• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.75-82
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• 2005

Shear strength parameters obtained from field tests are important factors in the analysis of slope stability. In this paper, sensitivity analysis was performed to evaluate the effect of input parameters on the analysis of slope stability. The input parameters selected for sensitivity analysis were slope angle, cohesion, and friction angle. Monte-Carlo Simulation method was to estimate input parameters for sensitivity analysis in slope stability, and the limit equilibrium method was used to calculate the factor of safety of slope stability. A rock slope, failed in the field, was used for the sensitivity analysis of input parameters in the analysis of slope stability. The result of analysis shows that the factor of safety of the rock slope was a little low. From partial correlation coefficient (PCC) of input parameters from the sensitivity analysis, slope stability was dependant mainly on cohesion and slope angle. The effect of friction angle was smaller than those of cohesion and slope angle on slope stability.

• Tribology and Lubricants
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• v.28 no.6
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• pp.278-282
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• 2012

Various bearings such as deep-groove ball bearings, angular-contact ball bearings, and roller bearings are used to support the load and to lubricate between the shaft and the housing. The bearings of potential rolling systems in a turbo pump are the deep-groove ball bearings as comparing with the bearings with rolling elements such as cylindrical rollers, tapered cylindrical rollers, and needle rollers. The deep-groove ball bearings consist of rolling elements, an inner raceway, an outer raceway and a retainer that maintain separation and help to lubricate the rolling element that is rotating in the raceways. In the case of water-lubricated ball bearings, however, fluid friction between the ball and raceways is affected by the entry direction of flow, rotation speed, and flow rate. In addition, this friction is the key factor affecting the bearing life cycles and reliability. In this paper, the characteristics of flow conditions corresponding to a deep-groove ball bearing are investigated numerically, with particular focus on the friction distribution on the rolling element, in order to extend the analysis to the area that experiences solid friction. A simple analysis model of fluid flow inside the water-lubricated ball bearing is analyzed with CFD, and the flow characteristics at high rotation speeds are presented.

• Journal of the Korean Geosynthetics Society
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• v.2 no.1
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• pp.3-13
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• 2003

Recently, construction of the reinforced earth structures, which adopts reinforcing materials of geosynthetic, is rapidly increasing due to its good economic advantages, beautiful appearance, and convenient construction. Nonetheless, the most important factor of interpretation and design of the reinforced earth structures, which is assessment ways of friction features between earth and geosynthetic, has not been standardized yet. It has great difference of interpretation and design methods which suggested to the design engineer. This study is to present the way how to assess more reasonably friction features between geogrid and weathered granite soil through the pullout test. Based on a large-scale pullout test of geogrid, the maximum shear stress, interface fricton angle, and friction efficiency are presented with consideration of various test condition.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.499-502
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• 2003

The purpose of this study is to understand the sliding characteristics of the infilling-joint surface using the new devised shear test apparatus with changeable slope for the original infilling materials and the infilling materials experienced cyclic freezing-thawing processes. Three types of the mother rock classified as the igneous rock, the metamorphic rock and the sedimentary rock and the infilling materials were collected for laboratory test. The cohesion according to the slope change of the rock joint shows large variation within ${\pm}$5 degrees but the internal friction angle shows appears the linear decreasing tendency. It is confirmed that the affecting factor of slope change of rock joint at the behavior of rock mass is larger than that of the infilling thickness. Test results show that the cohesion and the internal friction angle in 100 times of cyclic freezing-thawing processes are decreased about 50 percent compared with original one. A further study using various infillings materials would lead to a better understanding of the failure mechanism of rock mass by slope change of rock joint.

• Korean Journal of Materials Research
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• v.3 no.2
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• pp.140-144
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• 1993

Abstract To modify brittleness among the properties of thermosetting epoxy resin, a reactive additive. succinonitrile(SN) was introduced to Diglycidyl ether of bisphenol A(DGEBA)-4, 4'-methylene dianiline (MDA) system. Fracture behavior was microscopically studied during breaking of composite materials. As a result, post debond friction energy was the most significant for breaking the composite having glass fibres, pull-out energy was the next significant and debonding energy was the last. It was observed that shear stress between glass fibre and epoxy matrix was main factor for fracture behavior. Reactive additive, SN made shear stress deteriorated.

