• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.25 no.3
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• pp.131-137
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• 2019

Carton clamps, one of forklift attachments, allow users to quickly handle shipping units such as unitized loads, large shipping cases, or crates without the requirement of pallets. As the use of palletless handling by clamp trucks increases, so does the need for simulation research on clamp truck handling. The frictional characteristics for various contact conditions of corrugated paperboards and their constituent boards were analyzed to obtain the data needed in the computer simulation for the handling of carton clamp truck. The overall mean of static-frictional coefficients between selected corrugated paperboards was 0.38 (±0.01), which was 1.3~1.6 times greater than 0.23~0.29 of the frictional coefficients between boards. The overall mean of static-frictional coefficients between the corrugated paperboards and the rubber contact pad was 0.82 (±0.02), which was about 1.1 to 2.8 times greater than 0.29~0.78 of the static-frictional coefficient between the linerboard and the rubber contact pad. The overall mean of kinetic-frictional coefficients between the corrugated paperboards was 0.35 (±0.01), and 0.76 (±0.02) between the corrugated paperboards and the rubber contact pad.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2509-2522
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• 2021

A valve assembly used in nuclear power plants must be qualified and supervised. New technical standards such as ASME QME-1 2007 particularly require detailed qualification using experiment and analysis. Particularly, diagnostic tests and engineering studies are required for qualification of ASME QME-1 2007. Among these studies, the research on the measurement of friction coefficient and packing stress is important. The irregular change of packing stress along the stroke distance occurs because of the abnormal phenomenon, which must be found and studied with quantitative methods. Packing stress should be analyzed conservatively through experimentation and analysis. In this study, various formulas were applied to measure and calculate coefficient of friction and packing stress. This study can be used in relation to qualification and supervision of packing materials. And the calculation using static diagnosis test can be used to find the packing frictional force in dynamic diagnosis test with flow pressure in a pipe. This study has made it possible to reliably consider packing frictional force generated in a valve body. And so, it is believed that more margin can be secured when evaluating the capacity of valve actuator by applying the accurate frictional force generated in the valve assembly.

• Tribology and Lubricants
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• v.17 no.2
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• pp.97-108
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• 2001

This paper describes the development of performance analysis technique for a leaf-type gas lubricated fail bearing. Stiffness coefficient and frictional damping due to the slip between all contacts of leaves are evaluated for various leaf structures. The fluid film thickness and pressure distribution are computed but it is not considered the elastic deformation by film pressure. The analysis results include the effects that the curvature radius and the length of leaf and the friction coefficient have on the static and dynamic characteristics of the foil bearings.

• Tribology and Lubricants
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• v.24 no.5
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• pp.215-220
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• 2008

An internal friction model was developed to model the frictional behavior of automotive Constant Velocity (CV) joints by using the test data from an instrumented CV joint friction apparatus with actual driveshaft assemblies. Experiments were conduced under different realistic operating conditions of oscillatory speeds, CV joint articulation angles, lubrication, and torque. The experimental data were used to develop a physics-based semi-empirical CV joint internal friction coefficient model as a function of different CV Joint operating parameters. It was found that the proposed friction model captures the experimental results well not only the static behavior of friction coefficient, but also the dynamic friction terms, which is the main source of force that causes vehicle vibration problems.

• Journal of Biosystems Engineering
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• v.33 no.3
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• pp.173-178
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• 2008

Some physical properties of rapeseed were measured at five moisture levels of 10.03, 14.91, 20.07, 25.06 and 30.12% (w.b.), which include frictional properties (coefficient of static friction, emptying and filling angle of repose) and aerodynamic properties (terminal velocity and drag coefficient). The physical properties of rapeseed were evaluated as a function of seed moisture content. In the moisture content range, the coefficients of static friction, emptying and filling angle of repose increased linearly with increase of moisture content. The maximum values of coefficients of static friction were on the acrylic surface, varied from 0.34 to 0.43; the next is on the galvanized steel, varied from 0.30 to 0.38; and the minimum were on stainless steel surface, varied from 0.27 to 0.35. Emptying and filling angle of repose varied from 26.12 to 29.62 and 23.83 to 27.05 degrees, respectively. Terminal velocity increased linearly from 3.47 to 3.91 m/s with increase of moisture content. Drag coefficient varied from 1.84 to 1.64 as the moisture content increased. The relationship between drag coefficient and moisture content were expressed by non-linear equation.

• Advances in materials Research
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• v.4 no.3
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• pp.165-178
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• 2015

Friction coefficient of epoxy metal matrix composites were investigated. The main objective was to increase the friction coefficient through rubber sole sliding against the epoxy floor coating providing appropriate level of resistance. This was to avoid the excessive movement and slip accidents. Epoxy metal matrix composites were reinforced by different copper wire diameters. The epoxy metal matrix composites were experimentally conducted at different conditions namely dry, water and detergent wetted sliding, were the friction coefficient increased as the number of wires increased. When the wires were closer to the sliding surface, the friction coefficient was found to increase. The friction coefficient was found to increase with the increase of the copper wire diameter in epoxy metal matrix composites. This behavior was attributed to the fact that as the diameter and the number of wires increased, the intensity of the electric field, generated from electric static charge increased causing an adhesion increase between the two sliding surfaces. At water wetted sliding conditions, the effect of changing number of wires on friction coefficient was less than the effect of wire diameter. The presence of water and detergent on the sliding surfaces decreased friction coefficient compared to the dry sliding. When the surfaces were detergent wetted, the friction coefficient values were found to be lower than that observed when sliding in water or dry condition.

