• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.406-411
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• 2001

This paper shows the failure(wear) phenomena of automotive transmission bearings and investigate their characteristics. It was found that the wear mechanism was mainly abrasive wear by the presence of particles in the gear box and the balls was weared more severely than the other tribological contacting parts. The wear of balls alter the bearing contact angle and load ratings, and finally it cause the bearing failure. With close examination of the failed bearing, various countermeasures could be suggested.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.243-249
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• 2000

In case of the limitation of Deep RIE fabrication for Micro Gas Turbine, bearing aspect ratio is limited in very small value. The characteristics such as pressure distribution load capacity and non-linearity of a short bearing of L/D=0.083 and a conventional bearing of L/D=1.0 with coupled boundary effects are investigated far Micro Gas Tlubine bearings. The coupled efffect was analyzed by mass conservation at coupled end area. The results, increasing load capacity and non-linearity due to the coupled effect of thrust and journal bearing, are obtained and the selection of journal bearing type is discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.75-78
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• 2005

In this paper, an experimental study on porous air bearing stiffness for ultra precision positioning system was performed. In general manufacturer provide bearing stiffness under specific air pressure, but the air pressure used in the field is different. Therefore it is necessary to know the stiffness of air bearing under the pressure used in the field. In order to know that, experimental device which can realize actual operating conditions was made. Using this device, static and dynamic stiffness of air bearing can be obtained. As a result, displacement error occurred around 1 $\mu$m at recommended load.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.15 no.1
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• pp.9-21
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• 2009

Purpose : To know how much weight bearing on left and right leg on 14 different positions. The second is to know how about different the weight bearing ratio on same positions of ages group. Methods : The third is to know how about changes the weight bearing ration between exercise group and non exercise group. The group of age is divided 20s, 30s, 40s, 50s, over the 60 years. The subjects are 93 males(44), females(49). Results : The ordering of ratio of weight bearing on one side leg is as follows: The position of the highest weight bearing ratio is one leg standing with the other leg on chair(right 0.82, left 0.81) and the position of lowest weight bearing ratio is hooklying with natural leg position(both legs 0.08). There are statistically significant difference between right and left leg of weight bearing ratio on the 6 positions among the 14 positions. As for the ages, there are statistically significant difference on 5 different positions of 20 ages body weight bearing ratio between right and left leg. But as for the 50 ages there are no statistically significant difference on all of 14 positions between right and left leg body weight bearing. As for the exercise group there are statistically significant difference on only one position of one leg standing with the other leg on chair between right and left weight bearing ratio. But as for non exercise group there are statistically significant difference on 4 positions between right and left weight bearing ratio. Conclusion : When the therapist exercise with patient's always considerate of patient's position and weight bearing ratio.

• Tribology and Lubricants
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• v.22 no.6
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• pp.342-349
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• 2006

In this study, a dynamic behavior of rotor-bearing system used in CNG compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for roller bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at eccentric crank-pin part. And, the steady state displacements of the rotor are compared with a variation in stiffness coefficient of roller bearings. Results show that the loci of crankshaft considering unbalance forces and external compression forces are more severe in whirl motion than with only unbalance forces.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.2
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• pp.61-68
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• 1992

To meet the requirements for accuracy, productivity and reliability of machine tools, it is necessary to evaluate the chatter-free machining performance and to improve the dynamic performance of machine tools. In order to perform dynamic design of machine tools reasonably and effectively, the joint parts must be modelled accurately because their characteristics affect significantly on the total characteristics of machine tool. In this paper, an approach which identifies the effect of joint parts on the performance of total machine tool structure was proposed. That uses the experimental modal analysis, the finite element method and the sensitivity analysis method. The effectiveness of this approach was confirmed by applying it to structures with bearing joints. And as a result of the application, the change of dynamic characteristics of bearing joints was indentified.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.991-996
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• 2001

This study is the manufacture of solid lubricant oilless bearing using sintered parts. PTFE was as organic solid lubricant and $MoS_2$ as inorganic solid lubricant, and its characteristics were studied. Thickness of lubricant was suited 25~$100\mu\textrm{m}$ for lubricant characteristics. Curring temperature of MoS_2$ film was 12$0^{\circ}C$, 2 hours and that of PTFE film was $260^{\circ}C$, 20 minutes. The solid weight and solid volume of $MoS_2$ film was 51.7% and 27.4%, and that of PTFE was 44.9% and 24.3%. Chemical resistant of PTFE solid lubricant oilless bearing was excellent as salt test was 520hours, and usable temperature range was $-200~+280 ^{\circ}C$. Conduction of electricity can be increase by addition of graphite or $$\alpha$- PbO_2$. The electric conductivity was 100~180$\Omega$.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.1 s.24
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• pp.99-108
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• 2006

In this paper, we analyzed the characteristics of emitter geolocation coverage area within which the emitter lies with a specified probability based on the LOBs(Line of Bearing) of sensors. Stansfield and MSD algorithms were applied to calculate BPE(Best Point Estimate), EEP(Elliptical Error Probable) and CEP(Circular Error Probable), They used the weighting factors composed of ${\sigma}_{Phi}$ (bearing error), QF(quality factor), $P_{e}$ (probability being inside) to optimize the performance. The characteristics of EEP was investigated in the change of them and those of CEP was analyzed based on the deployment of sensors.

• Tribology and Lubricants
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• v.10 no.1
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• pp.46-55
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• 1994

The static and dynamic analysis of air lubricatied tilting pad journal bearing which considers tilting effect of each pad, preload but which neglects pad inertia effect and deflection are performed. A direct numerical method is used in evaluating the static characteristics such as load carrying capacity, friction force and small peturbation method is used for calculation of dynamic characteristics. Stiffness and damping coefficients are compared with the variation of the preload. And these coefficients are slightly decreased with increased compressibility number under the constant bearing load carrying capacity.

• Tribology and Lubricants
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• v.27 no.6
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• pp.338-343
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• 2011

Laser surface texturing (LST) methods are widely applied now to reduce friction and improve reliability of machine components such as thrust bearings, mechanical face seals and piston rings, etc. In this paper, the effect of dimple shapes on the lubrication characteristics of parallel thrust bearing are studied using a commercial computational fluid dynamics (CFD) code, FLUENT. Pressure and streamline distributions, variations of supporting load, leakage flow rate and friction force, are compared for three different dimple sectional shapes such as circle, pyramid and rectangle type. The lubrication characteristics are highly affected by dimple shapes and number of dimples. The pyramid type dimple shape can support the highest load while the rectangle type is the best in friction reduction.