• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.65-72
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• 2007

Large-scale direct shear tests were conducted in order to investigate both the shear strength of soil itself and the friction behavior at the interface of soil/geosynthetics in respect of efficiency in this study. Sand, crushed stone and three types of geotextile (i.e. one woven geotextile and two nonwoven geotextiles) were used in the experimental program. The considered interfaces for the evaluation of interface shear strength in this study included sand/sand, crushed stone/crushed stone, sand/woven geotextile, crushed stone/woven geotextile, crushed stone/nonwoven geotextile-A and crushed stone/nonwoven geotextile-B. The results showed that the efficiency of 84% was obtained at the interface of sand/woven geotextile compared with the shear strength of sand itself (i.e. sand/sand interface). The efficiencies of 74%, 83% and 72% were obtained at the interface of crushed stone/nonwoven geotextile-A, crushed stone/nonwoven geotextile-B and crushed stone/woven geotextile, respectively compared with the shear strength of crushed stone itself (i.e. crushed stone/crushed stone interface).

• Science of Emotion and Sensibility
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• v.14 no.2
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• pp.191-196
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• 2011

Fabric extraction force measured through nozzle tester reflects a comprehensive fabric handle. Nozzle tester takes advantage of low cost, and simple and fast operating procedure compared with KES system. The paper is to develop the semi-emprical equation for assessment of the fabric handle measured with nozzle tester on the basis of friction law. The variables considered in the equation arc fabric's frictional coefficient and drape coefficient which is determined in terms of fabric bending length and shear strain. The experiment of 12 different cotton and polyester fabrics and comparisons between experimental and theoretical results were conducted. Fabrics of high frictional coefficients, high bending length, and low shear strain showed high fabric handle forces (low handle values). The handle forces predicted from the equation agreed well with those measured, which indicates that the equation can be used to objectively evaluate fabric handle with respect to fabric's own properties and also provide an information for fabric design to improve the handle performance.

• Journal of the Korea Convergence Society
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• v.9 no.1
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• pp.283-289
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• 2018

In automotive disc brake systems, frictional heat is not uniformly dispersed for reasons such as heat flux and thermal deformation. The thermoelastic deformation due to the frictional heat affects the contact pressure distribution and the contact load may be concentrated on the contact portion on the the disc brake surface, resulting in thermoelastic instability. In this study, thermal analysis and thermal deformation analysis considering the contact between disk and pad occurred during braking through 3D axial symmetry model with reference to the experimental equation and Kao's analysis method of contact pressure of disk and pad. ANSYS is used to analyze the thermal and elastic instability problems occurring at the contact surface between the disk and the pad, considering both the thermal and mechanical loads. A 3D axisymmetric model with direct contact between the disk and the pad was constructed to more accurately observe the thermal behavior of the disk by observing the frictional surface temperature, thermal deformation and contact thermal stress of the disk.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.2
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• pp.73-78
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• 2010

Wave energy is dissipated mainly by friction on the seabed until the waves reach the surf zone. Many researchers have investigated the mechanism of wave friction and the bottom shear stress induced by wave motion at a certain point is now well estimated by introducing the wave friction factor related to the near bed velocity given by linear wave theory. The variation of wave energy or wave height over a long distance can be, however, estimated by an iteration process when the propagation of waves is strongly influenced by bed friction. In the present study simple semi-theoretical equation has been developed to compute the variation of wave height for the condition of wave propagation on a constant beach slope. The ratio of wave height is determined by the product of shoalng factor and wave height friction factor (frictional wave energy dissipation factor). The wave height estimated by the new equation is compared with the wave height estimated by the solution of numerical integration for the condition that the waves propagate on a constant slope.

• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.49-55
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• 2007

In order to utilize treads of waste tire as reinforcement material it is necessary to know the interface friction angle between tread surfaces and soil and tensile strength of connection joint of tire treads. In this research large direct shear tests were performed to get the interface friction angle between the inner and outer surfaces of treads and soil for different degree of compaction. From the large direct shear tests, the ratio of interface friction angle to the shear friction angle of sand, ${\delta}/{\phi}$, were 1.06 in outside surface of tire tread and 0.93 in inside surface of tire tread. For weathered granite soil the ratio of interface friction angle was 0.98 and 0.92 for outside and inside of tread, respectively. Also tensile tests were performed using universal testing machine for the connection joint of treads and Tirecell units using bolts. The tensile strength of connection joint increased with the number of bolts and with the sizes of washers. Connection by polypropylene ropes showed lower strength than those of bolts.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.3
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• pp.33-41
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• 1993

