• Tribology and Lubricants
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• v.31 no.6
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• pp.281-286
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• 2015

Automotive transmission systems are assembled with a large number of gears and shafts, and rolling bearings are used to ensure their smooth operation. Gear oil in the gear box contains solid particles such as wear debris from contacting gears and metallic chips. This particle-enriched lubricating oil can cause premature failure of the rolling bearings. Research aimed at improving the service life of these rolling bearings has been confined mainly to design and lubrication of the inner/outer rings and the rolling elements. In this paper, we redesigned the shape of the cage pocket of a deep groove ball bearing to reduce the premature failure due to particle contamination. Test bearings are assembled with this new cage design containing a hole punched in the cage pocket. Endurance tests are carried out using the contaminated lubricating oil with miracle grid as hard particle. The duration and damaged bearing component shapes are compared for two different cages. The B₁₀ life of bearing with new cage is increased by about 66% compared to the conventional cage. This is because the hard particles can be easily discharged through the pocket hole without staying for a long time in the lubrication regions. This greatly decreases abrasive wear and dents on the highly stressed ball bearing surfaces. Therefore, the cage design of this study, containing a pocket hole, can significantly delay the premature failure of rolling bearings and improve the endurance life.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1239-1246
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• 2022

This paper introduces the effect of grease on the degradation characteristics of bearings used as key components of packaging equipment and automation systems. Bearings parts are installed to fix and support the rotating body of the system, and performance degradation of the bearings has a great effect on the life of the system too. When bearings are used in various devices and systems, the grease is applied to reduce friction and improve fatigue life. Determining the type of lubricant (grease) is important because it has a great influence on the operating environment and lifespan and ensures long lifespan of systems and facilities. However, studies that simultaneously compared and analyzed the change in mechanical degradation characteristics and the comparison of chemical degradation characteristics according to grease types under actual operating conditions are insufficient. In this paper, three types of small harmonic drive, high-load reducer, and low-load reducer grease used in power transmission joint modules are experimentally selected and finally injected into ball bearings with a load (19,500N) to improve bearing durability. Degradation characteristics were tested by attaching to test equipment. At this time, after the durability test under the same load conditions, the mechanical degradation characteristics, that is temperature, vibration according to the three greases types. In addition, the chemical degradation characteristics of the corresponding grease was compared to present the results of mutual correlation analysis.

• Tribology and Lubricants
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• v.25 no.2
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• pp.108-113
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• 2009

This paper presents a experimental results for the performance evaluation of a double-bumped air foil bearing. The test results of a double-bumped AFB is compared with a single-bumped AFB at a heavily-loaded condition. The diameter of the test bearing is 50 mm, and the axial length is 50 mm. Nominal clearance of the single-bumped AFB is evaluated as $105{\mu}m$, and that of the double-bumped AFB is as $95{\mu}m$. The test of the AFBs are demonstrated at 3 test mode; the load variation mode, the speed variation mode, and start-stop mode. The single-bumped AFB demonstrated a upward load-carrying capacity of 95 N and a downward load-carrying capacity of 130 N at 20,000 rpm. The double-bumped AFB demonstrated a upward load-carrying capacity of 170 N and a downward load-carrying capacity of 170 N at 20,000 rpm. The single-bumped AFB demonstrated a downward lift-off speed of 16,300 rpm at 105 N. The double-bumped AFB demonstrated a downward lift-off speed of 15,400 rpm at 105 N. The start-stop test of the AFBs assure 5,000 cycle endurance life. The test results are compared with the theoretical calculation results. The test and theorectical results show thata double-bump air foil bearing provides a higher load-carrying capacity, stiffness and damping than a single-bump air foil bearing in a heavily-loaded condition.

• Journal of Applied Reliability
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• v.15 no.3
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• pp.139-144
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• 2015

Track drive unit adopted in the small sized excavator generally have been used in the construction equipment under the 10 tons as the driving device with forwarding and reversing of excavator. It is required to study the accelerated life test applied by over torque and speed to test the durability life test reflected the many driving modes of small sized excavator and also need to equip the comprehensive performance and life test equipments to do the various performance tests. This study had analyzed the failure modes of the components, and calculated the equivalent loads investigated the used loads in the real field conditions and elicits the acceleration factor adopted in the inverse power model. Also, this study have considered the changes of the acceleration factor and the durability test time in the case of the rotary group and the bearing through analyzing the main failure modes. It was calculated the no failure test time about 2 samples and confidence level 90% and elicited the accelerated life time 720 hours.

