• Journal of Biosystems Engineering
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• v.30 no.4 s.111
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• pp.229-234
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• 2005

Kinetic friction coefficient, bulk density, dynamic and static angle of repose, and terminal velocity of rice husk at the moisture range 7 to $23\%$ w.b. were determined. It could lead to better design and operation of the processing machinery and handling facilities. Friction coefficient was determined from the horizontal traction force measured by pulling the container holding a mass of rice husk on various plate materials. Dynamic angle of repose was calculated from the photos of bulk samples piled by gravity flow on a circular platform. Static angle of repose was determined by measuring the side angle of the bulk material which was left in a cylindrical container after natural discharge of the bulk sample through a circular hole in the bottom plate. Kinetic friction coefficients of rice husk were in the range of $0.254\~0.410,\;0.205\~0.520,\;0.229\~0.400,\;and 0.133\~0.420$ on PVC, mild steel, galvanized steel, and stainless steel, respectively. Bulk density, dynamic and static angle of repose, and terminal velocity were in the range of $91.7\~98.3$ $kg/m^3$, $40.2\~47.6^{\circ},\;52.8\~83.7^{\circ},$ and $1.36\~1.73$ m/s, respectively. These physical properties of rice husk increased linearly as the moisture content increased.

• Smart Structures and Systems
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• v.20 no.2
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• pp.151-162
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• 2017

In practical engineering, the friction damper is a widely used energy dissipation device because of its large deformation capacity, stable energy dissipation capability, and cost effectiveness. While based on conventional friction dampers, the double-sliding friction damper (DSFD) being proposed is different in that it features two sliding friction forces, i.e., small and large sliding friction forces, rather than a single-sliding friction force of ordinary friction dampers. The DSFD starts to deform when the force sustained exceeds the small-sliding friction force, and stops deforming when the deformation reaches a certain value. If the force sustained exceeds the large sliding friction force, it continues to deform. Such a double-sliding behavior is expected to endow structures equipped with the DSFD better performance in both small and large earthquakes. The configuration and working mechanism of the DSFD is described and analyzed. Quasi-static loading tests and finite element analyses were conducted to investigate its hysteretic behavior. Finally, time history analysis of the single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) systems were performed to investigate the seismic performance of DSFD-equipped structures. For the purpose of comparison, tests on systems equipped with conventional friction dampers were also performed. The proposed DSFD can be realized perfectly, and the DSFD-equipped structures provide better performances than those equipped with conventional friction dampers in terms of interstory drift and floor acceleration. In particular, for the MDOF system, the DSFD helps the structural system to have a uniform distributed interstory drift.

• Agricultural and Biosystems Engineering
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• v.7 no.1
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• pp.13-17
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• 2006

The planocentric gear, known as wobble mechanism, has been used for speed reducing mechanism as an ingenious mechanism. The modem application can be found in the backrest adjusting mechanism of a vehicle reclinable seat, fluid pumps and aircraft hoist and winches. Higher speed reduction ratios, high load capacity, lower weight, and compactness are the main advantages of this gear. This paper presents velocity and static force analysis to investigate the friction lock of the planocentric gear. The rectilinear tooth profile is used to maximize the speed reduction ratio. The equivalent linkage system is used for the analysis of instantaneous motion. As the results, the transmission efficiency of the planocentric gear is found and the friction lock of the system is determined for the friction coefficients of journals. A numerical example that illustrates the developed analysis is presented.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1-8
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• 2005

In this study, static pile load tests for instrumented drilled shaft pile and instrumented driven steel pipe pile were performed. Based on the results of pile load test, skin friction of each stratum was compared. Skin friction of drilled shaft were more than those of driven pile at the same settlement. This was based on the difference of surface roughness of piles and pile construction methods.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.803-809
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• 2005

This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.32-36
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• 1995

A study was conducted to evaluate the dynamic mechanical properties (modulus of elasticity, resonant frequency and interanal friction) of compression wood in Pinus densiflora. Vibration method was used for estimation of dynamic modulus of elasticity and the values were compared to those of static bending modulus of elasticity. The results obtained are as follows: 1. The dynamic modulus of elasticity of compression wood decreased, whereas that of normal wood increased, with increasing specific gravity. 2. The resonant frequency of compression wood decreased, whereas that of normal wood increased, with increasing specific gravity. 3. The internal friction of compression wood increased with increasing specific gravity. 4. The correlation coefficients between dynamic and static moduli of elasticity in compression and normal woods were high.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.813-818
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• 2009

Shear properties of plastic bottle film/plastic bottle film and plastic bottle film/granitic soil which were evaluated from static friction tests. The monotonic shear experiments were performed by using an tilt table apparatus and large direct shear device. The test results showed that the friction angle of each interface and the interface depended on the amount of normal stress, the type of the interface used. Therefore, the testing method should be determined carefully by considering the type of loads and normal stress expected in the field with using the materials installed in the site.

• The KSFM Journal of Fluid Machinery
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• v.9 no.1 s.34
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• pp.47-55
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• 2006

This paper presents the theoretical model to investigate the effect of Coulomb damping in the sub-structure of a foil bearing. Foil deflection is restricted by friction of bumps. Equivalent viscous damping of the bump foils is derived from the Coulomb friction. Dynamic equation of the bumps is constituted by stiffness and damping terms. This point give the difference from Heshmat's frictionless and simple compliance bump model. The fluid is modeled with the compressible Reynolds equation. A perturbation approach is used to determine the static and dynamic performance of the bearing from the coupled fluid-structural model. The analysis result shows that the static and dynamic performance is enhanced by bump friction. This analysis technique would be extended to development of a high performance bearing.

• Tribology and Lubricants
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• v.23 no.6
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• pp.312-317
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• 2007

In general, a brake system of axle for heavy duty machine as a wheel excavator makes use of wet-type multiple disk brakes. These disk bakes are very important parts of heavy duty machine because they are advanced in durability and braking power, and can be designed compactly. Thus, we designed and made wet-type multiple disk brakes of axle for the 14ton class wheel excavator to be localization of these imported all. These disk brakes were made a comparative test with the existing disk brakes by the SAE No.2 dynamometer, and the friction characteristics as dynamic and static friction coefficient and wear depth of friction paper were measured.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.924-927
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• 1996

In this work, we investigate the quasi-static crawling of the four-bar mechanism. Since the crawling of the mechanism is based on sliding of contact points of the mechanism with the ground, interaction forces and friction forces at contact points of the mechanism with the ground should be computed. For this purpuse, we introduce the concept of imaginary joints to find these forces. Therefore, we are able to treat the closed mechanism as a serial one. Also, sliding conditions of the mechanism in quasi-static equilibrium are examined. Lastly, the required torques for the mechanism to crawl with respect to various configurations of the mechanism but with a fixed ground friction are investigated.