• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.108-114
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• 1998

The mechanical characteristics of the high speed steel by powder metallurgy process(PM-HSS) has been reported to improve with several alloying constituents, such as high carbon, vanadium and cobalt. In this paper, sliding wear test has been conducted using a pin-on-disc machine for three PM-HSS which contains 0%, 5% and 12% cobalt respectively, in order to evaluate the effect of cobalt on wear properties of PM-HSS. The results of this study showed that the wear resistance of PM-HSS has been increased by the addition of cobalt on the range of experimental friction velocities. When compared with the effect of addition of cobalt, the wear resistance of PM-HSS with 5% cobalt has been found to be superior to that of PM-HSS with 12% cobalt.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.252-261
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• 1999

The troubles such as slipping, pinching and other behaviors in the service of cold rolling mills often induce thermal shock crack on the surface of work roll, and considerably reduce their service lives. In order to evaluate thermal shock resistibility we use thermal shock tester generating frictional heat caused by a rotating disc contacting with test specimens. Thermal shock produces two heat affected layers below the roll surface, one is rehardened layer and the other is succeeding tempered layer. The maximum depth of crack occurred in a thermal shocked area is a criterion for the thermal shock resistibility. This paper describes on the investigation to the influence of hardness and residual stress.

• Journal of the Korean Applied Science and Technology
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• v.3 no.1
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• pp.43-47
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• 1986

1.2-bis(aminoacyl)hydrazine derivatives and dipeptides were synthesized by conventional peptide synthesis procedures. Their antioxidant activity were inverstigated by over-storage test using corn oil as substrte. 1.2-bis (aminoacyl) hydrazine derivatives and dipetides containing hydrophobic side chain amino acid showed higher antioxidant activity. A free N-terminal amino group was also found to be important for the appearance of antioxidant activity. 1.2-bis (aminoacyl) hydrazine derivatives showed higher antioxidant activity than dipeptides. Antimicrobial activites of dipeptides and 1.2-bis (aminoacyl) hydrazine derivatives were also examined by the paper disc method. All of these compounds had shown no antimicrobial activity.

• KSTLE International Journal
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• v.9 no.1_2
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• pp.31-35
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• 2008

DLC (Diamond Like Carbon) films have predominant tribological properties like a high hardness, low friction and high chemical resistance; therefore, DLC films are applied in a wide range of industrial fields. This paper evaluated the characteristics of DLC films deposited on bearing steel with different hardness by RF-PECVD (Radio Frequency - Plasma Enhanced Chemical Vapor Deposition) method. Si-interlayer was deposited on bearing steel to improve adhesion strength by RF-Sputtering method. The DLC film structures were analyzed with Raman spectra and Gaussian function. Adhesion strength of DLC films was measured with a scratch tester. Friction and wear test were carried out with a ball-on -disc type to investigate the tribological characteristics. Experimental results showed that DLC films deposited on bearing steel under same deposition condition have typical structure DLC films regardless of hardness of bearing steel. Adhesion strength of DLC film is increased with a hardness of bearing steel. Friction coefficient of DLC film showed lower at the high hardness of bearing steel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.401-406
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• 2011

The abnormal vibration from the BTV(Brake Torque Variation) and DTV(Disc Thickness Variation) is transferred to the suspension and steering system during braking. In this paper, judder simulation is carried out using multi-body dynamic analysis program to analyze the relation of the judder and transfer mechanism which is composed of the suspension and steering system. In order to analyze the brake judder transfer system, the full vehicle model was composed with rigid body, non-linear bushing, non-linear constraints and joints. Full vehicle model analysis was compared by actual vehicle judder test and sensitivity analysis of the suspension system is carried out.

• Tribology and Lubricants
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• v.15 no.2
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• pp.156-163
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• 1999

The mechanical characteristics of the high speed steel by Powder metallurgy Process (PM-HSS) has been reported to improve with several alloying constituents, such as high carbon, vanadium and cobalt. In this paper, sliding wear test has been conducted using a pin-on-disc machine for three PM-HSS which contains 0%, 5% and 12% cobalt respectively, in order to evaluate the effect of cobalt on wear properties of PM-HSS. The results of this study showed that the wear resistance of PM-HSS has been increased by the addition of cobalt on the range of experimental friction velocities. When compared with the effect of addition of cobalt, the wear resistance of PM-HSS with 5% cobalt has been found to be superior to that of PM-HSS with 12% cobalt.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2063-2065
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• 1999

PD pulses have about one nanosecond rise time in the $SF_6$ gas insulation. These pulses propagate through GIS chamber to PD sensors in the form of the electromagnetic radiation. In this paper, we investigated the characteristics of disc sensors and monopole antenna, by putting high frequency signals into the test cell in $SF_6$ gas by means of a Ins rise time pulse generator and 60Hz power supply respectively. Also, we measured PD quantity from the needle electrode and the location effect of output terminal beneath the disk sensors.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.587-596
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• 1999

The use of Switching elements in power systems causes the current or voltage to involve harmonic waves. Harmonics bring about registration errors of the equipment for measuring power. In case the induction watthour meter designed on sinusoidal source is used in the measurement of power with harmonics, the precise measurement of power has many problems because harmonics cause a decrease of power factor and vibration by the unstable driving force on the aluminum disc. In this paper, analysis and test results on the harmonic sensitivity of an induction watthour meter is reported when the input voltage and current with harmonics were supplied to single-phase watthour meter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.43-48
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• 2005

In order to facilitate technical exchange among nations and/or institutes through the establishment of mutual recognition and the reliability guarantee of testing results by testing standards standardization, the interlaboratory comparison tests on brake discs and linings between KRRI and CARS were conducted. So far, two ways of comparison tests were performed for a better understanding of mutual recognition and standardization in railroad brake linings between Korea and China. In this paper, the first and second comparison testing results have been summarized, and the suggestions for the future research work are also presented to encourage extensive research on comparison study of railroad brake discs and linings between KRRI and CARS. Eventually, the final goal of the current research will be the establishment of standardization of railroad testing standards.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.12
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• pp.1147-1152
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• 2010

The wet brakes used in an industrial forklift often produce noise on braking. Elimination or reduction of this squeal noise is an important task for the improvement of comforts. In this paper, a test rig was developed which was possible for testing of brake noise and an experimental measurement on squeal noise was performed. The causes of the brake noise are identified by experimenting how the factors such as automatic transmission fluid, the groove of friction-plate pad and the material of friction-plate pad affect the squeal noise. In order to identify the squeal characteristics, the signal analyses for noise are performed by using frequency spectrums. Experimental results showed that the viscosity of automatic transmission fluid and the groove pattern of friction-plate pad largely affect the reduction of the wet brake squeal noise in an industrial forklift.