• Journal of Advanced Marine Engineering and Technology
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• v.15 no.1
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• pp.59-70
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• 1991

Rupture of lubricant film, thermal characteristics, and variation of viscosity are very important factors to evaluate the performance of journal bearing. Variation of external conditions, load or rotational speed, largely influence these facters. For example, if rotational speed increases lubricant bulk temperature increases and viscosity drops. In this paper the effect of rotational speed variation on the characteristics of lubricant film in a journal bearing is investigated by experiment and theoretical analysis. It has been measured number of lubricant film rupture and lubricant bulk temperature form journal bearing which have been established at the various operating speed of shaft. The range of speed variation is from 900rpm to 2100rpm. Theoretical analysis has been carried out for rupture of lubricant film and thermal characteristics, and these results are compared with experimental results.

• Tribology and Lubricants
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• v.22 no.1
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• pp.26-32
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• 2006

This work analyzes the behaviors of aerated lubricant in the gap between con-rod bearing and journal. Aerated lubricant influences two major factors on the film formation. One is the density characteristics of the lubricant due to the volume change by the bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble. Those two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Modified Reynolds' equation is developed with the consideration of aerated ratio in the lubricant and journal locus is computed with the Mobility method after the computation of two dimensional pressure distributions over the bearing area.

• Tribology and Lubricants
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• v.11 no.5
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• pp.47-54
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• 1995

An advanced liquid lubricants for heat engines has been developed and tested successfully in a prototype engine. The lubricant possesses superior oxidation stability and high temperature stability and is capable of surviving for a minimum of three minutes at 425$^{\circ}$C (800$^{\circ}$C) at the ring zone and maintains stability at an oil sump temperature of 171$^{\circ}$C. The lubricant has been evaluated by the Cummins Engine Co. Out of a field of several dozens of lubricant, six lubricant was selected for a prototype 200 hours endurance testing. The NIST lubricant was one of the two lubricants that successfully finished the endurance testing. This paper describes the key lubricant considerations including oxidation and thermal stability, volatility, deposit control. The engine test conditions and the results will be presented.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.220-228
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• 2001

Journal locus with aerated lubricant is analyzed under the dynamic loading condition. In this analysis, we have found that aerated lubricant influences two major factors on the film formation. One is the density variation of the lubricant due to the volume change by the bubbles and the other is the viscosity changes of the lubricant due to the surface tension of the bubble. Those two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Modified Reynolds'equation is developed with the consideration of aerated ratio in the lubricant and journal locus is computed with Mobility method with the computation of two dimensional pressure distribution over the bearing area.

• Journal of the Korean institute of surface engineering
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• v.36 no.2
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• pp.176-184
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• 2003

New lubricant film of organic and inorganic composite resin was developed to improve the press formability of galvannealed steel sheets (GA) for automotive body panels. The frictional coefficient of lubricant GA steel sheets is about 20% superior to that of uncoated GA. The current range of spot welding of lubricant GA is similar to that of the uncoated GA, but the burning trace of spot welding is inferior to that of the uncoated GA in the oiling condition. The alkaline degreasability of lubricant GA shows 100% in alkaline degreasing condition of automotive company. The size and shape of the phosphated coating layer are similar to those of the uncoated GA sheet. The powdering property of the lubricant GA gives rise to 20∼50% improved property compared with the uncoated GA sheet.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.263-270
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• 1999

The characteristics of lubricant for computer hard disk was investigated by surface analysis technique. The bonding state between carbon and lubricant is analysed to indentify the origin of adhesion. It is found that the thickness of lubricant is increased as pulling-up speed becomes faster and lubricant concentration is increased. The dominant surface contaminants on carbon overcoat are identified with C-OH and CO. The bond strength between carbon and lubricant is enhanced with heat treatment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.149-154
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• 2007

