• 기계와재료
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• v.21 no.2
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• pp.50-73
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• 2009

본 고는 중대형 풍력터빈의 핵심부품인 로터 블레이드, 대형베어링, 증속기, 발전기, 전략변환장치, 타워 등에 사용되는 주요재료에 대한 설명과 제조방법 및 평가 방법 등에 대해 다루어 졌다. 일반적으로 풍력터빈을 구성하는 소재는 금속소재와 비금속재료로 구분되며, 비금속재료는 대부분 복합재료로써 풍력 블레이드에 적용되고 있다. 현재 육상용 풍력터빈의 한계를 극복하기 위한 대안으로, 해상용 풍력터빈에 대한 관심이 집중되고 있으며, 이러한 극지 해상의 대형 시스템에 활용되고 있는 금속소재의 경우, 고강도, 저온인성, 내피로, 내식성 등이 우수한 강재를 요구하기에 이르렀다. 이에 따라, 여러 소재 측면의 요구를 충족하기 위한 소재설계의 비중이 점차 고조되고 있으며, 이러한 시점에 본 고를 통해 풍력터빈에 활용되고 있는 소재의 전반적인 내용과 관련 소재부품의 제조 및 평가 방법등의 이해를 돕고자 한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.746-752
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• 2011

In this paper, a novel bearingless switched reluctance motor (BLSRM) with double stator is proposed. This motor has two stators. Torque stator is outside, which mainly produces rotational torque. Radial force stator is inside, which mainly generates radial force to suspend the rotor. A novel structure and operating principle are presented. And characteristics of the proposed structure such as magnetic flux distribution, inductance, torque and radial force are analyzed through finite element method. From the analysis, the proposed BLSRM has linear characteristic of radial force and independence from torque current.

• Tribology and Lubricants
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• v.24 no.5
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• pp.228-233
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• 2008

In this study, the methodology for determination of shoulder height in the internal shape design of ball bearing using 3D contact analysis is proposed. The static analysis of a ball bearing was performed to calculate the distribution of applied contact load and angles among the rolling elements. From each rolling element loads and the contact geometry between ball and inner/outer raceway, 3D contact analyses using influence function are conducted. These methodology is applied to HDD ball bearing. A critical axial load and a critical shoulder height which are not affected by edge are calculated. The proposed methodology may be applied to other rolling element bearing for the purpose of reducing the material cost and improving the efficiency of the bearing design process.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.277-280
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• 2006

Using yaw system, Wind turbine can face the wind to make it's electricity generating maximum and to make it's fatigue load minimum. So, in wind turbine design process, selecting optimum yaw system is very important work. In this paper, the yaw moments on yaw bearing, yaw drive and yaw brake were calculated. and From the result, the duty cycle was obtained. At last, using this duty cycle, optimum yaw system is selected.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.742-747
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• 2000

The optical storage device has recently experienced significant improvements, especially for the aspects of high capacity and fast transfer rate. However, it is the fact that the optical storage device has the lower access time for the randomly scattered data compared to the hard disk drives. It is, therefore, necessary to develop a new type of optical storage system. In this study, we investigate the air bearing characteristics for the optical disk drives which have the swing arm actuator similarly to the hard disk drives. Considering the requirements of the optical disk drives, we parametrize the shape of the air bearing surface and investigate its sensitivity to the flying characteristics for further optimized design outputs.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.3
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• pp.62-72
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• 1995

The present study was undertaken to investigate the dry wear mechanism of the alumina ceramics in the purity variation for the wear of STB2. The wear test was carried out under different experimental condition various sliding speed, contact pressure and sliding distance. According as the alumina purity increased, wear volume of the STB2 decreased and minimum value of wear volume was over to high speed side. According as the sliding speed and sliding distance increased, friction coefficient decreased owing to drop of the shear strength, it decresed largely owing to decreased of elastic modulus and thermal conductivity with decrease in alumina purity. Indicative of minimum, value of wear volume, low speed side was abrasive wear, high speed side was wear of heat softening. The friction surface of ceramics protacted by oxide was transfer from STB2.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.391-398
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• 2020

If the lost energy produced by a propeller can be partially recovered, the propulsive efficiency can be increased, and the fuel consumption reduced. The devices installed for this purpose are called Energy Saving Devices, of which the Contra-Rotating Propeller system is one of the most effective devices. The first problem to be solved to install the Contra-Rotating Propeller system on a large ship is that the mean pressure generated in the journal bearing needs to meet the design criteria of the classifications. In Korea, however, the practical use is being delayed because it cannot overcome this step. The next step is to lower local pressure to increase the reliability. In this study, to solve the mean pressure problem as the first step of practical use, a product carrier with a short stern shape was selected to reduce the weight of the shafting system, and a suitable shafting-system design plan was proposed. Shaft analysis confirmed that the mean pressure of 0.8 MPa (8 bar), which is a design criterion of the classifications for a journal bearing lining material (white metal), was satisfied. In addition, the necessity of reducing the local pressure was also confirmed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.737-742
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• 2015

Course correction munition are a weapson system for precision attacks and are assembled by applying a ballistic control system to existing projectiles. The roll control system is a subsystem of the ballistic control system and is placed between the guidance and control units inside of the projectile, which undergoes a 5000g lateral acceleration. Thus, it is very important to design the system to endure this load. Many developed countries evaluate the performance and safety of course correction munitions' parts using live-fire gun launch tests or a soft recovery system. However, these methods are expensive and slow. Thus, in this study, we develop impact analysis model of the roll control system using CAE. We apply the code to simulate impact phenomenon and use Johnson-Cook material model for modeling the high strain rate effect on the materials. We also design bearings in detail to analyze their behavior and verify the reliability of CAE model through gas-gun impact tests of the roll control system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.669-677
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• 2009

In general, the pitch momentum biased system that induces inherently nutational motion in roll/yaw plane, has been adapted for geosynchronous communications satellites. This paper discusses the method of roll attitude control using yaw axis momentum management method for a low earth orbit(LEO) satellite which is a pitch momentum biased system equipped with only two reaction wheels. The robustness of wheel momentum management method with PI-controller is investigated comparing with wheel torque control method. The transfer function of roll/yaw axis momentum management system that is useful for attitude controller design is derived. The disturbance effect of roll/yaw axis momentum management system for attitude control is investigated to identify design parameters such as magnitude of momentum bias and to get the insight for controller design. As an example, the PID controller design result of momentum management system for roll/yaw axis control is provided and the simulation results are presented to provide further physical insight into the momentum management system.

• Journal of the Korea Convergence Society
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• v.9 no.5
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• pp.145-150
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• 2018

In the machine tool spindle, various tasks ranging from roughing to finishing must be possible, and the functions of constant speed movement or rotation positioning must be performed. Therefore, there are many variables to be considered in the spindle design. The Swiss Turn Type spindle automatic lathe is a good machine tool for working pins with thinner shafts than a fixed automatic lathe. The Swiss Turn Type spindle is mainly used for precision machining of small products, so the machining precision should be high. The maximum outer diameter limit shall be Ø32 and the inner diameter limit shall be Ø6. In this study, the static and dynamic characteristics of the SCM440 material used in the spindle type automatic lathe were analyzed by applying it to the Swiss turn type spindle automatic lathe. Numerical analysis was used to obtain optimal design technique with high speed and high accuracy considering the factors affecting the static and dynamic characteristics of the spindle.