• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1611-1617
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• 2013

Information about trafficability or the condition of road with regard to its being traveled over by vehicles is one of the most critical factors for roadway operation in winter. Specifically, when traveling on snowy or icy surfaces, the traction force varies per vehicle type including tire types, geometric characteristics of roads, and conditions of road surfaces. In general, front-wheel drive or four-wheel drive vehicles have better traction performance on snowy or icy surface than rear-wheel drive vehicles, and the latter type vehicle causes more serious traffic congestion when there is unexpected snowfall. Thus, traffic information regarding trafficability with respect to vehicle types, geometric characteristics of roadway sections, and roadway surface conditions can provide a foundation to make a decision whether to use the associated roadway sections for roadway operators as well as users. Based on the preceding premise, the objective of this study is to present a methodology for developing a trafficability index with respect to vehicle types, geometric characteristics of roadway sections, and roadway surface conditions.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.27-34
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• 2023

This paper presents the application of a magnetic gear to the electric propulsion system for an aircraft. Since high torque is required in aircraft electric propulsion systems, combining a speed reducer can amplify the torque. However, mechanical gears have issues, such as friction, vibration, and heat generation, which lead to maintenance challenges. In the case of a direct-drive motor that does not use mechanical gears, the size and weight of the motor increase to achieve high torque. This paper proposes the application of a magnetic gear to solve the maintenance issues of mechanical gears and the weight increase problem of direct-drive motors in aircraft electric propulsion systems. In this paper, a magnetic gear suitable for aircraft electric propulsion systems is designed, and it is compared with a direct-drive motor in terms of performance and the feasibility of applying the magnetic gear is verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.41-51
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• 2016

Friction generated from balls and grooves incurs temperature rise in the ballscrew system. Thermal deformation due to the heat degrades positioning accuracy of the feed drive system. To compensate for the thermal error, accurate prediction of the temperature distribution is required first. In this paper, to predict the temperature distribution according to the rotational speed, solid and hollow cylinders are applied for analysis of the ballscrew shaft and nut, respectively. Boundary conditions such as the convective heat transfer coefficient, friction torque, and thermal contact conductance (TCC) between balls and grooves are formulated according to operating and fabrication conditions of the ballscrew. Explicit FDM (finite difference method) is studied for development of a temperature prediction simulator. Its effectiveness is verified through numerical analysis.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.213-220
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• 2016

In order to drive on road safely, the type of road design and construction is basically needed to optimize driver's safety and vehicle performance. Although the heavy traffic highways were built by reflecting these factors, the national highways and local roads have still taken a lot of problems. In this study, we analyzed the behavior characteristics of a vehicle according to the speed variation of the vehicle using the PC-Crash program for the traffic accidents reconfiguration at GULUN interchange located Hongcheon in Gangwon Province. the conditions outlet surface of the road for analysis were dry road surface, wet road surface and icy road surface. As a result, we identified the fact that the friction coefficient of road surface and the speed of vehicle affected to vehicle behavior characteristics of outlet shape in GULUN interchange, and showed the possibility that we can verify a problem about road design through to this simulation in advance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.06a
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• pp.47-52
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• 1999

In recent years, the micro-tribological behavior of silicon has been the topic of much interest. peformance of thin film under light load is important for potential applications in MEMS. In this work under light load and various humidity, the tribological behavior of undulated surface with various width and shape was Investigated. The results show that undulated surface of linear type had good tribological properties abrasive wear occur depending on the sliding condition. Also the effect of humidity on friction and wear was not important if exist undulation. Finally, undulations on HDD were found to be effective in trapping wear particles.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.273-274
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• 2002

In order to evaluate the flying characteristics of slider, the acoustic emission (AE) as well as friction signals are typically utilized. In this work the frequency spectrum analysis is performed using the AE signal obtained during the head/disk interaction such as load/unload mechanism using ramp, impact situation in the presence of a bump on disk surface and other contact phenomena including particle interaction. It was shown that the influence of impact can be characterized effectively in the AE frequency spectrum. As a result of this work, frequency spectrum analysis will be utilized with better understanding for studying the head/disk interface (HDI) characteristics and monitoring the particle interaction in HDI effectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.6
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• pp.1060-1068
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• 2002

Compound continuously variable transmission(CVT) mechanisms are proposed, which can offer a backward mode, a geared neutral, an underdrive mode and an overdrive mode. They are composed of a 2K-H I type differential gear unit, a V-belt type continuously variable unit(CVU), a few friction clutches and gears, and not required of a starting device as a torque converter. Compound CVT mechanisms developed here present two distinct operating modes which are a power circulation mode and a power split mode. The transition of two modes takes place at the particular CVU speed ratio. For these CVT mechanisms, performance analysis related to speed ratio, power ratio and efficiency are executed and proven by experimental studies.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.975-979
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• 2005

The analysis of a mechanical system, body traveling along the elastic structure, has been a topic of interest. The establishment of analytical method for the development and control of this system is required in the fields of many machine operations such as modern weapons and high-speed feed drive system for a machine tool. The dynamic equations are derived on the torsion of a cantilever hollow shaft induced by the spin-up of a moving mass and the displacement of the mass. Influences of design parameters such as the inertia ratio, the mass moving speed and the friction coefficient are discussed on the transient response of the system.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.729-734
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• 2000

This paper proposes virtual-magnetic system by a force-reflecting interface to drive a ultrasonic motors(USMs) To approach virtual magnet in graphic the 6 dDOF force-reflecting interfaces provides force feedback to users as if I is magnetic-force, So users can feel real magnet Effectively to display the magnetic-force we need the interface with specific characteristics such as low inertia almost zero friction and very high stiffness As an actuator for the interface the USMs have many good advantage satisfied these conditions over conventional servo motors. To estimate capability of this virtual-magnetic system we did an experiment of magnetism based on coulomb's law when Coulmb's low apply this experiment it is vey conformable to real magnet

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.982-988
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• 2013

With conventional positioning apparatus, it is very difficult to simultaneously achieve the desired driving range and precision at the sub-micrometer level. Generally, lead screw and friction drive, etc., have been used as servo control systems. These have large driving ranges, and high-speed positioning is feasible. In this study, we present a global servo system controlled by a laser interferometer acting as a displacement measurement sensor for achieving positioning accuracy at the sub-micrometer level.