• Tribology and Lubricants
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• 제20권3호
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• pp.140-144
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• 2004

Water-lubrication ball bearings are required to install in aqueous medium where water is used as coolant or working fluid. However water-lubricated frictional characteristics of stainless steel ball bearing is not will known compared to oil-lubricated frictional characteristics. Furthermore study on friction at high temperature is rare because bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is mostly based on change of failed bearings and parts. Ball bearings and ball screws are used to transmit power in the control rod drive mechanism for an integral reactor and are lubricated with high temperature and high pressure chemically-controlled water. Bearings and power transmitting mechanical elements for a nuclear reactor require high reliability and high performance during estimated lifetime, and their performance should be verified. In this paper, experimental research results of frictional characteristics of water-lubricated ball bearing are reported.

• 한국분무공학회지
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• 제28권3호
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• pp.126-133
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• 2023

This study analyzes the flow characteristics and sponge ball recovery performance in a ball strainer according to vortex promoter design variables through flow-particle analysis based on actual experiments to derive a method for improving the recovery rate of cleaning sponge balls of CTCS applied to existing power plants. Based on the ball strainer in CTCS used in the power plant, the experiment was conducted by changing the design factor of the improved shape. In addition, flow and particle analysis were performed under the same conditions as the experiment to numerically the flow characteristics and recovery rate in the ball strainer according to the design factor of the vortex promoter. As a result of the study, it was confirmed that the recovery performance was improved by about 3% by changing the design height of the Vortex promoter. And when comparing the difference between maximum and minimum recovery rate, it was found that the effect on the recovery performance increased slightly according to the distance condition compared to the vortex promoter design height condition.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.122-128
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• 2009

이 논문에서는 모바일 환경에서 촉각적 사용자 체험 (User Experience)을 향상 시킬 수 있도록 디자인된 새로운 방식의 핸드헬드 볼 기반의 햅틱 인터페이스 "TouchBall" 을 소개하고 그 성능을 평가한다. 작은 모바일 디바이스(모바일 폰, PDA, PMP 등)에 적당하도록 볼 기반의 기계적 메커니즘을 사용하여 작은 회전력으로도 높은 감도의 다양한 촉감을 손에 전달할 수 있도록 구성되어 있다. 제안하는 인터페이스를 적용한 프로토타입 버전을 구현하였고, 정신물리학적 실험을 통해 사람의 감각 인식의 가장 기본적인 척도가 되는 감지 역치를 측정하였다. 그리고 구현 가능한 다양한 촉각 패턴들의 인식강도를 절대적 강도추정 방법으로 측정하여 정확도와 인식강도를 알아보고 그 응용 가능성을 찾아보았다.

• 한국분말재료학회지
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• 제19권2호
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• pp.122-126
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• 2012

The Fe-based self-fluxing alloy powders and TiC particles were ball-milled and subsequently compacted and sintered at various temperatures, resulting in the TiC particle-reinforced Fe self-fluxing alloy hybrid composite, and the microstructure and micro-hardness were investigated. The initial Fe-based self-fluxing alloy powders and TiC particles showed the spherical shape with a mean size of approximately 80 ${\mu}m$ and the irregular shape of less than 5 ${\mu}m$, respectively. After ball-milling at 800 rpm for 5 h, the powder mixture of Fe-based self-fluxing alloy powders and TiC particles formed into the agglomerated powders with the size of approximately 10 ${\mu}m$ that was composed of the nanosized TiC particles and nano-sized alloy particles. The TiC particle-reinforced Fe-based self-fluxing alloy hybrid composite sintered at 1173 K revealed a much denser microstructure and higher micro-hardness than that sintered at 1073 K and 1273 K.

• KSTLE International Journal
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• 제4권2호
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• pp.43-46
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• 2003

Water-lubricated frictional characteristics of a stainless steel ball bearings are not well known compared to the oil-lubricated frictional characteristics. Furthermore a study on friction at a high temperature is rare because the bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is generally based on the replacement of the failed bearings-and parts. Ball bearings and ball screw are installed in the power transmission for the newly developing integral reactor and these are lubricated with chemically-controlled pure water at a high temperature and a high pressure. Bearings and power transmitting mechanical elements for an atomic reactor requires high reliability and high performance during the estimated lifetime, and it should be verified. In this paper, experimental research results of the frictional characteristics for water-lubricated ball bearings are presented as a preliminary investigation.

