• Journal of Industrial Technology
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• v.22 no.A
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• pp.153-159
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• 2002

This paper is an experimental work of estimating friction angle of very coarse grained soil such as rubble mound by performing laboratory experiments. Two crushed rocks of rubble mound were used for tests. Triaxial compression tests with drained conditions were performed to measure friction angles of soils prepared by mixing the crushed soil having an identical coefficient of uniformity with different maximum grain size distribution. Centrifuge model experiments with those soils were also performed to measure angle of repose and to estimate friction angle of soil from measuring the slope of slip line in the active stress state. Model tests were carried out by changing the G-levels of 1G and 50G. From triaxial compression tests, the measured value of friction angle of soil is in the range of $41{\sim}57^{\circ}$. The measured value of repose angle is in the range of $32{\sim}35^{\circ}$. The values of friction angle are found not so sensitive to the maximum grain size of soil as long as the coefficient of uniformity is identical. Estimated value of friction angle from measuring the slope of slip line in the active stress state is in the range of $30{\sim}46^{\circ}$. Thus, the estimated angle of friction are found to be greater in the order of the measured angle of repose, the estimated value from the slope of active state, and triaxial compression test results. On the other hand, the measured values of friction angle from triaxial tests were compared with empirical equations, based on the relation between friction angle and void ratio. Equations proposed by Helenelund(l966) and Hansen(1967) found to be relatively reliable to estimate friction angles of soil.

• Fashion & Textile Research Journal
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• v.2 no.5
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• pp.443-449
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• 2000

An investigation of the relative velocity of friction surface for the newly developed cone drum twister texturing mechanism is reported. The cone drum twister is one of the outer surface contacting friction-twisting devices in false-twist texturing. In this cone drum twister, a filament yam passes over the surface of the cone drum that rotates by passing the yarn without a special driving device. This research is theoretically composed of the analysis of the false twisting mechanism. The equations were derived by using the conical angle of the cone drum, projected wrapping angle, and yarn helix angle. Theoretical values of the relative velocity of friction surface were calculated and discussed. It is shown that, as the projected wrapping angle increased, the relative velocity of friction surface decreased. But as the conical angle increased the relative velocity of friction surface also increased.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.2
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• pp.110-116
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• 2011

The current study investigated the friction property of angle and width effect for micro-scale grooved crosshatch pattern on SKD11 steel surface against bearing steel using pin-on-disk type. The samples fabricated by photolithography process and then these are carry out the electrochemical etching process. We discuss the friction property due to the influence of a hatched-angle and a width of groove on contact surface. We could be explained the lubrication mechanism for a Stribeck curve. So It was found that the friction coefficient depend on an angle of the crosshatch on contact surface. It was thus verified that micro-scale crosshatch grooved pattern could affect the friction reduction. Also, it is play an important a width of groove to be improved the friction property. I was found that friction property has a relationship between a width and an angle for micro-grooved pattern.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.3
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• pp.94-99
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• 2011

Micro-scale surface pattern has an benefit of tribological application under lubricated sliding contact. Therefore, a special pattern, that has to reduce the coulomb friction under contact, is considered to be necessary for improved efficiency of machines. The current study investigated the friction property of angle effect for micro-scale grooved crosshatch pattern on bearing steel surface using pin-on-disk type. The samples fabricated by photolithography process and then these are carry out the electrochemical etching process. We discuss the friction property due to the influence of hatched-angle on contact surface. We could be explained the lubrication mechanism for a Stribeck curve. It was found that the friction coefficient depend on an angle of the crosshatch on contact surface. It was thus verified that micro-scale crosshatch grooved pattern could affect the friction reduction.

• Tribology and Lubricants
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• v.38 no.6
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• pp.261-266
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• 2022

Notably, laser surface patterning facilitates tribological applications under lubricated sliding contacts. Consequently, a special pattern that can reduce the coefficient of friction under contact is considered necessary for improved machine efficiency. However, inappropriate pattern designs produce higher friction coefficients and cannot reduce friction. In this study, we use cast iron pins as specimens to investigate their friction and wear characteristics. Moreover, we experimentally investigate the correlation between the friction reduction effect and the design of groove crosshatch patterns fabricated with various angles and widths. We conduct a friction test using a pin-on-disc type tribometer under grease lubrication to study the friction reduction effect of the specimens, and we observe that the average coefficient of friction changes with the crosshatch angle and width. The experiment reveals that grooved crosshatch specimens with a crosshatch angle of 135°maximize friction reduction. The coefficient of friction of the groove specimens with a width of 120 ㎛ is lower than that of the specimens with a width of 200?. The friction reduction effect of the width of the groove is attributed to the density of the groove pattern. Thus, grooved crosshatch patterns can be designed to maximize friction reduction, and the friction property of a grooved crosshatch pattern is found to be related to its width and angle.

