• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.797-804
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• 2003

본 연구에서는 진동대 실험을 실시하여 매립지에서 널리 사용되고 있는 지오멤브레인과 지오텍스타일 사이의 동적 접촉 마찰 특성을 살펴보았다. 연직응력, 진동 주파수, 건조/수침 상태의 영향에 대해서 평가하였으며, 또한 지오멤브레인과 지오텍스타일 사이의 상대적인 미끄러짐의 정도를 측정하였다. 실험 결과, 지오멤브레인과 지오텍스타일 사이를 통해 전달되는 한계 가속도(limited acceleration)가 있음을 확인할 수 있었으며, 이를 통해 지오멤브레인과 지오텍스타일 사이의 동적 접촉 마찰각을 산정할 수 있었다. 이러한 가속도는 수침상태의 경우 건조상태보다 더 작게 산정되었으며, 변위의 경우 수침상태에서 더 크게 발생함을 관찰하였다. 또한 실험조건에 따라 지오멤브레인과 지오텍스타일 사이에 발생하는 상대적인 미끄러짐의 정도가 다르게 측정되었다. 본 연구에서는 지오멤브레인과 지오텍스타일 사이의 slip equation을 제안하였으며, 이 식을 통해 주어진 가속도와 주파수에서 지오멤브레인과 지오텍스타일 사이를 따라 발생되는 최대 미끄러짐의 정도를 예측 가능하게 하였다.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.265-275
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• 2003

In this study, shaking table tests were conducted to estimate dynamic interface properties between geosynthetics such as geomembrane, geotextile and geosynthetic clay liner. Accelerations of both shaking table and upper box, and relative displacements between geosynthetics under dynamic loading were measured. Also, the influence of normal stress, frequency of excitation and dry/wet conditions were investigated through the analyses of test results. from the test results, it was found that there is a limited acceleration below which dynamic farce can be transmitted between geosynthetics without the loss of horizontal acceleration. Dynamic interface friction angle between geosynthetics could be calculated through the limited acceleration. Relative displacements induced along geosynthetic interfaces under dynamic loading were not consistent depending on the type of interface and test conditions. The maximum slip displacements between geosynthetics are normalized and normalized slip equations were developed for each interface. By using the normalized slip equation, maximum slip displacements for the geosynthetic interface could be predicted for the given base acceleration and frequency of excitation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.554-570
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• 1990

he rolling contact behaviors between a smooth ball and a flat rough surface under dynamic load are intricately affected by many factors, such as the diameter of a ball, normal load and the roughness of a flat surface etc. Accordingly, the experimental study is done to find them on the base of elastic hysteresis loss as theoretical approach is very difficult. The experimental apparatus composed of damped-free vibration system is used. This paper investigates the damping characteristics on the rolling contact area through rolling friction force and logarithmic decrement versus displacement obtained in accordance with the variations of those factors, and presents a new experimental method to find out contact width using the relations of logarithmic decrement and rolling friction force with displacement.

• Composites Research
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• v.36 no.3
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• pp.141-153
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• 2023

This review paper presents an introduction of contact mechanics and rubber friction theory for sliding friction of elastomer composites in contact with rough surfaces. Particularly, Klüppel & Heinrich theory considers the self-affine (or fractal) characteristic for rough surfaces to predict adhesion and hysteresis frictions of elastomers based on the contact mechanics of Greenwood & Williamson. Due to dynamic excitation process of elastomer composites while sliding in contact with multiscale surface roughness (or asperity), viscoelastic properties in a wide frequency range becomes major contributor to friction behaviors. A brief description and examples are provided to construct a viscoelastic master curve considering nonlinear viscoelasticity of elastomer composites. Finally, application of rubber friction theory to tire tread compounds in traction with road surfaces is discussed with several experimental and theoretical results.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.173-180
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• 2003

