• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.193-196
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• 2006

Vibration overtests have been common problems in aerospace industry. A test item can be overtested at its resonances when it is excited by the traditional spectrum enveloping peaks in the field acceleration spectrum. This paper introduces the method of modifying the excitation specification to alleviate the overtesting problem. A vibration analysis was performed to estimate interface forces and acceleration responses. A finite element model that was verified by an extensive modal test enabled us to shape the acceleration input accurately The produced notched input will be used in the sinusoidal vibration test of the small satellite launch vehicle.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.04a
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• pp.139-146
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• 1998

The prototype ASME III motor actuated Y-type globe valve has been tested to identify dynamic characteristics. The valve is Seismic Category I equipment and has the function to control water flow in the safety-related system. In this study, two different types of structural identification test i.e. swept sine and broadband random, have been performed at various levels of excitation to verify the effects of test method and excitation level on cross coupling effect as well as natural frequencies and damping values. It was found that swept sine test and broadband random test showed similar natural frequencies, and that the primary interaction was exhibited between horizontal and vertical axes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2436-2441
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• 2015

BSR noise from automobiles is largely issued in recent as an emotional quality. This study describes the two test methods for determining BSR noise occurred in automotive seat system. First, the sine sweep test is found to be an effective excitation method for determining BSR noise with high frequency. Second, BSR operation test is introduced in such a way that BSR noise during operation of seat height system is measured by several accelerometer at each 800 cycles until 6400 cycles. The periodic noise signal is captured during one cycle after many cycles of operation. Two test method presented in this paper can be analyzed more efficiently BSR noise of the seat.

• Journal of Industrial Technology
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• v.18
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• pp.329-334
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• 1998

The purpose of this study is to design and manufacture a vibration exciter, which can be used in the education and research for the vibration engineering. For this purpose, a direct drive type vibration exciter is developed, which consists of a motor, an inverter, eccentric rotating sleeves and two excitation plates. Developed exciter is tested on some dynamic characteristics to evaluate its excitation performance. Test results show that the developed machine can excite bodies on the horisontal vibrating plates in x,y direction by the constant displacement amplitude in the frequency range below 50Hz, which confirm that the exciter can be used as a vibration testing machine in the low frequency range.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.4
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• pp.1-8
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• 2001

In this paper, a hybrid mass damper using AC-servomotor was designed and developed in order to reduce vibration levels of a 5-story test structure under base excitation. Control performances of the HMD under random and earthquakes excitations are compared with those of TMD through experimental test. It is confirmed that the HMD is more effective to reduce the vibration levels of the test structure especially for the earthquake excitation which excites more than 2 vibration modes of the structure simultaneously.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.371-371
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• 2006

The purpose of this study is to provide a fundamental data for efficient and economical reduction method and predict ion method of floor impact noise. In order to get the useful results, the measurement on the vibration transmission characteristics of standard test building with four rooms by using heavy and light-weighed impact source were carried out. In this measurement various conditions such as the change of test structure construction, the pick-up sensor location, the excitation posit ion, and the resilient material types were applied to get the vibration characteristics transmitted from excitation room to adjacent rooms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.105-108
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• 2004

This paper introduces a process of the development of a vibration test dummy for the posture of inclined seating. Experimental devices was invented to measure apparent mass curves on the contact point of the hip and the back of a seated human body. During the excitation of a rigid seat secured to a hydraulic exciter, force and acceleration signals were measured on the contact points to determine the apparent mass. In order to describe nonlinear characteristics of a human body, seven levels of Gaussian random signal were used for the base excitation. The modeling of the human body will be performed using measured apparent mass curves. The modeling will be done by June and the prototype of the test dummy will be invented in the following six months.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.235-240
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• 2007

For the identification of the 3 dimensional dynamic characteristics of the Bongjeong Temple, the dynamic test for 1/3 scaled model was performed. Dynamic test with impulse excitation and vibration table excitation can provide useful data for the estimation of dynamic characteristics such as natural frequencies, damping ratios, mode shapes and stiffness center. This will complement the previous research from the 2-dimensional static test and provide the reference data for the enhanced structural analysis of the traditional wooden structures.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1343-1350
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• 2007

This paper describes the tests on the reactive power output limit and the Over-Excitation Limiter (OEL) dynamics of a generation unit. The suggested test methods on reactive limit can identify the allowable maximum/minimum reactive power at 100% rated MW in the steady-state unit operation condition. The on-line OEL test method can identify the time characteristics of OEL with the generation output at 50% of the rated MW. These methods are validated by applying to four Yang-Yang pumped storage units with 282 rated MVA each.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.6
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• pp.596-605
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• 2022

In this study, analysis of dynamic characteristics and flight vibration was performed to unmanned aerial vehicles. The analysis model was supplemented by performing a dynamic characteristic test and a random vibration test using manufactured dummy aerial vehicle. For the dynamic characteristic test, a bungee cable was used to implement the free end boundary condition. Prior to the flight vibration test using a multiple electric shaker, a random vibration test was performed to predict the excitation force during the actual flight vibration test. It was judged that the actual test could be predicted more accurately by supplementing the analysis model from the test results. In addition, it was possible to determine the feasibility of the test by predicting the excitation force of the flight vibration test.