• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2004년도 춘계학술대회 논문집
• /
• pp.48-52
• /
• 2004

Ultrasonic machining is effective for machining of extreme hard and brittle materials, including glass, ceramic, carbide, graphite. The major machining principle involves the direct hammering as well as the impact of abrasive panicles on the workpiece. Also, it involve cavitation erosion. The general workpiece is flat side. This study attempted micro hole machining of a curved surface of glass tube. Ultrasonic machining is fault of the slow machining speed. An experiment does and got 16 seconds validity machining time as increasing the processing speed. Moreover, entrance crack and surface roughness was similar both machining speed is slow and fast. Several micro hole of glass tube machined using one micro tool, but tool wear is infinitesimal.

• 한국공작기계학회논문집
• /
• 제10권1호
• /
• pp.88-93
• /
• 2001

Carbon fiber epoxy composite are widely used in airframe structures, space vehicles, sports equipment, and high speed reciprocating parts for industrial machinery. In this paper, the groove processing characteristics of carbon fiber epoxy com-posite was experimentally investigated in order to study the endmill operation of fiber reinforce epoxy composites. Followings are main finding from the experimental results. First, the cutting and bending force in groove processing of the carbon fiber epoxy composite increased as the spindle speed deceased. They also deceased as the table feed increased. Second, the good cutting status obtained at the entrance of groove while delamination occurred at the exit of groove, Third, the regular high speed steel endmill was not efficient, thus the new endmill such as coated carbide rooter endmill or dia-mode endmill should be used for the effective endmll operation of carbon filber epoxy composites.

• 대한토목학회논문집
• /
• 제30권1D호
• /
• pp.1-10
• /
• 2010

고속도로 영업소의 경우 하이패스차량과 일반TCS이용차량간의 혼용 및 차로변경으로 인한 상충이 발생하는 구간으로 안전성에 대한 검토가 필요한 구간이다. 본 연구에서는 영업소 진출부에 설치된 중앙하이패스 이용차량과 일반차로 이용차량간의 상충 및 사고위험성을 현장비디오촬영 및 상충분석을 통해 알아보았다. 차량속도와 상대속도 및 상충으로 인한 차량 감속시간 등을 분석한 결과 하이패스이용차량과 일반TCS이용차량간의 상대속도가 클수록 상충으로 인한 차량 급감속이 발생한다는 문제점을 파악하였으며, 중앙 하이패스 설치시 상충 발생 위치 및 차로 운영형태에 따라 상충빈도 및 상대속도가 다름을 확인할 수 있었다. TA(Time to Accident)분석 결과, 고속도로 영업소 중앙 하이패스 설치시 차량간 상대속도, 상충위치 및 빈도에 따른 상충시 하이패스 차량의 급감속 및 감속시간이 큼에 따라 사고위험이 높은 것으로 분석되었다. 또한 합류 시점부가 영업소 진출부와 가까울수록 TA분석값이 낮은 것으로 분석되어 전반적으로 속도차이를 줄여 안전성을 증대시켜야 함을 알 수 있었다. 본 연구에서는 영업소 진출부 중앙 하이패스 설치로 발생하는 상대속도차에 의한 상충으로 급감속 및 사고를 억제함으로서 영업소 중앙 하이패스 차로 설치시 안전성을 높여줄 수 있을 것으로 기대된다.

• 수산해양기술연구
• /
• 제57권4호
• /
• pp.283-291
• /
• 2021

The Korean stow net is a fishing method that utilizes the changing direction of the net entrance with the tidal current. This study attempted to obtain basic data from the recent offshore stow net fisheries to improve the gear by analyzing the dynamic behavior of the nets affected by current speed and direction using computer simulations. A numerical calculation was performed at a current speed of 0.5 knot between 2.5 knot at each 0.5 knot. The time taken for the gear opening was the longest from 0.5 knot at 1,500 seconds and the shortest from 2.5 knot at 450 seconds in the simulations. In all cases, the net width and tension at net deployment gradually decreased as the current speed decreased. However, the net height tended to increase inversely proportional to the current speed. During the net rotation, the net height was maintained at all cases. The net width and tension fluctuated, but the regularity was very low. In this study, the calculated simulation data showed that the opening efficiency decreased proportional to the current speed. The opening efficiency is related to the catching efficiency; therefore, it is necessary to improve the gear to enhance its opening efficiency.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2002년도 춘계학술대회 논문집
• /
• pp.643-648
• /
• 2002

In the cutting of plate steel, the quality of the cut surfaces is strongly dependent on the cutting conditions such as cutting speed, kerf width, plate thickness, length of tip-specimen and oxygen pressure etc. the cutting tests of plate steel were carried out using CNC gas cutting machine. this paper deals with cutting characteristics of plate steel using CNC cutting machine. the width of cutting entrance and exit, the surface roughness of cutting surfaces and the cutting surface are examined at various cutting conditions.

