• 한국도로학회논문집
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• 제15권3호
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• pp.103-115
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• 2013

PURPOSES: The purpose of this study is to develop a method for distribution between superelevation and side friction factor by increasing design speed. METHODS: First of all, a method for distribution between superelevation and side friction factor and a theory for the functional formula of side friction factor in compliance with horizontal radius applied in South Korea and the United States are considered. Especially, design speed of 140km/h and numerical value of design elements are applied to the theory for the functional formula of side friction factor in AASHTO's methods. Also, the anxiety EEG upon running speed is measured to reflect ergonomic characteristics through field experiments at seven curve sections of the West Coast Freeway, and this data is applied to graph for the functional formula of side friction factor. RESULTS : Matching side friction factor against the anxiety EEG, the results that a critical points of driver's anxiety EEG sharply increase locate under existing parabola are figured out. CONCLUSIONS : Therefore, we could get a new type of the functional formula that driver's driving comfortability is guaranteed if the existing the functional formula of side friction factor goes down under boundary of the critical points of the anxiety EEG.

• 공학교육연구
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• 제21권3호
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• pp.12-19
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• 2018

In this study, a new experimental device was developed for measurement of the coefficient of kinetic friction using a photo gate timer system which have advantages of easy and accurate detection of motion. This device, consisting of a side air-guide track and a side friction-free glider, forces a friction sample to move in a straight line without producing unnecessary friction. The new device is compared to two conventional measuring methods of friction for four different friction samples: one is using a camera system and the other is using a force sensor. It is demonstrated that the developed friction device in this study is easier to operate and produces the most accurate and the least deviating results among them. On the basis of these results, we propose that friction experiment using the new friction device is included in general physics experiment, so that engineering students should have a chance to get correct understanding of classical mechanics including friction phenomenon.

• 한국지반환경공학회 논문집
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• 제9권3호
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• pp.61-68
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• 2008

압밀시험시 시료의 두께에 대한 직정의 비율이 크면 일반적으로 측면마찰은 없다고 간주된다. 그러나, 시료의 두께가 커질수록 측면 마찰의 영향은 무시할 수 없게 된다. 본 연구에서는 정규압밀된 카올리나이트 슬러리의 압밀시험시 측면마찰의 영향을 조사하였다. 압밀시험을 통해 압밀시험곡선, 과잉간극수압, 압밀-간극비, 투수계수-간극비 관계를 측정하였고, 압밀-간극비 관계에 있어 측면마찰의 영향을 고려하기 위해 Taylor(1942)가 제안한 식을 적용하였다. 측정된 압밀시험곡선과 과잉간극수압에 대해 수치해석 결과와 비교 분석을 통해 측면 마찰이 압밀시험에 미치는 영향을 검토하였다. 그 결과, 측면 마찰의 영향을 고려한 수치해석 결과는 측면 마찰을 무시한 결과보다 측정값에 근사한 것으로 나타났으며, 측면 마찰은 압밀-간극비 관계 뿐만 아니라 압밀시간에도 영향을 주는 요인이라는 결과를 얻을 수 있었다.

• International Journal of Korean Welding Society
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• 제3권2호
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• pp.46-52
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• 2003

The refinement of microstructure and phase transformation near the interface of pure copper/carbon steel dissimilar metals joints with various friction welding parameters have been studied in this paper. The microstructure of copper and carbon steel joints were changed to be a finer grain compared to those of the base metals due to the frictional heat and plastic deformation. The microstructure of copper side experienced wide range of deformed region from the weld interface and divided into very fine equaxied grains and elongated grains. Especially, the microstructures near the interface on carbon steel were transformed from ferrite and pearlite dual structure to fine ferrite, grain boundary pearlite and martensite due to the welding thermal cycle and rapid cooling rate after welding. These microstructures were varied with each friction welding parameters. The recrystallization on copper side is reason for softening in copper side and martensite transformation could explain the remarkable hardening region in carbon steel side.

