• 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.

• 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.

• 대한기계학회논문집A
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• 제25권5호
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• pp.899-905
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• 2001

The damage behavior of soda-lime glass was studied due to a steel ball of 1mm and 2mm at oblique impact test. The thickness of glass specimen were 3mm and 5mm and oblique degrees of impact were 90$^{\circ}$,70$^{\circ}$ and 50$^{\circ}$. After the steel ball impact test, the crack patterns were investigated using a stereo-microscope. In addition, the finite element method was performed to analyze the stresses distribution and variation in the oblique impacted glass by steel ball. As a result of the impact test, the crack length of 90$^{\circ}$impacted glass was the largest and that of 50$^{\circ}$impacted glass was the smallest. In particular, as the impact velocity and diameter of the steel ball increased, the difference of crack length was prominent. The finite element analysis showed the maximum principle stresses distribution in contact area of glass specimen. The result of analysis was accorded with the crack growth behavior by the oblique impact test.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1418-1423
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• 2004

High speed machining experiment on the heat-treated mold steel(STAVAX and CALMAX of hardness HRc 53) is carried using TiAlN coated ball endmill. Tool life and wear characteristics under the various machining parameters and cooling methods are investigated. Effect of cooling method on life and wear of the tool was compared. For most cases, tool life was not determined by the amount of wear but by th chipping on the cutting edge. It is found that tool manufacturer's cutting parameters generally agrees with the results of this experiment.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 춘계학술대회
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• pp.782-783
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• 2011

본 연구에서는 자동차 부품 가공공정에서 적용하는 캐스케이드 디버링(cascade deburring) 후 잔존하는 스틸볼(steel ball)을 자동으로 감지하기위한 시스템을 구현하였다. 구현된 시스템은 자화부, 검출부, 제어부, PC 모니터링부로 구성되었다. 스틸볼 착자화 및 감지 정밀도의 향상, 외부노이즈 대응능력 등의 환경 변화에 영향을 받지 않는 신뢰성이 뛰어난 성능을 갖는 시스템을 구현하고자 하였으며 이를 위한 미세 스틸볼 감지시스템의 착자화부를 구현하고 성능평가를 수행하였다.

• 자원리싸이클링
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• 제20권4호
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• pp.46-51
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• 2011

바렐도금에 사용되는 더미볼 스크랩에 함유되어 있는 주석 (Sn)을 회수하기 위하여 물리적 전처리, 침출 및 회수실험을 행하였다. 물리적 전처리를 통하여 철 성분의 회수율은 95% 이상 달성하였으며 또한, 후속 습식 공정에서 주석/니켈 분말에서 질산침출 조건에서 주석 성분의 회수율은 95% 이상의 결과를 얻었다.

• 한국공작기계학회논문집
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• 제17권1호
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• pp.7-15
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• 2008

Currently existing high-accuracy and high-speed die sets used in reciprocal press create scratches at the surface of guide posts, steel balls, and bushes due to vertical movement of balls with point-contacts between inner surface of bushes and guide posts. Consequently, accuracy of the die set and the life span of the metal mold are reduced. However, those scratches could reduce the pre-load of the steel ball. This research designed and developed a groove-type die set which improves life span of the die set by eliminating point-contacts of steel balls with guide posts. The guide post consisted of a steel-ball retainer, a steel-ball retainer stopper, a guide bush, a guide pin, a snap ring, and a spring. The steel-ball retainer has 72 holes with 8 columns of 9 holes in each column. The inner surface of the guide bush was grinded(surface roughness: $Ra\;\\;0.2{\mu}m$, accuracy: $0\;{\sim}\;-0.002mm$) after NC turning and heat treatment. Also, a line of small intermediate pocket was processed inside of the guide bush for lubrication and elimination of foreign materials. Guide grooves of steel balls were processed using a wire EDM(Electrical Discharge Machining) after heat treatment. With such a design of the guide post stated above, loads against steel balls could be dispersed greatly by the line contacts through the guide groove between the guide post and the guide bush, and the life span of the guide post could be expanded semi-permanently.

