• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.136.2-136.2
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• 2012

저궤도지구관측 위성의 광학탑재체는 위성이 궤도에 진입한 이후 관측과 같은 주요 임무를 전담하는 중요 시스템이다. 광학탑재체가 장착된 위성이 발사체에 탑재되어 발사하는 순간부터 우주의 궤도에 진입하기까지 극심한 진동 환경에 노출된다. 이러한 상황을 예측하여 설계된 해당 시스템은 발사 이전에 진동 환경을 모사하는 시험을 통해 완벽하게 검증되어야 한다. 본 논문에서는 저궤도지구관측위성용 광학탑재체에 대하여 실시한 진동 환경 시험 방법 및 분석 내용을 소개하고자한다.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.6
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• pp.11-18
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• 2011

Accurate modal identification analysis is required to reasonably perform a seismic qualification of safety-related electric equipment installed in nuclear power plants (NPPs). This study evaluates a variation of the modal properties of an electric equipment cabinet structure in NPPs according to the excitation levels. For the study, an actual electric equipment cabinet was selected as a specimen and was dynamically tested by using a portable exciter in accordance with the level of input vibration energy. Tests were classified into two sets: with-door cases, and without-door cases. Frequency response functions were computed from the signals of the acceleration responses and input motions measured from the vibration tests. A polynomial curve fitting algorithm was used to extract the modal properties from the frequency response functions. This study reviews the variation of the modal properties according to the variation of the excitation levels. The results of the study show that the modal frequencies and the modal dampings of the object specimen varies nonlinearly according to the excitation level of the test motion. Attaching the door increases the modal damping of the cabinet.

• Journal of KSNVE
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• v.8 no.1
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• pp.41-42
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• 1998

본고에서는 상용차 가속 주행소음 시험과 시험오차의 감소 방안과 주민의 정온성을 위한 실질적인 대책안을 제안 하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05b
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• pp.695-700
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• 1995

최근 일부 PWR 원전에서는 냉각수 유동유발에 의한 집합체 진동에 기인한 것으로 보이는 핵연료 손상이 잇달아 발생하고 있다. 본 시험에서는 모의 핵연료 집합체에 대해 원전운전시 유량(유속)에 따른 집합체외 진동특성을 규명하기 위해 모의 집합체에 대한 유동시험을 수행하였다. 시험결과 매져 모의 연료는 발전소 운전 유동영역 범위내에서 냉각수 유동에 기인한 집합체의 진동현상이 발생함이 확인되었다.

• Geotechnical Engineering
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• v.3 no.3
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• pp.7-20
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• 1987

To obtain meaningful data of the tests for cyclic loading triaxial test, cyclic loading simple shear test ; and Shake table studies, it is necessary to test uniformly densified specimens. However, there is still some question about the assumed uniform density within a specimen when subjected to the process of densification. A study is conducted to investigate the density variation It within the specimen and analyze the effect of various parameters during the process of vibratory densification. It is found that variation of the ideally graded sand having a homogeneous initial density results in large inhomogeneities within the specimen after vibration. The degree of density variation within the speimen becomes more pronounced by the gradation of sand, surcharge and the intensity of acceleration.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.6
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• pp.495-501
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• 2013

Korean Utility Helicopter (KUH) has been designed to avoid the blade passing frequency and any instability due to a coupling of dynamic characteristics between the main rotor and the airframe in ground operation. For these design objectives, the vibration analysis and the ground resonance analysis were performed to analyze the dynamic characteristics of the airframe and the main rotor. Then, the whirl-tower test was conducted to identify the dynamic characteristics of the main rotor and the ground vibration test (GVT) was conducted to identify the dynamic characteristics of the airframe. The GVT for KUH was conducted with the test conditions and test articles established in consideration of each flight and ground condition. This paper shows the method and technique for performing the GVT for KUH and presents the correlation technique and the results for the correlated analysis model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.125-128
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• 1990

조사후 시험시설(Post Irradiated Examination Facility, PIEF)은 내진범주 1 급 구조물로서 현재 각종 실험 및 연구가 진행중인 원자력 안전관련시설물 이다. 한편 이 건물로부터 30m - 120m 정도 떨어져 있는 다목적연구로 (Korea Multipurpose Research Reactor, KMRR) 및 조사재시험시설 (Irradiation Material Examination Facility, IMEF)의 건조사업을 위하여 기 초암반의 굴착작업을 수행할 경우 발파작업에 따른 그 진동 및 폭풍압영향 이 염려되어, 그 안전성 평가를 위하여 시험발파를 수행해야 할 필요가 제기 되었다. 우선 운전중인 원자력안전 시설물에서의 발파에 따른 진동허용 기준 을 설정하고, 둘째로 거리에 따른 폭발량을 경험식에 따라 잠정 결정한 후, 세째로 시험발파에 의한 진동 측정을 수행하여 그 영향을 평가하고, 끝으로 이에 따라 거리별 제한 폭발량을 결정한후 실제 본발파에 적용하고자 한다. 이로써 운전중인 원자력 안전관련시설물인 PIEF의 안전 운전을 도모하고 KMRR및 IMEF 시설의 건조를 원만하게 이룰 수 있을 것이다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.446-451
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• 2004

Over testing problems of satellites and theirs components have been issued due to their effects on satellite development cost and schedule. Force limited vibration tests were introduced as solution of the problems in 1980s. Over testing phenomena occurs due to the lack of similarity on interface impedance. Force limited vibration tests control interface force to simulate actual interface impedance. In this research, force limited vibration tests are applied on two satellites environmental tests. Force limits are calculated by using TDFS method and Semi-Empirical method. Four force sensors are employed to control interface force. The tests prove that force limited control reduced maximum interface acceleration in order of 3.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.59-65
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• 2018

The landing gear (L/G) handle of an aircraft is an essential piece of equipment for aircraft take-off and landing. The bracket in the landing gear handle was fractured during a vibration test when developing the landing gear handle. This paper summarizes the vibration test procedures performed during landing gear handle development. A cause analysis, design improvements, and verification results of the fault in the vibration test are also provided.

• Journal of KSNVE
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• v.5 no.4
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• pp.555-563
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• 1995

This paper proposes the method of antiresonance frequency analysis of multi-input multi-output system. The structural dynamic modification techniques by antiresonance frequency analysis are also applied to reduce the undertest at specimen attachment points on the fixture in environmental vibration test, which is resulted from the inconsistency of antiresonance frequencies at any specified points. Several computer simulations show that the proposed method can remove the undertest problem which is not removed in conventional vibration test control. And the effectiveness of the method is verified with the impact hammer excitation of aluminium fixture model.