• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.291-297
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• 2003

Fluid film tilting pad journal bearings are widely used for large steam turbines. However, bearing problems by pad fluttering, such as fatigue damage in the upper unloaded pad, the break of locking pins and the wear of pinholes etc., are frequently taken place in the actual steam turbines. The purpose of the present work is to investigate on the mechanism of pad fluttering and the prevention of pad fluttering with the variation of preload(m) in a tilting pad journal bearing. It is estimated that upper pad is easy to flutter because the film shape of upper pad is diverged one from the analysis of moment direction acting on pivot point. Effective preload range in order to be statically loaded pad under all operating conditions is suggested as m＞0.5. Also, as a bearing that can be prevented pad fluttering, design modified bearing is suggested. For the adjustment in actual steam turbines, bearing and rotor dynamic analysis are performed to identify bearing characteristics and to verify the reliability of rotor-bearing system.

• The Journal of Korean Physical Therapy
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• v.32 no.1
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• pp.29-33
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• 2020

Purpose: This study examined the effects of the weight-bearing pattern and calcaneal taping on the heel width and plantar pressure in standing. Methods: Fifteen healthy subjects with normal feet participated in this study. The heel width was measured using a digital caliper, and a pedoscan was used to measure the plantar pressure of the rear foot while standing. The participants were instructed to stand in three weight-bearing patterns (anterior, middle, and posterior weight bearing) before and after calcaneal taping. The heel width and plantar pressure were measured three times before and three times after calcaneal taping, with the three weight-bearing patterns applied in random order. A 2 (non-taping vs. taping) × 3 (anterior, middle, posterior weight bearing) two-way repeated ANOVA with a Bonferroni post hoc correction was used to assess the differences in heel width and plantar pressure. Results: The results revealed a significant main effect of the weight-bearing pattern (p<.01), but not of calcaneal taping (p>.05). Greater weight bearing applied to the heel resulted in a significantly increased heel width and planter pressure of the rear foot (p<.01). Conclusion: In standing, a posterior weight-bearing pattern increases the heel width due to side-to-side shifting of the plantar heel pad, which increases the heel plantar pressure. Therefore, to prevent high stress on the heel pad and plantar heel pain, it is important to refrain from posterior weight bearing while standing during the activities of daily living.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.6
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• pp.635-640
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• 2014

Detection and diagnosis of incipient bearing fault in an induction motor is important for the prevention of serious motor failure. This paper presents an analysis of the effect of a faulty bearing on the stator current of an induction motor. A bearing fault leads to torque oscillations which result in phase modulation of the stator current. Since the torque oscillations cause specific frequency components at the stator current spectrum to rise sharply, the bearing fault can be detected by checking out the faultrelated frequency. In this paper, a mathematical model of the load torque oscillation caused by a bearing fault is presented. The proposed model can be used to analyze the physical phenomenon of a bearing fault in an induction motor. In order to represent the bearing fault effect, the proposed model is combined with an existing model of vector-controlled induction motors. A set of simulation results demonstrate the effectiveness of the proposed model and represent that bearing fault detection using a stator current is useful for vector-controlled induction motors.

• Tribology and Lubricants
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• v.13 no.1
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• pp.76-81
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• 1997

The lubrication characteristics of high-speed roller bearings at oil-starvation have been investigated empirically using the bearings employed in small industrial gas turbine engines. Testing was done by simulating the oil-starvation conditions in engines, such as stopping the oil-supply to the bearing during normal operating, starting without oil-supply at atmospheric temperature, and accelerating with oil-supply at atmospheric temperature. During testing, the temperature of bearing, the power consumption, and the rotating resistance of the bearing were measured. From this study, on the contrary to the ball bearing, it was found that the resistance of the bearing was higher at the regime of without oil-supply than that at the regime of with oil-supply, despite less power consumption.

