build second-order analog circuits that emulate the quadratic absorber. Using a DC motor, piezoelectric ceramics, and Terfenol-D struts as actuators and potentiometers, strain gages, and accelerometers as sensors, we demonstrate successful single- and multi-mode vibration control. In order to realize a more versatile implementation of the control strategy, we resort to a digital signal processing (DSP) board. We compose a code in C and design a digital absorber by developing algorithms that, in addition to replacing the analog circuit, automatically detect the amplitude and frequency of oscillation of the plant and fine-tune the absorber parameters. We take advantage of the digital realization, implement a linear absorber, and compare the performance of the quadratic absorber with that of its linear counterpart. In the case of parametric excitation, we investigate two techniques. First, we explore application of the quadratic absorber. We prove theoretically and demonstrate experimentally that this control scheme is not reliable. Then, we propose an alternate approach. We devise a control law based on cubic velocity feedback. We conduct theoretical and experimental investigations and show that the latter strategy leads to effective vibration suppression and bifurcation control.
Ph. D.

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27

Yan, Zhimiao. "Modeling of Nonlinear Unsteady Aerodynamics, Dynamics and Fluid Structure Interactions". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71824.

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We model different nonlinear systems, analyze their nonlinear aspects and discuss their applications. First, we present a semi-analytical, geometrically-exact, unsteady potential flow model is developed for airfoils undergoing large amplitude maneuvers. Towards this objective, the classical unsteady theory of Theodorsen is revisited by relaxing some of the major assumptions such as (1) flat wake, (2) small angle of attack, (3) small disturbances to the mean flow components, and (4) time-invariant free-stream. The kinematics of the wake vortices is simulated numerically while the wake and bound circulation distribution and, consequently, the associated pressure distribution are determined analytically. The steady and unsteady behaviors of the developed model are validated against experimental and computational results. The model is then used to determine the lift frequency response at different mean angles of attack. Second, we investigate the nonlinear characteristics of an autoparametric vibration system. This system consists of a base structure and a cantilever beam with a tip mass. The dynamic equations for the system are derived using the extended Hamilton's principle. The method of multiple scales is then used to analytically determine the stability and bifurcation of the system. The effects of the amplitude and frequency of the external force, the damping coefficient and frequency of the attached cantilever beam and the tip mass on the nonlinear responses of the system are determined. As an application, the concept of energy harvesting based on the autoparametric vibration system consisting of a base structure subjected to the external force and a cantilever beam with a tip mass is evaluated. Piezoelectric sheets are attached to the cantilever beam to convert the vibrations of the base structure into electrical energy. The coupled nonlinear distributed-parameter model is developed and analyzed. The effects of the electrical load resistance on the global frequency and damping ratio of the cantilever beam are analyzed by linearizion of the governing equations and perturbation method. Nonlinear analysis is performed to investigate the impacts of external force and load resistance on the response of the harvester. Finally, the concept of harvesting energy from ambient and galloping vibrations of a bluff body is investigated. A piezoelectric transducer is attached to the transverse degree of freedom of the body in order to convert the vibration energy to electrical power. A coupled nonlinear distributed-parameter model is developed that takes into consideration the galloping force and moment nonlinearities and the base excitation effects. The aerodynamic loads are modeled using the quasi-steady approximation. Linear analysis is performed to determine the effects of the electrical load resistance and wind speed on the global damping and frequency of the harvester as well as on the onset of instability. Then, nonlinear analysis is performed to investigate the impact of the base acceleration, wind speed, and electrical load resistance on the performance of the harvester and the associated nonlinear phenomena. Short- and open-circuit configurations for different wind speeds and base accelerations are assessed
Ph. D.

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28

Pratt, Jon Robert Jr. "Vibration Control for Chatter Suppression with Application to Boring Bars". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29344.

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A mechatronic system of actuators, sensors, and analog circuits is demonstrated to control the self-excited oscillations known as chatter that occur when single-point turning a rigid workpiece with a flexible tool. The nature of this manufacturing process, its complex geometry, harsh operating environment, and poorly understood physics, present considerable challenges to the control system designer. The actuators and sensors must be rugged and of exceptionally high bandwidth and the control must be robust in the presence of unmodeled dynamics. In this regard, the qualitative characterization of the chatter instability itself becomes important. Chatter vibrations are finite and recognized as limit cycles, yet modeling and control efforts have routinely focused only on the linearized problem. The question naturally arises as to whether the nonlinear stability is characterized by a jump phenomenon. If so, what does this imply for the "robustness" of linear control solutions? To answer our question, we present an advanced hardware and control system design for a boring bar application. Initially, we treat the cutting forces merely as an unknown disturbance to the structure which is essentially a cantilevered beam. We then approximate the structure as a linear single-degree-of-freedom damped oscillator in each of the two principal modal coordinates and seek a control strategy that reduces the system response to general disturbances. Modal-based control strategies originally developed for the control of large flexible space structures are employed; they use second-order compensators to enhance selectively the damping of the modes identified for control. To attack the problem of the nonlinear stability, we seek a model that captures some of the behavior observed in experiments. We design this model based on observations and intuition because theoretical expressions for the complex dynamic forces generated during cutting are lacking. We begin by assuming a regenerative chatter mechanism, as is common practice, and presume that it has a nonlinear form, which is approximated using a cubic polynomial. Experiments demonstrate that the cutting forces couple the two principal modal coordinates. To obtain the jump phenomena observed experimentally, we find it necessary to account for structural nonlinearies. Gradually, using experimental observation as a guide, we arrive at a two-degree-of-freedom chatter model for the boring process. We analyze the stability of this model using the modern methods of nonlinear dynamics. We apply the method of multiple scales to determine the local nonlinear normal form of the bifurcation from static to dynamic cutting. We then find the subsequent periodic motions by employing the method of harmonic balance. The stability of these periodic motions is analysed using Floquet theory. Working from a model that captures the essential nonlinear behavior, we develop a new post-bifurcation control strategy based on quench control. We observe that nonlinear state feedback can be used to control the amplitude of post-bifurcation limit cycles. Judicious selection of this nonlinear state feedback makes a supplementary open-loop control strategy possible. By injecting a harmonic force with a frequency incommensurate with the chatter frequency, we find that the self-excited chatter can be exchanged for a forced vibratory response, thereby reducing tool motions.
Ph. D.