양벽면 모두 사각돌출형조도요소가 설치된 동심 이중관내에서 생기는 비대칭 난류유동과 열전달 특성을, 열전달과 마찰계수에 미치는 조도의 합성효과를 조사하기 위해, 연구하였다. 이론해석에서는 한쪽면에 거칠기가 있는 평행평판의 유동에 대한 수정 플란틀 혼합길이(mixing length)이론의 난류 모델을 속도분포와 마찰계수를 구하는데 사용하였다. 최대속도지점에서 안쪽과 바깥쪽의 두 속도형상들은 힘의 평형에 의해 일치시켰다. 그리고 나서, 온도 분포와 열전달 계수를 계산하였다. 속도형성과 마찰계수들의 해석결과는 실험과 매우 잘 일치하였다. 마찰계수와 Nusselt number에 미치는 조도비, 조도에 대한 피치비, 그리고 반경비등과 같은 여러 변수들의 효과들을 조사하였다. 본 연구는 일정의 조도 요소들이 전체적 효율 측면에서 볼때 유리하게 열전달을 향상시킨다는 것을 증명하였다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1988.11a
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• pp.35-48
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• 1988

상대 접촉하고 있는 물체에 미끄럼 운동이 가해질 경우 마찰에 의해 발생되는 거의 모든 에너지는 열로써 나타나게 된다. 이러한 마찰열은 주로 adhered junctions의 파괴 및 표면돌기(surface asperities)들의 소성 변형에 의한 열역할적 비가역 반응의 결과로 발생된다. 접촉부위의 발생열은 양 접촉제의 접촉면에 전달되어 접촉표면 온도의 급격한 증가를 초래하며 그 결과로 여러가지 surface phenomena, 즉 마찰, 마모, 산화(oxidation), 부식 및 구조적 열화(structural degradation) 금속학적 상변화등에 큰 영향을 미치게 된다. 딸서 볼 및 로울링 엘레먼트 베어링, 기어, 캠과 태핏, 브레이크 등 기계요소의 설계를 위한 주인자로서 근래에 들어 접촉표면의 온도가 주목받고 있다. 표면에 존재하는 layer로서는 금속표면에 응착시킨 coating layers, contaminant films, physisorbed 또는 chemisorbed films, oxide layers 또는 마찰열에 의해 형성되는 경도가 아주 높은 내마모층(hard wear-resistant layers) 등이 고려될수 있다. 낮은 열전도성을 가진 oxide film이 접촉 표면이 온도를 증가시킨다는 것이 Jaeger에 의해 지적되었으며 Ling과 Lai는 moving heat sjource가 가해지는 layered surface의 표면온도분포를 구하면서 substrate와 thermal property가 다른 layer가 존재하게 되면 그 두께가 아주 얇더라도 (1 마이크론 정도) 표면온도는 크게 변화됨을 보였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.11
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• pp.1075-1080
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• 2010

For the aeroelastic analysis of a wing with friction damping, coupled time integration method was used to obtain time responses in the subsonic and transonic regions. To take into account aerodynamic nonlinearity induced by shock wave on the lifting surface, transonic small disturbance equation with in-phase periodic boundary condition was used for unsteady aerodynamic calculation. For 2-DOF airfoil system with displace-dependent friction dampers, the effects of normal load slope and Mach number on flutter boundary were investigated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.226-233
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• 1994

The present paper considers the method to estimate the bottom friction driven by waves and current on rough turbulent flow. Parameter adjusting technique is suggested for the computation of bed shear stress driven by uni-directional flow. and the value of parameter is determined by comparing the computational results against Bijker's laboratory data. For the computation of combined flow bottom shear stress, two methods are presented; one is the modified Bijker approach (BYO Model) and the other is the modified Fredsoe approach (FY Model). both of which are refined by the present writer. Both models are again refined in two aspects, and tested against the Bijker's laboratory data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.691-697
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• 2008

Coating the high tension bolted frictional joint has been generally allowed for anti-corrosion purpose. However in case of painting on paying surface of the high tension bolt, the influence on a slip strength of the joint depending on precision of painting has remained controversial. The study thus was intended to identify the slip behavior on high tension bolted frictional joint when applying ceramic painting, which has been currently developed. A slip test was conducted on a high tension bolted frictional joint specimen on which ceramic painting has been applied and a slip load and slip coefficient were measured. Based on result, the safety and usability of ceramic painting-applied high tension bolted frictional joint was evaluated. As a result, a difference to some extent by specimen in terms of load-displacement when a slip occurred was observed but an average slip coefficient appeared to have exceeded 0.4, which is the design frictional coefficient set forth in the specification. To secure the safety and usability of ceramic painting-applied high tension bolted frictional joint, it's necessary to establish the standard for painting as well as to revise the relevant specification.