Torsional Vibration Attenuation in V-Type Locomotive Diesel Engine Crankshaft using Centrifugal Pendulum Absorber

The torque fluctuation due to the intermittent combustion pressure and inertia effect of the reciprocating parts generates torsional excitation on the crankshaft of all internal combustion engines. This excitation imposes considerable amount of torsional vibration on the crankshaft. Therefore the torsional vibration modeling and design of an auxiliary absorbing mechanism are very crucial, especially in locomotive diesel engines where the crankshaft is under excitation with high amplitude coupled with large inertia forces due to generators, compressors or fans. In this research, the capability of centrifugal pendulum vibration absorbers (CPVA) commonly used in rotating machinery to attenuate the torsional vibration in a Locomotive V-type diesel engine crankshaft is investigated. First, an advanced torsional modeling of the locomotive crankshaft has been carried out. This is followed by the development of an accurate excitation torque of a real locomotive engine to the 8th order. The torsional response of the crankshaft under the derived excitation torque has then been investigated. Finally, the model of the crankshaft incorporating the CPVA (auxiliary system) has been developed and then capability of CPVA to attenuate the torsional vibration of the crankshaft (main system) at resonance frequencies has been investigated. Moreover, the effect of pendulum parameters such as length and mass on the torsional vibration response of the crankshaft in both time and frequency domains has been studied

Application of Tuned Mass Dampers for Structural Vibration Control: A State-of-the-art Review

Given the burgeoning demand for construction of structures and high-rise buildings, controlling the structural vibrations under earthquake and other external dynamic forces seems more important than ever. Vibration control devices can be classified into passive, active and hybrid control systems. The technologies commonly adopted to control vibration, reduce damage, and generally improve the structural performance, include, but not limited to, damping, vibration isolation, control of excitation forces, vibration absorber. Tuned Mass Dampers (TMDs) have become a popular tool for protecting structures from unpredictable vibrations because of their relatively simple principles, their relatively easy performance optimization as shown in numerous recent successful applications. This paper presents a critical review of active, passive, semi-active and hybrid control systems of TMD used for preserving structures against forces induced by earthquake or wind, and provides a comparison of their efficiency, and comparative advantages and disadvantages. Despite the importance and recent advancement in this field, previous review studies have only focused on either passive or active TMDs. Hence this review covers the theoretical background of all types of TMDs and discusses the structural, analytical, practical differences and the economic aspects of their application in structural control. Moreover, this study identifies and highlights a range of knowledge gaps in the existing studies within this area of research. Among these research gaps, we identified that the current practices in determining the principle natural frequency of TMDs needs improvement. Furthermore, there is an increasing need for more complex methods of analysis for both TMD and structures that consider their nonlinear behavior as this can significantly improve the prediction of structural response and in turn, the optimization of TMDs

Review of Applications of Nonlinear Normal Modes for Vibrating Mechanical Systems

International audienceThis paper is an extension of the previous review Nonlinear Normal Modes for Vibrating Mechanical Systems. Review of Theoretical Developments done by the authors, and it is devoted to applications of nonlinear normal modes (NNMs) theory. NNMs are typical regimes of motions in wide classes of nonlinear mechanical systems. The significance of NNMs for mechanical engineering is determined by several important properties of these motions. Forced resonances motions of nonlinear systems occur close to NNMs. Nonlinear phenomena, such as nonlinear localization and transfer of energy, can be analyzed using NNMs. The NNMs analysis is an important step to study more complicated behavior of nonlinear mechanical systems. This review focuses on applications of Kauderer–Rosenberg and Shaw–Pierre concepts of nonlinear normal modes. The Kauderer–Rosenberg NNMs are applied for analysis of large amplitude dynamics of finite-degree-of-freedom nonlinear mechanical systems. Systems with cyclic symmetry, impact systems, mechanical systems with essentially nonlinear absorbers, and systems with nonlinear vibration isolation are studied using this concept. Applications of the Kauderer–Rosenberg NNMs for discretized structures are also discussed. The Shaw–Pierre NNMs are applied to analyze dynamics of finite-degree-of-freedom mechanical systems, such as floating offshore platforms, rotors, piece-wise linear systems. Studies of the Shaw–Pierre NNMs of beams, plates, and shallow shells are reviewed, too. Applications of Shaw–Pierre and King–Vakakis continuous nonlinear modes for beam structures are considered. Target energy transfer and localization of structures motions in light of NNMs theory are treated. Application of different asymptotic methods for NNMs analysis and NNMs based model reduction are reviewed

Projeto ótimo de neutralizadores dinâmicos com múlitplos graus de liberdade considerando os parâmetros físicos, localização e material viscoelástico

