• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.977-980
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• 2011

In this paper, explain to development of low pressure axial compressor performance test rig in KARI. Performance test rig consist of a entrance section, rotor, stator, shaft, rig housing, bearing housing and exit section. Test rig design structural optimization to rotor dynamics analysis of the simplified rotor-shaft assembly and flow analysis of entrance/exit section.

• Nuclear Engineering and Technology
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• v.21 no.4
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• pp.341-345
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• 1989

The distribution behaviors of beryllium which may produce a deleterious damage in the zircaloy cladding have been investigated by the X-ray line scanning of EPMA. The results obtained are as follows; 1) The alloy phase formed by the brazing contains ~6.3 mass % of beryllium. 2) The beryllium diffusion in the base metal (cladding and bearing pad) is recognized only in the range ~5 $\mu$m from the brazing interface.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.1
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• pp.95-102
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• 2007

The issues of preventive and condition-based maintenance, online monitoring, system fault detection, diagnosis and prognosis are of increasing importance. This study introduces a technique to detect and identify faults in induction motors. Stator currents were measured and stored by time domain. The time domain is not suitable for representing current signals, so wavelet transform is used to convert the signals onto frequency domain. The raw signals can not show the significant feature, therefore difference values between the signal of the health conditions and that of the fault conditions are applied. The difference values were transformed by wavelet transform and the features are extracted from the transformed signals. The dynamic time warping method was used to identify the fault type. This study describes the results of detecting fault using wavelet analysis.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.110-123
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• 1994

The development of automatic production systems have required inteligent diagnostic and monitoring function to repair system failure and reduce production loss by the failure. In order to perform accurate functions of intelligent system, inferencing about total system failure and fault analysis due to each mechanical component failures are required. Also the solution about repair and maintenance can be suggested from these analysis results. As an essential component of mechanical system, a bearing system is investigated to define the failure behavior. The bearing failure is caused by lubricant system failure, metallurgical defficiency, mechanical condition(vibration, overloading, misalignment) and environmental effect. This study described roller bearing fault train due to stress variation and metallurgical defficiency from lubricant failure by using FTA.

• Tribology and Lubricants
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• v.23 no.5
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• pp.195-200
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• 2007

This paper presents the friction induced scuffing and wear defects analysis of a pin bushing bearing based on the chemical composition using a scanning microscopy (SEM) and an energy dispersive X-ray analyzer (EDX). The SEM/EDX system, which may provide good information on the surface thermal defects and chemical compositions, provides impurities such as an aluminum, a silicon, a ferrous component and an oxygen, especially. The EDX measured results show that the oxygen may reduce the strength and a hardness of a pin busing, which may lead to a scuffing and a seizure on the rubbing contact surface. The current technology fabricated by a sintering for a pin bushing bearing should be modified or changed to reduce the oxygen composition and the impurities in pin bushing materials.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.101-102
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• 2012

Thermal Diffusion Process(TD Process)을 통하여 베어링강 소재인 SUJ2 표면에 Vanadium Carbide를 석출시켜 표면 물성에 관한 연구를 진항하였다. $900{\sim}950^{\circ}C$ 온도와 2~6H 공정시간에 따라 TD Process에 의한 코팅층의 변화를 Micro Vikers Hardness Tester와 광학현미경, SEM, EDS를 통하여 관찰하였다. 그 결과 공정시간 및 온도는 코팅층 성장과 비례한다는 것을 확인 할 수 있었고 SUJ2 표면에 성장된 코팅층은 높은 경도값을 갖는 VC, CrC 코팅층임을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.50-50
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• 2008

본 연구에서는 전방항성 초음파 액추에이터의 제작, 시뮬레이션, 구동 드라이버 제작, 제어 방법에 대하여 연구하였다. 우선, 시뮬레이션 툴인 ATILA를 사용하여 전방향성 초음파 액추에이터를 설계하였고 구동 주파수, 어드미턴스 특성 그리고 액추에이터의 움직임을 분석하여 최적의 구동 주파수 영역을 파악하였다. 실제 구동을 확인하기 위하여 액추에이터 스테이지와 구동 드라이버를 개발 하였다. 전방항성 액추에이터 스테이지의 구조는 액추에이터와 4개의 볼 베어링이 알루미나 볼을 압착하는 형태이며 세라믹에 인가되는 사인파의 위상차에 의하여 4개의 방향으로 구동 할 수 있다. 또한, 액추에이터를 위치 제어를 위하여 로터리 엔코더 두 개를 사용하여 구의 움직임을 파악하였고 PID 제어기법을 사용하여 액추에이터의 움직임을 제어하였다. 스테이지 구조상 엔코더의 $70^{\circ}$ 내에서만 구동 가능하며, 실험 결과를 통하여 전방향성 초음파 액추에이터는 약 $1.2^{\circ}$의 분해능을 가지고 구동영역 내 원하는 좌표로의 이동이 가능했고, 향후 고 정밀 관절 및 인공 눈에 응용 가능할 것으로 사료된다.

• Journal of the Korean Society of Safety
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• v.20 no.3 s.71
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• pp.1-8
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• 2005

The industrial induction motor is widely used in the rotating electrical machine for the transmission of power. It is very reliable equipment, but it could lead to the loss of production and lift when failure occurs. Therefore, the failure data is acquired and analyzed by attaching an exclusive instrument to existing induction motor. However, these instruments could lead to side effects, increasing the production costs, because they are very expensive. The purpose of this study is the development of an induction motor bearing failure diagnosis system constructed using LabVIEW which can be supplied the kernelled function, process monitoring and current signature analysis. In addition, the availability and reasonability of the constructed system was examined for an induction motor with failure defects in outer raceway and ball bearing. From the results, it shows that failure diagnosis system constructed is useful for real-time monitoring with detection of bearing defects over the web.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.3
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• pp.63-69
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• 1996

Recently, vibrational signal processing as a tool of machinery diagnosis has been actively studying. In this study, a new scheme for detection and diagnosis of localized defects in ball bearings, using unwrapped phase spectrum of FFT is described. The characteristic phase spectra for such defects shows linearly varying patterns due to the repetitive impact signals generated by localized defects, i.e., one linear line for single defect and various linearly changing shape according to angle between the two defect located points. The effectiveness of this method is confirmed by computer simulation and experiments on bearing with single or double defects at different locations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.2
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• pp.122-129
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• 2002

An optimization of satellite honeycomb platforms under sever space environment is performed. There are many optimization constraints for space environment to be considered. A modified method of feasible direction and a genetic algorithm are used to optimize the satellite platform structures. The design constraints are concerned with bearing stresses at joints and natural frequencies. The results from the optimization methods are compared. The numerical results show that natural frequency constraints are dominant to reach the optimum design. This study verifies the design of satellite honeycomb platforms and suggests an optimal platform design.