• Tribology and Lubricants
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• 제22권3호
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• pp.137-143
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• 2006

The sliding contact interface of machine components such as bearings, gears frequently operates in lubrication at the inception of sliding failure under high loads, speed and slip. The surface temperature at the interface of bodies in a sliding contact is one of the most important factors influencing the behavior of machine components. Most surface failure in sliding contact region result from frictional heat generation. However, it is difficult to measure temperature rise experimentally. So the calculation of the surface temperature at a sliding contact interface has long been an interesting and important subject for tribologist. The surface temperature rise is related in contact pressure, sliding speed, material properties and lubrication thickness. Though roughness, load, ect all of the condition, are same, film thickness varies with velocity. In this study, surface temperature rise due to frictional heating in lubrication is calculated with various velocities. Surface film shearing and dry solid asperity contact are used to simulate the change of frictional heat in lubricated contact

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.193-199
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• 2002

Analyzing working conditions with shape characteristics of wear debris in a lubricated machine, it can be effect on diagnosis of hydraulic machining system. And it can be recognized that results are processed threshold images of wear debris. But, in order to predict and estimate a working condition of lubricated machine, it is need to analysis a shape characteristic of wear debris and to identify. Therefor, If shape characteristics of wear debris are identified by computer image analysis and the neural network, it is possible to find the cause and effect of wear condition. In this stud)r, wear debris in the lubricant oil are extracted by membrane filter $(0.45{\mu}m)$, and the quantitative value of shape characteristic of wear debris are calculated by the digital image processing. This morphological information are studied and identified by tile artificial neural network. The purpose of this study is to apply morphological characteristic of wear debris to prediction and estimation of working condition in hydraulic machining systems.

• Tribology and Lubricants
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• 제23권3호
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• pp.123-129
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• 2007

This paper presents a theoretical model for the analysis of double-bumped AFBs. The stiffness and damping coefficients of the double bump vary depending on the external load and its friction coefficient. In the case of a lightly loaded condition where only the upper bump contributes to deformation, the double bump is in the single active region. In the case of a heavily loaded condition where both the upper and lower bumps contribute to deformation, the double bump is in the double active region. So the double bump can be either in the single or double active region depending on vertical deflection. The equivalent stiffness and damping coefficients of the bump system are derived from the vertical and horizontal deflection of the bump, including the friction effect. A static and dynamic performance analysis is carried out by using the finite difference method and the perturbation technique. The results of the performance analysis for a double-bumped AFB are compared with those obtained for a single-bumped AFB. This paper successfully proves that a double bumped AFB has higher load capacity, stiffness, and damping than a single-bumped AFB in a heavily loaded condition.

• 대한기계학회논문집
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• 제16권12호
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• pp.2261-2267
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• 1992

본 연구에서는 시일 립의 간섭량과 접촉력에 관련된 이론적 연구를 수행한다. 시일의 접촉면에서 축방향 접촉력이 크게 설계되면 시일 립 선단에서는 마찰과 마멸이 심하게 진행되어 시일수명을 크게 단출시킬 우려가 있고, 접촉력이 작으면 밀봉된 유 체의 누설유려가 증가되면서 볼과 레이스사이의 윤활상태를 나쁘게 하여 베어링 수명 을 크게 단축하는 결과를 초래하게 되므로 시일 립의 접촉력에 관련된 연구는 대단히 중요하다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.175-185
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• 2004

Rotating disks are used in various machines such as data storage device, gyroscope, circular saw, etc. Transverse vibration of a rotating disk is very important for the performance of these machines. This work proposes a method to suppress transverse vibration of a very flexible rotating disk in non-contacting manner. A system considered in this study is a very flexible rotating disk with a thrust bearing pad which is located underneath the rotating disk. The pressure force generated in the gap between the rotating disk and the thrust pad pushes the rotating disk in the direction of axis of rotation while the centrifugal force and the elastic recovery force push the rotating disk in reverse direction. The balance between these forces suppresses the transverse vibration of the rotating disk. A coupled disk-fluid system is analyzed numerically. The finite element method is used to compute the pressure distribution between the thrust pad and the rotating disk while the finite difference method is used to compute the transverse vibration of a rotating disk. Results show that the transverse vibration of the rotating disk can be suppressed effectively for certain combination of air bearing and operating parameters.

