• 열처리공학회지
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• 제36권6호
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• pp.367-373
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• 2023

600 MPa-grade deformed bar samples were manufactured by conventional hot rolling and subsequent Tempcore heat treatment processes. Considering the short-time water quenching step of the Tempcore process for hot-rolled steel, it is inevitable that the temperature profile of the deformed bar depends strongly on its position throughout the sample thickness. As a result, its microstructure can be easily divided into two regions, the surface and the core regions. The former is expected to have a fresh martensite microstructure under rapid cooling conditions, but self-tempering occurs due to the intense heat flow from the hot core region after the process. The latter is generally known to exhibit a mixed microstructure of ferrite and pearlite due to its slow cooling rate. In this study, detailed microstructural evolutions were examined through the thickness direction. The large variation of the microstructure through the thickness direction in the deformed bar samples is partly due to the easy carbon diffusion from the limited additions of alloying elements.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.188-197
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• 1999

Grain refinement of the structural steels was selected as the most effective method to meet improvement of strength and toughness without heat treatment. So, the future research and developing direction of ultra fine grain steels are more and more required to response to the production of eco - materials(environmental consciousness - materials) In this paper, the product of surface fine grain steels by CRCT and Inverse Transformation Method by warm deformation of martensite is carried out in order to improve the production process of Dowel Bar. It is possible to obtain surface ultra fine grain steel, when warm deformation of martensite formed after quenching is carried out from 730$^{\circ}C$ to 800$^{\circ}C$ in the finishing rolling step. The characters of surface with ultra fine grain steel is showing the cementite particles inside the ferrite grain and fine ferrite grain of about 1.2$\mu\textrm{m}$ in size.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.24-26
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• 1995

The Development of A.C. Induction Motor for Railway Rolling Stock. The traction motor is designed as 4-pole induction motor with self ventilation. The winding insulation is throughout of materials of class C. The rotor is designed as a squrrel rotor with copper bar and casting. The rotor speed is detected by means of a pulse generator. The newer tection motor have no casting(frame). Punched-in holes make up the air duct and transfer the heat losses in complete. Maximim motor rpm is higher due to rotor construction. New is the entry of water-cooled traction motors in urban, However the water cooling design in - unfortunately - not applicable in traction motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 A
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• pp.41-43
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• 1997

This paper represents the comparison of harmonic loss characteristics of the inverter-driven 3-phase squirrel cage induction motor with slit and U-iron bridge slots of rotor. Two-dimensional time-stepped finite element method is used for electromagenetic field analysis. And spectrums of bar current, phase current, and torque are compared in each case.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.393-400
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• 1998

In this study, the crash situations and general crash analysis methods of railway rolling stocks were explained. To calculate the applied load and the maximum stress in the carbody when two aluminum railway vehicles were shunted, the finite element models for the carbody and the coupling system were made. The characteristic curve of draft gear which had a function to reduce impact force was modeled by nonlinear bar elements and the carbody was modeled by shell elements. Two shunting speeds, 5km/h and 8km/h, were considered and the results were analyzed and compared with static analysis case. Also, the aluminum railway vehicle with 60km/h was crashed against rigid wall to examine the global behavior of the carbody.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.89-91
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• 1994

The Development of A.C. Induction Motor for Railway Rolling Stock. The traction motor is designed as 4-pole induction motor with self ventilation. The winding insulation is throughout of materials of class H. The rotor is designed as a squirrel rotor with copper bar. The rotor speed is detected by means of a speed sensor.

• 오토저널
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• 제9권1호
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• pp.49-56
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• 1987

This study is a part f the research on the coupled vibration of train wheel with stepped thickness and rail. The research was conducted for the purpose of examining the dynamic characteristics of train wheel which considered the effect of rotatory inertia and preventing the vibrations of the high speed railway. The In-plane compressive stresses were computed by the rotation of train wheel and the reaction depending on the condition of rolling. The equation of transverse vibration of the train wheel was obtained by Lagrange's equation. As a result of study, it is known that the effect of rotatory inertia and the increment of thickness ratio, h over bar decrease frequency but the increment of radius ratio, r over bar increase frequency.

• 한국정밀공학회지
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• 제30권10호
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• pp.1023-1029
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• 2013

Water running animals such as basilisk lizards have an advantage of high-speed movement and high power efficiency on water; so researchers in robotic fields have been interested in the water running locomotion. This paper presents prototype-design and experimental study on the fourand six-legged water running robot. Based on the previously proposed quadruped water running robot, we assemble a hexapedal water running robot. The legs of the water running robot are designed based on four-bar parallel link for repeated motion along to pre-defined path. Stability performance of the quadruped and hexapedal water running robot are investigated by experiments on rolling criterion. As a result, hexapedal robot performs better stability than quadruped robot. Based on the hexapedal robot design, we are planning to optimize the position of legs and operating frequency.

• 한국분말재료학회지
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• 제10권1호
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• pp.15-20
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• 2003

Hybrid $A1_2O_3-TiC$ ceramic particle reinforced 6061 and 5083 Al composite powders were prepared by the combination of twin rolling and stone mill crushing process, followed by consolidating processes of cold compaction, degassing and hot extrusion. The composite bar consists of lamellar structure of ceramic particle rich area and matrix area, in which the hybrid was decomposed into each TiC of about $3-4\mutextrm{m}$ and $AI_2O_3$ particles of about $1-2\mutextrm{m}$ in diameter. It also found that fine $Mg_2Si$ precipitates of about 30 nm were embedded in the matrix, which have grains of about 3 $\mutextrm{m}$. Higher UTS was measured at the 5083 composite bar compared to the conventionally fabricated composite, due to again refinement effect by the rapid solidification. No particle was shown to form in the interface between the matrix and reinforcement, whereas carbon was diffused into the matrix.

• 유공압시스템학회논문집
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• 제7권1호
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• pp.1-5
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• 2010

This paper presents the experimental results of the radial piston type oil pump with new mechanism for a metal diaphragm hydrogen compressor. Generally, metal diaphragm type hydrogen compressor systems are operated by oil hydraulic power. In this system an oil compensating pump has been demanded to compensate for a leakage oil head chamber. The metal diaphragm type hydrogen compressor consists of an oil compensating pump, commonly used hydraulic piston pump and driven by main crank shaft. The radial piston type oil compensating pump with new rolling contacted piston mechanism is developed and experimented. The developed piston element of the radial piston pump consists of piston, steel ball, return spring, two check valves, eccentric cam and ball racer. In this study, designed 4 type pistons as and orifice hole. Operating characteristics and pressure ripple characteristics are tested under no load to 60bar loaded with every 20bar increasing step and pressure ripple and flow rate are experimentally investigated.