• 한국주조공학회지
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• 제29권1호
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• pp.45-51
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• 2009

Conventionally, Al-Sn bearing manufacturing involves casting the Al-Sn alloy and roll-bonding to a steel backing strip. This article will describe the microstructural control of Al-Sn metal bearing alloy following heat treatment. When the pure aluminum rod dipped in the melt of tin maintained below the melting point of aluminum, the melting of aluminum was accelerated with penetration of tin along the grain boundary of aluminum. The length of plate-shaped eutectic tin was decreased with heat treatment time. With even longer heat treatment time over 1 hour the length of eutectic tin didn't decrease any more, while resulting in coarsening of aluminum matrix. Exuded liquid of eutectic tin was formed at the surface of Al-Sn alloy after heat treatment even at below eutectic temperature.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1545-1551
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• 2002

The optical storage device has recently experienced significant improvement, especially for the aspects of high capacity and fast transfer rate. However, it is necessary to study a new shape of air bearing surface for the rotary type actuator because the optical storage device has the lower access time than that of HDD (Hard Disk Drives). In this study, we proposed the air bearing shape by using SA (Simulated Annealing) algorithm which is very effective to achieve the global optimum instead of many local optimums. The objective of optimization is to minimize the deviation in flying height from a target value 100nm. In addition, the pitch and roll angle should be maintained within the operation limits.

• 센서학회지
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• 제17권5호
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• pp.338-345
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• 2008

Steel bearing balls are important component in machines having moving parts. In this paper we describe a vision-based automatic inspection system designed for sensing defects on the surface of steel bearing balls. The system has a camera looking down over a rail on which balls roll. Two mirrors are installed at both sides of the rail so that the side parts of a ball can be well inspected. The entire ball surface can be sufficiently seen by taking three images at $120^{\circ}$ rotation interval. Defects are detected by thresholding the difference image between an image captured and the reference image of a good ball.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제29회 춘계학술대회
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• pp.182-188
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• 1999

A theoretical study of elastohydrodynamic lubrication of elliptical contacts with both rolling and spin has been carried out. A finite difference method and the Newton-Raphson method are applied to solve the problem. The velocity vectors resulting from combined spin and rolling/sliding motion lead to asymmetric pressure distributions and film shapes. Film contours and variations of the minimum and central film thicknesses are compared with various spin-roll ratios. At high spin-roll ratios the minimum film thickness is considerably reduced, whereas the central film thickness decreases less dramatically, The present numerical scheme can be used in the analysis of general elliptical contact problems.

• 소음진동
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• 제4권1호
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• pp.43-50
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• 1994

Chatter vibration of a rolling machine in steel plants has a significant effect on thickness quality of the products. The cause and mechanism of the mill chattering is addressed through measurement of vibration and dynamic torque. An FFT system and an FM telemetry system are employed to collect data at several locations of possible damages. The results reveal the followings as sources of the mill vibration. The first is defects in roller bearings of a work roll chock. The second is instability of an oil film bearing in a backup roll chock, which has been investigated with a theoretical model describing the phenomenon. Dynamic torque is not the direct cause of mill vibration but rather influenced by the vibration. Appropriate treatment methods are suggested to address each of the above sources.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2002년도 추계학술발표논문집
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• pp.81-90
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• 2002

Air entrainment of a winding roll with a nip roller was studied numerically. The amount of air entrainment between two rotating rollers was obtained by solving lubrication equation, Reynolds equation, which neglect the existence of a web. However, the numerical model of this study included the web existence, therefore it considered the two lubricating air films between a winding roll and a web and also between a nip roller and the web. The pressure profiles and gap profiles of the two films were obtained by solving lubrication equation for the two air films and force balance equation of the web. Ballooning phenomenon was examined in terms of nip force, wrap angle, web stiffness, web speed, and web tension. This ballooning phenomenon caused by the back flow of the air film blocked by the nip roller. Air entrainment of the two numerical models was compared.

• 동력기계공학회지
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• 제18권4호
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• pp.112-116
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• 2014

Roll and pitching motions of a vessel can seriously degrade the performance of mechanical systems and the effectiveness of personnel. Many studies on roll stabilization and trimming control system design have focused on stabilizing the vessel through the use of fins, tanks, rudders and flaps. However the ultimate objective of such approaches must be to improve boarding sensitivity. This paper presents an anti-seasickness bed that consists of a rotator and bearing system that does not make use of electric power. The advantages of this system are its simple construction, usefulness, and safe operation. In this study, the rotation angles of the upper plate of a bed according to change weight of the rotator have been calculated to determine the stability. As a result, it can be concluded that proposed stabilizing bed can be of practical use in the field.

• 한국정밀공학회지
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• 제30권12호
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• pp.1321-1325
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• 2013

In this paper, we proposed an air bearing stage with active magnetic preloads in vertical directions compensating motion errors and attenuating vibrations to improve dynamic characteristics. This preloaded design gives simpler configuration of the stage, and active control of preload can be used for compensating motion errors by feedforward method. To improve dynamic characteristics, vibration of the table is monitored by an accelerometer, and controlled by a DSP based digital controller with integrator and band pass filters for suppressing roll and pitch vibration modes. The modes were evaluated by measuring frequency response functions, and compared with compensated responses. This showed effective results for suppressing poorly damped regenerative vibration of air bearings.

• 한국주조공학회지
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• 제22권4호
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• pp.174-183
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• 2002

Twin-roll process is a relatively new continuous casting process which can produce high-quality strip products directly, and solidification rate can reach $10^3$ to $10^4$ K/s, leading to fine and uniform microstructures with enhanced mechanical properties. The strip casting condition for producing fine Al-Sn alloy strip was obtained experimentally, and defects appearing on the strip was examined. Crack formation and surface quality of the strip was found to depend mainly on process parameters such as melt temperature, roller gap and rolling speed. Sn structure of network type was observed in Al-20Sn and Al-40Sn alloy strips, and cell spacing of Al-40Sn alloy was smaller than that of Al-20Sn. Banding strength of the heat treated specimens increased with increasing of soaking time and temperature, and bonding strength of Al-20Sn alloy was more superior than that of Al-40Sn alloy. However wear resistance of Al-40Sn alloy contained large amount of soft Sn which possess good anti-friction characteristics was superior than that of Al-20Sn alloy.

• 한국융합학회논문지
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• 제8권5호
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• pp.179-184
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• 2017

테이퍼 롤러 베어링은 중량이 큰 승합차, 화물차, 열차에 사용되며, 큰 부하하중에서도 안정적으로 차량을 지지할 수 있다. 테이퍼 롤러 베어링 부품 중 케이지는 롤러 간 간격을 유지해 주며, 이를 통해서 마찰 방지 및 마모, 발열의 억제 등의 역할을 한다. 공진으로 인해 케이지가 심하게 변형되면 롤러가 구름을 하지 못하거나, 케이지를 이탈하는 경우가 발생하게 된다. 케이지는 경량화 추세에 따라 금속소재에서 플라스틱소재로 변화하고 있다. 본 논문에서는 "화물열차와 고속열차에 사용되는 테이퍼 롤러 베어링의 부품 중 하나인 케이지를 대상으로 연구하였으며" 케이지 재료에 따른 동특성 해석과 열차가 최고속도로 주행한다는 가정 하에, 최고속도에 해당하는 주파수의 고조파를 계산하고 공진범위를 피하기 위해 케이지의 설계 변수 중 가변이 쉬운 두께를 다르게 하여, 최적의 두께를 선정하고자 비교해석을 진행하였다. 재료에 따른 동특성 해석과 비교해석은 Abaqus 6.16을 사용하였다.