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

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.2 no.1
• /
• pp.34-39
• /
• 1999

Removal of spilled oil over the sea and the river has become one of the urgent problems in these days. Removing oil using mechanical devices by adhesion method is known to be closely related with the problem of estimating the thickness of film remaining on the surface of solid withdrawn from a quiescent liquid. In the present study a series of experimental results are compared with the analytic estimation for the thickness of film remaining on the solid surface using non-dimensional analysis. For the case of pure water both results show the remarkable agreement. However, discrepancy has been found for the case of Bunker C oil and diesel oil. The analytic estimation over-predicts the experimental value for the case of Bunker C oil and under-predicts it for the case of diesel oil. Further study is required to investigate the real situation including a contact angle and the property difference between oil and water.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1585-1590
• /
• 2002

This paper reports on the balance weight effect on the lubrication and friction characteristics of crankshaft system. To determine the main bearing loads, the crankshaft was treated as statically determinate system. Four and eight-balance weight crankshafts were considered, and minimum oil film thickness and friction loss were calculated. The main bearing loads were increased in the four-balance shaft due to the increasing of unbalanced rotating mass at No. 1 and 3 main bearing sides. The minimum oil film thickness of four-balance shaft became thinner than eight-balance, and friction loss was increased.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.8
• /
• pp.1183-1188
• /
• 2001

This paper reports on the starved lubrication for the piston ring. In this analysis, two types of inlet boundary conditions, fully flooded and starved condition, are considered at the leading edge. The inlet position of effective lubrication and squeeze term are obtained by numerically iterative method. The effective lubricated region is reduced due to the starved condition at the inlet. The starved condition at the inlet significantly reduced the minimum oil film thickness(MOFT) at the midstroke of piston, and the friction force is also increased due to the thin oil film thickness. In the starved conditions, the power loss is significantly increased.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.364-373
• /
• 2001

This paper describes the variation of lubricant's temperature effects on elastohydrodynamic lubrication. The Newton-Raphson technique was used to solve the simultaneous system of Reynolds and elasticity equations. To show effects of lubricant's temperature, average temperature across the oil film was calculated using the energy equation. Pressure distribution, film shape, and temperature distribution were obtained for fully flooded conjunctions, and various dimensionless speed parameters while load and material parameters were held constant. Minimum film thickness were obtained for various material properties while load and velocity were held constant. It is drawn that the thermal effects have a strong influence on a minimum film thickness under high rolling velocity and slip ratio.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.3 no.6
• /
• pp.55-68
• /
• 1995

Approximately 30 to 70 % of the mechanical losses in a reciprocating engine are contributed by the friction at the piston ring-cylinder interface. The friction characteristics of the piston ring during engine operation is known to as mixed lubrication experimentally. The mixed lubrication models based on the Average Reynolds Equation have been used by this time in order to study the tribological performance of the ring. However, the Average Reynolds Equation contains the expected value term(${\bar{h}}_r$) of local film thickness as well as nominal film thickness(h), so that the work of numerically solving ${\bar{h}}_r$ must be included to obtain the pressure in the oil film. The process of solving ${\bar{h}}_T$ causes a greater multiplying in the numerical solution. In this paper the mixed lubrication analysis using the Simplified Average Reynolds Equation in the piston ring is presented. This equation has only h as oil film thickness term. Therefore the tedious numerical procedure required to obtain ${\bar{h}}_T$ is not needed, and also, computation time can be reduced.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.113-114
• /
• 2002

Radial, tilting 12-pad proceeding bearings are applied as the radial bearings of vertical rotors of water turbines. The mean loads are stable at the peripheral speeds of proceeding reaching 50 m/s. The operation of tilting 12-pads proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions have been obtained by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss, oil flow, maximum oil film pressure, maximum temperature have been computed for different load angle of bearing.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.51 no.2
• /
• pp.140-148
• /
• 2024

This study aimed to enhance the physicochemical properties of sodium iodide-based root filling materials, particularly solubility. In earlier developmental stages, the iodoform-containing paste exhibited high antibacterial efficacy but failed to meet only the solubility requirement among the ISO 6876 criteria. Therefore, this study focused on enhancing the physicochemical properties of the paste under development, particularly centering on reducing its solubility. Four experimental groups were established, including three control group. The previously developed D30 paste was named the Oil 33 group, and the control group was named the Vitapex^® group. The Oil 50 group, in which the oil content was increased, and the Oil 45L group, in which lanolin was incorporated. The physical properties (solubility, pH, flowability, and film thickness) of the four pastes were evaluated according to the ISO 6876 standards. No significant differences were observed between the Oil 45L and Vitapex^® groups in any of the physical property evaluations. While the Oil 33 and Oil 50 groups met the ISO 6876 standards for flowability and film thickness, the Oil 45L group met all the physical properties. However, reducing the overall oil content may be necessary to enhance the antimicrobial properties. The result of the physicochemical experiments showed that the Oil 45L group with the newly formulated composition and incorporated lanolin exhibited low solubility meeting the ISO 6876 standard of ≤ 3%. We were able to develop a paste with more stable solubility than previous iodide-based root-filling materials. Therefore, the oil content must be further adjusted to improve its antimicrobial properties. If other physical properties also meet the ISO 6876 standards and demonstrate excellent results in cytotoxicity tests, this root filling material could potentially replace existing options.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1993.04a
• /
• pp.39-53
• /
• 1993

The minimum oil film thickness(MOFT) in the connecting-rod bering of a 1.5 liter, L-4, gasoline engine is measured up to 5500 rpm and calculated to study the dynamically loaded engine bearing. Short bearing approximation and Mobility method are used for theoretical analysis of oil film charactrtistics. And cylinder pressure, crank-pin surface temperature and bearing tenp ture are measured as the input data of theoretical analysis. The MOFT are measured by the total capacitance method(TCM). To improve the reliability of the test results, a reasonable detmuuination method of bearing clearance is introduced and used, and the effects of cavitation and aeration on the test results are neglected. The crankshaft is grounded by means of a slip ring. A scissor type linkage system was developed to measure the MOFT and bearing temperature. The effects of engine speed, load and oil viscosity on the measured and calculated minimum oil film thicknesses are investigated at 1500 to 5500 rpm. From the comparison between the measured and calculated MOFT, it is found that a qualitative similarity exists between them, but in all cases, the measured MOFT are smaller than those calculated.

• Tribology and Lubricants
• /
• v.10 no.1
• /
• pp.14-26
• /
• 1994

The minimum oil film thickness(MOFT) in the connecting-rod bearing of a 1.5 liter, L-4, gasoline engine is measured up to 5500 rpm and calculated to study the dynamically loaded engine bearing. Short bearing approximation and Mobility method are used for theoretical analysis of oil film characteristics. And cylinder pressure, crank-pin surface temperature and bearing temperature are measured as the input data of theoretical analysis. The MOFT are measured by the total capacitance method(TCM). To improve the reliability of the test results, a reasonable determination method of bearing clearance is introduced and used, and the effects of cavitation and aeration on the test results are neglected. The crankshaft is grounded by means of a slip ring. A scissor type linkage system was developed to measure the MOFT and bearing temperature. The effects of engine speed, load and oil viscosity on the measured and calculated minimum oil film thicknesses are investigated at 1500 to 5500 rpm. From the comparison between the measured and calculated MOFT, it is found that a qualitative similarity exists between them, but in all cases, the measured MOFT are smaller than those calculated.