• 대한기계학회논문집A
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• 제29권9호
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• pp.1253-1261
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• 2005

Cast stainless steel (CSS) is thermally aged by a long term exposure in the range of nuclear power plant operating temperature. The thermal aging is a cause of concern for the continued safe and reliable operation of CSS nuclear components. Therefore, an assessment of degradation in material properties of these components has been importantly considered. In this study the ball indentation tests were performed on four cast stainless steels aged at $400^{\circ}C$ for 3600 hours, to investigate the applicability of ball indentation test to the assessment of aging degradation of cast stainless steels. Thus, the reliability of ball indentation test for aged CSS was analyzed by evaluating the scattering of data tested from each material and by comparing tensile properties obtained from ball indentation test and standard tensile test. Also, the tensile properties of aged CSS obtained from ball indentation test were compared with those predicted by the evaluation procedure developed on the basis of material database for aged CSS.

• 한국진공학회지
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• 제15권3호
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• pp.287-293
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• 2006

R.F. PACVD법을 이용하여, 벤젠을 반응기체로 사용하여 순수한 DLC필름을 증착하였다. DLC필름의 마찰마모특성은 시험 환경을 제어하기 위하여 챔버로 고립된 ball-on-disk형식의 마모시험기를 이용하여 측정하였다. 상대습도에 따른 필름의 마찰특성을 관찰하기 위하여, 상압에서 챔버 내의 습도를 0-90%로 조절하면서 관찰하였다. 그리고 상대면 물질의 영향을 알아보기 위하여 스틸볼과 함께 DLC필름이 코팅된 스틸볼을 사용하였다. 스틸볼을 사용시 습도가 0%에서 90%로 증가함에 따라 마찰계수가 0.025에서 0.2로 크게 증가하였다. Ferich debris가 생성되지 않는 DLC가 코팅된 볼을 사용하여 실험한 경우에, 마찰계수는 상대 습도가 90%인 경우에도 0.08정도로, 스틸볼을 사용하였을 경우보다 훨씬 더 낮은 습도의존성을 보여주었다. 스틸볼 사용시 나타나는 DLC필름의 마찰계수의 큰 습도의존성은 습도가 증가함에 따라 debris의 크기 증가와 함께 스틸볼의 마모로 인한 Fe-rich debris의 생성과 밀접한 관계가 있음을 확인 할 수 있었다. 그리고 스틸볼을 사용하여 90%의 습도에서 마모시험을 하는 중간에 습도를 0%로 변화시키며 관찰한 결과, 마찰계수 값이 급격히 감소하였다. 이와 같은 결과를 통하여, Fe-rich debris가 마찰계수에 미치는 영향은 debris내의 Fe원소가 습도에 매우 민감한 흑연상의 전이층을 형성시킨다는 것을 확인 할 수 있었다.

• Tribology and Lubricants
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• 제32권1호
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• pp.32-37
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• 2016

The wear characteristics of metal ball and seat in a metal-seated ball valve significantly affect the performances such as leakage and valve torque. In this work, the wear characteristics of metal ball and seat are experimentally investigated. A stainless steel ball and seat with a high corrosion-resistant coating are prepared and a component level test was performed. The hardness and surface roughness of specimens cut from the metal ball and seat are measured before and after the test using a micro-Vickers hardness tester and confocal microscopy, respectively. In order to assess the wear characteristics, the surfaces of the specimens are carefully examined after the test. The confocal microscope data show that the surface roughness values of both the ball and seat increase by a factor of 3-4, which may lead to an increase in valve torque. However, the wear of the seat is found to be more significant than that of the ball. In addition, a comparison of the surfaces of the ball and seat before and after testing revealed that adhesive and abrasive wear are the major wear mechanisms. The results of this study may aid in the design of metal-seated ball valves from the tribological point of view.