• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.121-125
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• 2012

This paper presents the friction and anti-wear characteristics of nano-oil with a mixture of a refrigerant oil and carbon nano-particles in the thrust slide-bearing of scroll compressors. Frictional loss in the thrust slide-bearing occupies a large part of total mechanical loss in scroll compressors. The characteristics of friction and anti-wear using nano-oil is evaluated using the thrust bearing experimental apparatus for measuring friction surface temperature and the coefficient of friction at the thrust slide-bearing as a function of normal loads up to 4,000 N and rotating speed up to 3,200 rpm. It is found that the coefficient of friction increases with decreasing rotating speed and normal force. The friction coefficient of carbon nano-oil is 0.023, while that of pure oil is 0.03 under the conditions of refrigerant gas R-22 at the pressure of 5 bars. It is believed that carbon nano-particles can be coated on the friction surfaces and the interaction of nano-particles between surfaces can be improved the lubrication in the friction surfaces. Carbon nano-oil enhances the characteristics of the anti-wear and friction at the thrust slide-bearing of scroll compressors.

• Tribology and Lubricants
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• v.33 no.4
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• pp.141-147
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• 2017

The vibration data of bearings are very useful for monitoring and determining the condition of the bearings. The defect frequencies of ball bearings have been used for monitoring there condition. However, it is not easy to verify the defect frequencies as the wear progress. Therefore there is a need for an easy method to monitor the damages of bearings in real-time and to observe the variations in vibration characteristics as the wear progress. In this study, a bearing test equipment is constructed to diagnose the damage of bearings. The friction coefficient and vibration data are measured by using a torque sensor and an acceleration sensor, and the correlation between the measured data is analyzed to diagnose the condition of the bearing. We reached the following conclusions from the results. When the ball surface, inner and outer rings of a ball bearing are damaged, the friction coefficient increases to over 0.02 with an adhesion on the surface. Moreover this damage occurs more quickly with an increase in the number of revolutions. In the vibration characteristics, the amplitude of vibration wave appears high with an increase in the friction coefficient. In the high frequency range between 1000 and 2000 Hz, a wide range of frequency components with high amplitude occurs continuously irrespective of the number of revolutions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.196-202
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• 1998

Because the journal and bearing surface are fully separated by the oil film during the normal operation, fluid film bearings operating in the hydrodynamic lubrication region are expected to have an infinite life. However, there are many parameters that lead to interfere with the normal operation of the bearing and lead to its failure. In this paper, both the causes and countermeasures of the bearing failure are described. Also, the characteristics of wiped bearing surface are investigated through mechanical and chemical test.

• Tribology and Lubricants
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• v.39 no.5
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• pp.203-211
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• 2023

This study experimentally investigates the effects of angular acceleration on the friction and wear performances of a gas foil thrust bearing (GFTB) using a typical GFTB with six pads. The outer radius of the bearing is 31.5 mm, the total bearing area is 2,041 mm² , and the bump foil and incline (ramp) height are both 500 ㎛. The newly developed GFTB test rig for measuring the friction torque and coefficient measures the axial load, drag torque, lift-off speed, and touch-down speed. The experiment is conducted for angular accelerations of 78.5, 314.2, and 328.3 rad/s² at axial loads of 5, 10, and 15 N, respectively. The test shows that the start-up friction coefficient increases with increasing axial load at the same angular acceleration, and the friction coefficient decreases with increasing angular acceleration under the same axial load. As the angular acceleration increases, the lift-off speed at the motor start-up increases, and the touch-down speed at the motor stop decreases. The wear distance of the GFTB for a single on/off cycle increases with increasing axial load at the same angular acceleration and decreases nonlinearly with increasing angular acceleration under the same axial load. The test results suggest that adjusting the rotational angular acceleration helps reduce bearing friction and wear.

• Tribology and Lubricants
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• v.17 no.3
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• pp.221-227
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• 2001

The effect of silver particles on the sliding behavior of bearing steels was studied experimentally by using a ball-on-disk tribometer. Tests were performed in ambient air, dry air and vacuum. Disks of AISI 52100 were silver-coated by a thermal evaporation method, and the effects of silver particle transfer on friction were analyzed. In order to understand further the mechanism of silver particle transfer and its effect on friction and wear, pre-compressed silver particles were artificially introduced into the friction interface and the results were compared to those of silver-coated specimens. Results showed that the introduced silver particles produced transfer layers and resulted in low friction. It also showed that this low friction is closely related to the characteristic behavior of transfer layers. Shakedown occurred at the friction interface affected the friction and wear.

