• 한국압력기기공학회 논문집
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• 제8권1호
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• pp.19-24
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• 2012

This paper presents the results of finite element analysis for the effects of hydrostatic test and operating condition on the weld residual stress at dissimilar metal weld of a pressurizer safety nozzle in a nuclear power plant. For the study, the weld residual stress at ambient condition was analyzed using ABAQUS in the first place. After the weld residual stress analysis, the hydrostatic test condition and operating condition was applied to the same model one after another. The weld residual stress was observed to change due to the successive hydrostatic test and operating condition. The axial residual stresses on inner surface of the dissimilar metal weld and HAZ region were decreased by hydrostatic test and operating condition, which gives beneficial effect on preventing primary water stress corrosion cracking.

• 한국정밀공학회지
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• 제20권4호
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• pp.136-142
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• 2003

The morphological analysis of wear debris can provide early a failure diagnosis in lubricated moving system. It can be effective to analyze operating conditions of oil-lubricated tribological system with shape characteristics of wear debris in a lubricant. But, in order to predict and recognize an operating condition of lubricated machine, it is needed to analyze and to identify shape characteristics of wear debris. Therefore, If the morphological characteristics of wear debris are recognized by computer image analysis using the neural network algorithm, it is possible to recognize operating condition of hydraulic driving members. In this study, wear debris in the lubricating oil are extracted by membrane filter (0.45 ${\mu}{\textrm}{m}$), and the quantitative values of shape parameters of wear debris are calculated by the digital image processing. This shape parameters are studied and identified by the artificial neural network algorithm. The result of study could be applied to prediction and to recognition of the operating condition of hydraulic driving members in lubricated machine systems.

• 동력기계공학회지
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• 제12권5호
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• pp.65-70
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• 2008

The purpose of this study is to verify availability of the acoustic emission in-situ monitoring method to the internal leak and operating conditions of the turbine major valves relating to safety for turbine operating and prevention of turbine trouble at nuclear power plants. In this study, acoustic emission tests are performed when the pressurized electro-hydraulic control oil flowed through turbine electro-hydraulic controller oil check valve and turbine power/trip fluid solenoid valve in the condition of actual turbine operating. The acoustic emission method was applied to the valves at the site, and the background noise was measured far the abnormal plant condition. To judge for the leak existence ell the object valves, voltage analysis and frequency analysis of acoustic signal emitted from infernal leak in the valve operating condition are performed. It was conformed that acoustic emission method could monitor for valve internal leak to high sensitivity.

• International Journal of Precision Engineering and Manufacturing
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• 제4권6호
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• pp.44-49
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• 2003

The morphological analysis of wear debris can provide early a failure diagnosis in lubricated moving system. It can be effective to analyze operating conditions of oil-lubricated tribological system with shape characteristics of wear debris in a lubricant. But, in order to predict and recognize an operating condition of lubricated machine, it is needed to analyze and to identify shape characteristics of wear debris. Therefore, If the morphological characteristics of wear debris are recognized by computer image analysis using the neural network algorithm, it is possible to recognize operating condition of hydraulic driving members. In this study, wear debris in the lubricating oil are extracted by membrane filter (0.45$\mu\textrm{m}$), and the quantitative values of shape parameters of wear debris are calculated by the digital image processing. This shape parameters are studied and identified by the artificial neural network algorithm. The result of study could be applied to prediction and to recognition of the operating condition of hydraulic driving members in lubricated machine systems.

• 대한기계학회논문집A
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• 제37권9호
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• pp.1159-1168
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• 2013

가압형 경수로 원자로의 압력용기 상부헤드 관통노즐 J-groove 용접부 주변에서 일차수응력부식균열(PWSCC)로 인한 냉각수 누설사례가 발생하고 있다. 본 연구에서는 PWSCC 의 주요 원인 중 하나인 용접 잔류응력을 유한요소 해석을 이용해 평가하고 원자력 발전소의 정상가동 조건을 해석에 반영하는 방법이 용접잔류응력 분포에 미치는 영향에 대한 분석을 수행하였다. 또한 반복되는 원자력 발전소의 가동 주기가 용접잔류응력 분포에 미치는 영향을 확인하여 정상가동조건에서의 정확한 용접 잔류응력을 예측할 수 있는 방법을 분석하였다.