• Geomechanics and Engineering
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• v.17 no.3
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• pp.253-259
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• 2019

Concrete-to-concrete bedding planes (CCBP) are observed from time to time due to the multistep hardening process of the concrete materials. In this paper, a series of direct/cyclic shear tests are performed on CCBP under static and dynamic normal load conditions to study the frictional behavior effect by the shear velocities, normal impact frequencies, horizontal shear frequencies, normal impact force amplitudes, horizontal shear displacement amplitudes and normal load levels. According to the experimental results, apparent friction coefficient k ($k=F_{Shear}/F_{Normal}$) shows different patterns under static and dynamic load conditions at the stable shear stage. k is nearly constant in direct shear tests under constant normal load conditions (DCNL), while it is cyclically changing with nearly constant peak value and valley value for the direct shear tests under dynamic normal load conditions (DDNL), where k increases with decreasing normal force and decreases with increasing normal force. Shear velocity has little influence on peak values of k for the DCNL tests, but increasing shear velocity leads to increasing valley values of k for DDNL tests. It is also found that, the valley values of k ascend with decreasing impact normal force amplitude in DDNL tests. The changing pattern of k for the cyclic shear tests under constant and dynamic normal load conditions (CCNL and CDNL tests) are similar, but the peak value of k is smaller in CDNL tests than that in CCNL tests. Normal load levels, shear displacement amplitudes, vertical impact frequencies, horizontal shear frequencies and normal impact force amplitudes have little influence on the changing pattern of k for the cyclic shear tests. The tests of this study provide useful data in understanding the frictional behavior of the CCBP under distinct loadings, and these findings are very important for analyzing the stability of the jointed geotechnical structures under complicated in situ stress conditions.

• Journal of the Korean GEO-environmental Society
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• v.18 no.9
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• pp.19-31
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• 2017

In case of USA, the drilled shaft and the driven pile in the field showed a good correlation in the analysis of the bearing capacity between the dynamic load test and the static load test. However, in Korea, we mainly install the bored pile, which is not widely used overseas and we tried to confirm the reliability of the dynamic load test on the bored pile, because many people questioned the reliability of it. In this study, load tests were carried out on PHC bored piles in LH field (Cheonan, Incheon, Uijeongbu), and the bearing capacity of the dynamic load test (EOID 7times, Restrike 7times) and the static load test (7times) were compared and analyzed. As a result, the average of the bearing capacity of the static load test was 27% higher than that of the dynamic load test (reliability : 0.73, coefficient of variation : 0.3). And the average of the bearing capacity of the static load test (Davisson) was 27% higher than that of the bearing capacity of the dynamic load test (Davisson) (reliability : 0.73, coefficient of variation : 0.2). To reduce the difference between the bearing capacity of the dynamic load test and the static load test, we proposed modified bearing capacity of dynamic load test (base bearing capacity of EOID + skin frictional force of restrike) and difference between the bearing capacities was reduced to 9% (reliability : 0.91, coefficient of variation : 0.2). And the coefficient of variation was reduced to 0.2 and the consistency of analysis increased.

• Transactions on Electrical and Electronic Materials
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• v.6 no.6
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• pp.249-255
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• 2005

In recent years, a novel tiny piezoelectric linear motor converting a radial mode vibration to a longitudinal mode vibration driven by the impact force has been developed for a camera optical module. The tiny piezoelectric motor is consisted of a shaft, mobile element, and piezoelectric transducer. In this work, the frictional coefficient and static friction force of the interface between the shaft and the mobile element have been investigated according to their respective materials. It was found that two combinations, namely Pyrex glass or stainless steel for the shaft and stainless steel (SUS) for the mobile element, exhibited good dynamic behaviors in the tiny ultrasonic linear motor, which was newly developed based on operating concepts based on Newton's law.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.362-370
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• 2019

The internal pressure capacity of a modular containment structure requires analysis to prevent the release of radioactive material in the case of an accident. To analyze the capacity, FEM models were prepared while considering the tendon arrangements and the contact surfaces between precast concrete modules, and then static analyses were carried out. The changing characteristics in the displacement and stress under step-wise loading were analyzed, along with the effects of selected parameters. For comparison, the capacity of a monolithic containment structure was also analyzed. Parametric analyses were done to suggest ranges of parameters such as the tendon force, tendon spacing, tendon location in concrete thickness direction, friction coefficient, and concrete thickness. The tendon force and frictional force provide a combined effect between contact surfaces of modules. The same level of internal pressure capacity can be secured even in the modular containment structure as in the monolithic containment structure by increasing the tendon force with additional tendons.