• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.891-894
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• 2007

This study presents fault diagnosis of low speed bearing using support vector machine (SVM). The data used in the experiment was acquired using acoustic emission (AE) sensor and accelerometer. The aim of this study is to compare the performance of fault diagnosis based on AE signal and vibration signal with same load and speed. A low speed test rig was developed to simulate various defects with shaft speeds as low as 10 rpm under several loading conditions. In this study, component analysis was also performed to extract the feature and reduce the dimensionality of original data feature. Moreover, the classification for fault diagnosis was also conducted using original data feature without feature extraction. The result shows that extracted feature from AE sensor gave better performance in faults classification.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.768-771
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• 2003

The impulse between launch vehicle and atmosphere can generate a lot of noise and vibration during the process of launching a satellite. Structurally, electronic equipment (KOMPSAT 2, RDU : Remote Drive Unit) of a satellite consists of aluminum case containing PCB (Printed circuit boards). Each PCB has resistors and IC (Integrated circuits). Noise and vibration of wide frequency band are transferred to the inside of fairing, subsequently creating vibration of the electronic equipment of the satellite. In this situation. random vibration can cause malfunctioning of the electronic equipment of the device. Furthermore, when tile frequency of random vibration meets with natural frequency of PCB. fatigue fracture nay occur in the part of solder joint. The launching environment, thus. needs to be carefully considered when designing the electronic equipment of a satellite. In general. the safety of the electronic equipment is supposed to be related to the natural frequency, shapes of mode and dynamic deflection of PCB in the electronic equipment. Structural vibration analysis of PCB and its electronic components can be performed using either FEM(Finite Element Method) or vibration test. In this study. the natural frequency and dynamic deflection of PCB are measured by FEM, aud the safety of the electronic components of PCB is being evaluated according to the results. This study presents a unique method for finite element modeling and analysis of PCB and its electronic components. The results of FEA are verified by vibration test. The method proposed herein may be applicable to various designs from the electronic equipments of a satellite to home electronics.

• 항공우주시스템공학회지
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• 제10권3호
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• pp.15-22
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• 2016

The on-board appendages of satellites with mechanical moving parts such as the fly-wheel, the control-moment gyro, the cryocooler, and the gimbal-type directional antenna can generate an undesirable micro-vibration disturbance, which is one of the main causes of the image-quality degradation that affects high-resolution observation satellites. Consequently, the isolation of the micro-vibration issue has always been considered as salient, and the micro-vibration is therefore the focus of this study wherein a complex system that can provide the dual functions of a guaranteed vibration-isolation performance and electrical energy harvesting is proposed. The vibration-isolation and energy-harvesting performances of the complex system are predicted through a numerical analysis based on the characteristics that are obtained from component-level tests. In addition, the effectiveness of the complex system that is proposed in this study is verified through an assembly-level functional-performance test.

• 항공우주기술
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• 제3권2호
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• pp.25-33
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• 2004

본 논문에서는 인공위성 반작용휠의 미소진동 측정을 위한 테스트 장비와 이를 이용하여 실측한 반작용휠의 미소진동을 측정 및 분석 결과를 소개한다. 위성의 미소진동은 KISTLER dynamic platform 이라는 400Hz 이내의 3축의 힘과 3축의 토크를 동시에 측정할 수 있는 장비에 의해 측정되며 측정된 데이터는 회전 속도에 따라 3차원 주파수 분석, order tracking 등의 방법을 이용하여 분석된다. 반작용휠의 미소진동 분석 결과, 회전 속도와 비례하는 일차 성분 외에 고차 조화 성분, 구조 진동 성분, 회전 속도에 따라 고유진동수가 변하는 rocking 모드 성분 등을 관찰할 수 있었으며, 휠의 정적 및 동적 불균형은 각각 0.79gcm과 17.4gcm²으로 나타났다. 이러한 다양한 진동 성분들은 회전체의 특성, 구조물의 특성 및 베어링의 영향으로 기인한다.

• 한국소음진동공학회논문집
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• 제14권10호
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• pp.962-967
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• 2004

A bogie is the device that connects a car body and wheel sets of a rail vehicle. It is the critical component that determine:; the running safety, The bogie consists of a frame, suspensions, brakes and wheel sets. Various analyses including a numerical simulation using a finite element method, a static load test, a fatigue test, ai)d r running test should be carried out to design the bogie. However cracks have been found at some end beams of the bogies mounted on the freight cars running with the high speed. The cracks of the end beam results in deterioration of the brake performance an the running safety, A new design has been suggested to solve this problem by ROTEM company and it's performance has been tested in this paper. Numerical simulations and dynamic tests are carried out to figure out the causes of cracks in the conventional bogie, and the vibrational characteristics of the improved bogie are compared with those of the conventional one.