• Tribology and Lubricants
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• v.33 no.4
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• pp.153-167
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• 2017

The aim of this study is to find the change in trend in the eccentricities of two journal bearings supporting the crankshaft of a single cylinder engine and the degree of misalignment of the shaft. We analyze the change in oil film thickness considering the wear scar under mixed-elasto-hydrodynamic lubrication regime at potential wear regions. For this, we first calculate the central eccentricities of the two journal bearings by using the mobility method. Then we calculate the outer end eccentricity by using the geometry of the bearings. Further, the tilting angle and degree of misalignment of the shaft are calculated by using the eccentricities of the two bearings. We show that the eccentricity of bearing #1, on which higher load is applied, increases at the beginning of the start-up cycle and during the coast-down cycle. However, the eccentricity of bearing #2, on which lower load is applied, decreases at the beginning of the start-up cycle and increases during the coast-down cycle. From the results of the analysis of oil film thickness, we show that the mixed-elasto-hydrodynamic lubrication regime for a misaligned shaft is at the initial stages of the start-up cycle for both bearing #1 and #2 and at the final stage of the coast-down cycle for only bearing #1.

• Clinics in Shoulder and Elbow
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• v.27 no.1
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• pp.18-25
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• 2024

Background: The Discovery Elbow System (DES) utilizes a polyethylene bearing within the ulnar component. An exchange bearing requires preoperative freezing and implantation within 2 minutes of freezer removal to allow insertion. We report our outcomes and experience using this technique. Methods: This was an analysis of a two-surgeon consecutive series of DES bearing exchange. Inclusion criteria included patients in which exchange was attempted with a minimum 1-year follow-up. Clinical and radiographic review was performed 1, 2, 3, 5, 8 and 10 years postoperative. Outcome measures included range of movement, Oxford Elbow Score (OES), Mayo Elbow Performance Score (MEPS), complications and requirement for revision surgery. Results: Eleven DESs in 10 patients were included. Indications were bearing wear encountered during humeral component revision (n=5); bearing failure (n=4); and infection treated with debridement, antibiotics and implant retention (DAIR; n=2). Bearing exchange was conducted on the first attempt in 10 cases. One case required a second attempt. One patient developed infection postoperatively managed with two-stage revision. Mean follow-up of the bearing exchange DES was 3 years. No further surgery was required, with no infection recurrence in DAIR cases. Mean elbow flexion-extension and pronosupination arcs were 107°(±22°) and 140° (±26°). Mean OES was 36/48 (±12) and MEPS was 83/100 (±19). Conclusions: Our results support the use of DES bearing exchange in cases of bearing wear with well-fixed stems or acute infection. This series provides surgeons managing DES arthroplasty with management principles, successful and reproducible surgical techniques and expected clinical outcomes in performing DES polyethylene bearing exchange. Level of evidence: IV.

• Tribology and Lubricants
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• v.9 no.2
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• pp.56-62
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• 1993

Al-Pb-Cu and Al-Si-Pb-Cu bearing alloys were produced by forced-stirring method and water-cooled copper mold casting to investigate the effect of the precipitation hardening on the wear properties. Sliding of produced alloy pin against a steel disc were performed under various applied loads. Lowering the wear rate and material transfer phenomena were explained by the strengthening of $\theta'$ precipitates on AI matrix. The transmission electron microscope observation reveals the role of the precipitates in the alloys with Cu. The movement of dislocations was hindered by precipitates which resulted in the reduction of plastic deformation at the worn surfaces.

• Advances in materials Research
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• v.7 no.2
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• pp.137-148
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• 2018

The present paper is a contribution in characterising end milling process of AISI 52100 ball bearing steel through statistical analyses of variance (ANOVA). The latter has been performed to identify the effect of the cutting parameters on the machined surface roughness and the cutting tool life. Wear measurements have been carried on multilayer coated carbide inserts and the respective surface roughness has been recorded. Taguchi's technique has been adapted to conduct the design experiments in terms of orthogonal arrays according to the cutting parameters (cutting speed, feed rate and depth of cut), the type of coating (TiN, TiCN, TiAlN) and lubricating condition. Regression analyses have conducted to the development of simplified empirical models that can be effectively used to predict surface roughness and tool wear in the present milling process.

• Journal of the KSME
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• v.16 no.2
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• pp.122-127
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• 1976

It was reported in the Journal of KSME Vol. 15, No. 3 and No. 4, 1975 that could be finished the best smooth surface by applying frictional work to the metal surface. Even if we can finish the best smooth surface of methal, it is not available when it has not anti-wear. Present study tried to investigate the anti-wear and the characteristics of frictional worked surface by using the sliding contact between plain bearing of brass and frictional worked jornal of mild steel. The results were compared with the case of ground journal.