• 수산해양기술연구
• /
• 제42권2호
• /
• pp.111-118
• /
• 2006

It is indispensable to grasp the turning ability of a ship to operate her effectively. For this purpose, the author measured the turning ability of training ship, A-RA by use of bow thruster and stem rudder. The turning ability of this ship, in case of using both of stem rudder and bow thruster at the same time, caused by increase of steering angle provides more influence to the size of tactical diameter than it caused by the power of bow thruster. But the influence of bow thruster on the turning ability is available only within rudder angle $5^{\circ}\;-\;10^{\circ}$, so it is possible to grasp that the effect of bow truster is reduced as rudder angle become bigger. In case of the influence of bow thruster by her speed, the ability of bow thruster is very effective at low speed, but it is almost not available in normal turning speed. Therefore, the using both of stem rudder and bow thruster can be useful in case of low speed proceeding at entrance or departure of the narrow waterway or inside port which sea traffic is congest for collision avoidance.

• 플랜트 저널
• /
• 제4권2호
• /
• pp.66-72
• /
• 2008

In this inquiry, I would suggest jet ventilation system for effective elimination of welding flaw at machinery material welding shop on plant and evaluate the airstream on inner space and property of welding flaw's density through the examination. We can know outer atmosphere inflows at the speed of about 0.05m/s from western entrance in case of stopping the jet ventilation system, but airstream is accumulated on entire space. At height of worker's breathing surface(Ground Level = 1.5 m, below of GL) and welding work center, density of welding flaw on upper part(GL = 12m) is appeared 4 times higher than outer atmosphere at surplus range besides nearby of western entrance. At operation of jet ventilation system, since the smooth air current transfer at inner space and exhaust effect the wind speed is maintained at 0.932 m/s at the point of height of worker's breathing surface on inner space and it's concluded about the working conditions have been better than before operation of jet ventilation system because of that results show that inner space density of welding flaw at height of worker's breathing surface is 40.5%, and in the work shop, it is 20.3% at upper part.

• 대한기계학회논문집A
• /
• 제31권10호
• /
• pp.1039-1045
• /
• 2007

Ultrasonic machining (USM) is suitable for machining hard, brittle and non-conductive materials such as silicon, glass and ceramics. Usually, when micro holes are machined on glass by USM, roundness of hole entrance is poor and cracks appear around the hole exit. In this paper the machining characteristics were studied for roundness improvement and exit crack prevention. From experiments, the tool bending and the shape of tool tip affect hole roundness. When the tool tip is hemispherical, good roundness of holes was obtained. The feedrate and the rotational speed of the tool affect the exit crack. With the machining conditions of 150 rpm in spindle speed and $0.5\;{\mu}m/s$ in feedrate, micro holes with less than $100\;{\mu}m$ in diameter were machined without an exit crack.

• 한국생산제조학회지
• /
• 제7권4호
• /
• pp.117-122
• /
• 1998

Glass fiber epoxy composite material is widely used in the structures of aircrafts, robots and other machines because of their high specific strength, high specific stiffness and high damping. In order for the composite materials to be used in the aircraft structures or machine elements, accurate surfaces for bearing mounting or joint must be provided, which require precise machining. In this paper, the machinability of the glass fiber epoxy composite material was experimentally investigated. The results can be summarized as follows : 1. The entrance of hole is very good manufacturing existing, but exit come to occur sever surface exfoliation. 2. The cutting force in drilling of the glass fiber epoxy composite material is decreased as the drilling speed increased. 3. If the glass fiber epoxy composite material is drilling by the standard twist drill, then the hole recommand cutting condition is spindle speed 400∼600rpm, feed 40∼50mm/min.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
• /
• pp.596-603
• /
• 1998

The entry compression wave, which is generated at the entrance of the tunnel, is almost always associated with the pressure transients in the tunnel as well as the impulse noise at the exit of the tunnel. It is highly required to design the train nose shape that can minimize such undesirable phenomena. The objective of the current work is to investigate the effects of the train nose shape on the entry compression wave. Numerical computations were applied to one-dimensional unsteady compressible flow in high-speed railway train/tunnel systems. A various shape of train noses were tested for a wide range of train speeds. The results showed that the strength of the entry compression wave is not influenced by the train nose shape, but the time variation of pressure in the entry compression wavefront is strongly related to the train nose shape. The current method of the characteristics was able to represent a desirable nose shape for various train speeds. Optimum nose shape was found to considerably reduce the maximum pressure gradient of the entry compression wave.