• 한국기계가공학회지
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• 제6권1호
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• pp.43-49
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• 2007

Multi-function and miniaturization of the medical equipment and tele-communication systems need small and high precision machined parts. For the economic machining of the small size workpiece it should be machined by small and high precision machine tools with high speed machining. The belt type driving system in turning lathe has a limitation of spindle speeds because of the vibrations from driving mechanism, built-in type of driving mechanism is used to reduce the vibration. However, the main spindle of the built-in motor is connected directly to the motor, so the heat generation of the motor and bearing makes bad influence of the accuracy of machine tools. In this study, the analysis of heat generation from motor and bearings supporting main spindle and experiment were carried out. The results of theoretical simulation of temperature and deformation of the main spindle are good agreement with those of measured.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.886-891
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• 2000

One of the domestic co-generation plants have undergone excessive vibration problems of turbine attributed to external force for years. The root cause of turbine vibration may be shan alignment problem which sometimes is changed by thermal expansion and external farce, even if turbine technicians perfectly performed it. To evaluate the alignment condition from plant start-up to full load, a strain measurement of turbine and main steam piping subjected to thermal loading is monitored by using strain gages. The strain gages are bonded on both bearing housing adjusting bolts and pipe stoppers which. installed in the x-direction of left-side main steam piping near the turbine inlet in order to monitor closely the effect of turbine under thermal deformation of turbine casing and main steam piping during plant full load. Also in situ load of constant support hangers in main steam piping system is measured by strain gages and its results are used to rebalance the hanger rod load. Consequently, the experimental stress analysis by using strain gages turns out to be very useful tool to diagnose the trouble and failures of not only to stationary components but to rotating machinery in power plants.

• Earthquakes and Structures
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• 제3권5호
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• pp.767-781
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• 2012

The residual capacity against collapse of a main shock-damaged bridge can be coupled with the aftershock ground motion hazard to make an objective decision on its probability of collapse in aftershocks. In this paper, a steel tower suspension bridge with a main span of 2000 m is adopted for a case-study. Seismic responses of the bridge in longitudinal and transversal directions are analyzed using dynamic elasto-plastic finite displacement theory. The analysis is conducted in two stages: main shock and aftershocks. The ability of the main shock-damaged bridge to resist aftershocks is discussed. Results show that the damage caused by accumulated plastic strain can be ignored in the long-span suspension bridge. And under longitudinal and transversal seismic excitations, the damage is prone to occur at higher positions of the tower and the shaft-beam junctions. When aftershocks are not large enough to cause plastic strain in the structure, the aftershock excitation can be ignored in the seismic damage analysis of the bridge. It is also found that the assessment of seismic damage can be determined by superposition of damage under independent action of seismic excitations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1676-1681
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• 2004

The main reason for applying positive pressure variable clearance packing in fossil power plant is high efficiency and energy saving movement in the government. This study intends to analyze the turbine efficiency through the shaft packing improvement in thermal power plant and makes its comparison to that of the each packing type

• Journal of Biosystems Engineering
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• 제43권1호
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• pp.81-81
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• 2018

• 대한조선학회논문집
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• 제49권6호
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• pp.491-497
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• 2012

A hull-form for a 32,000G/T class Ro-Pax ferry has developed in accordance with a need of ferry operators to reduce fuel oil consumption(FOC) due to the drastic increase in oil prices recently and strengthening of environmental rules and regulations such as CO2 emission. A twin-skeg type is applied as the hull-form in lieu of an open-shaft type in order to improve propulsion performance. In order to achieve this object, flow control devices are installed to reduce a propeller induced vibration which is a main reason to obstruct the application of twin-skeg type passenger vessels owing to an uncomfortable vibration level. Numerical simulation by using an in-house code and a commercial code (Fluent) has performed to find out an optimum design of the flow control devices and to check an improvement in cavity volume. Model tests in Samsung Ship Model Basin are carried out to evaluate propulsion performance with the developed twin-skeg type hull and a reference hull of open-shaft type. In conclusion, it is shown that the twin-skeg type hull is better than the open-shaft in FOC by around 7% and in cavity volume by 20% as well.