• Journal of the Korean Geotechnical Society
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• v.25 no.4
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• pp.105-112
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• 2009

In this study, a series of direct shear tests were performed to investigate the characteristics of friction angles for sands and interface friction angle between sands and construction materials with respect to different relative density of the Nak-dong River sands and shearing velocity. The result of the test shows that friction angles of sands are always higher than interface friction angle between sands and construction materials. As the shearing velocity get faster, the friction angles of sand became higher. With respect to the density of sand by reducing void ratio, friction angles increase linearly, and relevant equations were proposed to calculate the friction angle by changing void ratio and relative density of sand. The interface roughness of construction materials was also an important factor in interface friction angle.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.415-421
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• 2018

A location determining method is proposed for critical sliding surface in the stability analysis of the filling materials in karst caves. First, a preliminary location of the sliding surface is determined based on simulation results which includes displacement contour and plastic zone. The sliding surface will locate on the bottom contact interface when the friction angle is relative small. However, a weakened contact interface always becomes the critical sliding surface no matter what the friction angle is. Then when the friction angle becomes larger, the critical sliding surface inside fillings can be determined by a parabola, the coefficient of which increases linearly with the friction angle under the same cohesion. Finally, the critical sliding surface approximately remains unchanged with friction angle. The influence of cohesion is similar to that of friction angle. Although affected by shape, size or position of the karst cave, the critical sliding surface mainly depends on both friction angle and cohesion. Thus, this method is always useful in determining the critical sliding surface.

• Fashion & Textile Research Journal
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• v.3 no.5
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• pp.473-478
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• 2001

The newly developed cone drum twister is one of the outer surface contacting friction-twisting devices in false-twist texturing. An investigation of the drag angle for the newly developed cone drum twister texturing mechanism is reported. An analysis is given from which equations can be derived that relate to the conical angle of cone drum, wrapping angle, drag angle, and yam helix angle. Theoretical values of drag angle are calculated and discussed. It is shown that, as the helix angle and the projected wrapping angle increases, the drag angle also increases slowly until the helix angle of $40^{\circ}$ but after the helix angle of $40^{\circ}$ the drag angle increases rapidly. Furthermore the higher the projected wrapping angle and conical angle, the higher the drag angle of friction surface.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1998.10a
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• pp.467-472
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• 1998

The interface friction angle between soil and fibers is important to evaluate improvement of the shear strength on fiber mixed soils. Direct shear test and pullout tort conducted by an apparatus made specially for the purpose of this study, was analyzed to know how fiber and soils affect on interface friction angle. By the results, The value of interface friction angle of sandy soils is larger than that of clayey soils. As a diameter of fiber is large, the value of friction coefficient of sandy soil is increase and that of clayey soil is decrease. An interface friction angle of well graded soil is larger value than that of uniform graded soil

• Tunnel and Underground Space
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• v.16 no.1 s.60
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• pp.58-72
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• 2006

In recent years, not only the occurrences but the magnitude of earthquakes in Korea are on an increasing trend and other sources of dynamic events including large-scale construction, operation of hi띤-speed railway and explosives blasting have been increasing. Besides, the probability of exposure fir rock joints to free faces gets higher as the scale of rock mass structures becomes larger. For that reason, the frictional behavior of rock joints under dynamic conditions needs to be investigated. In this study, a shaking table test system was set up and a series of dynamic test was carried out to examine the dynamic frictional behavior of rock joints. In addition, a computer program was developed, which calculated the acceleration and deformation of the sliding block theoretically based on Newmark sliding block procedure. The static friction angle was back-calculated by measuring yield acceleration at the onset of slide. The dynamic friction angle was estimated by closely approximating the experimental results to the program-simulated responses. As a result of dynamic testing, the static friction angle at the onset of slide as well as the dynamic friction angle during sliding were estimated to be significantly lower than tilt angle. The difference between the tilt angle and the static friction angle was $4.5\~8.2^{\circ}$ and the difference between the tilt angle and the dynamic friction angle was $2.0\~7.5^{\circ}$. The decreasing trend was influenced by the magnitude of the base acceleration and inclination angle. A DEM program was used to simulate the shaking table test and the result well simulated the experimental behavior. Friction angles obtained by shaking table test were significantly lower than basic friction angle by direct shear test.