• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.729-734
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• 2001

A 3-dimentional finite element model for vibration analysis of steam-turbine blade groups is presented, employing the 3-dimentional incompatible brick element with 8 nodes. The skew coordinate system is introduced in the model for considering multi-axis symmetry and specialty of displacement constrain condition of blade groups. Vibration characteristics of blade groups are analyzed, and compared with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.146-149
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• 2005

Thesedays, the reduction of hand-transmitted vibration of hand-held power tools is important issue for operators' welfare, In the study, frequency response function is measured and vibration total value is evaluated for solving the principle and effect of the BOSCH's vibration-proof handle. This handle functions as a dynamic damper and has the effect, 22% vibration total value reduction under idling condition using a system that consists of a PC with data acquisition system and LabVIEW program. The program in the system makes it possible to evaluate vibration total value according to ISO 5349. This handle offers a good example for figuring out the physical contradiction between the work efficiency and operators' health.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.6
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• pp.440-447
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• 2013

In this paper, a higher harmonic control (HHC) methodology is applied to find the optimum input scenario for the vibratory hub loads reduction. A comprehensive aeroelastic analysis code, CAMRAD II, is used to model the HART (Higher-harmonic-control Aeroacoustic Rotor Test) II rotor, and parametric study is conducted for the best HHC inputs leading to a minimum vibration (MV) condition. The resulting outcomes are compared with the earlier HART II test results. It is indicated that the control input adopted in the MV condition showed less satisfactory results. The new MV condition obtained in the present investigation can achieve 45% lower vibration level than the baseline uncontrolled condition. The optimum HHC input results lead to 3/rev harmonic input having $0.8^{\circ}$ amplitude and $350^{\circ}$ phase angle. About 5% reduction in the required power is possible but accompanies with the increase of vibration level.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.601-605
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• 2011

In general, the rolling stock has been designed and manufactured in accordance with the requirements of purchaser. The requirements of the noise and vibration performance are called the international standard (ISO, UIC, TSI etc.) and are demanded based on the special conditions for the regional regulation and the characteristics for operating condition in detail. In this paper, the noise and vibration performance in the train at stationary condition has been investigated and the design parameter of the cooling fan to control the noise and vibration performance has been examined.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.273-276
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• 2004

Dynamic model of the Korea standardized rubber-tired AGT light rail vehicle, and boundary conditions between vehicle and infrastructures (running track, guidance rail) were defined to analyze vehicular vibration behaviors occurred at the worst condition for straight running track. Using the commercialized software RecurDyn, resultant forces and vibration accelerations of car body and bogies were analyzed. Based on the Korea performance test criteria for urban transit, vertical and lateral vibration of car body were calculated and evaluated as wearing condition of guide wheels. And resultant forces between bogie guidance frame and guide rail in straight running track were analyzed. As the results, the Korea standardized rubber-tired AGT light rail vehicle satisfied the performance criteria and design requirement .

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.965-970
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• 2002

The purpose of this paper is to investigate the free vibration characteristics of tapered beams with general boundary condition(translational and rotational elastic support) at one end and carrying a tip mass with translational elastic support at the other end. The beam model is based on the classical Bernoulli-Euler beam theory which neglects the effects of rotatory inertia and shear deformation. The governing differential equation for the free vibrations of linearly tapered beams is solved numerically using the corresponding boundary conditions. Numerical results are compared with existing solutions by other methods for cases in which they are available. The lowest four natural frequencies are calculated over a wide range of section ratio, dimensionless spring constant and mass ratio.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.107-113
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• 2017

The dynamic characteristics including natural frequencies and excitation frequencies are evaluated for a small 10 kW vertical axis wind turbine. Acceleration responses were measured at 12 distributed locations for impact vibration tests, ambient vibration tests during non-operational and operational conditions, and braking tests during operational condition. The natural frequencies for the lowest 2 bending modes and the first torsional mode were estimated and also the excitation frequencies, i.e. 1P, 2P, 4P, were also estimated according to the rotational speed using the responses under operational conditions (i.e. power generation condition).

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.209-213
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• 2003

It is advantage of accelerated vibration testing to compress service exposures to operating vibration into a reduced laboratory test by increasing the amplitude or frequency of the applied input excitations. This paper proposes an accelerated test method to estimate the high-cycle fatigue life under random excitation. The method consists of conducting a test with amplified input excitation and extrapolating linearly the lift in the accelerated condition into the real lift in field condition. The extrapolation is carried out applying the high-cycle irregular excitation fatigue theory including the rainflow counting, Miner’s damage accumulation rule, and Goodman’s mean stress correction. As a verification, those estimated lift is compared with that acquired by experiment f3r the simple case of spot welding specimen with good agreement. This testing procedure will provide an useful scheme that can reduce testing period associated with developing time schedule of new product.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.664-667
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• 1997

In this study, it is attempted to obtain the optimized size of holes in 15 square plate models where a hole exists on every quadrant of a plate, and to get eigenvalues and mode shapes by performing free vibration analysis for each model. For free vibration analysis and optimization of' hole sizes, the uniaxial tension is applied for the loading condition. From the results of this study, it is known that more stable structures can be designed by changing the natural frequency depending on the location and the optuiiunl size of holes. and further studies are considered to be necessary for the basic design information.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.359-360
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• 2009

In this study, we propose a practical method to improve the clarity and the period of the beat in a Korean bell. Proper beating in vibration and sound is very important feature in Korean bell. An equivalent ring theory is applied and finite element analysis is performed to determine the condition of the asymmetry of the bell. The clearity and the period of the beat are improved by attaching a counter mass or decreasing local thickness. This paper shows that the improved the attaching a counter mass or decreasing local thickness. This paper of the beat are improved by attaching a counter mass or decreasing local thickness. This paper shows that the amount and position of the local variation for the required beat condition can be predicted by using the equivalent model, The predicted results are verified by the experiment.