• Proceedings of the KSR Conference
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• 2011.10a
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• pp.656-662
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• 2011

Recently, rolling stock technology has rapidly developed. Nevertheless, ride quality and vibration vibration on vehicle still need more study. EMU to be operated on SMRT Line 7(SR001) extension section is applied to oil-free reciprocating air compressor considering maintainability and convenience of inspection. But reciprocating air compressor compresses the air by back-and-forth motion of piston, and spreads the vibration to surrounding structures by its force of inertia. Optimum design of mounting bracket is able to reduce the vibration. As a result, we analyzed the frequency spectrum on vibration upon value by measuring vibration during operation of air compressor. On this study, we comprehend the vibration transmission process of reciprocating air compressor and consider the measure for reducing vibration by minimizing propagation of vibration.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.3-12
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• 1984

Up to now, it has been common to treat the maneuvering motion of a ship as a 3-degree-freedom motion i.e. surge, sway and yaw on the sea surface, for the simplicity and mathematical calculation, and it is quite acceptable in the practical point of view. Meanwhile, considering the maneuverability of a ship under the special conditions such as in irregular waves, in wind or at high speed with small GM value, it is required that roll effect must be considered in the equation of ship motion. In this paper the author tried to build up the 4-degree-freedom motion equation by adding roll. And then, applying the M.M.G.'s mathematical model and with captive model test results the roll-coupled hydrodynamic derivatives were found. With these the author could make some simulating program for turning and zig-zag steering. Through the computer simulations, the effect of roll to the ship maneuver became clear. The effect of the wind force to the maneuverability was also found. Followings are such items that was found. 1) When roll is coupled in the maneuvering motion, the directional stability becomes worse and the turning diameter becomes smaller as roll becomes smaller as roll becomes larger. 2) When maneuver a ship in the wind, the roll becomes severe and the directional stability becomes worse. 3) When a ship turns to the starboard side, the wind blowing from 90 degree direction to starboard causes the largest roll and the largest turning diameter, and the wind from other direction doesn't change the turning diameter. 4) When a ship is travelling with a constant speed with rudder amidship, if steady wind blows from one direction, the ship turns toward that wind. This phenomenon is observed in the actual seaways.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.882-887
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• 2012

This paper describes on the aerodynamic characteristics of the first domestically manufactured aircraft, Buhwalho, in Korea. The computational fluid dynamics(CFD) calculations and wind tunnel test were utilized to investigate the basic aerodynamic characteristics of aircraft with control surface deflections and attitude changes. Variations of lift, drag and pitching moment due to angles of attack and control surface deflections were analyzed and also flight stability due to side force, yawing and rolling moments caused by the change of sideslip angles, rudder and aileron deflections were discussed. Through this study, the meaningful aerodynamic data by CFD calculations and wind tunnel tests were obtained and the flight characteristics based on these data were confirmed accordingly by the flight tests.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.28-34
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• 2017

The vehicle stabilizer link is one of the suspension components that reduces the bumping and rolling during vehicle driving. However, this stabilizer link could be a source of the abnormal noises when its free gaps have higher than normal values. Therefore, the current study aims at investigating the quantitative relationships between the abnormal noises and free gaps of the vehicle stabilizer links, as well as the length of time that the vehicle stabilizer links could be used without generating abnormal noises. In this study, the abnormal noises were measured based on the magnitude of the stabilizer link vibration, while the free gaps were quantified through the force-displacement curves of the stabilizer links. Harsh durability tests were also conducted in order to quantify the operating cycles of the stabilizer links before generating the abnormal noises, along with the concomitant measurements of the free gaps. The current results showed that the abnormal noises of the stabilizer links were detected when its free gaps were larger than 0.12 mm. However, the free gaps of the stabilizer links, which are bigger than 0.1 mm, produced the abnormal noises at 1.5 million cycles under harsh durability test conditions. A parametric study in the future that would reflect the different shapes and sizes of the stabilizer links for diverse vehicles could determine more generalized relationships between the abnormal noises and free gaps of the vehicle stabilizer links.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.225-235
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• 2013

Cutter forces acting on a disc cutter in TBM are the key parameters for TBM design and its performance prediction. This study aimed to experimentally evaluate cutter forces with different ring shapes in a hard rock. The stiffness of a cutter ring was indirectly estimated from a series of full-scale linear cutting tests. From the experiments, it was verified that the rolling stress acting on a V-shape disc cutter was much higher than on a CCS disc cutter even though the penetration depth by a V-shape disc cutter could be increased in the same cutting condition. Finally, it is suggested that a prediction model considering the shape parameters of a disc cutter should be used for its better prediction.