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29

Grenat, Clément. "Nonlinear Normal Modes and multi-parametric continuation of bifurcations : Application to vibration absorbers and architectured MEMS sensors for mass detection". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI078/document.

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Un des buts de cette thèse est d’approfondir la compréhension de la dynamique non-linéaire, notamment celle des MEMS, en proposant de nouvelles méthodes d’analyse paramétrique et de calcul de modes normaux non-linéaires. Dans une première partie, les méthodes de détection, de localisation et de suivi de points de bifurcation selon un unique paramètre sont rappelées. Ensuite, une nouvelle méthode d’analyse multiparamétrique basée sur la continuation récursive d’extremums est présentée. Cette méthode est ensuite appliquée à un absorbeur de vibration non-linéaire afin de repousser l’apparition de solutions isolées. Deuxièmement, une méthode de calcul de modes normaux non-linéaires est présentée. Une condition de phase optimale et une régularisation de l’équation de mouvement sont proposées afin d’obtenir une méthode de continuation plus robuste au niveau des interactions modales. Ensuite, un problème quadratique aux valeurs propres modifié pour le calcul de stabilité et de points de bifurcation est présenté. Finalement, le calcul de modes normaux non-linéaires a été étendu aux systèmes non-conservatifs permettant la continuation des résonances d’énergie en déplacement et des résonances de phase. Troisièmement, la dynamique non-linéaire de réseaux de MEMS basé sur plusieurs micro-poutres résonantes est analysée à l’aide des méthodes proposées. Tout d'abord, un phénomène de synchronisation de points de bifurcations dû au couplage électrostatique dans les réseaux de MEMS est expliqué. Puis, la dynamique non-linéaire d'un réseau dissymétrisé par l'ajout d'une petite masse sur une micro-poutre est analysée. Enfin, des mécanismes de détection de masse exploitant ces phénomènes non-linéaires sont présentés
One of the goals of this thesis is to enhance the comprehension of nonlinear dynamics, especially MEMS nonlinear dynamics, by proposing new methods for parametric analysis and for nonlinear normal modes computation. In a first part, methods for the detection, the localization and the tracking of bifurcation points with respect to a single parameter are recalled. Then, a new method for parametric analysis, based on recursive continuation of extremum, is presented. This method is then applied to a Nonlinear Tuned Vibration Absorber in order to push isolated solutions at higher amplitude of forcing. Secondly, a method is presented for the computation of nonlinear normal modes. An optimal phase condition and a relaxation of the equation of motion are proposed to obtain a continuation method able to handle modal interactions. Then, a quadratic eigenvalue problem is shifted to compute the stability and bifurcation points. Finally, nonlinear normal modes are extended to non-conservatives systems permitting the continuation of phase and energy resonances. Thirdly, the nonlinear dynamics of MEMS array, based on multiple resonant micro-beams, is analyzed with the help of the proposed methods. A frequency synchronization of bifurcation points due to the electrostatic coupling is discovered. Then, the nonlinear dynamics of a MEMS array after symmetry breaking event induced by the addition of a small mass onto one of the beam of the array is analyzed. Finally, mass detection mechanisms exploiting the discovered phenomena are presented

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30

Marques, Rodrigo França Alves. "Estudo teórico e numérico de absorvedores dinâmicos de vibrações ativos e adaptativos". Universidade Federal de Uberlândia, 2000. https://repositorio.ufu.br/handle/123456789/14815.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Dynamic Vibration Absorbers (DVAs) have been used to attenuate vibrations in various types of mechanical systems. In its simplest form, a DVA is formed by an association of passive elements (inertia, stiffness and damping). The values of these parameters are selected so as to tune the DVA to a given value of the excitation frequency, assumed to be fixed. As a result, the attenuation capability of a passive DVA significantly decreases as the excitation frequency deviates from the nominal tuning frequency. To avoid this drawback, active and adaptive DVAs have been extensively studied lately, in an attempt to achieve larger effective bandwidths and self tunning capability. Active DVAs contain, besides the passive elements, an actuator, which applies a control force determined by an appropriate control law. Adaptive DVAs are understood as those constructed in such a way that the values of their physical parameters can be adjusted according to well-defined laws. In this work, some configurations of active and adaptive DVAs are assessed, namely: a) an active DVA using as feedback signal the timedelayed displacement response of the reactive mass (delayed resonator); b) a novel active DVA using a control law in which the control force is expressed as a linear combination of the displacement, velocity and acceleration of the reactive mass, relative to the primary mass; c) an active DVA exploring linear quadratic optimal control theory; d) a vibrating string-type adaptive DVA; e) a pendulum-type adaptive DVA; f) an adaptive DVA formed from a beam with piezoelectric patches. For each configuration the theoretical foundations are first developed. Then, numerical applications are presented to assess their main features and performance.
Os Absorvedores Dinâmicos de Vibrações (ADVs) vêm sendo largamente utilizados para a atenuação de vibrações estruturais, com aplicações nas engenharias mecânica, civil, naval e aeroespacial. Os ADVs mais comumente usados são os passivos, compostos por elementos de parâmetros concentrados de inércia, rigidez e amortecimento. Classicamente, os ADVs passivos são projetados de forma que sua freqüência natural seja sintonizada para a freqüência de excitação, admitida fixa. Entretanto, a banda de operação dos ADVs passivos é relativamente estreita, o que inviabiliza a sua aplicação para casos em que a freqüência de excitação passa a variar. Como forma de contornar esta limitação, recentemente foram desenvolvidas as concepções de ADVs ativos e adaptativos, que têm capacidade de sintonização em bandas freqüenciais mais largas. Os ADVs ativos são aqueles em que um atuador, colocado paralelamente aos elementos passivos do ADV, exerce uma força de controle que permite modificar sua sintonização. Por ADVs adaptativos entendem-se aqueles cujos parâmetros físicos de inércia, rigidez e amortecimento podem ser variados, de forma controlada proporcionando a sintonização desejada. Neste trabalho são estudadas três configurações de ADVs ativos e outras três de ADVs adaptativos. São elas: a) o ADV ativo com realimentação do sinal de deslocamento da massa do ADV, defasado no tempo (ressonador defasado); b) uma nova configuração proposta de ADV ativo com realimentação dos sinais de deslocamento, velocidade e aceleração relativos; c) o ADV ativo com controle ótimo; d) o ADV adaptativo tipo corda vibrante; e) o ADV adaptativo pendular; f) o ADV adaptativo tipo viga com atuadores piezelétricos. Neste estudo se incluem o desenvolvimento teórico e as simulações numéricas no domínio da freqüência e do tempo, realizadas com o objetivo de avaliar as características operacionais e o desempenho das configurações estudadas.
Mestre em Engenharia Mecânica

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31

Del, Claro Vergilio Torezan Silingardi. "Concepçâo e avaliação numérica e experimental de um absorvedor dinâmico de vibrações termicamente sintonizável". Universidade Federal de Uberlândia, 2016. https://repositorio.ufu.br/handle/123456789/18666.