• 한국유체기계학회 논문집
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• 제14권4호
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• pp.38-44
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• 2011

This paper deals with the detail rotordynamic analysis for BB5 eight stages pump as development of API 610 BB5 type pump. Dry-run analytical model, not considering operating fluid, and wet-run analytical model, considering operating fluid are established. In addition, plain circular and pressure dam bearings are chosen and it was discussed that each bearing has an effect on dynamic characteristics of pump rotor system. A rotordynamic analysis includes the critical speed map, Campbell diagram, stability, and unbalance response. As results, it was predicted that rated speed of the pump rotor passes through 1st critical speed in dry-run condition regardless of bearings, however, it was verified that, in wet-run condition, the rotor system doesn't have critical speeds even if more than twice rated speed. Hence the resonance problem caused by the critical speeds does not happen since actual operating is in wet-run condition including operating fluid. As a result of unbalance response analysis, the pump rotor has stable vibration response at rated speed, regardless of operating fluid and the proposed bearing types.

• 한국정밀공학회지
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• 제14권5호
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• pp.143-149
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• 1997

This paper was undertaken to do image analysis of wear debris on operating condition of the lubricated moving surfaces. This lubricating wear test was performed under different experimental conditions using the wear test device was made in our laboratory and wear testing specimen of the pin on dist type was rubbed in paraffine series base oil, by materials, varying applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) to describe wear debris have been developed and are outlined in the paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology for machine condition monitoring, this to overcome many of the difficulties with current methods and facilitating wider use of wear particle analysis in machine condition monitouing.

• International Journal of Fluid Machinery and Systems
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• 제9권2호
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• pp.137-142
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• 2016

Variable Geometry System (VGS) is widely applied to the nozzle vane for the radial inflow turbine constituting automotive turbochargers for the purpose of optimizing the power output at each operating condition. In order to improve the performance of radial turbines with VGS, it is necessary to clarify the influences of the setting angle of nozzle vane on the internal flow of radial turbine. However, the experimental measurements are considered to be difficult for the flow in radial turbines because of the small size and the high rotational speed. In the present study, the numerical calculations were carried out for the flow in the radial turbine at three operating conditions by applying the corresponding nozzle vane exit angles, which were set up in the experimental study, as the inlet boundary condition. The numerical results revealed the characteristic flow behaviors at each operating condition.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제24회 춘계학술대회
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• pp.60-67
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• 1996

This paper was undertaken to analyze the morphology of wear debris on operating condition of lubricated machine surfaces. The lubricating wear test was carried out under different experimental conditions using the wear test device was made in our laboritory and wear testing spcimen of the pin on disk type was rubbed in paraffine series base oil, by varying specimen, applied load, sliding distance. The four shape parameters (50% volumetric diameter, aspect, roundness and reflectivity) to describe morphology of wear debris have been developed and are outlined in the paper. A system using such techniques promises to obviate the need for subjective, human interpretation of particle morphology for machine condition monitoring.

• 전력전자학회논문지
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• 제25권6호
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• pp.451-458
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• 2020

In this study, a trade-off analysis of a power conversion system (PCS) is performed in accordance with a power semiconductor device to establish the suitable operating frequency range for the anyplace induction heating system. A resonant network is designed under each operating frequency condition to compare and analyze the PCS losses depending on the power semiconductor device. On the basis of the simulation results, the PCS losses and frequency condition are calculated. The calculated results are then used for a trade-off analysis between Si-MOSFET and GaN-HEMT based on PCS. The suitable operating frequency range is determined, and the validity of the analysis results is verified by the experiment results.