• Progress in Superconductivity
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• 제10권1호
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• pp.17-22
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• 2008

We have examined the effect of ball-milling on the superconducting properties of $MgB_2$ doped with C. The ball-milling of pre-reacted $MgB_2$ powder was carried out in dry or wet state using C or diethylenetriamine ($C_{4}H_{13}N_3$) as additives. The diethylenetriamine, whose chemical formula contains no oxygen, was chosen to avoid an excess oxidation during doping. The superconducting transition temperature (Tc) of the ball-milled or doped $MgB_2$ powders was only slightly smaller than that of undoped $MgB_2$. The critical current density (Jc) of the highly ball-milled $MgB_2$ was higher than that of C-doped $MgB_2$. The addition of diethylenetriamine was detrimental to Jc, although Tc was almost unchanged.

• 한국응용과학기술학회지
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• 제36권2호
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• pp.448-455
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• 2019

본 연구는 오르막 퍼팅 시 좌, 우 경사에 따른 볼의 움직임이 어떻게 변화되는지에 대해 알아보는 것을 목적으로 한다. 본 연구를 위해 한국프로골프협회에서 15년 이상의 골프경기 경험이 있는 피험자들이 참여하였고, 본인들의 퍼터를 이용하여 실제 그린과 유사한 환경에서 퍼팅 동작을 수행하였다. 비디오 카메라를 이용하여 피험자들의 오르막 그린 경사에 따른 퍼팅 동작을 수집 후 동작분석을 실시하였으며, 통계적 유의수준을 a=.05로 설정하였다. 연구결과로 좌, 우 경사별 오르막 퍼팅에서 볼의 위치가 왼쪽에서 오른쪽으로 위치 할 때 볼 움직임의 속도와 각속도가 증가하는 것이 확인되었으며, 여러 경사도 중 성공률을 높여야 하는 오르막 퍼팅에서 경사에 따른 어드레스 볼 위치를 변화할 때, 임팩트 시 클럽 페이스와 볼 움직임이 어떻게 변화하는지를 검증하고, 현장적용 측면에 도움을 주는 과학적 자료를 제시하고자 본 연구를 진행하였다.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.1639-1644
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• 2015

볼밸브용 볼의 로봇 육성용접시스템에서 포지셔너의 설계 및 구조강도 해석에 관한 연구를 하였다. 포지셔너의 일부분인 터닝 유닛을 모델링하였고, 보로 가정하여 해석을 진행하였다. 볼의 무게가 $9,000kg_f$ 일 때 터닝 유닛에 가해지는 응력이 366.85MPa로 나왔다. 이 값은 재료의 항복강도보다 높은 값이다. 앞의 결과를 토대로 터닝 유닛을 수정하여 모델링을 하였다. 수정된 모델링으로 해석한 결과, 응력의 값은 296.11MPa로 확인되었다. 이 값은 재료의 항복강도보다 낮은 수치이며, 볼의 무게를 버티는 것을 알 수 있었다.

• 한국유체기계학회 논문집
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• 제18권5호
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• pp.13-18
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• 2015

This study has been performed to evaluate the safety of the retainer-type ball valve for a high-pressure pipeline to a district heating plant. The retainer-type ball valve is an improved design for conventional ball valves, such as the floating ball valve and the trunnion ball valve. Numerical analysis of the valve design verification has been applied to investigate the safety factor and seat leakage of the DN300 and DN400 sizes. The given condition to solve the structural analysis was based on the international standard for ISO 5208. In this study, the methods for structural analysis are described in detail. The structural analysis results present the deformations, the equivalent stresses, and the safety factors. Through these results, this study successfully demonstrates the safety and seat leakage of the retainer-type ball valve. They also streamline the process of development for valve manufacturing.

• Tribology and Lubricants
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• 제33권6호
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• pp.296-302
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• 2017

Ball milling of elemental powders in advance and using an induction heating system for intermetallic coatings are known to enhance the reactivity of combustion synthesis. In this work, the effects of simultaneously applying these two incentive methods on the properties of intermetallic coatings are studied. Ni-Al powder compacts ball-milled with three different ball-to-powder weight ratio mixtures are synthesized and coated on mild steel by combustion synthesis in an induction heating system. Consequently, similar to an electrical heating system, the positive effects of ball milling on the combustion synthesis are confirmed in the induction heating system. The enhancement in synthetic reactivity achieved by applying the two incentive methods at the same time is greater than that by applying each incentive method separately. In particular, the enhancement is remarkable at low reaction temperature. However, there are limitations to improving the reactivity by simultaneously applying the two incentive methods to the combustion synthesis, unlike the reaction temperature. The microstructure and hardness of the coating layer are both influenced by the ball-charging ratio employed in the ball-milling process.