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A presente dissertação trata do estudo de um absorvedor dinâmico de vibrações (ADV) sintonizável por meio da geração voluntária de tensões induzidas por campos de temperatura aplicados a estruturas do tipo placas finas, explorando o efeito conhecido por enrijecimento por tensões (stress stiffening). Após apresentação da teoria subjacente aos absorvedores dinâmicos de vibrações e à modelagem numérica do comportamento dinâmico de placas sob a ação de tensões de origem térmica, foram realizadas simulações numéricas baseadas em discretização por elementos finitos visando à caracterização do comportamento dinâmico de placas retangulares sujeitas a diferentes tipos de carregamento térmico e condições de contorno mecânicas. Para este efeito, foi desenvolvido um procedimento de modelagem multifísica utilizando um programa comercial de análise por elementos finitos que permite considerar formas arbitrárias de carregamento térmico e condições de contorno térmicas e mecânicas. Os resultados destas simulações comprovaram que variações substanciais dos valores das frequências naturais de vibração podem resultar das tensões induzidas por campos térmicos. Com base nestes resultados, foi projetado um ADV consistindo de uma placa metálica fina circular confinada em sua borda externa por dois anéis metálicos, de sorte que a frequência natural correspondente ao primeiro modo de flexão axissimétrico possa ser ajustada pela diferença entre as temperaturas impostas à placa e aos anéis. Diversas simulações numéricas baseadas em elementos finitos foram realizadas visando à otimização da geometria e previsão do desempenho do ADV. Um protótipo do absorvedor dinâmico foi construído, dispondo de aquecedores resistivos de película para aquecimento independente e controlado de seus componentes. Diversos ensaios dinâmicos foram realizados com o protótipo visando à caracterização de seu comportamento sem e com efeitos térmicos. Os resultados experimentais confirmaram a influência significativa das tensões térmicas sobre o comportamento dinâmico do ADV e a possibilidade de obter sua sintonização.
The present work is devoted to the study of a dynamic vibration absorber (DVA) that can be tuned by the voluntary introduction of stress induced by temperature distributions in plate-like structures, based on the effect known as stress-stiffening. After summarizing the underlying theory of dynamic vibration absorbers and modeling the dynamic behavior of thin plates in the presence of thermally-induced stresses, numerical simulations based on finite element discretization have been made to characterize the dynamic behavior of rectangular plates under different thermal loads and mechanical boundary conditions. For this purpose, a general multiphysic modeling procedure based on a finite element commercial code has been developed, enabling to considerer all the possible forms of thermal load and thermal and mechanical boundary conditions. The results of these simulations have shown that significant variations of the natural frequencies can result from the induction of thermal stresses. Based on these results, a DVA has been designed, consisting of a thin circular metallic plate constrained at its outer border by thick metallic rings, in such a way that the natural frequency associated to the first axissymmetric bending mode can be adjusted according to the difference between the temperatures of the plate and the rings. A number of numerical simulations based on finite elements have been made aiming at optimizing the geometry and predicting the performance of the DVA. A prototype of the absorber has been built, having foil resistive heaters for the controlled application of heat to the plate and the rings. Dynamic tests have been carried-out on the prototype for the characterization of its dynamic behavior with and without thermal effects. The experimental results confirmed the significant influence of the thermal stresses on the natural frequencies of the DVA and the possibility of achieving frequency tuning.
Dissertação (Mestrado)

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32

Fontes, Yuri Correa. "Resposta ao desbalanço de rotor com absorvedor dinâmico rotativo com elemento viscoelástico". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-25072016-170222/.

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O presente trabalho consiste no projeto de um modelo em elementos finitos de um absorvedor dinâmico rotativo utilizando-se um material viscoelástico como componente dissipador do sistema. O absorvedor é composto por um anel de material viscoelástico interposto entre dois anéis de aço, o qual é fixado na extremidade livre de um sistema rotativo representado por um eixo flexível, suportado por dois rolamentos, no qual estão fixos dois discos igualmente espaçados do centro entre os dois mancais. O modelo em elementos finitos do sistema rotativo é validado com os dados experimentais do modelo real e suas velocidades críticas são determinadas baseadas no diagrama de Campbell e na resposta ao desbalanço em um dos discos. O modelo inicial do absorvedor dinâmico rotativo é replicado de um modelo da literatura e as respostas a uma excitação na forma de impulso são comparadas. O modelo desenvolvido equipara-se ao da literatura para frequências até 600 Hz, intervalo que compreende as velocidades críticas a serem amortecidas. A otimização do absorvedor é realizada através de variações da geometria do mesmo e são traçadas curvas de influência de cada parâmetro sobre suas frequências naturais. Com base nestas curvas são realizadas análises de influência conjunta dos parâmetros geométricos sobre tais frequências. Pelos resultados obtidos verifica-se a possibilidade da obtenção de um modelo que atue sobre modos de flexão específicos do sistema rotativo, atenuando as amplitudes de vibração das velocidades críticas correspondentes a cada modo. Uma vez obtidos os modelos de absorvedores dinâmicos correspondentes aos dois primeiros modos de flexão do sistema rotativo, ambos são acoplados ao sistema e se observa grande redução dos picos de amplitude do primeiro modo de flexão, enquanto os picos do segundo modo sofrem baixa alteração.
The present work concerns the development, optimization and validation of a finite element model of a dynamic vibration absorber using a viscoelastic material as the damping component. The dynamic absorber consists of a ring of viscoelastic material interposed between two rings of steel, which is fixed to the free end of a rotary system represented by a flexible shaft supported by two bearings, on which are fixed two discs equally spaced in the center of both bearings. The finite element model of the rotating system is validated with experimental data from the actual model and its critical speeds are determined based on the Campbell diagram and in its response to the imbalance. The initial model of the dynamic absorber is replicated from a model of the literature and the responses to an impulse excitation are compared. The developed model matches the literature one for frequencies up to 600 Hz, range comprising the critical speeds to be damped. The absorber\'s optimization is accomplished through variations of its geometry and influence curves of each parameter over its natural frequencies are drawn. Based on these curves, combined influence analyzes of the geometrical parameters over such frequencies are performed. From the results obtained, it can be seen the possibility of achieving a model that acts on specific bending modes of the rotation system, reducing the vibration amplitudes of the critical speeds corresponding to each mode. Once obtained the dynamic absorbers models corresponding to the first two modes of vibration of the rotatative system, both models are coupled to the system and it is observed great reduction of the amplitude of the first bending mode peaks, while the second mode suffer low peaks reduction.