In spite of its potential importance in the assessment of geosynthetic-related dynamic problems, no serious attempt has yet been made to investigate a probable dependence of dynamic friction resistance of the geosynthetic interface on shear displacement rate. Hence, an experimental study of geosynthetics was carried out on a shaking table, and the relationship between dynamic friction resistance and shear displacement rate of geosynthetic interfaces was investigated. A cyclic, displacement rate-controlled experimental setup was used. The subsequent multiple rate tests showed that interfaces that involve geotextiles have such unique shearing characteristics that shear strengths tend to increase with displacement rate. In contrast, once submerged with water, the shear strength appears to be no longer dependent on the displacement rate, partly due to lubrication effect of water trapped inside the interface. The results of the experimental study can be used in the seismic safety assessment of a landfill cover and slope where the geosynthetic materials are exposed to a relatively low normal stress.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.2
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• pp.61-69
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• 2011

In this paper, the factors affecting the dynamic characteristics of a polyurethane spring restoring disk bearing are analysed to predict the dynamic behavior of the bearing. The prediction results and the test results are compared. The Young's modulus of the polyurethane spring, which varies according to strain of spring and the friction coefficient, of PTFE (PolyTetraFluoroEthylene), which varies according to the velocity and pressure of PTFE, are considered as the factors influencing the dynamic characteristics. W-PTFE virgin products are used and polyurethane springs are produced for the tests. The equation related to changing the friction coefficient and the modulus of elasticity are obtained through an inverse estimation of the test results. The estimation results, considering the factors affecting the dynamic characteristics, simulate the test results more appropriately than the estimation without the consideration of those factors.

• Explosives and Blasting
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• v.37 no.4
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• pp.26-35
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• 2019

In designing a gravity-type anchorage of earth-anchored suspension bridge, the contact friction between a blasted rock mass and the concrete anchorage plays a key role in the stability of the entire anchorage. Therefore, it is vital to understand the shear behavior of the interface between the blasted rock mass and concrete. In this study, a portable 3D LiDAR scanner was utilized to scan the blasted bottom surfaces, and rock surface roughness was quantitatively analyzed from the scanned profiles to apply to 3D FEM modelling. In addition, based on the 3D FEM model, a three-dimensional dynamic fracture process analysis (DFPA-3D) technique was applied to study on the shear behavior of the interface between blasted rock and concrete through direct shear tests, which was analyzed under constant normal load (CNL). The effects of normal stress and the joint roughness on shear failure behavior are also analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.869-876
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• 2011

It is important to analyze the dynamic behavior of counter-rotating rigid/deformable rolls in the roll-coating process, because the stability of the process is affected by the dynamic characteristics. In the present study, the effects of material property, angular velocity, and gap size on the contact pressure and contact shape of the deformable roll are numerically investigated. The behavior of two rolls with a negative gap was analyzed using the finite element method, and the material property of the deformable roll was applied with the Mooney-Rivlin coefficients of the hyper-elastic model. The contact shape is affected by the gap size, and the contact pressure mainly depends on the stiffness of the deformable roll and the gap size. To maintain a negative gap between two rolls, controls such as load and displacement controls must be used. The results indicate that displacement control can reduce the instability.

• Journal of the Korean Geophysical Society
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• v.7 no.1
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• pp.31-40
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• 2004

When surveying the cultural heritages especially in the case of stone structures, preserving their original state is of primary importance. For the effective assessment of survey results of stone structure, the dynamic characteristics of that system should be considered. Dynamic characteristics of stone masonry structures depend on several factors such as coefficients of friction, contact conditions, and number of layers of bonding stones. These factors can be estimated by using the dynamic analysis results. This paper describes a method for natural frequency determination of traditional stone arch bridge subjected to compressive force. For this purpose, multi-layered granite brick models of for arch bridge were made and fundamental frequencies corresponding increasing axial forces were measured.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.179-182
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• 2002

Geosynthetics are widely used in landfill for filtration, drainage, separation and so on. For many landfill failure cases, interfaces of geosynthetics can be potential failure surfaces. Therefore, it is very Important to estimate the interface properties of geosynthetics. In this study, shaking table tests were peformed between smooth geomembrane and geotextile. From the test results, it was found that there is a limited acceleration that can be transmitted from smooth geomembrane to geotextile. And the influence of normal stress and frequencies of excitation were discussed.