• KSTLE International Journal
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• 제3권1호
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• pp.1-6
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• 2002

The purpose of this paper is to investigate the effects of design parameters on the friction loss in piston skirt. An analytical model to describe the friction characteristics of piston skirt has been presented, which is based on the secondary motion of piston and mixed lubrication theory, It could be shown that the skirt friction closely depends on the side force acted on the piston pin. The side force is inf1uenced by cylinder pressure at low engine speed, but by inertia force at high engine speed. The usage of extensive skirt area and low weight piston is effective to reduce the friction loss at high speed. The low viscosity oil considerably decreases viscous friction as engine speed increases, but it increases boundary friction at low engine speed. From the parametric study, it is found that the skirt axial profile is the most important design parameter related to the reduction of skirt friction.

• 한국도로학회논문집
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• 제17권1호
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• pp.105-118
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• 2015

PURPOSES : This study aims to evaluate the road safety of the super-elevation transition section of a left turn curve and suggest the minimum longitudinal grade of a super-elevation transition section to be used before and after a left curved section. METHODS : We evaluated the road condition by means of the safety-criterion-evaluation method involving side friction factors, and then solve the problem by introducing the minimum longitudinal grade criterion based on conditions described in the hydraulics literature. RESULTS : It was calculated that when a road satisfies hydroplaning conditions, the difference between side friction assumed and side friction demanded is less than -0.04. In this case, the safety criterion for the condition is unsatisfied. Conversely, when a road is in a normal state under either wet or dry conditions, it was calculated that the difference between side friction assumed and side friction demanded is more than 0.01. Thus, the safety criterion for this condition is found to be satisfied. After adjusting the minimum longitudinal grade applied to a super-elevation transition section, the hydroplaning condition can be eliminated and the safety criterion can be met for all sections. CONCLUSIONS : It is suggested that a minimum longitudinal grade should be provided on super-elevation transition sections in order to prevent hydroplaning.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.1012-1015
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• 2005

This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$. Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.549-554
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• 2003

EPRI PPM (Performance Prediction Methodology), a method used for the prediction of required thrust of valves, can not be applied to unbalanced-disk globe valves operated in the fluid when the fluid temperature is above $150^{\circ}F$ because the thrust increase caused by the friction between the valve disk and body is not considered in the PPM. In order to apply PPM to the valves, EPRI suggested new friction prediction method to be added in the code. This paper analyzes the applicability of the prediction method comparing the disk-to-body friction load predicted from the method with the measured friction load from the field tests. The maximum values from the prediction method and those obtained from the test were 268lbs and about 1500lbs, respectively. It is included that the prediction method should be improved for the realistic prediction of disk-to-body friction load.

• Geomechanics and Engineering
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• 제32권1호
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• pp.97-110
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• 2023

The coefficient of lateral earth pressure at rest in loose sand during virgin loading, K₀ , and during unloading, K'₀ , have been determined from laterally confined load-unload tests. The tests included measurement of lateral pressure with null pressure gauges, side wall friction with newly designed friction meters and applied pressure and base pressure with load cells. The importance of accounting for side-wall friction when evaluating the distribution of vertical pressure over the height of the soil specimen was demonstrated. Relatively uniform friction was observed during loading, but this was not the case during unloading unless friction reduction measures were employed. While the measured value of K₀ was found to be close to, if slightly higher than the value commonly estimated on the basis of friction angle, φ', the ratio of K'₀ to K₀ was found to reasonably fit an expression of the form K'₀/K₀ = 1 + C·log(OCR), with C equal to 1 in the present tests.

• 한국정밀공학회지
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• 제23권4호
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• pp.109-115
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• 2006

This paper is designed to estimate friction and powdering characteristic of coating layer on galvannealed sheet steel with different annealing temperature, which is 465, 505, 515 and $540^{\circ}C$, Estimations of powdering and friction were done using a $60^{\circ}$ bending test and one side friction test, respectively. In order to obviously understand the effect of coatings on friction cross-section of coatings before and after friction test was also observed by SEM. The results show that powdering of coatings is increased with increasing of annealing temperature and that friction characteristic greatly depends on powdering which leads to increase of real contact area between tools and coatings.