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33

Aydan, Goksu. "Ride Comfort Improvement By Application Of Tuned Mass Dampers And Lever Type Vibration Isolators". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12612131/index.pdf.

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In this study, the efficiency of linear and rotational tuned mass dampers (TMD) and lever type vibration isolators (LVI) in improving ride comfort is investigated based on a vehicle quarter-car model. TMDs reduce vibration levels by absorbing the energy of the system, especially at their natural frequencies. Both types of TMDs are investigated in the first part of this study. Although linear TMDs can be implemented more easily on suspension systems, rotational TMDs show better performance in reducing vibration levels
since, the inertia effect of rotational TMDs is higher than the linear TMDs. In order to obtain better results with TMDs, configurations with chain of linear TMDs are obtained in the second part of the study without changing the original suspension stiffness and damping coefficient. In addition to these, the effect of increasing the number of TMDs used in the chain configuration is investigated. Results show that performance deterioration at lower frequencies than wheel hop is reduced by using chain of TMDs. In the third part of this study, various configurations of LVIs with different masses are considered and significant attenuation of vibration amplitudes at both body bounce and wheel hop frequencies is achieved. Results show that TMDs improve ride comfort around wheel hop frequency while LVIs are quite efficient around body bounce frequency. Finally, parameter uncertainty due to aging of components and manufacturing defects are investigated.

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34

Pinto, Luis Antonio Chávez. "Modelo estrutural numérico que simula a alocação de absorvedores dinâmicos para redução de ruído acústico emitido por um transformador de potência". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-18082009-144121/.

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Os transformadores de potência elétrica produzem um elevado nível de ruído que em alguns casos gera desconforto à comunidade vizinha. O presente trabalho desenvolve um modelo estrutural de elementos nitos que, com carregamento adequado, é capaz de reproduzir o deslocamento, medido durante a operação, de um transformador de potência elétrica. Este modelo estrutural é utilizado para calcular a redução do deslocamento das superfícies deste transformador decorrentes do emprego de absorvedores dinâmicos de vibração. Este modelo estrutural foi desenvolvido para estimar o número de absorvedores dinâmicos, sua massa e sua localização que permitiria reduzir o ruído acústico emitido por este transformador de potência até alcançar níveis de intensidade de som em comformidade com a legislação brasileira.
Electrical power transformers produce a high level of noise, which, in some cases, generate discomfort to the surrounding community. The present work develops a structural model by the Finite Element Method that, with adequate loading conditions, is capable of reproducing the displacement, measured during operation, of the transformer tank. The structural model has been used to compute the displacement reduction of the transformer surfaces by using dynamic vibration absorbers. The structural model was developed to estimate the number of dynamic absorbers, the mass and localization that could reduce the acoustic noise to levels of intensity of sound in accordance to the Brazilian law.

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35

Snoun, Cherif. "Contrôle passif des vibrations des systèmes mécaniques à l’aide d’absorbeurs dynamiques non linéaires avec prise en compte des incertitudes". Thesis, Tours, 2020. http://www.theses.fr/2020TOUR4001.

