• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.622-627
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• 2001

The paper presents the possibilities of a wide practical application of the modal analysis methods in dynamic testing of vertical pump. A pneumatic impact of testing vertical pumps submerged under deep water was developed and successfully applied. The problem with the enviroment is the it causes significants changes in modal parameters, compared with those in the airenviroment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.278-282
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• 1997

This paper describes results of modal testing for a high head pump-turbine runner of the Muju pumped storage power plant. The head of the pump-turbine is 601 m and the outside diameter of its runner is 4,410 mm. The modal testing was done for two conditions : 1) the runner in air ; 2) the runner in water. For both conditions, obtained are natural frequencies, corresponding mode shapes and damping ratios. From the testing, it is found that the natural frequencies of the pump-turbine runner in water is reduced approximately 40 % due to additional mass effect of the water.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1159-1164
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• 2006

Torsional vibration is an important vibration mode when shafts, cylinders and pipes are considered. However, the modal testing of torsional vibrations is not an easy job to carry out because of the lack of proper transducers. This work presents a new torsional vibration transducer based on the magnetostrictive principle and its application to torsional modal testing. The transducer is so designed as to generate/measure only torsional vibrations excluding other vibration modes such as longitudinal and bending vibrations. The transducer is composed of ferromagnetic patches bonded to a test structure, permanent magnets, and a solenoid. Though patches and magnets are bonded to a structure, torsional vibrations are generated and measured wirelessly by a solenoid encircling a test structure. The proposed transducer works even at considerably high frequencies, say, tens of kilohertz. Furthermore, the transducer can be manufactured at a low price. To check the performance of the proposed method, the torsional modal testing on a hollow aluminum shaft was conducted. The results, such as eigenfrequencies, obtained by the proposed transducer agreed favorably with theoretical results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.8 s.113
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• pp.879-885
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• 2006

Torsional vibration is an important vibration mode when shafts, cylinders and pipes are considered. However, the modal testing of torsional vibrations is not an easy task to carry out because of the lack of proper transducers. This work presents a new torsional vibration transducer based on the magnetostrictive principle and its application to torsional modal testing. The transducer is so designed as to generate/measure only torsional vibrations excluding other vibration modes such as longitudinal and bending vibrations. The transducer is composed of ferromagnetic patches bonded to a test structure, permanent magnets, and a solenoid. Though patches and magnets are bonded to a structure, torsional vibrations are generated and measured wirelessly by a solenoid encircling a test structure. The proposed transducer works even at considerably high frequencies, say, tens of kilohertz. Furthermore, the transducer can be manufactured at a low price. To check the performance of the proposed method, the torsional modal testing on a hollow aluminum shaft was conducted. The results, such as eigenfrequencies, obtained by the proposed transducer agreed favorably with theoretical results.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.4_2
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• pp.475-480
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• 2021

The purpose of this study is to obtain the natural frequency of fuel supply pipes for vehicle engines through modal analysis and testing and compare the resulting values to ensure the reliability of the analysis. In other words, in this study, we obtain the unique frequency of the fuel pipe of the vehicle engine through analysis and testing and compare its results. Comparing the natural frequency obtained through analysis and testing, the first and third vibration modes obtained accurate natural frequency results of less than 1% and very similar results of less than 5% maximum error over the fourth vibration modes. These results are determined that if design changes of fuel pipes are made depending on the vehicle in the future, there will be no problem in obtaining the natural frequency of pipes that have been changed by analysis. Through future analysis and testing, durability and stability evaluation of connections of fuel supply pipes for vehicle engines will be carried out.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.467-477
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• 1997

A series of experimental tests have been performed on a tube beam in which artificial damage is applied in order to address damage detectability using modal analysis. Modal parameters considered are frequency, displacement mode shape and strain mode shape CoMAC(Coordinate Modal Assurance Criterion) and Modal Vector Error have been adopted for presenting the change of displacement mode shape and strain mode shape. It is revealed strain mode shape is the most sensitive to damage.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2619-2627
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• 2000

In this paper, the vibrational characteristics of a foot mount type gearbox for epicyclic gear train have been studied. The modal parameters and mode shapes of a gearbox have been computed using AN SYS code. Modal testing was carried out to verify the FEM analysis model. It has been shown that the analysis results are in good agreements with the experimental results. Harmonic analysis has been executed to verify the effect of thickness variance of gearbox housing on the modal response. Analyzing the calculated results, some guides for optimal vibration response has been deduced.

• Structural Engineering and Mechanics
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• v.51 no.2
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• pp.229-248
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• 2014

In this paper, the development of a new optimization software for finite element model updating of engineering structures titled as FemUP is described. The program is used for computational FEM model updating of structures depending on modal testing results. This paper deals with the FE model updating procedure carried out in FemUP. The theoretical exposition on FE model updating and optimization techniques is presented. The related issues including the objective function, constraint function, different residuals and possible parameters for FE model updating are investigated. The issues of updating process adopted in FemUP are discussed. The ideas of optimization to be used in FE model updating application are explained. The algorithm of Sequential Quadratic Programming (SQP) is explored which will be used to solve the optimization problem. The possibilities of the program are demonstrated with a three dimensional steel frame model. As a result of this study, it can be said that SQP algorithm is very effective in model updating procedure.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.837-842
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• 2000

In this Paper, the vibrational characteristics of a gearbox for epicyclic Rear train have been studied The modal parameters and mode shapes of a gearbox have been computed using ANSYS code. Modal testing was carried out to verity the FEM analysis model. It has been shown that the analysis results are m good agreements with the experimental results. Harmonic analysis has been executed to verify the effect of thickness variance of gearbox housing on the modal response. Analyzing the calculated results, some guides fer optimal vibration response has been deduced.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1643-1653
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• 1992

A method, which uses analytical or numerical modal analysis results, e.g. from finite element analysis, to select desirable response measurement and excitation points for an efficient modal testing is introduced. First, points of master degree of freedom(DOP) are determined so as to statistically minimize errors between responses of a full order model and those estimated from the reduced order model. Such master DOF's are selected as the response measurement points. Then a criterion named 'driving point model constant(DPMC)' related to the magnitudes of resonance peaks of the driving point freqency response functions used to select the point of excitation out of the master DOF's. In this work, the method is demonstrated through applications to modal testing on a one dimensional cantilever beam and an aluminum plate and the results are compared with those by another technique. also, the method is applied to a two dimensional structural component of a passenger car.