• Tribology and Lubricants
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• 제21권1호
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• pp.39-45
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• 2005

Investigation of the mass effect on the journal traces in the clearance of engine bearing has been performed for better design of mass distribution of crank system components such as crank pin, piston, con-rod, balance weight, crank throw weight, etc. as well as for better oil reaction behaviors to the applied forces from the cylinder pressures on the bearing. In this preliminary study, crank pin traces in the engine bearing clearance are computed by varying the equivalent magnitude of crank pin mass that includes the masses of crank pin, piston, con-rod. etc.. while most previous studies regarding journal traces in the bearing clearance neglect the inertia effects of crank pin mass. Although the inertia effect of pill mass is negligibly small compared to viscous force by ${\pi}bearing$ theory, it is found that it gives a great amount of influences on the journal traces in full bearing computation $(2\pi\;bearing\;theory)$ under the dynamic loading conditions.

• Tribology and Lubricants
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• 제12권3호
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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.

• 대한기계학회논문집
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• 제18권7호
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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.

• 대한기계학회논문집A
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• 제24권3호
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• pp.543-549
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• 2000

Results of theoretical investigations of the stability characteristics of an actively controlled externally pressurized air journal bearing are presented. Proportional control and derivative control are used for the control algorithm of active air bearing. The stability characteristics of the actively controlled bearing operating at zero steady-state eccentricity is investigated with the step jump method. The speed at onset of instability is raised for both proportional control and derivative control of bearing. Proportional control increased the stability threshold without affecting the whirl ratio. But for derivative control of bearing, stability threshold increase is accompanied by a parallel reduction of the whirl ratio. Results show active control of bearing can be adopted for the stability improvement of air journal bearing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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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.

• 대한기계학회논문집A
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• 제20권8호
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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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.961-966
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• 2004

The cylinder without seal has a piston with air bearing which is partly cylindrical and conical shape. The description of system geometry is deviation by the flow rate equation. Then pressure distribution and bearing force equations are derived. Several non-dimensional parameters are suggested. The relationship among bearing force, leakage flow and geometry of the bearing is investigated by simulation. And determination method for optimal design of sealless cylinder is given. A prototype of sealless cylinder which had rod bearing with four pockets, five pockets, and six pockets was built respectively. As a result of leakage flow test, it is evaluation to air bearing in sealless cylinder.

• 한국산업융합학회 논문집
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• 제24권6_1호
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• pp.659-667
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• 2021

This paper develops the theory for a novel fault-tolerant, permanent magnet biased, 4-active-pole, double plane, homopolar magnetic bearing. The Lagrange Multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrices for the failed bearing. If any of the 4 coils fail, the remaining three coil currents change via a novel distribution matrix such that the same opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. Magnetic flux coupling in the magnetic bearing core and the optimal current distribution helps to produce the same c-core fluxes as those of unfailed bearing even if one coil suddenly fails. Thus the magnetic forces and the load capacity of the bearing remain invariant throughout the failure event. It is shown that the control fluxes to each active pole planes are successfully isolated. A numerical example is provided to illustrate the new theory.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.199-206
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• 2002

This paper describes a reliability characteristics of an air foil journal bearing for high speed turbomachinery at room temperature. To verify the reliability of air foil journal bearing, lift-off characteristics, load carrying capacity, and 10,000 cycle start-stop test were performed with motor driven test rig. Lift-off test shows the relationship between the rotating speed of the shaft and the frictional torque with bearing surface. About load carrying capacity, the tested air foil journal bearing produced a load capacity of 500N at an operating speed of 15,000rpm, which is compared with results of numerical analysis and empirical coefficients. Finally, The trends in change of start torque, stop torque, and bearing temperature were shown during 10,000 cycle start-stop test of an air foil journal bearing. from the results of this work, an air foil bearing will be done well, as a supported bearing for high speed turbo-compressor.

• 한국정밀공학회지
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• 제23권1호
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• pp.145-151
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• 2006

Wheel bearing unit has been exclusively applied to car wheel supporting device. The seal for wheel bearing is required to have both high sealing effects and low reaction forces because wheel bearing are operated on adverse environmental conditions such as mud and splash water. High sealing effects are for the protection of bearing ball wear from dust influx. In order to ensure high sealing effects, it is a easiest way to increase contact force which are affected by geometric characteristics, material properties and interferences between seal and inner bearing but induces higher wear phenomena. Interferences in all variables are most important factor to determine the performance of wheel bearing. In this study, optimization of interference amount was performed with finite element analysis with commercial code ABAQUS. For the sake of finite element analysis, tensile tests of rubber material were conducted and governing equation of nonlinear behavior was achieved. Hock-up bearing was manufactured with optimized interference amount. Results of torque and mud spray tests using this bearing unit are performed. Less torque and moisture influx of bearing with optimized interference amount is evidence to validity of this study.