• International journal of steel structures
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• v.18 no.5
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• pp.1699-1709
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• 2018

Suspen-dome structures are extensively used due to their superiority over traditional structures. The friction between cable and joints may severely influence the distribution of cable force, especially during the pre-stressing construction period. An accurate and efficient numerical method has not yet been developed that can be used for estimating the influence of friction on cable force distribution. Thus, this study proposes an efficient friction element to simulate friction between cable and joint. A flowchart for estimating the value of friction force is introduced. These novel numerical methods were adopted to estimate the influence of friction on cable force distribution. The accuracy and efficiency of these numerical methods were validated through numerical tests.

• Tribology and Lubricants
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• v.23 no.6
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• pp.278-282
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• 2007

Friction characteristics of a low-steel friction material were examined to investigate creep groan phenomena. The amount of three ingredients (steel fiber, $ZrSiO_4$, cashew) were changed to produce test specimens using a constrained mixture design. Tribological properties of the friction material specimens were obtained by using a 1/5 scale dynamometer. Results showed that the amount of three different ingredients strongly affected the level of friction coefficient and the difference between the static friction coefficient and the kinetic friction coefficient $({\Delta}{\mu}).\;ZrSiO_4$ and steel fiber tended to increase the average friction coefficient and aggravated the stick-slip phenomena suggesting high creep groan propensity. On the other hand, cashew tended to decrease average friction coefficient and ${\Delta}{\mu}$.

• Tribology and Lubricants
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• v.23 no.6
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• pp.266-271
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• 2007

The brake performance of sintered friction materials for the high speed train was studied. In this study, newly developed sintered materials based on copper were compared with the commercial products for high speed trains. They were tested on a 1/5 scale dynamometer using low carbon steel disks. Effectiveness, fade, and recovery tests were carried out to examine friction performance and the change of disk thickness variation (DTV) during brake applications and noise propensity were also evaluated. Results showed that the two sintered friction materials exhibit similar friction coefficients and braking performance, whereas the newly developed friction material was superior in terms of DTV generation and noise propensity to the commercial friction material. The improvement of the newly developed friction material was attributed to the high graphite content which reduced the stick-slip phenomena and prevented uneven disk wear by producing friction films on the counter disk.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.83-92
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• 1997

In a study on the development of Cu-based sintered friction materials, the specimens pressed with various compacting pressures $(3-6 ton/cm^2/)$ have been evaluated to find the optimum condition of compacting pressure. As compacting pressure increased up to $(5 ton/cm^2/)$, mechanical properties such as density, hardness, bending strength, wear and coefficient of friction, etc. improved remarkably, but up to 6 ton/cm$^{2}$, decreased slightly because of traps of gases and water vapors in specimen. Disk assembly composed of 12 pieces of Cu-based friction materials has been compared with one of asbestos-and nonasbestos-based friction materials. In dynamic and driving tests to find burst spin strength, corrosion area rate and friction properties, etc., Cu-based sintered friction materials showed better properties than the others, especially in severe conditions because oxides such as $Cu_2O; and; SnO_2$ in the friction surface of friction materials were formed.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.90-98
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• 1997

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of friction pressure on bonding strength and a charicteristic of fracture. The tensile strength of the friction welded joint was increased up to 90% of the Cu base metal under the condition of friction time 1.2 sec, friction pressure 4.5kgf/$\textrm{mm}^2$ and upset pressure 10kgf/$\textrm{mm}^2$. From the results of fracture surface analysis, the increase of friction pressure could remarkably decrease the force and the time to be normally acted on weld interface. The W particles which were included in the plastic zone of Cu side could induce fracture adjacent to the weld interface because their existance in Cu induces a decrease in available section area and an increase in notch effect. Therefore, the tensile strength was decreased at high friction pressure (6kgf/$\textrm{mm}^2$) because the destruction of W was increased by an increase in mechanical force and crack was formed at weld interface.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1668-1679
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• 2004

