• Tribology and Lubricants
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• 제28권1호
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• pp.33-37
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• 2012

Automotive wheel bearing grease helps to reduce stresses and prevent wear of wheel bearings. But it is easily contaminated by water and other contaminants. Previously, our research group reported the change of grease physical properties such as dropping point, work penetration and oxidation work stability, water washout characteristics, leakage tendency, oil separation, evaporation loss and rust protection by water contamination. In this paper, we analyzed the physical characteristics of grease such as lubricity, viscosity and total acid number to investigate the mechanism of thickener decomposition. In water contaminated grease, the total acid number and wear scar were increased, the viscosity was decreased due to the decomposition of lithium complex thickener.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.310-314
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• 1999

A prototype of Flywheel Energy Storage System with high Tc superconducting bearings was fabricated and tested to verify its applicability for the energy industry. The moment of inertia of assembled wheel with rotor magnets is about 1.072${\times}$10$^{-1}$ Kg-m$^2$. The wheel was designed to withstand its integrity up to the rotation speed of 20,000 rpm. YBCO bulk superconductors prepared by seed growth method were used as bearing to levitate and stabilize the rotating wheel. High speed rotation of the flywheel without mechanical contact was achieved by using specially designed Halbach type motor. The flywheel system showed very high stability during test operation performed up to the speed of about 10,000rpm. The energy loss measured by free decay test performed between 9,300 rpm and 7,000 rpm was calculated as about 45 W.

• 한국융합학회논문지
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• 제11권11호
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• pp.47-53
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• 2020

최근 모니터링 및 예측 시스템을 이용하여 사전에 결함을 발견하고 이를 경고하는 시스템이 활발히 연구되고 있다. 차량 안전 관리에 있어서도 예측 결함 분석 기술을 적용하여 자동차 휠 베어링의 고장 유무 및 고장 유형을 조기에 경고하는 시스템이 필요하다. 본 논문에서는 휠 베어링과 결합 된 센서 모듈과 각 센서 모듈에서 차량 가속 정보 및 진동 정보를 수집, 저장 및 분석하는 진단 시스템을 제시하였다. 제안된 센서 모듈은 저비용으로 차량의 휠 베어링 상태를 모니터링하며, 이렇게 수집된 데이터를 활용하여 진단 및 고장 예측 기능을 수행하는 방안을 연구하였다. 개발된 센서 모듈과 예측 분석 시스템은 가진 테스트 장비 및 실제 차량을 이용하여 테스트하고 그 유효성을 평가하였다.

• 한국정밀공학회지
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• 제13권10호
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• pp.139-145
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• 1996

The machining accuracy and performance is largely influenced by the static, dynamic and thermal characteristics of spindle systems in machine tools, because the spindle system is a intermedium for cutting force from tool and machine powef from motor. Large cutting force and power are transmitted by bearing with a point or line contact. So, the spindle system is the static and dynamic weakest point in machine structure. For improvement of static stiffness of spindle system can be changed design parameters, such as diameter of spindle, stiffness of bearing and bearing span. But for dynamic stiffness, the change of the design parameters are not useful. In this paper, the combined bearing arrangement is suggested for high damping spindle system. The combined bearing arrangement is composed of tandem double back to back arrangement type ball bearins and a high damping hydrostatic bearing. The variation of static deflection and amplitude in first natural frequency is evaluated with the location of hydrostatic bearing between front and rear ball bearing. The optimized location of hydrostatic bearing for high static and dynamic stiffness is determined rapidly and exactly using the mode shape and transfer function of spindle. The calculation of damping effect on vibration by unbalance of grinding wheel and pulley in optimized spindle system is carried out to verify the validity of the combined bearing arrangement. Finally, the simulation of grinding process show that the surface roughness of workpiece with high damping spindle system is 60% better than with ball bearing spindle system.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.117-121
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• 2005

In this paper, an approximate time-effective approach to rigid-plastic finite element method is presented with its solution scheme and a volume compensation method is proposed to simulate rotary forging processes. The applicability is examined by comparing the results obtained by the presented approach with those by the conventional approach. The approach is applied to simulation of a rotary forging process fur a wheel bearing assembly. The analyzed results are compared with the experimental results.

• International Journal of Precision Engineering and Manufacturing
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• 제8권1호
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• pp.32-37
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• 2007

The outer diameter finishing grinding process required for ferrules, which are widely used as fiber optic connectors, is carried out by high-precision centerless grinding machines. In this study, the thermal characteristics of such a machine, for example, the temperature distribution, temperature rise, and thermal deformation, were estimated based on a virtual prototype and the heat generation rates of heat sources related to normal operating conditions. The prototype consisted of a concrete-filled bed. hydrostatic grinding wheel (GW) and regulating wheel (RW) spindle systems, a hydrostatic RW feed mechanism, a RW swivel mechanism, and on-machine GW and RW dressers. The reliability of the predicted results was demonstrated using temperature characteristics measured from a physical prototype. The predicted and measured results indicated that this particular high-precision centerless grinding machine had very stable thermal characteristics.

• 한국생산제조학회지
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• 제9권4호
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• pp.34-47
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• 2000

Since carbon fiber epoxy composite materials have excellent properties for structures due to their high specific strength, high specific modulus, high damping and low thermal expansion, the hollow shafts made of carbon fiber epoxy composites have been widely used for power transmission shafts for motor vehicles , spindles of machine tools, motor base, bearing mount for tool up and manufacturing. The molded composite machine elements are not usually accurate enough for mechanical machine elements, which require turning drilling , cutting and grinding. The experiment are surface grinding wheel GC60 to the carbon fiber epoxy composite specimen with respect to staking angle [0]nT , [45]nT, [90]nT on the CNC grinding machine. In this paper, the surface grinding characteristics of composite plate, which are surveyed experimentally and analytically with respect to the grinding force, surface roughness and wheel loading according to the variable depth of cut, wheel velocity and table feed rate are investigated.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1995년도 추계 학술발표 강연 및 논문개요집
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• pp.113-114
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• 1995

• 한국항공우주학회지
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• 제31권3호
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• pp.101-110
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• 2003

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.231-232
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• 2007