• Ocean Systems Engineering
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• v.6 no.2
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• pp.191-201
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• 2016

Stern bearing is a key component of marine propulsion plant. Its environment is diverse, working condition changeable, and condition severe, so that stern bearing load is of strong time variability, which directly affects the safety and reliability of the system and the normal navigation of ships. In this paper, three affecting factors of the stern bearing load such as hull deformation, propeller hydrodynamic vertical force and bearing wear are calculated and characterized by random theory. The uncertainty mathematical model of stern bearing load is established to research the relationships between factors and uncertainty load of stern bearing. The validity of calculation mathematical model and results is verified by examples and experiment yet. Therefore, the research on the uncertainty load of stern bearing has important theoretical significance and engineering practical value.

• Tribology and Lubricants
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• v.12 no.3
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• pp.63-71
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• 1996

The connecting rod bearing, which is subjected to periodical dynamic loading, is an impoRant component of the reciprocating engine. In the operation of this bearing, significant parameters are the oil film thickness and the film pressure. Peak film pressures of 20-30 MPa are not uncommon. So the elastic deformation of the bearing housing can have a significant effect on the bearing performance. In this study, a numerical analysis of connecting rod bearing is investigated. Elastic deformation of the bearing housing is considered in the analysis. Separate hydrodynamic and structural analysis are coupled through a direct iterative process. It is shown that as the result of the elastic deformation of the bearing housing, the eccentricity ratio is increased, and the minimum value of the minimum film thickness and the maximum value of the maximum film pressure are decreased. The variations of rotational speed and cylinder pressure affect the minimum film thickness and the maximum film pressure variations of the connecting rod bearing.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1654-1663
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• 1994

Even if the ball bearing was conservatively designed considering the dynamic capacity and the rating life, sometimes the bearing was early failed on account of the misalignment and the lubricant contaminations etc. Misalignment was generated when bearing-shaft system transmitted large power and when the bearing was inadequately mounted. It was possible to predict the fatigue life of ball bearing under the misalignment considering the motions of ball, cage and raceway, and the factors of the effect on fatigue life. Misalignment affected on ball bearing as radial and moment load and the relationships between misalignment and moment were obtained. In this paper, the analysis of the load distributions between ball and raceway, and the prediction of fatigue life of deep groove ball bearing under radial and moment loads were carried out. And, the new formulation of equivalent dynamic load considering the effects of moment load was proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.578-583
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• 1997

Abstract-Crosshead bearing in two-stroke marine diesel engine is operated under quite severe condition since the load on the bearing is sybject to the loading in a unidirectional and the sliding speed is very slow and oscillatory. So it is very difficult to form oil film and maintain the load. In this paper, two types of bearing are compared. One has large sized oil pocket and the seleted as multi-small oil grooves. Bearing clearance, oil inlet oressure and bearing types are selected as analysis parameters. Loci of journal center are presented to compare several cases. It is found that bearing clearance and shape affect to minimum film thickness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.8
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• pp.2501-2507
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• 1996

In this paper actively controlled air bearing is investigated to overcome the defects of air bearing such as low stiffness and damping coefficients. The actively controlled air beairng is composed of an air bearing, a gap sensor, a controller, and a piezo actuator. By controlling the position of air bearing with piezo actuator, the position of floating object is controlled. In this study the proportional-Integral-Derivative controller is employed. Active air bearing is investigated numerically and experimentally. There is good agreement between the simulation and the experimental results. It is shown that the stiffness and damping characteristics and positioning experimental results. It is shown that the stiffness and damping characteristics and positioning accuracy of air bearing can be improved by means of adopting actively controlled air bearing.

• Tribology and Lubricants
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• v.2 no.1
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• pp.69-77
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• 1986

The motion of journal in a bearing is considered separately as rotation and translation, and then the equations of motion are derived. The bearing load capacities for these motions are calculated from the lubrication theory. The numeric integration of the equations of motion gives various journal orbit depending on force cycles and bearing parameters.