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Face à l’augmentation des exigences à la fois économiques et de santé publique, les industriels sont dans la nécessité de concevoir des systèmes mécaniques de plus en plus performants et respectant un certain niveau de confort acoustique. En mécanique ou en acoustique, le contrôle de vibrations est un champ de recherche très actif. Trois grands types de technologie sont majoritairement utilisées dans l’industrie : le contrôle passif par dissipation, le contrôle passif à l’aide d’absorbeurs linéaires accordées et le contrôle actif, chacune de ses techniques possédant ses avantages et ses inconvénients. Depuis une quinzaine d’années, l’utilisation d’absorbeurs non linéaires de type NES (« Nonlinear Energy Sink » en anglais), typiquement un système masse-ressort-amortisseur à raideur purement non linéaire, a montré son efficacité comme solution alternative de contrôle passif des vibrations en conciliant les avantages des technologies existantes. Cependant, le comportement dynamique du système couplé constitué du NES et du système primaire à protéger peut s’avérer très sensible aux paramètres qui admettent une dispersion importante. Notamment, lorsqu’il s’agit d’atténuer une instabilité dynamique (comme c’est le cas dans cette thèse) une discontinuité dans le profil de l’amplitude vibratoire du système peut s’observer, ce dernier passant brutalement d’un régime atténué (où le NES agit) à un régime non atténué (où le NES n’agit pas). Un régime non atténué étant potentiellement dangereux, il est important d’être en mesure, en prenant en compte les incertitudes paramétriques auxquelles le système primaire peut être confronté, de concevoir un NES qui soit robuste, c’est-à-dire fonctionnant au maximum dans l’espace des paramètres incertains correspondant à des régimes non atténués du système primaire.Dans la première partie, des méthodes basées sur le formalisme du chaos polynomial sont proposées pour la localisation, dans l’espace des paramètres incertains du système primaire, de la frontière entre la région correspondant aux régimes atténués et celle correspondant aux régimes non atténués, permettant ainsi le calcul de la propension du système couplé à être dans un régime atténué. Ces méthodes sont ensuite appliquées aux cas d’un système frottant à deux degrés de liberté (le modèle dit de Hultèn) couplé à deux NES identiques. Les résultats montrent d’une part que les méthodes basées sur le chaos polynomial permettent de réduire significativement le cout de calcul par rapport à la méthode de référence en conservant une bonne précision et d’autre part que la méthode basée sur le chaos polynomial multi-éléments (appelée méthode ME-gPC) est la plus efficace.Dans la deuxième partie, une méthodologie d'optimisation des NES sous incertitudes est développée. Deux approches sont proposées, à chaque fois basées sur la maximisation, sous incertitudes des paramètres du système primaire, de la propension du système couplé à être dans un régime atténué. La première approche considère que les paramètre des NES sont déterministes et sont donc les variables de conception à optimiser. La seconde méthode considère que les paramètres des NES sont également incertains mais avec une loi de probabilité connue. Ainsi, les variables de conception à optimiser ne sont plus directement les paramètres des NES mais l’une de leurs statistiques (la moyenne ou l’écart-type par exemple) appelées hyper-paramètres. Les résultats obtenus sont comparés à une optimisation déterministe de référence. L’efficacité des méthodes proposée, basées sur le chaos polynomial, à réduire significativement le cout de calcul en gardant une bonne précision est mise en évidence
Faced with increasing economic and public health requirements, industrialists are faced with the need to design increasingly efficient mechanical systems that respect a certain level of acoustic comfort. In mechanics or acoustics, vibration control is a very active field of research. Three main types of technology are mainly used in industry: passive control by dissipation, passive control using tuned linear absorbers and active control, each of these techniques having its advantages and disadvantages. Over the past 15 years, the use of NES (Nonlinear Energy Sink) non-linear absorbers, typically a purely non-linear stiffness mass-spring-damper system, has proven its effectiveness as an alternative solution for passive vibration control by combining the advantages of existing technologies. However, the dynamic behaviour of the coupled system consisting of the NES and the primary system to be protected can be very sensitive to parameters that allow for high dispersion. In particular, when attenuating dynamic instability (as is the case in this thesis) a discontinuity in the vibration amplitude profile of the system can be observed, as the system suddenly switches from an attenuated regime (where the NES acts) to an unattenuated regime (where the NES does not act). Since an unattenuated regime is potentially dangerous, it is important to be able, taking into account the parameter uncertainties that the primary system may face, to design an NES that is robust, i.e. operating at maximum within the space of the uncertain parameters corresponding to unattenuated regimes of the primary system.In the first part, methods based on the formalism of polynomial chaos are proposed for locating, in the space of the uncertain parameters of the primary system, the boundary between the region corresponding to attenuated regimes and that corresponding to non-attenuated regimes, thus allowing the calculation of the propensity of the coupled system to be in an attenuated regime. These methods are then applied to the cases of a two-degree-of-freedom friction system (the so-called Hultèn model) coupled to two identical NES. The results show, on the one hand, that the methods based on polynomial chaos allow a significant reduction of the calculation cost compared to the reference method while maintaining a good accuracy and, on the other hand, that the method based on multi-element polynomial chaos (called ME-gPC method) is the most efficient.In the second part, a methodology for optimizing NES under uncertainty is developed. Two approaches are proposed, each based on maximizing, under uncertainties of the primary system parameters, the propensity of the coupled system to be in a mitigated regime. The first approach considers that the SNF parameters are deterministic and are therefore the design variables to be optimized. The second approach considers that the SEL parameters are also uncertain but with a known probability distribution. Thus, the design variables to be optimized are no longer directly the parameters of the NES but one of their statistics (the mean or the standard deviation for example) called hyper-parameters. The results obtained are compared with a reference deterministic optimization. The effectiveness of the proposed methods, based on polynomial chaos, to significantly reduce the cost of calculation while maintaining good precision is highlighted

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Fernandes, Fernando Vitoriano. "Diagnose de falhas via observadores de estado em sistemas mecânicos com absorvedores dinâmicos de vibrações tipo lâmina vibrante /". Ilha Solteira : [s.n.], 2008. http://hdl.handle.net/11449/94545.

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Orientador: Gilberto Pechoto de Melo
Banca: Aparecido Carlos Gonçalves
Banca: Cleudmar Amaral de Araújo
Resumo: Neste trabalho foi desenvolvida uma metodologia de detecção e localização de falhas, para sistemas mecânicos que utilizam absorvedores dinâmicos de vibrações tipo lâmina vibrante (ADVLV). Através de modificações em alguns de seus parâmetros estruturais, o ADVLV desenvolvido absorve toda ou parte da vibração do sistema mecânico onde se encontra acoplado. Durante o trabalho foi utilizada a teoria de algoritmos genéticos baseada na evolução das espécies como ferramenta de otimização e em seguida, aplicou-se a metodologia de diagnóstico de falhas via observadores de estado para detecção e identificação de possíveis irregularidades no sistema. Na seqüência, a fim de validar a metodologia desenvolvida foram apresentados resultados obtidos através de simulações computacionais e experimentais, realizados com a construção de um ADVLV em uma estrutura primária pertencente ao laboratório de vibrações mecânicas do Departamento de Engenharia Mecânica da UNESP, Campus de Ilha Solteira.
Abstract: In this work it was developed a technique of fault detection and location, to mechanical systems using dynamic vibration absorbers type blade vibrant (DVABV). Through changes in some of its structural parameters, the DVABV developed absorbs all or part of the mechanical vibration of the system which it is attached. During the work, it was used the theory of genetic algorithms based on the evolution of species as a tool for optimization, then applied to the methodology for the diagnosis of faults by state observers in the detection and identification of possible flaws in the system. Following, in order to validate the methodology developed present themselves results through computer simulations and experimental made with the construction of a DVABV and their use in a structure primary, in the Mechanical Vibrations Laboratory, at Mechanical Engineering Department of UNESP, Ilha Solteira.
Mestre

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37

Paulo, Júnior Wellington Luziano. "Modelagem e avaliação numérica de absorvedores dinâmicos de vibrações sintonizáveis baseados em ligas com memória de forma". Universidade Federal de Uberlândia, 2012. https://repositorio.ufu.br/handle/123456789/14941.

