• International Journal of Highway Engineering
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• v.2 no.2
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• pp.129-138
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• 2000

This study presents the mechanical characteristics, such as the permanent deformation and the crack, of the large stone asphalt mixtures. The large stone mixture was studied by Kandhal at NCAT(National Center for Asphalt Technology) in 1989. Japan and Arabian countries adopted the large stone mixture for the pavement construction. The experience and the study results showed that the interlocking of the aggregate system of the large stone mixtures is stable and less dependent on the binder characteristics in high temperature. These properties are known as the rutting resistant parameters. However, the mechanical test results should be supported to prove the benefits of the large stone mixtures. The creep test, resilient modulus tests on three different temperature, wheel tracking test and ravelling tests were conducted to evaluate the performance of the large stone mixtures in this study. The test results were compared with the conventional mixtures and modified asphalt concrete mixtures. The large stone mixtures showed better rutting resistance performance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.21-30
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• 2022

This paper describes the design, manufacture, and testing of servos applicable to small tracking radars. First, Chapter 1 describes the necessity of this study. Chapter 2 describes the development of servos applicable to future tracking radars in small missile systems. Chapter 3 describes the design and test results for current control of brushed DC motors, brushless DC motors, and permanent magnet synchronous motors. And Chapter 4 describes the design and test results for speed control of the test wheel. And in Chapter 5, the results of the previous tests are summarized. In this paper, some pictures were intentionally blurred for security reasons, and the control result of test wheel was described, not the test with the developed gimbals.

• Bulletin of the Korean Space Science Society
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• 2005.04a
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• pp.133-137
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• 2005

This paper describes the design and performance verification of a pitch momentum bias control system being built by students at the Space System Research Laboratory(SSRL). HAUSAT-2 ADCS(Attitude Determination and Control of Subsystem) op-elation mode is divided into two parts, initial mode and on-orbit mode. This paper describes design of the HAUSAT-2 performance of attitude control results using pitch momentum bias control method in initial mode and on-orbit mode and momentum dumping method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.1
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• pp.16-21
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• 2004

In order to investigate the characteristics of diamond wheel grinding of ceramic materials, grinding resistance, surface roughness of ground surface and image of grinding wheel were acquired using experimental method. Through the experiments, this makes it possible to observe grinding wheel behavior by grinding resistance, surface roughness and cutting edge ratio. In case of $Al_2O_3$, cutting edge ratio is bigger than that of $ZrO_2$ and $Si_3N_4$. That's because $Al_2O_3$ has a characteristic of low fracture toughness and bending stress.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.308-313
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• 2002

In order to investigate the characteristics of grinding and diamond wheel grinding ceramic materials, grinding resistance, surface roughness of worked surface and image of grinding wheel were acquired using experimental method. Through the experiments, this makes it possible to observe grinding wheel behavior by grinding resistance, surface roughness and cutting edge ratio. In case of A1$_2$O$_3$, cutting edge ratio is begger than that of ZrO$_2$and Si$_3$N$_4$. That's because A1$_2$O$_3$has a characteristics of low fracture toughness and bending stress.

• Tribology and Lubricants
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• v.16 no.3
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• pp.173-181
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• 2000

Friction, wear and corrosion characteristics of various MoS$_2$ bonded film lubricants were investigated to apply them to automotive wheel joints. MoS$_2$ bonded film lubricants were formulated by combinations of several additives and binders, and they were coated onto the pre-treated surfaces of specimens. Friction and wear characteristics were evaluated with Falex pin & vee-block test and LFW-1 block-on-ring test. For the corrosion resistant characteristics of the films, salt solution spray corrosion tests were performed. Results showed that MoS$_2$ bonded films containing both inorganic and organic corrosion-resistant additives yielded a synergy effect on anti-corrosion resistance. Also, binders having the better water-proof and thermal stability showed the lower friction and higher corrosion resistance.