The design of an axial piston pump for electro-hydrostatic transmission systems requires accurate information where and how much the internal friction and flow losses are produced. This study is particularly focused on the friction losses of a bent-axis type hydraulic piston pump, aiming at finding out which design factors influence its torque efficiency most significantly. To this end, the friction coefficients of the pump parts such as piston heads, spherical joints, shaft bearings, and valve plate were experimentally identified by a specially constructed tribometer. Applying the experimental data to the equations of motion for pistons as well as to the theoretical friction models for the pump parts, the friction torques produced by them were computed. The accuracy of the computed results was confirmed by the comparison with the practical input torque of the pump. In this paper, it is shown that the viscous friction forces on the valve plate and input shaft bearing are the primary source of the friction losses of the bent-axis type pump, while the friction forces and moments on the piston are of little significance.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.51-61
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• 2002

A tracking control scheme on the XY ball-screw drive system in the presence of nonlinear dynamic friction is proposed. A nonlinear dynamic friction is regarded as the Lund-Grenoble friction model to compensate effects of friction. The conventional VSC method that often has been used as a non-model-based friction controller has poor tracking performance in high-precision position tracking application since it cannot compensate the friction effect below a certain precision level completely. Thus to improve the precise position tracking performance, we propose the integral type VSC method combined with the friction-model-based observer. Then this control scheme has the high precise tracking performance compared with the non-model-baked VSC method and the PID control method with a similar observer. This fact is shown through the experiment on the XY ball-screw drive system with the nonlinear dynamic friction.

• Tribology and Lubricants
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• v.26 no.4
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• pp.246-253
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• 2010

Friction characteristics of the brake friction materials without environmentally regulated ingredients were examined to find their role in the brake performance. Five friction materials were produced based on a nearcommercial formulation by changing the relative amount of potentially hazardous ingredients to health and environment, such as $Sb_2S_3$, potassium titanate, and brass fiber. Tribological properties of the friction materials were obtained using a scale dynamometer and Krauss type tribometer. Results showed that the excluded three ingredients played important synergetic effects on tribological properties in terms of fade resistance, wear resistance and friction effectiveness. In particular, brass fibers played important roles in the friction stability by providing excellent thermal diffusivity at the friction interface. Potassium titanate whiskers showed excellent fade resistance and wear resistance compared to the substituted barite. Antimony trisulfide, on the other hand, showed little effect on the high temperature fade resistance and wear resistance, while it increased friction effectiveness at moderate temperatures. The friction materials without the three ingredients showed severe fade, indicating antisynergy effects.

• Tribology and Lubricants
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• v.14 no.1
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• pp.70-78
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• 1998

Two different friction materials (organic and low-metallic pads) for automotive brakes were studied to investigate the anti-fading phenomena during stop. The anti-fading phenomena were pronounced more in the case of using low metallic friction materials than organic friction materials. The main cause of the anti-fading phenomena was the high dependence of friction coefficient on a sliding speed. The anti-fading was prominent when the initial brake temperature was high in the case of low-metallic friction materials due to the strong stick-slip event at high temperature. On the other hand, the anti-fading was not severe in organic friction materials and the effect was reduced at high braking temperature due to the thermal decomposition of organic friction materials. The strong stickslip phenomena of low metallic friction materials at high temperature induced high torque oscillations during drag test. During this experiment two different braking control modes (pressure controlled and torque controlled modes) were compared. The type of the control mode used for brake test significantly affected the friction characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.93-93
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• 2010

We developed friction welded bimetallic sleeve for 220kV aluminum conductor XLPE cable. Not only friction welded bimetallic sleeve for Termination(EB-A, EB-G) but also friction welded sleeve for Joint of Al to Cu conductor was developed regardless of this project. Generally, friction welded sleeve used to connect Al conductor cable to Cu conductor cable and used for improvement of mechanical property of terminal by offer the copper side of friction welded bimetallic sleeve at the Termination. Connection method for Al-Cu conductor has mainly used friction welding at the solid state, because it is difficult to connect by using conventional welding method. this investigation introduces development of friction welded bimetallic sleeve by friction welding and test result of 220kV Al conductor XLPE cable and accessories using friction welded sleeve.