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Fundação de Amparo a Pesquisa do Estado de Minas Gerais
In the context of the so-called smart materials, shape memory alloys (SMA) have been extensively investigated aiming at various applications in different types of engineering prob- lems as well as interdisciplinary problems. Specifically, SMAs have been used for the mitiga- tion of mechanical vibrations, owing to their characteristic pseudoelastic effect, which is re- sponsible for the occurrence of hysteresis. Another relevant feature of these materials is the coexistence of two crystallographic phases (martensite and austenite), which have dissimilar mechanical properties, whose relative fractions depend on temperature and stress. In the present dissertation, this latter feature is explored in association with a strategy of passive vibration control which is based on tunable dynamic vibration absorbers (TDVA). These de- vices, once connected to a vibrating structure, can have their inertia and/or stiffness and/or damping adjusted to match the excitation frequency. Specifically, such tuning is achieved by controlling the martensite/austenite fraction by applying convenient thermal loads. By means of numerical simulations, which include the integration of the equations of motion, it is put in evidence the possibility of tuning a TDVA applied to a single degree-of-freedom system, with- in a given frequency band using two configurations of the resilient element (SMA rod and helicoidal spring). The results enable to evaluate the levels of vibration mitigation achieved and confirm that the strategy investigated can provide improved performance in terms of vibration attenuation.
No contexto dos chamados materiais inteligentes, as ligas com memória de forma (Shape Memory Alloys SMA) vêm sendo intensivamente investigadas com vistas a aplicações em diversos tipos de sistemas de engenharia e em problemas interdisciplinares. Especificamente, as SMA têm sido utilizadas para a mitigação de vibrações mecânicas, graças ao chamado efeito pseudoelástico, responsável pela ocorrência de histerese. Outra característica relevante desses materiais é a coexistência de duas fases cristalográficas (martensita e austenita), com propriedades mecânicas distintas, cujas frações relativas dependem da temperatura e da tensão. No presente trabalho, esta última característica é explorada em associação com uma estratégia de controle passivo de vibrações, baseada nos chamados absorvedores dinâmicos de vibrações sintonizáveis (ADV), que são dispositivos conectados à estrutura vibratória, cuja rigidez e/ou inércia podem ser ajustados em conformidade com a frequência de excitação, de modo que a vibração da estrutura seja altenuada. Especificamente, explora-se a possibilidade de confecção de ADVs sintonizáveis cuja rigidez pode ser ajustada por meio de variações controladas da fração relativa martensita/austenita induzidas por alterações da temperatura. Por meio de simulações numéricas, evidencia-se a possibilidade de sintonizar um ADV aplicado a um sistema vibratório de um grau de liberdade, dentro de uma dada faixa de valores de frequência, utilizando duas configurações do elemento resiliente (barra e mola helicoidal de SMA), e quantificam-se as reduções de amplitudes obtidas. Os resultados das simulações confirmam o aumento da eficiência na atenuação de vibrações proporcionado pela estratégia empregada.
Mestre em Engenharia Mecânica

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38

Fernandes, Fernando Vitoriano [UNESP]. "Diagnose de falhas via observadores de estado em sistemas mecânicos com absorvedores dinâmicos de vibrações tipo lâmina vibrante". Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/94545.

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Made available in DSpace on 2014-06-11T19:27:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-19Bitstream added on 2014-06-13T19:35:08Z : No. of bitstreams: 1 fernandes_fv_me_ilha.pdf: 2370293 bytes, checksum: dd12c9f677a5b0c0516c7c8361bbee5e (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho foi desenvolvida uma metodologia de detecção e localização de falhas, para sistemas mecânicos que utilizam absorvedores dinâmicos de vibrações tipo lâmina vibrante (ADVLV). Através de modificações em alguns de seus parâmetros estruturais, o ADVLV desenvolvido absorve toda ou parte da vibração do sistema mecânico onde se encontra acoplado. Durante o trabalho foi utilizada a teoria de algoritmos genéticos baseada na evolução das espécies como ferramenta de otimização e em seguida, aplicou-se a metodologia de diagnóstico de falhas via observadores de estado para detecção e identificação de possíveis irregularidades no sistema. Na seqüência, a fim de validar a metodologia desenvolvida foram apresentados resultados obtidos através de simulações computacionais e experimentais, realizados com a construção de um ADVLV em uma estrutura primária pertencente ao laboratório de vibrações mecânicas do Departamento de Engenharia Mecânica da UNESP, Campus de Ilha Solteira.
In this work it was developed a technique of fault detection and location, to mechanical systems using dynamic vibration absorbers type blade vibrant (DVABV). Through changes in some of its structural parameters, the DVABV developed absorbs all or part of the mechanical vibration of the system which it is attached. During the work, it was used the theory of genetic algorithms based on the evolution of species as a tool for optimization, then applied to the methodology for the diagnosis of faults by state observers in the detection and identification of possible flaws in the system. Following, in order to validate the methodology developed present themselves results through computer simulations and experimental made with the construction of a DVABV and their use in a structure primary, in the Mechanical Vibrations Laboratory, at Mechanical Engineering Department of UNESP, Ilha Solteira.

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39

Selim, André Baroni. "Influência das forças de inércia e do balanceador de massas na dinâmica do motor de combustão interna". [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264881.

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Orientador: Airton Nabarrete
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho visa estudar a influência do balanceador de massas e das forças de inércia dos componentes internos móveis do motor na dinâmica do motor de combustão interna apoiado sobre amortecedores de vibrações. Para o estudo da influência do balanceador de massas, diversas análises experimentais foram realizadas com um motor em dinamômetro. Chegam-se nas conclusões através da comparação dos deslocamentos medidos do motor com e sem balanceador de massas. Para que a influência das forças de inércia dos componentes internos móveis do motor fosse estudada, um modelo matemático foi criado. Neste modelo consideram-se as forças vindas dos componentes internos móveis atuando em um corpo rígido, neste caso o bloco do motor, apoiado sobre quatro amortecedores de vibrações com seis graus de liberdade. Variam-se dados construtivos como massas e geometria dos componentes internos móveis do motor observando a sua influência sobre o comportamento dinâmico do motor de combustão interna. A validação deste modelo matemático ocorre por meio da comparação de seus resultados com os resultados reais observados nas análises experimentais
Abstract: This work aims at studying the influence of mass balancer and inertia forces coming from engine internal components on internal combustion engine dynamics supported by vibration dampers. For mass balancer study several experimental analyses were performed with a dynamometer. The conclusions are obtained by comparison between measured engine displacements with and without mass balancer. To study the influence of inertia forces from engine internal components, a mathematical model was developed. In this model the inertia forces act on a rigid body, the engine crankcase, supported by four vibration dampers and with six degrees of freedom. Some modifications are made on engine internal components such as mass and geometry observing what is their influence on internal combustion engine dynamics. The mathematical model is validated by comparison against experimental analyses
Mestrado
Dinâmica
Mestre em Engenharia Automobilistica

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40

Hušek, Martin. "Londýnské oko". Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227180.