Orientador: Prof. Dr. Carlos Alberto BavastriTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Mecânica. Defesa : Curitiba, 10/04/2019Inclui referências: p. 131-142Área de concentração: Mecânica dos Sólidos e VibraçõesResumo: Neutralizadores dinâmicos de vibração, também chamados de absorvedores dinâmicos de vibração, são dispositivos ressonantes que, ao serem fixados em uma estrutura mecânica, conseguem reduzir as vibrações. O projeto desse tipo de dispositivo, utilizando materiais viscoelásticos, é de baixo custo, fácil construção e produz excelentes resultados na redução dos níveis de vibração devido à capacidade daqueles materiais em armazenar e dissipar a energia de vibração. Entretanto, projetá-lo de maneira adequada indicará o seu sucesso no controle da vibração. Nos últimos 20 anos, o grupo de pesquisa GVIBS da UFPR/CNPq tem trabalhado no projeto ótimo de neutralizadores simples, aplicados no controle de vibração em banda estreita e banda larga de frequências. Neste contexto, o presente estudo visa desenvolver uma metodologia de projeto ótimo de neutralizadores dinâmicos viscoelásticos de um e de múltiplos graus de liberdade considerando os parâmetros físicos, a posição do dispositivo na estrutura e o material viscoelástico ótimo como variáveis a serem otimizadas, para uma dada temperatura de trabalho e para uma determinada banda de frequências. A configuração ótima é obtida através de Algoritmos Genéticos (AG) considerando variáveis contínuas e discretas no mesmo vetor de projeto. Inicialmente, a metodologia de projeto ótimo de neutralizadores é implementada para o modelo de neutralizador simples e aplicada no controle de vibração, em banda larga de frequências, de uma placa de aço apoiada em seus quatro cantos. Os resultados mostram que esta metodologia é interessante e robusta para o controle de vibração de estruturas geometricamente complexas. Agregando a esta metodologia o projeto ótimo de um neutralizador de múltiplos graus de liberdade, as propriedades dinâmicas do neutralizador passam a ser descritas por matrizes de tamanhos consideráveis, que estão associadas ao número de graus de liberdade considerados na modelagem do neutralizador. A obtenção dessas matrizes é realizada utilizando o método dos elementos finitos via software ANSYS e as características dinâmicas do material viscoelástico são introduzidas no modelo através de uma metodologia própria utilizando o software Matlab. Para validar a metodologia proposta, uma análise numérica é aplicada para o controle de uma viga de aço engastada-livre. Com os parâmetros de projeto ótimos fornecidos pelo algoritmo, o neutralizador pode ser construído e inserido na viga para a realização do experimento. O resultado mostra que o modelo numérico é muito semelhante ao experimental, logo esta metodologia pode ser reproduzida fisicamente. O presente estudo apresenta três modelos de neutralizadores de múltiplos graus de liberdade: viga sanduíche, viga sanduíche com massa de sintonização na extremidade livre modelada por elementos finitos, e viga sanduíche com massa concentrada na extremidade livre. Os resultados numéricos para o controle da viga de aço engastada livre são comparados com o modelo de um grau de liberdade, mostrando que os três modelos de neutralizadores de múltiplos graus de liberdade reduzem a vibração da viga de forma mais eficiente que o neutralizador simples. Os resultados apresentados mostram que a metodologia proposta é promissora para o controle passivo de vibração de estruturas, especialmente quando muitos modos estão presentes. Palavras-chave: Controle passivo de vibrações. Neutralizadores dinâmicos. viscoelásticos de múltiplos graus de liberdade. Otimização. Algoritmos genéticos.Abstract: Dynamic vibration neutralizers, also called dynamic vibration absorbers, are mechanical devices attached to a structure aiming at controlling or reducing vibration levels. Designing such devices using viscoelastic materials result in low costs, easy construction, and produce excellent results in the vibration reduction levels due to their ability to dissipate vibration energy. However, their suitable design will indicate their success in the vibration control. In the last 20 years, the research group GVIBS from the UFPR/CNPq, has been working in the optimal design of simple neutralizers, applied to vibration control in both narrow and broad bands of frequency. In this context, the present study aims at developing a methodology for an optimal design of DVNs with one and multiple degrees-of-freedom considering the physical parameters, the positions to attach them onto the structure, and the viscoelastic materials as variables to be optimized, for a given working temperature and for a determined frequency band. The optimal configuration is obtained through Genetic Algorithms (GA) considering continuous and discrete variables in the same design vector. Initially, the methodology of optimal design of the neutralizers is implemented to a simple neutralizer model applied to vibration control, in a broadband of frequency, of a simplysupported steel plate its four corners. The results show that this methodology is interesting and robust to handle the vibration control of geometrically complex structures. Adding to this methodology the optimal design of a multi-degrees-offreedom neutralizer, the dynamic properties of the neutralizer are described by matrices of considerable sizes, which are associated to the number of degrees-offreedom considered in the neutralizer modeling. The obtaining of those matrices for the metallic part is carried out using the finite element method through the ANSYS software and the dynamic characteristics of the viscoelastic material are introduced to the model through an own methodology using the Matlab software. To validate the methodology of optimal design of multi-degree-of-freedom viscoelastic neutralizers, a numerical analysis is applied to the control a clamped steel beam. With the parameters of optimal design provided by the algorithm, the neutralizer can be built and attached to the beam for the experiment. The results show that the numerical model is very similar to the experimental one, thus this methodology can be reproduced physically. The present study shows three models of multi-degree-of-freedom neutralizers: sandwich beam, sandwich beam with a tuning mass modeled by finite elements and sandwich beam with a concentrated mass in the free end. Both models are able to handle the vibration control and the numerical results to the clamped steel beam control are compared with those of the one degree-of-freedom model, showing that all the three models of multi-degree-of-freedom neutralizers reduce the beam vibration more efficiently than the simple neutralizer. The results also show that the methodology is promising for passive vibration control of structures, especially when many modes are present. Keywords: Passive vibration control. Multi-degrees-of-freedom dynamic viscoelastic neutralizers. Optimization. Genetic algorithms