• 한국산학기술학회논문지
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• 제20권8호
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• pp.181-189
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• 2019

항공기용 전원 분배 장치는 발전기에서 생성된 전원을 분배 및 제어하고, 과전류를 보호하는 역할을 한다. 항공기 비행 중에 교류 전원 분배 장치의 결함으로 인해 교류 전원 분배가 불가능해지는 현상이 다수 발생하였다. 이로 인해 정상적인 교류 전원 분배가 불가능하고 일부 전자장비가 구동을 상실하는 문제점이 제기되었다. 본 논문에서는 결함 발생 조건인 항공기 비행 중 진동 조건을 진동 시험 장비로 모의하여, 결함의 근본 원인을 도출한 과정을 기술하였다. 이를 통해 결함의 원인이 교류 전원 분배 장치의 접촉기가 진동에 의해 내부 배선 손상이 발생한 것임을 확인하였으며, 결함 해소를 위해 접촉기 개선 형상을 도출하였다. 또한 결함이 내재된 접촉기를 검출하기 위해, 진동 시험 장비를 활용한 결함 검출 시험을 수행하는 방식으로 시험 절차를 개선하였다. 개선활동 결과 교류 전원 분배 장치의 결함 현상이 개선되었음을 구성품 인증 시험 및 비행 시험을 통해 입증하였다.

• 전산구조공학
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• 제5권3호
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• pp.105-112
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• 1992

원자로 내부구조물의 설계시 필요한 동적응답해석을 위하여 각 구조물의 정확한 진동특성을 파악할 필요가 있다. 한국 표준형 원자력발전소를 위하여 설계된 제어봉집합체 보호구조물은 기존의 설계로 부터 많은 설계변경이 있었고, 또 이 구조물은 튜우브와 얇은 판이 사각격자 형태로 이루어져 있고 연결봉에 의해 고정되는 등 매우 복잡한 형태로 구성되어 있어서 해석과 시험에 의한 진동측정 프로그램을 수행할 필요성이 대두되었다. 따라서 본 논문에서는 진동측정 프로그램의 첫 단계로서 범용구조해석코드인 ANSYS를 이용하여 시험전 해석을 수행하였다. 또 자유도의 수와 얇은 판에 있는 구멍 및 연결봉의 pre-load가 구조물의 자유진동수에 미치는 영향을 검토하였다. 이로부터 결정된 유한요소모델에 대하여 모우드해석을 수행하여 구조물의 고유진동수와 모우드형상을 구하였고, 조화운동해석(Harmonic Analysis)을 행하여 주요모우드에 대한 응답을 측정함으로써 추후에 수행될 진동측정 시험조건 즉 응답측정부위, 측정위치의 수, 측정진동수의 범위 및 가진력의 크기 등을 결정하였다.

• 대한조선학회논문집
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• 제41권4호
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• pp.77-84
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• 2004

Active control is regarded as one of the most efficient and economic countermeasures to reduce excessive vibration of ship superstructure. However, it is difficult to find its practical application in real ships in spite that many studies on such systems have been done. In this study, for the practical use of an active control system to reduce ship superstructure vibration, we have developed an active vibration compensator consisting of a mechanical actuator having compact size and expected lifetime over 20 years, its control panel including exclusive signal processing and computing board, sensors to detect phase and vibration, and its operation software providing various user-interface functions. From the performance verification test of the system at a 5,500 TEU container carrier, we have confirmed the system could reduce ship superstructure vibration of a harmonic component of main engine rotating frequency up to 0.1 mm/s.

• 한국지진공학회논문집
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• 제28권3호
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• pp.141-147
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• 2024

Earthquakes of magnitude 3.0 or greater occur in Korea about 10 times on average yearly, and the number of earthquakes occurring in Korea is increasing. As many earthquakes have recently occurred, interest in the safety of nuclear power plants has increased. Nuclear power plants are equipped with many cabinet-type control facilities to regulate safety facilities, and function maintenance is required during an earthquake. The seismic performance of the cabinet is divided into structural and functional performances. Structural performance can be secured during the design procedure. Functional performance depends on the vibration performance of the component. Therefore, it is necessary to confirm the seismic performance of the components. Generally, seismic performance is confirmed through seismic simulation tests. When checking seismic performance through seismic simulation tests, it is difficult to determine the effect of frequency and maximum acceleration on an element. In this paper, shaking table tests were performed using various frequencies and various maximum accelerations. The seismic performance characteristics of the functions of electrical equipment components were confirmed through tests.

• Smart Structures and Systems
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• 제31권2호
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• pp.171-181
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• 2023

Using the most up-to-date system identification methods in both time and frequency domains, the dynamic monitoring data from the reinforced concrete Egebaekvej Bridge near Holte, Denmark, is examined in this investigation. The bridge was erected in the 1960s and was still standing during test campaign before demolishing. The ARTeMIS Modal was adopted to derive the modal parameters from ambient vibration data. Several Operational Modal Analysis (OMA) approaches were applied, including Enhanced Frequency Domain Decomposition (EFDD), Curve-fit Frequency Domain Decomposition (CFDD), and Frequency Domain Decomposition (FDD). Afterward, Principal Component (SSI-PC), Unweighted Principal Component (SSI-UPC) Stochastic Subspace Identification methods were utilized. Danish engineering consulting company, COWI with the allowance of the bridge contractor BARSLUND, allow the researcher for this experimental test to demonstrate the impact of OMA applications.