• 대한기계학회논문집A
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• 제37권1호
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• pp.105-111
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• 2013

주축은 공작기계의 핵심요소로서 주축의 정 동적 특성은 공작물의 가공정밀도에 직접적으로 영향을 미친다. 주축의 특성은 축 크기, 베어링 간격, 내장모터의 위치 등에 의해 결정된다. 그러므로 축 크기, 베어링 간격, 모터위치의 선정은 주축 특성을 개선하는데 중요한 요소라 할 수 있다. 본 논문은 40,000rpm 고속주축의 정 동적 해석과 최적 설계에 관한 연구로, 유한요소해석과 최적화를 위한 통계분석을 하였다. 이를 위하여 반응표면법을 사용하여 목적함수와 설계변수를 최적화하였다. 최적화 대상은 주축의 고유진동수의 최대화와 변위의 최소화이다. 설계변수는 축길이, 축직경, 베어링 간격, 모터위치로 선정했다. 최적설계를 통해 도출된 설계안으로 초기모델보다 개선된 결과를 얻을 수 있었고, 본 연구의 결과를 주축 설계에 적용하면 주축의 정 동적 특성 개선에 도움이 될 것으로 기대된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.252-255
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• 2005

가스터빈 엔진은 작동시간이 축적됨에 따라 엔진 주요부품의 성능이 점차적으로 저하되며, 내부구성부품 사이에 결함이 발생하기도 한다. 이러한 엔진의 손상여부를 진단하기 위해 가스경로해석(GPA, Gas Path Analysis)이 사용되고 있다. 본 연구에서는 상용 프로그램에 의존하지 않고, 각 성능변수들과 측정 변수들과의 열역학적 민감도를 이용하여 엔진성능진단 코드를 개발하였으며, 스마트무인기용 터보축 엔진에 적용하여 엔진의 단일 성능 저하를 예측하여 보았다.

• International Journal of Fluid Machinery and Systems
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• 제3권2호
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• pp.102-112
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• 2010

Artificial heart pumps have attracted the attention of researchers around the world as an alternative to the organ used in cardiac transplantation. Conventional centrifugal pumps are no longer considered suitable for long-term application because of the possibility of occurrence of blood leakage and thrombus formation around the shaft seal. To overcome this problem posed by the shaft seal in conventional centrifugal pumps, the magnetically suspended centrifugal pump has been developed; this is a sealless rotor pump, which can provide contact-free rotation of the impeller without leading to material wear. In Europe, clinical trials of this pump have been successfully performed, and these pumps are commercially available. One of the aims of our study is to numerically examine the internal flow and the effect of leakage flow through the gap between the impeller and the pump casing on the performance of the pump. The results show that the pressure head increases compared with the pump without a gap for all flow rates because of the leakage of the fluid through the gap. It was observed that the leakage flow rate in the pump is sufficiently large; further, no stagnant fluid or dead flow regions were observed in the pump. Therefore, the present pump can efficiently enhance the washout effect.

• 한국정밀공학회지
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• 제21권2호
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• pp.43-51
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• 2004

In this paper, the element combination algorithm for designing an arbitrary type of the automatic transmissions is proposed. The powertrain simulation software using this algorithm is then developed. The deliveries of the angular velocities and torques are only considered for the motion characteristics of the automatic transmissions. The effects of the vibration and noise are not considered. The automatic transmission is defined by the basic elements, i.e., planetary gear set, clutch, brake, shaft, general gear, and inertia. The transmission system is defined by the combination of these elements. The element combination matrices automatically generate the equations of motion for each shift. The self error-correcting algorithm is also developed to verify the element combination algorithm. This automotive powertrain simulation/design software with user-friendly graphic user interface has two main modules. The first module, the automatic powerflow generation module, mainly consists of the automatic powerflow and component generation algorithms. This paper covers the theory and application for the first module. The second module deals with the automatic system generation algorithm and will be discussed in the second paper.