The zinc prosphate film treatments used to lubricating treatment of mostly cold forging processes. But there are several problems happened to lubricating treatment process such as happening harmful environment on person, complex lubrication processing occurring in energy and time consumption, eco-destructive and chemical by-product generation, the needs of waste disposal etc. As a result, a water-soluble lubricant was developed to replace the perfect or some of the zinc prosphate film in the world. In order to solve these problems, this study evaluated the performance of the typical water-soluble. In this study, for these requirement inquiry of two part. First, about possibility of replace zinc phosphate lubricant, quantitatively evaluation developed of water-soluble lubricant for cold forging vs zinc phosphate lubricant. Second, About optimization of coating Process use to equipment with practicable automatic coating Process. The performance evaluation of these lubricants was conducted using the double cup extrusion test and spike forging test. With the use of the commercial FE code DEFORM, friction factor calibration curves, i.e. cup height ratio vs. punch stroke and spike height vs. punch stroke, were established for different friction factor values. By matching the cup height ratio and the punch stroke and spike height vs. punch stroke from experiment to that obtained from FE simulations, the friction factor of the lubricants was determined. Survey of comparative analysis use to SEM that sprayed lubricant surface structure of grain shape and characteristic of lubricant performance based on grain shape and deformed lubricant surface expansion. As a result, developed lubricant were found to perform comparable to or better than zinc phosphate. And thought this result, innovatively cope with generated problem of existing lubrication process.

• Tribology and Lubricants
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• v.24 no.4
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• pp.190-195
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• 2008

Many researchers have tried to improve the tribological characteristics of lubricant by adding various nano particles in the base lubricant. But the reliability evaluation of the lubricants are rarely performed in its real operation condition. In this study, the physical property and the tribological characteristics of the graphite nano lubricant were evaluated and compared with raw lubricant after thermal degrading. In order to evaluate the tirbological characteristics, the disk-on-disk tribotester was adopted to measure the friction coefficient of the graphite nano lubricants. Also the temperature variations of friction surfaces were measured by the thermocouple installed on the fixed plate in the test chamber of the tribotester. The kinematic viscosity was measured using a capillary viscometer on the temperatures of 40, 60 and $80^{\circ}C$. The results showed that the graphite nano lubricant had lower friction coefficient and less wear on the friction surfaces than raw lubricant. After thermally degrading, the friction coefficients of graphite nano lubricant increased, but the friction coefficients after thermal degradation were still maintained lower than those of raw lubricant.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.6-12
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• 2015

In this study, the performance test was carried out under various operation conditions targeting four representing types of lubricant which are mostly used in nuclear power plants, and mutually compared the characteristic and performance of lubricant. Especially, introducing the concept of the thread friction coefficient (hereinafter, TFC), which makes the friction relation between the stem nut and stem screw dimensionless. The test was performed to compare the lubricant performance for the four kinds of lubricant (Texaco, Alvania, Mobilux, MOVLL). In a test of the room temperature stem, the TFC of MOV Long Life shows the lowest value, next to Alvania EP2, Texaco EP2, and Mobilux EP0 in that order. And in a test of the high temperature stem, the TFC of Texaco EP2 shows the lowest, next to MOV Long Life, Alvania EP2, and Mobilux EP0 in that order. From the test result of the aging condition, three types of lubricant (MOV LL, Texaco EP2, Alvania EP2) show similar patterns up to 36 months, but in 60 months, the TFC of lubricant are increased rapidly.

• Tribology and Lubricants
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• v.15 no.4
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• pp.343-353
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• 1999

The role of viscosity index improver's(Ⅶ) additives for modem engine lubrication is complex. Under the condition of atmosphere or low shear rate, the characteristics of Ⅶ added lubricant is verified and quoted frequently for mathematical model of lubricant behavior. However, recent research shows that added lubricant has the characteristics of shear thinning at high shear rate condition although it performs well enough over the whole range of working temperature. At high shear rate, they show significant decrease of apparent viscosity irrespective of temperature. Many experimental researches verify that Ⅶ added lubricant shows boundary film layer formation on the solid surface as well as shear thinning effect by its polymeric molecular characteristics. The intend of our research is to verify the effects of Ⅶ from the viewpoint of continuum mechanics, because conventional Reynolds'equation with only pressure-viscosity relation cannot fully predict the lubricant behavior under the Ⅶ added condition. In these aspects, Reynolds'equation of Newtonian fluid model lacks the reflection of real fluid behavior and there is no way to explain the non-linear characteristics of Ⅶ added lubricant. In this research, we mathematically modeled the Ⅶ added lubricant behaviors which are the characteristics of non-Newtonian fluid behavior at high shear rate and boundary film formation on the solid surface. The consideration of elastic deformation in the contact region is also included in our computation and finally the converged film pressure and the film thickness with elastic deformation are obtained. The results are compared with those of Newtonian fluid model.