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황희정(Heejeong Hwang),장호(Jang Ho),이완규(Wan gu Lee),장국현(Gug hyun Jang) 한국트라이볼로지학회 2009 한국트라이볼로지학회 학술대회 Vol.2009 No.6
In this study, friction and wear of stainless steel was examined as functions of time, speed, load, and grinding fluids. Surface roughness and the friction coefficient were monitored during tribotests using a block-on-disk tester. The surface roughness of the steel after tests was strongly affected by the load and type of grinding fluid used during grinding. Results showed that the steel ground with mineral oil as grinding fluid showed high surface roughness while the coefficient of friction was lower than other cases. In this paper, the possible mechanism for this salient result is discussed, providing a possible methodology for improving corrosion resistance of the steel surface after grinding operation.
김기정(KiJung Kim),황희정(Heejeong Hwang),장호(Ho Jang),김성진(SeongJin Kim),박흥식(HongSik Park) 한국트라이볼로지학회 2008 한국윤활학회지(윤활학회지) Vol.24 No.4
Tribological properties of ceramic brake discs were investigated using a commercial friction material. The discs were manufactured by liquid silicon infiltration (LSI) into a C-C preform. The disc surface was modified by two different methods, producing sliding surfaces with chopped carbon fibers and carbon felt. In addition, the composition of the surface was also changed. Friction characteristics of the discs were examined using a 1/5 scale dynamometer. Results showed that the type and composition of the disc surface significantly affected the level of braking effectiveness and high temperature brake performance. The discs with felt surfaces showed higher friction levels than those with chopped fiber surfaces and SiC tended to increase the friction level while C lowered the friction coefficient. The ceramic disc was more sensitive to the deceleration rate than gray iron, showing high speed sensitivity.
저속모드에서 자동차용 마찰재의 마찰 거동에 대한 상대 습도의 영향
이완규(WanGyu Lee),황희정(HeeJeong Hwang),장호(Ho Jang) 한국트라이볼로지학회 2009 한국트라이볼로지학회 학술대회 Vol.2009 No.6
The effect of humidity on friction characteristics of automotive brake materials were studied using a pinon-disk type friction tester. The coefficient of friction behavior was measured at the speed range from 0.01 to 55㎜/s in relative humidity (R.H.) from 15 to 95%. The friction coefficient obtained in low relative humidity (R.H. < 15%) was unchanged in spite of speed change. However, the friction coefficient increased to a typical value of automotive friction materials as relative humidity is increased (15% < R.H. < 70%) and speed is decreased. The change of the friction characteristics in both speed and humidity tests appeared to be in good agreement with the effect of relative humidity and speed. On the other hand, the friction coefficient in high relative humidity (R.H. > 95%) was decreased as the speed decreases, which is in contrast with the friction behavior in the low or middle relative humidity conditions. This trend of friction coefficient showed that adsorbed water had lubrication effects on friction behavior.