• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.840-845
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• 2004

Development of the linear motors is recently required to control a high-speed and high-resolution in the high-integrated and speed process industry. This paper presents vibration analyses as well as measurement standards of the newly developed linear motors through analyzing the vibration characteristics of the advanced products. Vibration experiments are conducted for identifying vibration level during operation. They are also included in the modal test to analyze dynamic characteristics. Analytic data using Finite Element Method (FEM) are compared with the results of the modal. The FEM and experiments make it possible to understand these characteristics. Further, through computer simulation for the behavior of moving part to be vibration source, the best acceleration pattern of moving part movement can be verified to achieve effective moving part positioning and reduce the vibration due to moving part movement.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.7
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• pp.619-625
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• 2012

Since the fuel is always exposed to turbulent flow, the grid strap shows flow induced vibration characteristics that impact on the nuclear fuel soundness. The dynamic behavior of grids in nuclear fuels is quite complex, since two pairs of spring and dimple support are contacted with rods by friction in the limited space. This paper focuses on investigation of the grid strap(test fuel strap, TFS) vibration in one cell. TFS consists of a single spring and double dimples. To identify the grid strap vibration, modal analysis of the strap is performed using finite element method(FEM). Modal testing on a $5{\times}5$ grid structure without rods is performed. The modal testing results are compared to analytic results. In addition, random test considering rod effect is performed about a $5{\times}5$ grid with rods under real contact condition in the air. Finally, the strap vibration of a $5{\times}5$ fuel bundle in investigation of flow induced vibration(INFINIT) facility is measured in real fluid velocity condition without heating. It is shown that modal frequencies from the test are almost equal to those peak frequencies in the INFINIT test.

• Journal of the Korean Society for Railway
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• v.6 no.4
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• pp.286-293
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• 2003

The prototype of Korean high speed train (HSR350), composed of two power cars, two motorized cars and three trailer cars, has been designed, fabricated and tested. In this paper, the body vibration has been reviewed from the viewpoint of the vehicle's safety and the vibration limits for components and sub-assemblies mounted on the car-body using by the experimental method. And, the dynamic characteristics, such as jerk, natural mode and kinematic mode, have been reviewed. The KHST has been run to 300 km/h in the KTX line and the results of on-line test show that it has no problems in the vehicle's safety and the vibration limits. And the characteristics of body vibrations has been predicted at 350 km/h by fitting curve about the measured acceleration signals.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.381-385
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• 1998

Vibration-resistant rubbers, whose elastic and shear behaviors are similar to viscoelastic materials, are used to make brace-typed dampers to reduce the building vibration. Experimental study is carried out to find the vibration characteristics of the dampers installed in the building model. The natural frequencies and modal damping ratios are obtained from the free vibration test and Fourier analysis. Analytical model of the modal strain energy method are used to find the viscoelastic characteristics of the brace-typed dampers from the experimental results. Finally shaking table test is performed to find the response behavior of the building model under earthquake loading. The present experimental study shows that the brace-typed dampers have the behavior of viscoelastic dampers, which increase the modal damping ratios and viscoelastic characteristics.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.249-257
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• 1998

Vibration-resistant rubbers, whose elastic and shear behaviors are similar to viscoelastic materials, are used to make bracing dampers to reduce the building vibration. Experimental study is carried out to find the vibration characteristics of the dampers installed in the building model. The natural frequencies and modal damping ratios are obtained from the free vibration test and Fourier analysis. Shaking table test is performed to find the response behavior of the building model under earthquake loading. The present experimental study shows that the bracing dampers have the behavior of viscoelastic dampers, which increase the modal damping ratios and viscoelastic characteristics.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.3
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• pp.252-261
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• 2023

Analysis of dynamic characteristics and flight vibration test for unmanned aerial vehicles was studied by using dummy test body. The FEM model for dummy test body was supplemented by results of modal and random vibration test. The free end boundary condition to simulate flight environments was made by test setup using bungee cable. Prior to the flight vibration test using a dual electric vibration exciters, the test procedure to calculate quantitative vibration level was studied by using military specification. The actual test was successfully done by using the analysis and pretest results. From the analysis results, it was possible to determine the feasibility of the test by predicting the excitation force of the flight vibration test and to get the response of any point which could not be measured by the test. The results of this study will much contribute to the Test and Evaluation of unmanned aerial vehicles.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.338-347
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• 2010

Heunginjimun designated as a Treasure No.1 is a two-story wooden structure with 5 bay and 2 bay in its front and side views, respectively. This paper presents an investigation on vibration characteristics of Heunginjimun through both ambient vibration and impact hammer tests. Ambient vibration test was performed to identify the natural frequency of Heunginjimun from the spectrum analysis of time history. Impact hammer test was undertaken to find the frequency of Heunginjimun which is affected by the surrounding traffics and to verify the reciprocal principle for the wooden structural system. Ambient vibration test results of Heunginjimun showed that the natural frequencies in two principal axes 1.5 Hz and 1.1 Hz, respectively. It was confirmed from impact hammer tests for a ground that the frequency of 4.2 Hz is caused by the traffics surrounding Heunginjimun. It was also observed that from the impact hammer test results between two locations in Heunginjimun that the transfer functions measured from two corresponding locations coincided well with each other. This result shows that the wooden structural system is globally linear, and the reciprocal principle is established.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.515-518
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• 2006

A vibration test for a cylindrical rod inserted on the grid support structure was tested using the sine sweep excitation method with closed loop force control. The effect of the mounting location of a test rod on the vibration characteristics of a rod continuously supported by the full size($16{\times}16$) grid support was identified. An electromagnetic vibration shaker, non-contact displacement sensor and HP/VXI data acquisition device were used and TDAS software was also used as a data sampling and processing tools. The natural frequencies and mode shape of the test rod were consistent with the previous works of a rod vibration test with partial grids($3{\times}3,\;5{\times}5\;and\;7{\times}7$). The frequency characteristics of the rod according to the mounting location were shown clear discrepancies, but mode shapes were nearly same. As the test rod closes to the bottom clamping region of the spacer grid, peak vibration amplitudes of the rod become smaller.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.113-121
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• 2009

Shaker system is used to simulate the vibration from the launch environment. The vibration tests are performed in the vertical and lateral direction. For the lateral vibration test, the slip table system is used with shaker system. For the latest large satellite, vibration test adaptor is made of the steel. But slip table of lateral vibration is made of magnesium, so there is big difference of thermal expansion ratio between slip table and vibration test adaptor. This paper encompasses the following items; verification process of thermal characteristics and overturning moment and a solution for lateral vibration test with steel vibration test adaptor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1332-1339
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• 2005

The vibration of Powertrain are one of the import design characteristics of a vehicle. Powertrain is mostly mounted to the front subframe and powertrain mounting has an important role in determining the vehicle vibration characteristics. In this paper, the accuracy of the vibration analysis for the front subframe is discussed. The dynamic characteristic of subframe are measured from vehicle test and the finite element model updating are performed that natural frequency, mass and MAC of the experimental and theoretical modal analysis are compared. The subframe mounting stiffness are obtained the iteration method based on the vibration of subframe from vehicle test. Finally, the result of dynamic analysis which is operated dynamic load is compared with experimental one of vehicle test.