• Journal of Advanced Research in Ocean Engineering
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• v.2 no.2
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• pp.86-98
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• 2016

In this study, after the installation of a subsea pipeline, backfilling was performed in the trenched area. During these operations, a stability problem in the subsea pipeline occurred. The pipeline was directly impacted by environmental loading such as waves and currents that were caused by backfill material when scouring or sediment transport and siltation was carried out. Therefore, this study reviewed whether trenching was necessary, and conducted research into an indigenous seabed property that contains granular soil. A study of cohesive soil was also conducted in order to cross-correlate after calculating the values of the critical Shields parameter relevant to elements of the external environment such as waves and current, and the shear Shields parameter that depends on the actual shearing stress. In case of 1), sedimentation or erosion does not occur. In the case of 2), partial sedimentation or erosion occurs. If the case is 3), full sedimentation or erosion occurs. Therefore, in the cases of 1) or 2), problems in structural subsea pipeline stability will not occur even if partial sedimentation or erosion occurs. This should be reflected particularly in cases with granular and cohesive soil when a reduction in shear strength occurs by cyclic currents and waves. In addition, since backfilling material does not affect the original seabed shear strength, a set-up factor should be considered to use a reduced of the shear strength in the original seabed.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.739-756
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• 2016

The shear strength reduction finite element method (SSRFEM) is a powerful tool for slope stability analysis. The factor of safety (FOS) of the slope can be easily calculated only through reducing effective cohesion (c′) and tangent of effective friction angle ($tan{\varphi}^{\prime}$) in equal proportion. However, this method may not be applicable to soil slope under wetting-drying cycles (WDCs), because the influence of WDCs on c′ and $tan{\varphi}^{\prime}$ may be different. To research the method of estimating FOS of soil slopes under WDCs, this paper presents an experimental study firstly to investigate the effects of WDCs on the parameters of shear strength and stiffness. Twelve silty clay samples were subjected to different number of WDCs and then tested with triaxial test equipment. The test results show that WDCs have a degradation effect on shear strength (${\sigma}_1-{\sigma}_3)_f$, secant modulus of elasticity ($E_s$) and c′ while little influence on ${\varphi}^{\prime}$. Hence, conventional SSRFEM which reduces c′ and $tan{\varphi}^{\prime}$ in equal proportion cannot be adopted to compute the FOS of slope under conditions of WDCs. The SSRFEM should be modified. In detail, c′ is merely reduced among shear strength parameters, and elasticity modulus is reduced correspondingly. Besides, a new approach based on sudden substantial changes in the displacement of marked nodes is proposed to identify the slope failure in SSRFEM. Finally, the modified SSRFEM is applied to compute the FOS of a slope example.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1749-1757
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• 1995

The structure of turbulence of fully developed flow through three concentric annuli with both rough inner and outer walls was investigated experimentally for Reynolds number range Re=15000-93000. Turbulence intensities were measured in three (u, v, w) directions, and turbulence shear stresses in annuli of radius ratios .alpha.= 0.26, 0.4 and 0.56, respectively. The result showed that the structure of turbulence for these asymmetric flows was not the same as that for the annulus with smooth walls. The velocity fluctuations of all three components (u, v, and w-directions) showed little discernible variation with Reynolds numbers, but became apparent with the influence of radius ratio (.alpha.) The experimental results for an annulus with the roughened outer wall and a smooth annulus were shown in the figures as a reference. The eddy diffusivities and friction factors were also presented and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.7
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• pp.905-912
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• 2013

Rubber is one of the most commonly used materials in various fields because of its unique viscoelastic properties. Friction occurs when a tire constantly makes contact with the ground. As a result, friction causes wear. The frictional energy caused by friction is a primary factor in the wear mechanism. The frictional energy is affected by various conditions (temperature, roughness of ground, shape of rubber, load, and materials). In this study, the analysis was preceded by considering the vertical load and the horizontal velocity to the rubber using ABAQUS/explicit. The contact pressure, and friction energy are derived using the shear force and slip distance. The actual behavior of the rubber test data were compared with the analysis results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2C
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• pp.49-60
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• 2012

In this study, the behaviors of friction pile groups are investigated using 3D finite element (FE) analysis. The emphasis was quantifying on the shear load transfer (f-w) characteristics of pile groups and the shaft group effects. A framework for determining the f-w curve is proposed based on both theoretical analysis and field load test database. Through comparisons with case histories and FE results, it is shown that the proposed f-w curve is capable of predicting the behavior of a friction pile in deep soft clay. Additionally, a numerical analysis that takes into account the group efficiency factors were performed for major parameter on group pile-soil interaction, such as the pile spacing, pile arrangement, soil condition, and location of pile cap. Based on these results, the shaft group efficiency factors were also proposed.