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Performance of static analysis of the London Eye structure is the subject of this diploma thesis. First chapters of the thesis analyses overview of realized structures of the Ferris wheel. The main part of the thesis analyses the London Eye structure itself. Specifically are described response analyses, sensitivity analyses, analyses of ultimate limit state and serviceability, stress analyses, analyses of fatigue stress and lifetime analyses. The thesis describes among static analysis also a design of dynamic vibration absorbers. The results of each analysis are evaluated in the final chapters.

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41

YuHan y 韓妤. "Dynamic Vibration Absorber for Reducing Vibration from Rail". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/22371195223662123128.

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碩士
國立成功大學
土木工程學系
102
Rail transport systems have some complaint about noise from the railway. The noise causes the vibration of the rail. To reduce the noise, a efficient way to reduce the rail vibration. To achieve this, dynamic vibration absorbers are sometimes designed. In this paper, rail’s frequency was found from experiment. Rail’s horizontal frequency is 450Hz, and vertical frequency is 1000Hz. The frequency is 200Hz to 270Hz, because of the sleeper. The frequency is about 3000Hz, because of the train. The same, decay rate on the track was found from experiment. The dynamic vibration absorber can be used to reduce the vertical decay rate on the low frequency and high frequency, and reducing the vertical acceleration’s root mean square value. On the contrary, the dynamic vibration absorber’s decay rate in horizontal was useless.

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42

Ting-Kong, Christopher. "Design of an adaptive dynamic vibration absorber". 1999. http://hdl.handle.net/2440/37922.

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The aim of this thesis is to investigate the use of a Dynamic Vibration Absorber to control vibration in a beam. Traditional means of vibration control have involved the use of passive and more recently, active methods. This study is different in that it involves an adaptive component in the design of vibration absorber using two novel designs for the adaptive mechanism. The first design incorporates the use of an enclosed air volume to provide the variable stiffness component in the absorber. By adjusting the volume of compressible air within the absorber, the stiffness characteristics of the absorber can be altered, enabling the device to adapt to changing vibration frequencies. Work here includes a theoretical investigation of the device. Following this, two prototypes are constructed and tested, the second of which is the refined model used for further testing. The second design incorporates the use of two concentrated masses cantilevered from two rods. The adaptive solution is achieved by moving the two masses along the length of the rod, producing a changing natural frequency for the absorber device. An analytical model of this device is developed as well as a finite element model. Results from both are compared to those obtained experimentally. Finally, a tuning algorithm is derived for the second absorber, and a control system constructed to make the dynamic vibration absorber "adaptive". Experiments are undertaken to determine the effectiveness of the absorber on the beam subject to changing excitation frequencies. The outcome of this research is that an Adaptive Vibration Absorber has been constructed with a computer interface such that the device can be used "on line".
Thesis (M.Eng.Sc.)--Mechanical Engineering, 1999.

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43

Chen, Kuan-Chih y 陳冠智. "Vibration Reduction Analysis of Dynamic Vibration Absorber in Beam Structure". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/wz8ssn.

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碩士
國立臺北科技大學
製造科技研究所
105
In this paper, based on continuous system beam structure as a dynamic vibration absorber and analyzed the vibration reduction of beam structure. The equation of motion of the beam structure with base excitation is derived by using energy principle. The dynamic vibration absorber model of the continuous system is derived from the dynamic vibration absorber model with two-degree of freedom, and then the effect of vibration absorber on the structure of viscous damped beam is analyzed by Transfer Matrix Method. The influence of design parameters, which are the mass ratio and damping ratio, is analyzed to research the vibration reduction of the first two modes of the beam structure. When the resonance frequencies of the vibration absorber are the same as the excitation frequencies of the base, the amplitude of the free end of the beam structure is the smallest. Finally, the results show that the viscous damping is located on the maximum bending moment of the beam structure or absorber can reduce the amount of displacement in the resonance.

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44

LIN, HSI-HSIANG y 林熙翔. "The Study of an Active Dynamic Vibration Absorber". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/67373704888827514507.

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碩士
國立中央大學
機械工程學系
86
The successful design of vibration absorber for absorbing the torsional vibration in the rotating machinery depends chiefly on the performance of the absorber. The centrifugal pendulum vibration absorber is a passiveabsorber. This absorber does not have the best efficiency if the disturbancefrequency varies with time. In this thesis, the pendulum with feedbackcontrol is used as a dynamic vibration absorber for the rotating machinery.We will derive the equations of the motion for rotating machinery and theactive pendulum absorber. The dynamics can be analyzed by utilizingthose equations. The nonlinear dynamic response of the rotating machinery and theactive pendulum absorber is analyzed using the method of harmonic balance.Periodic solutions are approximated by the first harmonic of the response and calculated by simulations. The anti-resonance frequency, that theoperating frequency for that which the absorber is tuned, can be found fromthe linearized system. From the analysis, we can obtain the effectfeedback control upon the system and the performance of the active absorber.In this thesis, the nonlinear dynamic analysis and the performance of the active pendulum absorber can help the design of the control algorithm.Experiments are carried out for verifying the analysis.

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45

Lu, Hsueh-Chi y 呂學奇. "Vibration Mitigation of a dynamic vibration absorber on a nonlinear simple beam". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/99179458478616969909.

