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Vikas Arora - One of the best experts on this subject based on the ideXlab platform.
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Identification of viscous and Structural Damping in the dynamic system
International Journal of Structural Engineering, 2017Co-Authors: Vikas AroraAbstract:Damping still remains one of the least well-understood aspects of general vibration analysis. In this paper, a new experimental Damping identification method, which can be able to identify both viscous and Structural Damping in the dynamic system, is proposed. The proposed method is a direct method and gives explicit Structural and viscous Damping matrices. The proposed method requires prior knowledge of accurate mass and stiffness matrices. So, experimental viscous-Structural Damping is identified in two steps. In the first step, mass and stiffness matrices are updated and subsequently viscous and Structural Damping matrices are identified using updated mass and stiffness matrices obtained in Step 1. The identified viscous-Structural Damping matrices are both symmetric and positive definite. The effectiveness of the proposed Structural Damping identification method is demonstrated by numerical and experimental examples. First, two numerical study of lumped mass system and fixed-fixed beam are presented which is followed by an experimental example of cantilever beam. The effects of coordinate incompleteness and different level of Damping are investigated. The results have shown that the proposed method is able to identify accurately both viscous and Structural Damping in the dynamic system.
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Direct Structural Damping identification method using complex FRFs
Journal of Sound and Vibration, 2015Co-Authors: Vikas AroraAbstract:Abstract Most of the identification methods are based only on the viscous Damping model and uses modal data. In this paper, a new FRF-based direct Structural Damping identification method is proposed. The proposed method is a direct method and identifies Structural Damping matrix explicitly. As the new method is a FRF-based method, it overcomes the problem of closely spaced modes for Damping identification. The accuracy of identified Structural Damping matrix depends upon the accuracy of finite element model. In this paper, FRF-based model updating method is used to obtain accurate mass and stiffness matrices. Thus, the procedure to obtain accurate Structural Damping matrix is a two-step procedure. In the first step, mass and stiffness matrices are updated and in the second step, Structural Damping matrix is identified using updated mass and stiffness matrices, which are obtained in the previous step. The effectiveness of the new method is demonstrated by three numerical examples and one experimental example. The numerical studies of lumped mass system, fixed-fixed beam and L-shaped frame structure are carried out. The effects of coordinate incompleteness, ill-conditioning and robustness of method under presence of noise are investigated. The proposed method is able to predict FRFs accurately for the frequency range covering the modes considered. However, beyond the considered modes, the predicted FRFs do not match the experimental FRFs. It is suggested in this work that ill-conditioning problem should be dealt by considering all the modes in the frequency range of interest. The performance of the proposed method is investigated for cases of light, medium and heavily damped structures. The numerical studies are followed by experimental case study of cantilever beam structure. The effectiveness of the proposed method is evaluated by comparing the predicted and the experimental FRFs. The results have shown that the proposed method is able to predict accurately the experimental FRFs with all levels of Damping in the system.
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Hybrid Viscous-Structural Damping Identification Method
Mechanisms and Machine Science, 2014Co-Authors: Vikas AroraAbstract:Damping still remains one of the least well-understood aspects of general vibration analysis. The effects of Damping are clear, but the characterization of Damping is a puzzle waiting to be solved. A major reason for this is that, in contrast with inertia and stiffness forces, it is not clear which state variables are relevant to determine the Damping forces. In this paper, a new hybrid viscous-Structural Damping identification method is proposed. The proposed method is a direct method and gives explicit Structural and viscous Damping matrices. The effectiveness of the proposed Structural Damping identification method is demonstrated by two numerical examples. First, numerical study of lumped mass system is presented which is followed by a numerical study of fixed-fixed beam. The effects of coordinate incompleteness and different level of Damping are investigated. The results have shown that the proposed method is able to identify accurately the Damping of the system.