• Journal of the Korean Professional Engineers Association
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• v.17 no.3
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• pp.6-21
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• 1984

A rock slide in amount of 100 tons in weight happened at 7: 10 a.m., 4th October 1982, on the southwestern ridge of Mt. Seunghag, Busan City. The original rock mass of the rock slide is located 850m west from the Dangri Crushed Stone Quarry. The geology of the area consists of agglomerate, andesite, andesitic tuff, and shale hornfels of the Cretaceous Yucheon Group. The rock blocks were first shifted along the steep joint plane on an andesite outcrop at the site and then to the eastern foot of the mountain slope where some private houses are placed. The mountain slope is covered with thick superficial soil. A slided monolithic-block with 83 tons in weight from the rock slide met with an accident of striking against a house with a tremendous force, to which much damage was done as much as its half was destroyed. The rock-slided block pierced the board-floored room only posited at the center and by the bedroom of the house making a pass like a bullet hole, and hence cut a big pine tree with 24 centimeters in diameter at a distance of 26 meters down the house. However nobody was killed or injured in the stricken house, though seven family members were stayed therein at the very time of accident. They really met a rare opportunity in an unhappy disaster. Measurements of the rock slide were made in the course of the field survey. The monolithic mass was transported by way of saltation, rolling, and sliding to a distance of 300 meters down along the slope dipping 30$^{\circ}$ east. It took about 16 seconds front tile outcrop to the terminal. The acceleration value of the monolithic rock slide is 2.35m/sec$^2$.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.4
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• pp.366-374
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• 2003

In electric motor coaches, the rolling stocks move by the adhesive effort between rail and driving wheel. Generally, the adhesive effort is defined by the function of both the weight of electric motor coach and the adhesive effort between rails and driving wheel. The characteristics of adhesive effort is strongly affected by the conditions between rails and driving wheel. When the adhesive effort decreases suddenly, the electric motor coach has slip phenomena. This paper proposes a re-adhesion control algorithm which uses the maximum adhesive effort by instantaneous estimation of adhesion force using load torque disturbance observer. Based on this estimated adhesive effort, the re-adhesion control Is peformed to obtain the maximum transfer of the tractive effort.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.459-467
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• 2012

In this work, the configuration of a haptic gripper featuring magnetorheological(MR) brakes is proposed and an optimal design of the MR brakes for the haptic griper is performed considering the required braking torque, the uncontrollable torque(zero-field friction torque) and mass of the brakes. Several configurations of MR brake is proposed such as disc-type, serpentine-type and hybrid-type. After the configurations of the MR brakes are proposed, braking torque of the brakes is analyzed based on Bingham rheological model of the MR fluid. The zero-field friction torque of the MR brakes is also analyzed. An optimization procedure based on finite element analysis integrated with an optimization toolbox is developed for the MR brakes. The purpose of the optimal design is to find optimal geometric dimensions of the MR brake structure that can produce the required braking torque and minimize the mass of the MR brakes. In addition, the uncontrollable torque of the MR brakes is constrained to be much smaller than the required braking torque. Based on the developed optimization procedure, optimal solution of the proposed MR brakes are achieved and the best MR brake is determined. The working performance of the optimized MR brake is then investigated.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.1
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• pp.37-52
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• 1990

In this study, the characteristics of cooling and rolling during strip casting process is obtained in comparison with the experimental and analytical results. The prupose of this study is to effectively analyze the thermal and mechanical deformation of roller applying the results of the heat transfer and the pressure distribution to boundary conditions. And then the relation between strip thickness and roll deformation is shown. The second purpose is to obtain the proper condition of the continuous casting for stainless steel. The summary and conclusions can be made on the basis of the results obtained by the theories and experiments. a) The strip casting condition for the fine surface quality of tin-alloy as-cast material was obtained in accordance with the velocity of roll rotation and initial roll gap. b) The experimental condition that the dimension of the cast strip thickness coincide with that of the initial roll gap was according to the experimental result of continuous casting by twin-roll type. c) The thermoelastic finite element model to calculate the roll deformation is represented. Thermoelastic model prediction for the roll deformation are in good agreement with the experimental results considering the thermal expansion of the roll. d) The higher cooling rates were obtained by a twin-roller quenching technique. Also quenched microstructure of the rapidly solidified shell was verified. e) The magnitude of roll deformation due to the thermal expansion and roll separating force is quantit- atively represented in the analysis of continuous casting for stainless steel.

• Progress in Superconductivity
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• v.6 no.2
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• pp.133-137
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• 2005

We fabricated the Au/Ni template for YBCO coated conductors and evaluated texture formation and the microstructural evolution. The cube textured Ni substrate was fabricated by rolling and recrystallization annealing, and subsequently Au layer formed on the substrate by electroless-plating method. The texture was evaluated by pole-figure with x-ray goniometer with orientation distribution function (ODF) analysis. The surface roughness and grain boundary morphology of template were characterized by atomic force microscopy (AFM) We observed that Au layer deposited epitaxially on Ni substrate and formed a strong cube texture when plating time was optimized. The full-width at half-maximum (FWHM) was $8.4^{\circ}$ for out-of-plane and $9.98^{\circ}$ for in-plane texture for plating time of 30 min. Microstructural observation showed that the Au layer was homogeneous and dense without formation of crack/microcrack. In addition, we observed that root-mean-square (RMS) and depth of grain boundary were 14.6 nm and 160 $\AA$ for the Au layer, respectively, while those were 27.0 nm and 800 $\AA$ for the Ni substrate, indicating that the electoless-plated Au layer had relatively smooth surface and effectively mollified grain groove.