• Tribology and Lubricants
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• 제21권2호
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• pp.53-62
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• 2005

In this study a general Galerkin FE lubrication analysis method was utilized to analyze the complex lubrication performance of a spiral groove seal having an additional inner circular groove, which was designed for a chemical process mixer operating at a low speed of the maximum 500 rpm. Equilibrium seal clearance analyses under varying outer pressure revealed that the seal maintains a certain levitation seal clearance under the outer pressure of more than about 1.5 bar, regardless of a rotating speed. Also, under the normal outer pressure of 11 bar, the axial stiffness of the seal was predicted to have a high value of more than 7.0 e + 07 N/m, regardless of a rotating speed and thereby, the seal is expected to maintain a stable thickness of lubrication film under a certain external excitation acting. A seal levitation test rig was designed and constructed. Experimental results at 500 rpm agreed well with analytical predictions and the applied lubrication analysis method was verified.

• Tribology and Lubricants
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• 제21권1호
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• pp.8-15
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• 2005

In this study a general Galerkin FE lubrication analysis method is utilized to analyze the complex lubrication performance of a spiral groove seal, which is being designed and developed for a high-speed flying object application operating at a high-speed of over 50,000 rpm. As at the equilibrium seal clearance the axial stiffness of the seal is predicted to have almost such a constant high value of $1.04\times10^8\;N/m$ regardless of a rotating speed, the seal is expected to maintain a stable thickness of lubrication film under a certain external excitation acting. Also, as even at an ultra high-speed of 80,000 rpm the axial damping of the seal is shown to have a rotatively high value of 5,775 N-s/m, the dynamic stability of the seal system at the axial degree of freedom is assured well enough.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.111-121
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• 1997

The stability of a rotor-bearing system supported by swirl-controlled hybrid journal bearing with pair-type angled injection orifices is investigated for improvement of the whirl frequency ratio by allowing effective control of the tangential flow inside the bearing clearance, i.e., by achieving more freedom in controlling strength and direction of the supply tangential flow inside the bearing clearance. It is suggested that the system instability can be improved through the change of bearing dynamic characteristic parameters with the swirl control. The orifice diameter d$_0$ and recess injection angle $\alpha$ along with combinations of swirl/anti-swirl supply pressures and directions (3.0-3.0MPa, 4.0-2.0MPa, 2.0-4.0MPa) are selected for design parameters for swirl-controlled effective factors dependent on journal speeds (3000, 9000, 15000, 21000 rpm). It has been found that the orifice diameter do shows strong effects on effective maneuverability of direct-stiffness and direct damping values, while recess injection angle $\alpha$ results in substantial magnitude and direction of cross-stiffness. Specifically, recess injection parameters which are functions of angle of orifice feeding flow and recess dimensions showed very feasible effect on the stability of swirl-controlled rotor-bearing system.

• Tribology and Lubricants
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• 제20권2호
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• pp.68-76
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• 2004

Applying a general Galerkin FE lubrication analysis method to spiral groove dry gas seals, this study intends to analyze in detail the effects of groove design parameters, such as a spiral angle, groove width ratio, groove radius ratio, groove depth ratio, and groove taper ratio, on the lubrication performances of an opening force, leakage, axial stiffness and damping, and angular stiffness and damping at low and high rotating speeds: 3,600 and 15,000 nm. Results show that, for the primary design consideration performances such as the opening force and axial and angular stiffnesses, a spiral angle of $25^{\circ}$, a groove width ratio of 0.46, a groove radius ratio of 1.1, a groove depth ratio of 1.0, and a groove taper ratio of 0.0 are preferred. Where the recommended relatively low values of groove depth and taper ratios are to keep the axial and angular dampings positive or higher than 0 particularly at the high rotating speed.

• 대한기계학회논문집
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• 제8권2호
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• pp.111-118
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• 1984

본 연구에서는 상계해 이론으로부터 마찰 상수 m에 대한 해석을 시도하여 조 직의 치밀화, 링의 내경감소율 등의 소결금속에 대한 성형특성을 여러가지 상대밀도, 마찰상수에 대해서 계산했다. 실험은 철 분말 소결금속인 시편을 상대밀도가 0.75, 0.85, 0.9이고 링의 외경:내경:높이의 비가 6:3:1과 6:3.1:1.5로 제작했고, 평 금형 (parallel platens) 사이에서 여러가지 윤활상태로 시행하여 그 실험치와 이론치들을 비교 하였다.