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Direct Structural Damping Identification Method
Dynamics of Civil Structures Volume 4, 2014Co-Authors: Vikas AroraAbstract:All structures exhibit some form of Damping, but despite a large literature on the Damping, it still remains one of the least well-understood aspects of general vibration analysis. The synthesis of Damping in Structural systems and machines is extremely important if a model is to be used in predicting vibration levels, transient responses, transmissibility, decay times or other characteristics in design and analysis that are dominated by energy dissipation. In this paper, a new Structural Damping identification method is proposed. The proposed Structural Damping identification is a direct method and requires prior knowledge of accurate mass and stiffness matrices. The proposed method doesn’t require initial Damping estimates. The effectiveness of the proposed Structural Damping identification method is demonstrated by numerical and experimental studies. Firstly, a numerical study is performed using lumped mass system. The numerical study is followed by a case involving actual measured data of cantilever beam structure. The results have shown that the proposed Structural Damping identification method can be used to derive accurate model of the system. This is illustrated by matching of the complex FRFs obtained from the analytically damped model with that of experimental data.
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Structural Damping identification method using normal FRFs
International Journal of Solids and Structures, 2014Co-Authors: Vikas AroraAbstract:Abstract All structures exhibit some form of Damping, but despite a large literature on the Damping, it still remains one of the least well-understood aspects of general vibration analysis. The synthesis of Damping in Structural systems and machines is extremely important if a model is to be used in predicting vibration levels, transient responses, transmissibility, decay times or other characteristics in design and analysis that are dominated by energy dissipation. In this paper, new Structural Damping identification method using normal frequency response functions (NFRFs) which are obtained experimentally is proposed and tested with the objective that the damped finite element model is able to predict the measured FRFs accurately. The proposed Structural Damping identification is a direct method. In the proposed method, normal FRFs are estimated from the complex FRFs, which are obtained experimentally of the structure. The estimated normal FRFs are subsequently used for identification of general Structural Damping. The effectiveness of the proposed Structural Damping identification method is demonstrated by two numerical simulated examples and one real experimental data. Firstly, a study is performed using a lumped mass system. The lumped mass system study is followed by case involving numerical simulation of fixed–fixed beam. The effect of coordinate incompleteness and robustness of method under presence of noise is investigated. The performance of the proposed Structural Damping identification method is investigated for cases of light, medium, heavily and non-proportional damped structures. The numerical studies are followed by a case involving actual measured data for the case of a cantilever beam structure. The results have shown that the proposed Damping identification method can be used to derive an accurate general Structural Damping model of the system. This is illustrated by matching the damped identified FRFs with the experimentally obtained FRFs.
Reza S Abhari - One of the best experts on this subject based on the ideXlab platform.
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experimental study of aerodynamic and Structural Damping in a full scale rotating turbine
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2003Co-Authors: Jason J Kielb, Reza S AbhariAbstract:Damping in turbomachinery blades has been an important parameter in the study of forced response and high-cycle fatigue, but because of its complexity the sources and physical nature of Damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple Damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and Structural Damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic Damping was a large component of the total Damping for all modes. A study of Structural Damping as a function of rotational speed was also included to show the effect of friction Damping at the blade and disk attachment interface. To the best of the authors' knowledge, the present paper is the first report of independent and simultaneous Structural and aerodynamic Damping measurement under engine-level rotational speeds.
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experimental study of aerodynamic and Structural Damping in a full scale rotating turbine
Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 2001Co-Authors: Jason J Kielb, Reza S AbhariAbstract:Damping in turbomachinery blades has been an important parameter in the study of forced response and high cycle fatigue, but because of its complexity the sources and physical nature of Damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple Damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and Structural Damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic Damping was a large component of the total Damping for all modes. A study of Structural Damping as a function of rotational speed was also included to show the effect of friction Damping at the blade and disk attachment interface. To the best of the authors’ knowledge, the present paper is the first report of independent and simultaneous Structural and aerodynamic Damping measurement under engine-level rotational speeds.© 2001 ASME
H. Harbi - One of the best experts on this subject based on the ideXlab platform.
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Stability of suspension bridges: II. Aerodynamic vs. Structural Damping
Smart Structures and Materials 1998: Smart Systems for Bridges Structures and Highways, 1998Co-Authors: N. U. Ahmed, H. HarbiAbstract:In this paper we consider a few dynamic models of suspension bridges described by partial differential equations with linear and nonlinear couplings. We study analytically the stability properties of these models and the relative effectiveness of aerodynamic and Structural Damping. Increasing either of these Damping coefficients indefinitely does not necessarily increase the decay rate indefinitely. In view of possible disastrous effects of high wind, Structural Damping is preferable to viscous Damping. These results are illustrated by numerical simulation.