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碩士
淡江大學
航空太空工程學系碩士班
102
Beam vibration has always been a concern for researchers and engineers and vibration within nonlinear systems is particularly problematic. This study considered a slender hinged-hinged nonlinear elastic beam with suspension cables simulated using nonlinear cubic springs and linear dampers to allow greater amplitude in the transverse direction. The model in this study could be applied to the engineering of structures with nonlinear suspension systems. In addition, inverting the system, we could simulate the beam placing on a Winkler-type elastic foundation. Therefore, there is a wide range of applications for this system. The primary objective of this study was to add a mass spring dynamic vibration absorber (MSDVA) on the beam to avoid internal resonance within this beam and achieve effective vibration damping. The internal resonance condition based on the ratio of the elastic foundation frequency to the beam frequency of the main structure was obtained. The influence of stretching effect and the location of the mass-spring were also taken into account. We employed the method of multiple scales (MOMS) to analyze this nonlinear problem. The Fixed point plots (steady state frequency response) were obtained. MSDVA with various locations and spring constants were considered and the optimal mass range for the MSDVA to reduce vibration in the main structure was also proposed by using the novel concept of 3-dimensional maximum amplitude contour plots (3D-MACP). The results of this study were verified using numerical simulation, which, in addition to confirming the accuracy by through comparison, established the applicability in this study.

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46

Zhang, Yu-Cheng y 張育誠. "Design of Dynamic Vibration Absorber for Vehicle Ride Comfort". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/53xg94.

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碩士
國立臺北科技大學
車輛工程系所
100
The goal of this study is improving the riding comfort, because it is an important issue in vehicle design. Nowadays, the electric vehicle has been developing rapidly, and there is one kind of electric vehicle called wheel-hub motor vehicle, that means, the energy source-motor is install in the wheel, so that it can simplify transmission system of vehicle; however, it makes riding comfort poorer because the unsprung mass is overweight. For improving this negative effect, this research used the dynamic vibration absorber to absorb the wheel vibration. Dynamic vibration absorbers can be divided among three types: extra mass, sprung mass transfer and unsprung mass transfer. The extra mass and unsprung mass transfer can also be used in vehicle with no overweight unsprung problem. This research optimizes the dynamic vibration absorber parameter, and then evaluates the effect of random road input on human body weighted acceleration R.M.S value, so that it can get improvement of the riding comfort. The conclusion of this thesis can give suggestions for application of vibration absorber on vehicle suspension in the future.

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Chang, Chao-Wei y 張晁瑋. "Application of Dynamic Vibration Absorber for Vehicle Ride Comfort". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/gw7z69.

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碩士
國立臺北科技大學
車輛工程系所
102
The goal of this study is improving the riding comfort, because it is an important issue in vehicle design. The electric vehicles have been noticed because of the oil depletion and rise of environmental consciousness in recent years. However, in order to reduce more energy consumption, there is one kind of electric vehicle called wheel-hub motor vehicle, that means, the energy source-motor is installed in the wheel, so that it can simplify transmission system of vehicle; however, it makes riding comfort poor because the unsprung mass is overweight. To improve this negative effect, some research used the dynamic vibration absorber to absorb the wheel vibration in the past. This thesis used Double-Dynamic vibration absorber which is composed of two kinds of dynamic vibration absorbers to improve the riding comfort. Dynamic vibration absorbers can be divided among three types: transfer sprung mass to sprung, transfer sprung mass to unsprung and transfer unsprung mass into unsprung. Transfer sprung mass to sprung and transfer sprung mass to unsprung can also be used in vehicle with no overweight unsprung problem. This research optimizes the dynamic vibration absorber parameter, and then evaluates the effect of random road input on human body weighted acceleration R.M.S value, so that it can get improvement of the riding comfort. The conclusion of this thesis can give suggestions for application of vibration absorber on vehicle suspension in the future.

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48

Tsao, Yuan-min y 曹淵閔. "A Study of Dynamic Vibration Absorber for Engineering Applications". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/8q8x9j.

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碩士
國立臺灣科技大學
機械工程系
94
The purpose of this thesis is to explore the application of dynamic vibration absorber for engineering. First, the two conventional dynamic vibration absorbers are reviewed. By deriving the equation of motion, the parameters of the main system response were obtained, and they are mass ratio, frequency ratio, and damping ratio. And by changing the parameters, the changing tendency of the main system response were then gained. Afterward, the models of dual reaction mass dynamic vibration absorber and auxiliary dual mass dynamic vibration absorber were constructed, and the analysis model followed the model of the conventional vibration absorber. Next, we analyzed the optimization in order to compare the absorption effects of these four absorbers in different frequency domains, and the result showed that dual reaction mass dynamic vibration absorber revealed better absorption effects. Besides, three examples of optimization analysis of dual mass dynamic vibration absorber are also presented by the way of numerical results. In the end of the paper, some suggestions of future study of dynamic vibration absorber are also provided.

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49

Lo, Chung-Yen y 羅仲延. "Study of A Hybrid Dynamic Balancer and Vibration Absorber". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/44461717075373885935.

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碩士
淡江大學
航空太空工程學系碩士班
101
This study proposes an economical and effective method of reducing vibration in a rigid-plate mechanism. The vibrating mechanism comprises a rigid body plate joined by a spring at each of the four corners. Three kinds of slots (longitudinal, cross and diagonal slots), were embedded under the plate. We attached a 2-DOF (rotation and transverse) Tuned-Mass-Damper (TMD) to the slot at the bottom of the rigid plate. This“self-adjust-position”hybrid dynamic balancer TMD is allowed to move along the slot and is capable of balancing and diminishing the vibration of the plate. Lagrange’s equation was used to derive the motion of the rigid plates. Vibration reduction effect was studied analytically and numerically following attachment of the TMD at different fixed positions in the system. We implemented a practical model with different kinds of slot under the plate to measure the amplitude of vibration with the dynamic balancer TMD, and conducted a comparison between the theoretical and empirical results. The experimental results demonstrate that the optimal vibration reduction effect was achieved when the TMD was attached initially at a position far from the applied force point. The results also show that the diagonal slot reveals the most effective in reducing the amplitude of vibrations of the plates, when the force was applied on the end of the diagonal slot. The frequency response graph shows that theoretical estimates correspond to experimental results.

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50

ZHENG, FU-GUO y 鄭復國. "A study of semi-active dynamic vibration absorber systems". Thesis, 1989. http://ndltd.ncl.edu.tw/handle/62652653410405280568.

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