• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.211-215
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• 2000

Bi-2212 HTS tube was fabricated by CFP(Centrifugal Forming Process). Slury was prepared in the mixing ratio of 8:2 between powder and binder and ball-milled for 24 hrs. Slurry was initially charged into the rotating mold with 300${\sim}$450 rpm and heated at the temperature ranges of 840${\sim}$860$^{\circ}$C for partial melting to finally obtain a uniformly textured tube shape. It was observed the plate-like grains with more than 20 ${\mu}$m were well oriented along the rotating axis and the measured T$_c$ was around 67K. In this paper we will discuss and analyze the tube characteristics depending on many different processing parameters such as, powder composition, binder mixing ratio between powder and binder, motor speed, heating temperature and etc.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.317-323
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• 1987

A pressure tracking control of hydroforming processes, which is used in the precision forming of. sheet metals, is considered in this paper. The hydroforming of sheet metal is performed between the high-pressure chamber controlled by pressure control valve and the punch moving with constant speed. Since the pressure in the forming chamber is a critical factor to the quality of the product severely. It is important to control the pressure to follow a prescribed pressure trajectory, depending upon the material volume and shape of the parts to be formed. Taking into consideration of the volume chamge of forming chamber during the process and the nonlinearity of the electro-magnetic relief valve, a mathematical formulation of the model describing the dynamic characteristics of this model obtained. Based upon this model a PID controller is designed for the pressure tracking.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.6-8
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• 2005

The purpose of this study is to evaluate characteristics of plate forming by flame heating for E and EH36 TMCP steel. The characteristics of interest were heat-formability of TMCP steel and mechanical properties of heated area. For a given dimension, heat-formability of TMCP steel was inferior to that of a conventional steel because TMCP steel required more heating passes and time. Angular distortion and transverse shrinkage of TMCP steel decreased with an increase in line heating speed for given heating conditions. The mechanical properties of TMCP steel after plate forming by flame heating were high enough to satisfy the requirements.

• Design & Manufacturing
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• 제2권4호
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• pp.11-15
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• 2008

In the sheet metal forming using a high speed press machine, driving device, such as crank, link, and knuckle mechanism, has to be designed in consideration of impact at a moment when press die contact with material, because the impact affects a dimensional accuracy of products and a life span of press die. In this study, dynamic analysis was performed using numerical simulation in order to verify the impact reduction effect for proposed double knuckle mechanism by estimating rolling and pitching moment of slide.

• 한국공작기계학회논문집
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• 제15권1호
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• pp.82-87
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• 2006

The cutting tests of aluminum alloy with heat treatmented various hardnesses after rheo-fonning were carried out using CNC milling machine. The surface roughness(Ra, Rmax) of cut surface and cutting forces are measured at various cutting conditions such as low spindle speed, feed speed and hardness. In the CNC end-milling, the surface roughness increases as feed speed increases and decreases as spindle speed increases. However, the bulit-up edge has occurred on in case of low hardness and low feed speed. In experimental conditions, as the hardness of aluminum alloy increases, the surface roughness(Ra, Rmax) decreases

• 한국분말재료학회지
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• 제14권6호
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• pp.367-371
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• 2007

P/M high speed steel (1.26% C, 4.42% Cr, 6.54% W, 4.92% Mo, 3.21 % V, 8.77% Co, bal. Fe) was applied to hot former die. It showed that the die life became 2.7 times higher than that of cast/wrought SKH 55 tool steel which is commercially used. The increase of die life was corresponding to the improved hardness and transverse rupture strength of PM high speed steel due to the finer grain and carbide as well as the uniform carbide distribution. The P/M high speed steel with the promoted die life could be an alternative to the conventional SKH55.

• 한국안전학회지
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• 제23권4호
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• pp.13-18
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• 2008

This study deals with finish roll forming by forced displacement can be conceived as a method of eliminating errors in conventional form rolling under constant loads. This method produces a high-precision tooth profile by low-speed form rolling when a high rigid screw or cam is used at the pressurized section. Tooth profile is decided in the beginning of roll forming and ${\delta}_{max}$ mainly increases if the number of roll forming process is increased. Gear class is improved by one or two class after roll forming if the gear has convex type error and pressure angle error in KS 4 class. If the gear have concave type error and pressure angle error and pressure angle error, gear class is not improved in theory, but improved a little in practice. In the finishing roll forming, it inevitably yields both the concaving of tooth profile and plastic deflection of addendum of teeth. Experiments show that the concaving and the plastic deflection are successfully reduced, the accuracy of tooth profile reaches to KS 0 class.

• 소성∙가공
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• 제14권7호
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• pp.628-634
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• 2005

The drawability of AZ31B magnesium sheet is estimated at various temperatures (200, 250, 300, 350, $400^{\circ}C$), forming speeds (20, 50, 100mm/min), thicknesses (0.8, 1.4mm) and blank holding forces (2.0, 2.8, 3.4kN). The deep drawing process (DDP) of circular cup is used in forming experiments. The results of deep drawing experiments show that the drawability is well at the range from 250 to $300^{\circ}C$, 50mm/min forming speed and 2.0kN blank holding force. The 0.8mm magnesium sheets were deformed better than 1.4 mm. Blank holding force was controlled in order to improve drawability and prevent the change of cup thickness. When blank holding force was controlled, tearing and thickness change were decreased and limit drawing ratio was improved from 2.1 to 3.0.

• International Journal of Railway
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• 제5권3호
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• pp.129-134
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• 2012

Contact fatigue damages on the rail surface, such as head checks and squats are a growing problem. The fatigue cracks forming on the contact surface grow according to load and lubricating conditions and may end up breaking the rail. Rail fracture can be avoided by preventing the cracks from reaching the critical length. Therefore, the crack growth rate needs to be estimated precisely according to the conditions of the track and load to develop a maintenance plan against rail damages. Therefore, it is important to understand the mechanism of cracks initiation and growth on a rail due to repetitive rolling contact. In this study, we have investigated the crack growth behavior on the rail surface by using the twin-disc tests and the finite element analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.717-722
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• 2011

In this paper, noise source localization of the Korean high speed train was conducted by using delay and sum beam-forming method of a microphone array. At first, the microphone array having irregular configuration was designed and the resolution of which was analyzed from parameters such as 3-dB bandwidth and maximum side-lobe level. After the demonstration, the microphone array was applied on the high speed train and noise localization of the high speed train driving at 300 km/h was performed successfully.