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Stability of suspension bridge I: Aerodynamic and Structural Damping
Mathematical Problems in Engineering, 1998Co-Authors: N. U. Ahmed, H. HarbiAbstract:In this paper we consider a few dynamic models of suspension bridge described by partial differential equations with linear and nonlinear couplings. We study analytically the stability properties of these models and the relative effectiveness of aerodynamic and Structural Damping. Increasing aerodynamic or Structural Damping indefinitely does not necessarily increase the decay rate indefinitely. In view of possible disastrous effects of high wind, Structural Damping is preferable to aerodynamic (viscous) Damping. These results are illustrated by numerical simulation.
Daniel Guyomar - One of the best experts on this subject based on the ideXlab platform.
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semi passive piezoelectric Structural Damping by synchronized switching on voltage sources
Journal of Intelligent Material Systems and Structures, 2006Co-Authors: Elie Lefeuvre, Adrien Badel, Lionel Petit, Claude Richard, Daniel GuyomarAbstract:Semi-passive Damping techniques have been developed recently to address the problem of Structural Damping. Contrary to the standard passive piezoelectric Damping, these new techniques adapt to environmental variations. Moreover, they present interesting multimodal Damping performances. However, their efficiency is strongly correlated with their electromechanical coupling. The enhanced semi-passive Damping technique presented herein compensates for this drawback. It reinforces the electromechanical coupling by artificially increasing the voltage amplitude delivered by the piezoelectric patches. Theoretical predictions and experimental results show a −24 dB attenuation on the vibration of a resonant cantilever steel beam, while reducing the piezoelectric material volume by 83%.
Jason J Kielb - One of the best experts on this subject based on the ideXlab platform.
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experimental study of aerodynamic and Structural Damping in a full scale rotating turbine
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2003Co-Authors: Jason J Kielb, Reza S AbhariAbstract:Damping in turbomachinery blades has been an important parameter in the study of forced response and high-cycle fatigue, but because of its complexity the sources and physical nature of Damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple Damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and Structural Damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic Damping was a large component of the total Damping for all modes. A study of Structural Damping as a function of rotational speed was also included to show the effect of friction Damping at the blade and disk attachment interface. To the best of the authors' knowledge, the present paper is the first report of independent and simultaneous Structural and aerodynamic Damping measurement under engine-level rotational speeds.
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experimental study of aerodynamic and Structural Damping in a full scale rotating turbine
Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls Diagnostics and Instrumentation; Education; IGTI Scholar, 2001Co-Authors: Jason J Kielb, Reza S AbhariAbstract:Damping in turbomachinery blades has been an important parameter in the study of forced response and high cycle fatigue, but because of its complexity the sources and physical nature of Damping are still not fully understood. This is partly due to the lack of published experimental data and supporting analysis of real rotating components. This paper presents the results of a unique experimental method and data analysis study of multiple Damping sources seen in actual turbine components operating at engine conditions. The contributions of both aerodynamic and Structural Damping for several different blade vibration modes, including bending and torsion, were determined. Results of the experiments indicated that aerodynamic Damping was a large component of the total Damping for all modes. A study of Structural Damping as a function of rotational speed was also included to show the effect of friction Damping at the blade and disk attachment interface. To the best of the authors’ knowledge, the present paper is the first report of independent and simultaneous Structural and aerodynamic Damping measurement under engine-level rotational speeds.© 2001 ASME