• YAKHAK HOEJI
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• v.45 no.6
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• pp.641-649
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• 2001

In this study, the antitumor activities were investigated using $\beta$-lmmunan, a proteoglycan obtained from cultured mycelia of the IY009 strain of Ganoderma lucidum belonging to basidiomycetes. The result showed the significant effect of cytotoxicity test against murine sarcoma 180 and murine lymphocytic leukemia L1210 using immunized macrophage cultures by $\beta$-lmmunan. When intraperitoneally injected at 40 mg/kg/day daily for 10 days, $\beta$-lmmunan inhibited the growth of sarcoma 180 solid tumor in ICR mice by 88.8% (p<0.05). It was also observed that $\beta$-lmmunan increased life span by 85.2% (p<0.01) after treatment of 100 mg/kg/day in BDF1 mice bearing lymphocytic leukemia L1210. And combination therapy with cisplatin (dosage: 4 mg/kg) increased life span by 140.4% (p<0.05) after treatment of 100 mg/kg/day daily in BDF1 mice bearing lymphocytic leukemia L1210.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.395-401
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• 2003

In this paper, the dent printing phenomena and critical dent size which lead to premature failure of deep grooved ball bearing for automobiles are presented. The results of newly assembled test bearings showed that the ball dent size strongly affect the bearing life and inner ring raceways were the major failed parts in spite of using the dented balls. The dent printing phenomena are a root cause of premature failure, which was not reported until now. And there exist the critical ball dent size for given rolling bearings and operating conditions. So, the initial condition of tribologically mating parts should be treated as important as the failed body itself.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.10-11
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• 2019

Interior stone walls are using commonly in non-bearing lightweight walls of apartments. The stones of interior wall were two types, one is a granite stone, another is a marble stone. Granite stone is attached by the epoxy adhesive and marble stone is attached by dedicated anchor and fastener. The impact resistance test was carried out interior stone walls in accordance with KS F 2613. The test methods included the impact resistance tests by each of soft impact body and hard impact body. The results of the test have proved that interior stone walls can withstand the soft impact bodies and hard impact bodies that are likely to happen in everyday life.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.2
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• pp.1-7
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• 2005

For the reliability evaluation of the track drive unit(TDU), firstly, we analyzed the major failure modes through FMEA(failure mode & effects analysis), FTA(failure tree analysis), and 2-stage QFD(quality function deployment), and then quantitatively determined the priority order of test items. The Minitab analysis was also performed for prediction of life distribution and parameters of TDU by use of field failure data collected from 430 excavators for two years. In addition, we converted the fluctuation load in field conditions into the equivalent load, and for evaluation of the accelerated lift by the cumulative fatigues, the equivalent load is again divided into the fluctuation load by reference of test time. And then, by use of the test method in this paper, the acceleration factor(AF) of needle bearing inside planetary gear which is the most weakly designed part of TDU is achieved as 5.3. This paper presents the quantitative selection method of test items for reliability evaluation, the determination method of the accelerated life test time, and the method of non-failure test time based on a few of samples. And, we proved the propriety of the proposed methods by experiments using a TDU for a 30 ton excavator.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.4
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• pp.262-269
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• 1994

This study has been carried out to evaluate effects of alloying elements and nitrocarburizing on rolling contact fatigue life. Manganese has a significant influence on the distribution of retained carbides and microstructural changes after rolling contact fatigue test. The effect of the manganese addition stabilized fine retained carbide particles during rolling contact fatigue life test, and so increased fatigue life markedly. High carbon chromium bearing steel with different matrixes were nitrocarbunzed by austenitic nitrocarburizing process at $850^{\circ}C$ for 4hrs. Rolling contact fatigue life of the nitrocarburized specimen was increased 2 times than full hardening treated.

• Physical Therapy Korea
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• v.8 no.2
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• pp.73-85
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• 2001

The purpose of this study was to investigate whether the standing balance could be influenced by the different foot positions. Seventeen patients with hemiplegia were tested for the static and dynamic balance under the different foot positions. In the balance test, subject stood by bearing weight on one foot, and the other foot was positioned in three different positions (symmetric, $45^{\circ}$ anterolateral, and anterior position). This study used the Kinesthetic ability trainer (KAT2000) to measure the standing balance. The results were as follows: 1) There were significant differences in the static standing balance in different foot positions with both weight-bearing on the paretic limb and on the nonparetic limb (p<.05). 2) There were also significant differences in the dynamic standing balance in different foot positions with both weight-bearing on the paretic limb and on the nonparetic limb (p<.05). 3) There was a significant difference when the paretic weight-bearing and the nonparetic weight-bearing were compared (p<.01). 4) when the paretic weight-bearing and the nonparetic weight-bearing were compared, anterior foot position showed a significant difference in the dynamic standing balance (p<.05), but $45^{\circ}$ anterolateral foot position did not show a significant difference (p>.05). In this study, the standing balance showed a significant difference according to different foot positions in hemiparetic patients, and standing balance was better when they stood by bearing weight on the nonparetic limb. These results indicate that it is a necessary to consider both weight-bearing limb and foot position not only in the rehabilitation program but also in achieving the stability in the independent life.