• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.5
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• pp.381-389
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• 2014

This study is concerned with the estimation of vibration-field of a cylindrical structure by modal expansion method(MEM). MEM is a technique that identifies modal participation factors using some of vibration signals and natural modes of the structure: The selection of sensor locations has a big influence on predicted vibration results. Therefore, this paper deals with four optimal sensor placement( OSP) methods, EFI, EFI-DPR, EVP, AutoMAC, for the estimation of vibration field. It also finds optimal sensor locations of the cylindrical structure by each OSP method and then performs MEMs. Predicted vibration results compared with reference ones obtained by forced response analysis. The standard deviations of errors between reference and predicted results were also calculated. It is utilized to select the most suitable OSP method for estimation of vibration field of the cylindrical structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.72-77
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• 2011

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FEM building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FEM reflecting the results of the modal testing of a pod is built through the optimization, applied to the structural dynamic model of an Aircraft, used to verified the stability of vibration and flutter of an aircraft.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.604-605
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• 2008

Modal participation factor (MPF) is a widely used in a mode-coupling squeal noise problem for finding the most sensitive component over a complex brake system in a vehicle using eigenvectors of sub-components. This methodology requires the problematic total response of system by the unstable squeal noise at a specific frequency as well as eigenvectors of each component belonging to brake system. In this paper, a unit-force response analysis is performed for intact total system to obtain eigenvectors of each component and then such data is directly used for the contribution analysis of a squeal noise problem. Since the eigenvectors of each component induced from virtual unit-excitation is most reliable owing to the intact boundary condition, it can be expected that the corresponding contribution analysis with MPF also provides a trustworthy result.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.10
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• pp.677-684
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• 2015

It is often necessary to predict the vibration patterns of the structures from the signals of finite number of vibration sensors. This study presents the optimal placement of vibration sensors by applying the genetic algorithm and the modal expansion method. The modal expansion method is used to estimate the vibration response of the whole structure. The genetic algorithm is used to estimate the optimal placement of vibration sensors. Optimal sensor placement can be obtained so that the fitness function is minimized in the genetic algorithm. This paper discusses the comparison of the performances of two types of fitness functions, modal assurance criteria(MAC) and condition number( CN). As a result, the estimation using MAC shows better performance than using CN.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.6
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• pp.495-501
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• 2012

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FE model building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FE model reflecting the results of the modal testing of a pod is built through the optimization and will be applied to the structural dynamic model of an aircraft which is used to verified the stability of vibration and flutter of an aircraft.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.10
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• pp.1074-1080
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• 2009

A method for determining the geometric stability characteristics of a brake corner module (BCM) is presented. Since disc brake "squeal" noise typically occurs at unstable resonant frequencies of a system, the likelihood of disc brake squeal for a particular design can be determined. Finite element methods are used to derive complex eigenvalue for a brake corner module. Some unstable modes calculated by finite element methods correspond to squeal noise data. Through kinetic energy participation analysis for each part of BCM, we can efficiently predict squeal noise data.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.39-42
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• 2000

In stressed power system, due to the presence of increased nonlinearity and the existence of nonlinear modal interactions, there exist some limitations to the use of conventional linear system theory to identify the optimum sites for controller. This paper proposes an approach to identify the optimum sites for controller using the method of normal forms. In this paper nonlinear participation factor and coupling factor are proposed as a measures of identification of optimum sites for controller and a selection procedure is also proposed. The proposed procedure is applied to the 10-generator New England System and the KEPCO System in the year of 2010 to illustrate its capabilities.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1773-1778
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• 2010

To evaluate the structural integrity of the main cooling-water pump of a nuclear power plant under different seismic conditions, the seismic analysis was performed in accordance with IEEE-STD-344 code. The finite element computer program, ANSYS, was used to perform both mode frequency analysis and response spectrum analysis for the pump assembly. The natural frequencies, the mode shapes, and the mode participation factors were obtained from the results of the mode frequency analysis. The stresses resulting from various loadings and their combinations were within the allowable limits specified in the above-mentioned IEEE code. The results of the seismic evaluation fully satisfied the structural acceptance criteria of the IEEE code. Thus, it was proved that the structural integrity of the pump assembly was satisfactory.

• Journal of KSNVE
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• v.8 no.4
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• pp.690-699
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• 1998

This paper discusses the techniques, procedures and the results of the ground vibration test(GVT) performed on the development aircraft and the simple procedure of FE model updating technique from the GVT results. The GVT was carried out using random excitation technique with MIMO(Multi-Input-Multi-Output) data acquistion method, and taking full advantage of poly-reference global parameter estimation technique to identify the vibration modes. In dynamic FE modeling, the aircraft was represented by beam elements and all dynamic analysis was performed using MSC/NASTRAN for this model. In updating procedure, the stiffness of the beam model was adjusted iteratively so as to get the natural frequencies and mode shapes close to the GVT results.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.596-600
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• 2001

The seismic design for an axial blower is the procedure in which the required response spectrum (RRS) is computed by using the floor response spectrum (FRS). The seismic design is very important to reduce severe damages from an earthquake; therefore, the seismic design has been a great concern in engineering society. In this study, after finite element modeling is established by using Ansys, the modal data are obtained such as the natural frequencies, the participation factor, and so on. With these data, the RRS is acquired by a numerical approach. The seismic safety of the axial blower is evaluated.