Passive control of structures: experimental verification using tuned mass dampers

The focus of this thesis is to review and experimentally verify the effect of vibrational control systems applied in tall and flexible structures. The installation of these systems on new and existing structures aim at the spectacular improvement of the structural dynamic behavior under different types of manmade and ambient excitations on the concepts of structural safety and operational conditions. The control theory of this thesis is applied for the design of Passive Control Systems and more specifically for the design of Tuned Mass Damper (TMD) installed properly on the main structure. The main mass of the Tuned Mass Damper, which is named as secondary system, is significantly smaller than the main mass of the primary system which is a Single Degree of Freedom (SDOF) system. A series of experiments with one and two TMDs installed on a SDOF modeled small laboratory structure are designed, constructed and performed. The structural behavior of the laboratory structure was tested by subjecting to artificially induced harmonic excitation and one of the components available during the strong El Centro earthquake. The main modal characteristics of the combined primary-secondary system studied are the modal frequencies, the damping coefficients and the mass ratios between primary and secondary systems. A smart laboratory technique for damping improvement of structures was also employed to both primary and secondary systems and it is shown that sensibly contributes to vibration attenuation of the primary system. All the experimental concepts and results are discussed herein and demonstrate the effectiveness and reliability of Passive Control Systems installed on tall and flexible structures that are susceptible to strong winds and earthquake events

Seismic effectiveness and robustness of tuned mass dampers versus nonlinear energy sinks in a lifecycle cost perspective

Tuned mass dampers (TMDs) and nonlinear energy sinks (NESs) are two viable options for passively absorbing structural vibrations. In seismic applications, a trade-off exists in their performance, because TMDs’ effectiveness varies with the structural stiffness while NESs’ effectiveness varies with the earthquake intensity. To investigate this trade-off systematically, a lifecycle cost- (LCC-) oriented robust analysis and design method is here proposed, in which the effectiveness of a solution is measured by the reduction it entails in the expected cost of future seismic losses. In it, structural stiffness variability is modelled using a worst-case approach with lower and upper bounds, while seismic intensity variability is inherently captured by the incremental dynamic analyses underlying every LCC evaluation. The resulting worst-case lifetime cost provides a rational metric for discussing pros and cons of TMDs and NESs, and becomes the objective function for their robust optimization. The method is applied to the design of TMDs and NESs on a variety of single- and multi-story linear building models, located in a moderate-to-high seismic hazard region. Mass ratios from 1 to 10% and structural stiffness reductions up to 4 times are considered. Results show that TMDs are consistently more effective than NESs even in the presence of large stiffness reductions, provided that structural stiffness uncertainty is considered in design. They also show that a conventional robust H∞ design provides for TMDs a solution which is very close to that obtained by minimizing the proposed LCC metric

14th Conference on Dynamical Systems Theory and Applications DSTA 2017 ABSTRACTS

From Preface: This is the fourteen time when the conference “Dynamical Systems – Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and the Ministry of Science and Higher Education. It is a great pleasure that our invitation has been accepted by so many people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcome nearly 250 persons from 38 countries all over the world. They decided to share the results of their research and many years experiences in the discipline of dynamical systems by submitting many very interesting papers. This booklet contains a collection of 375 abstracts, which have gained the acceptance of referees and have been qualified for publication in the conference proceedings [...]