• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.06a
• /
• pp.177-178
• /
• 2008

• Tribology and Lubricants
• /
• v.21 no.1
• /
• pp.39-45
• /
• 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.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.961-966
• /
• 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.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.35 no.6
• /
• pp.128-137
• /
• 2023

In this study, the bearing pressure on the rubble mound of a gravity-based harbor structure with an arbitrarily shaped bottom was targeted. Assuming that the bottom of the structure is a rigid body, the rubble mound was modeled as a linear spring uniformly distributed on the bottom that resists compression only, and the bearing pressure evaluation formula was derived. It was confirmed that there were no errors in the derivation process by showing that when the bottom was square, the derived equation was converted to the equation used in the design. In addition, the validity of the derived equation was proven by examining the behavior and convergence value of the bearing pressure when an arbitrarily shaped bottom converges into a square one. In order to examine the adequacy of the method used in the current design, the end bearing pressure for the pre-designed breakwater cross-section was calculated and compared with the values in the design document. As a result, it was shown that the method used for design was not appropriate as it gave unsafe results. In particular, the difference was larger when the eccentricity of the vertical load was large, such as in the case of extreme design conditions.

• Nuclear Engineering and Technology
• /
• v.37 no.6
• /
• pp.565-574
• /
• 2005

The CANFLEX Mk-V bundle is designed to improve upon the critical heat flux (CHF) characteristics of the CANFLEX Mk-IV bundle. The main difference between these two bundles is an increase in bearing pad height of about 0.3 mm in the CANFLEX Mk-IV bundle. This change in bearing pad height leads to an increase in gap flow at the bottom of the bundle, primarily eliminating the localized narrow-gap effect that limits the CHF of the CANFLEX Mk-IV bundle. The objective of this paper is to examine the effects of bearing pad height and pressure tube creep on the sheath-temperature distribution, dryout power, and dryout location, as observed ken full-scale bundle tests, between CANFLEX Mk-IV and Mk-V bundles In uncrept and crept channels. A comparison of surface-temperature differences between the top and bottom elements of the bundles showed that increasing the bearing pad height has led to a more homogeneous enthalpy distribution in subchannels of the bundle. Initial dryout locations of the CANFLEX Mk-V bundle were mainly observed at the mid-spacer plane of either the $10^{th}$ (about $80\%$) or $11^{th}$ ($20\%$) bundle in the 12-bundle string, as compared to the mid-spacer and downstream-button planes for the CANFLEX Mk-IV bundle. Dryout power and boiling-length-average (BLA) CHF values exhibit consistent trends and little scatter with varying flow conditions for both types of CANFLEX bundles in uncrept and crept channels. An increase in pressure tube creep has led to a reduction in dryout power (about $20\%$ far the $3.3\%$ crept channel and $27\%$ for the $5.1\%$ crept channel as compared to dryout powers for the uncrept channel). Increasing the bearing pad height of the CANFLEX bundle has led to an increase in the dryout power. Overall, the dryout power of the CANFLEX Mk-V bundle is 7 to $10\%$ higher than that of the CANFLEX Mk-IV bundle at the inlet temperature range of interest (i.e., between 243 and $290^{\circ}C$).

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.355-358
• /
• 2003

This paper presents characteristics of vacuum preloaded porous air bearing. Pressure distribution of a porous pad and vacuum pocket are calculated. And load capacity and stiffness of the bearing are analyzed with various vacuum parameters, that is. clearance height. tube diameter, tube length. pumping speed of vacuum pump, vacuum pocket to porous pad area ratio. From the simulation results, optimum clearance for best performance can be selected adjusting these parameters, especially tube diameter which is the most dominant source.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1993.12a
• /
• pp.63-69
• /
• 1993

In this paper the characteristics of Hydrostatic Bearing of piston of cylinder are investigated . The dynamic characteristic equations of piston considering both parallel and rotational motion and time dependent modified Reynolds Equation are analyzed and the dynamic pressure distribution of oil film is numerically calculated by perturbation method and finite difference method. and the atatic analysis is carried out. so, the influence of design parameter of piston on the characteristic of bearing is analyzed.

• Tribology and Lubricants
• /
• v.17 no.4
• /
• pp.297-306
• /
• 2001

Under the condition of variable density and specific heat, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined within some degree of Journal misalignment. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the condition of variable density and specific heat play important roles in determining friction and load of Journal bearing at high speed operation.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.2
• /
• pp.244-251
• /
• 1999

Large dynamic loads act on the rotor in rotary compressors. There are unbalance forces due to eccentric rotation parts and gas forces induced by the pressure difference between compression and suction gases. Rotor-journal bearing system is nonlinear since the stiffness and damping coef-ficients of the lubrication oil film are not constant in the bearings. in this paper the program for predicting the behaviors of rotor-journal bearing system of rotary compressor is developed. Finite element modeling is used to analyze the flexible rotor. The numerical results are compared with experimental results.

• Physical Therapy Rehabilitation Science
• /
• v.6 no.4
• /
• pp.159-163
• /
• 2017

Objective: Persons with stroke have a tendency to exhibit asymmetric weight-bearing during sit-to-stand because due to the attempt to support themselves with the non-paretic foot. However, there are few devices that can assist with sit-to-stand (STS) performance. This study was designed to investigate the use of the elastic band with rings (EBR) in improving weight-bearing effectively in persons with stroke during STS training. Design: Cross-sectional study. Methods: Thirteen stroke survivors participated in the study. An EBR was applied onto the patient during STS activity. The foot pressure was measured before and after wearing the EBR, with a 5-minute rest period between measurements. Subjects were asked to perform each test twice with and without the EBR. Bilateral feet pressures were measured with standing posture being divided into the forward and backward aspects. The foot contact pressure during STS activity was measured with the CONFORMat System. Results: With EBR, the forward pressure of the affected foot significantly increased while the less-affected forward foot pressure significantly decreased (p=0.015 and p=0.023, respectively). The backward foot pressure did not differ significantly in the two limbs, and there was no difference with and without the EBR in terms of the total pressure of the affected foot. There was a significant difference with and without the EBR in the total pressure of the less-affected foot (p<0.05). Conclusions: STS training with the EBR has been shown to improve weight-bearing of both feet while decreasing the total pressure of the less-affected foot in stroke survivors. Therefore, we suggest that the EBR is a useful tool for STS training for persons with stroke in the clinic.