• The Journal of the Korea Contents Association
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• v.15 no.5
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• pp.18-26
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• 2015

In this paper, we presented a design and control method of multi-stage with wagon and lift stage. Multi-stage system has 4 degree-of-freedom(DOF), i.e., forward/backward/left/right/rotate and up/down motion. Wagon mechanism in the type of two wheel and steering is proposed in order to improve for the maneuverability compared to the existing differential-type wagons. Also, the lift mechanism is designed by interlocking type in order to make the maximum height bigger than 10 times of the original height. We also proposed a path planning algorithm. The performance of the propped system is validated via multi motion experiments, so that the multi-stage system is useful for various performances production.

• Tribology and Lubricants
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• v.35 no.5
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• pp.267-273
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• 2019

Wheel bearings are important automotive parts that bear the vehicle weight and translate rotation motion; in addition, their seals are components that prevent grease leakage and foreign material from entering from the outside of the bearings. Recently, as the need for electric vehicles and eco-friendly vehicles has been emerging, the reduction in fuel consumption and $CO_2$ emissions are becoming the most important issues for automobile manufacturers. In the case of wheel bearings, seals are a key part of drag torque. In this study, we investigate the prediction of the drag torque taking into consideration the hyperelastic and viscoelastic material properties of automotive wheel bearing seals. Numerical analysis based on the finite element method is conducted for the deformation analyses of the seals. To improve the reliability of the rubber seal analysis, three types of rubber material properties are considered, and analysis is conducted using the hyperelastic material properties. Viscoelastic material property tests are also conducted. Deformation analysis considering the hyperelastic and viscoelastic material properties is performed, and the effects of the viscoelastic material properties are compared with the results obtained by the consideration of the hyperelastic material properties. As a result of these analyses, the drag torque is 0.29 Nm when the hyperelastic characteristics are taken into account, and the drag torque is 0.27 Nm when both the hyperelastic and viscoelastic characteristics are taken into account. Therefore, it is determined that the analysis considering both hyperelastic and viscoelastic characteristics must be performed because of its reliability in predicting the drag torque of the rubber seals.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.10a
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• pp.167-172
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• 1997

초전도체를 기계요소중 하나인 베어링에 응용하기 위한 연구는 임계온도가 액체질소의 비등점(77K)보다 높은 산화물 고온 초전도체가 발견된 이후 시작되었으며, 특히 최근에는 $10^4A/cm^2$이상의 임계전류밀도를 갖는 덩어리형 고온 초전도체가 용융공정을 통해 개발되어, 큰 부하지지력을 갖고 10$^{-8}$ 이하의 마찰계수를 갖는 초전도 마그네틱 베어링으로서 플라이휠 같은 에너지 저장장치에 적용시키는 연구가 국내외적으로 진행되고 있다. 고온 초전도체를 사용한 반발식 수동형 미그네틱 베어링은 Meissner effect뿐 아니라 Fluxpinning effect에 의해 자체적으로 외란에 대한 위치안정성을 가지며, 히스테리시스 손실에 의한 에너지 소산을 통해 외란에 대해 강한 감쇠능력을 가진다는 장점을 가지고 있으며, 대중량을 지지할 수 있다. 이러한 초전도체의 특성에 관한 정량적 수치해석은 초전도 베어링의 설계에 필수적이나 아직 국내에서는 그러한 시도가 없었다. 이러한 여건을 고려하여 본 연구에서는 초전도체와 자석간의 부상력 변화를 2차원 Slab모델로 수치해석하여 히스테리시스라는 주요한 특성을 고찰하고자 한다.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1888-1893
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• 2011

Considering the dynamic performance and stability of railroad vehicles has begun to grab the attention because of developing the high speed train recently. A development based on an analysis of dynamics and verification has to be required to study the stability of vehicle performance. Several ways of analysis were using the look-up table to apply the wheel-rail contact characteristics quickly, whereas there is a constraint of the wheelset lateral displacement. In this study, an development of searching the wheel-rail contact position has been provided. The 2-point contact between wheel and rail during the driving condition can be calculated by numerical analysis. Moreover, a reliability is verified by comparing the result with a commercial program.