• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.328-334
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• 2001

Up to now. vibration analysis and vibration engineering have been developed, encompassing the aspects of both experimental and analytical techniques. Using experimental modal analysis or modal testing, the mode shapes and frequencies of practical structure can be measured accurately. Curve-Fitting Method is realized through experimental modal identification. In the experimental modal parameter estimation, the estimation of modal damping factor is difficult for complicated and large structure. Also numbers of Selected mode are determined before the procedure. This paper describes the vibration shape of the super-structure model of ship through experimental modal analysis.

• Structural Monitoring and Maintenance
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• v.5 no.3
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• pp.345-361
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• 2018

The set of processes performed to determine the dynamic characteristics of the constructed structures is named experimental modal analysis. Using experimental modal analysis and interpreting its results, structural failure can be assessed and then it would be possible to plan for their repair and maintenance. The purpose of the experimental modal analysis is to determine the resonance frequencies, mode shapes and Mode damping for the structure. Diverse methods for determining the shape of the mode by various researchers have been presented. There are pros and cons for each of these methods. This paper presents a method for determining the mode shape of the structures using the response spectrum in the experimental modal analysis. In the first part, the principles of the proposed method are described. Then, to check the accuracy of the results obtained from the proposed method, single and multiple degrees of freedom models were numerically and experimentally investigated.

• Journal of KSNVE
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• v.10 no.6
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• pp.1009-1016
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• 2000

This paper describes the procedure of increasing the efficiency of experimental modal analysis and updating the quality of FE model using the scaled commercial vehicle frame. In this study, it was found that the experimental modal analysis could be more efficient when the measurements were made on the areas with high kinetic energies. Such areas could be located with the aid of FE modal analysis. Also, the number of measurement points could be decided by considering the dynamic characteristics of full FE model. The correlation of FE model and experimental modal analysis was assessed by the differences between the natural frequencies and MAC matrix, which is based on normal modes. These differences of modal parameters were reduced through the sensitivity and optimization analysis of which objective function consisted of the errors of natural frequencies and the diagonal terms of MAC matrix.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1718-1723
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• 2003

This paper presents a computational method for deformation modes of a flexible body in multibody system from the experimental modal analysis and an efficient method for flexible multibody dynamic analysis by use of the modes. It is difficult to directly use experimental modal parameters in flexible multibody dynamic analysis. The major reasons are that there are many inconsistencies between experimental and analytical modal data and experimental noises are inherent in the experimental data. So two methods, such as, a method for ortho-normalization of experimental modes and the other one for mode expansion, are suggested to gain deformation modes of a flexible body from the experimental modal parameters. Using the virtual work principle, the equation of motion of a flexible body is derived. The effectiveness of the proposed method will be verified in the numerical example of cab vibration of a truck by comparing analysis and test results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.43-51
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• 2001

An experimental modal analysis is the process to identify structure's dynamic characteristics such as resonant frequencies, damping values and mode shapes. An experimental model was made of stainless steel in the shape of a circular cylindrical shell and installed on the test bed with jigs. For investigating vibrational characteristics of the continuous circular cylindrical shell with intermediate supports, modal testing is performed by using impact hammer, accelerometer and 8-channel FFT analyzer. The frequency response function(FRF) measurements are also made on the experimental model within the frequency range from 0 to 4kHz. Modal parameters are identified from resonant peaks in the FRF's and animated deformation patterns associated with each of the resonances are shown on a computer screen. The experimental results are compared with analytical and FEA results.

• Journal of Ocean Engineering and Technology
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• v.26 no.1
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• pp.34-40
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• 2012

This paper presents an experimental modal analysis of a caisson-type breakwater to produce basic information for the structural health assessment of a caisson structure. To achieve the objective, the following approaches are implemented. First, modal analysis methods are selected to examine the modal characteristics of a caisson structure. Second, experimental modal analyses are performed using finite element analyses and lab-scale model tests. Third, damage scenarios that include several damage levels in a foundation-structure interface are designed. Finally, the effects of damage on the modal characteristics are analyzed for the purpose of utilizing them for damage identification.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.233-237
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• 1998

In this work, to identify the dynamic characteristics of disk-spindle system in hard disk drive, experimental modal analysis was performed. And an experimental analysis system including testing apparatus, precision sensors, and analysis software was established in order to perform the testing effectively. From the experimental results, coupled and uncoupled modal characteristics of 3-disk spindle system are clearly identified.

• Journal of Navigation and Port Research
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• v.26 no.3
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• pp.281-288
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• 2002

It might be true that both experimental and analytic techniques have been developed in the vibration analysis end engineering. It could not be said, however, that the experimental method has been also developed as much as analytic method, such as Finite Element Method One of the reason is that computation time becomes longer and that the solution often diverges depending on the choice of initial value in solving nonlinear equation. The equation in experimental modal analysis is usually composed of the nonlinear term of natural frequency and modal damping ratio, and the linear one of equivalent stiffness. In this study, the nonlinear terms were solved first, and then the linear term was obtained. The experimental modal parameters were estimated, applying the developed experimental modal analysis curve-fitting method to the super-structure model. In addition, the number of modes and modal damping ratio could be easily determined by the developed program with the application of graphical techniques and with easy handling button.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.119-128
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• 2012

In this study, experimental vibration tests are performed on a real full-scale railway steel plate girder bridge, which resides in open-space environments. Using experimental modal analysis techniques, the modal parameters of the railway steel plate girder bridge yielded by the modal testing of the impact hammer are compared and investigated with the natural frequencies and mode shapes obtained by finite element analysis. This work focuses on the application of model updating techniques to measured experimental data and output-only data from an analytical vibration study that takes into account various geometric and material properties of the bridge members. A finite element model of the railway bridge structure is used to verify the modal experimental results. It is subsequently updated using the corresponding modal identification technique. The basic database is provided to evaluate damage, which can be determined based on the changes in the element properties, resulting from the process of updating the finite element model benchmark and experimental data.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.2
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• pp.39-45
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• 1988

The analytical model of an engine mount system with six degrees of freedom is identified using the modal parameters obtained from the experimental modal analysis. The structural parameters, mass moment of inertia of the engine block and stiffness of the rubber mounts, of the engine mount system are determined by using the condition that the estimated model parameters should satisfy the corresponding eigenvalue problem. The simulated modal parameters of the identified analytical model are in good agreement with the measured modal parameters.