• Transactions of the Korean Society of Mechanical Engineers
• /
• v.15 no.3
• /
• pp.887-897
• /
• 1991

본 연구에서는 이와 같은 배경에서, Fig. 1(f)와 같이 가장 일반적인 이방성 재료가 접합된 경우의 응력확대계수를 명확히 정의하고, 수치해석법으로 구할 수 있는 외삽식을 제안한다. 또한, 탄성문제의 수치해석 방법으로 적은 요소의 분할로써 고 정밀도의 수치해석 결과를 얻을 수 있는 경계요소법(boundary element method:BEM), 특히 저자들이 개발한 복합재료에 대한 2차원 경계요소법 프로그램을 이용하여 이방성 이종재료 접합계면 균열의 응력확대계수를 해석하고, 복합재료내의 섬유방향에 대한 접합계면 균열의 정성적 거동을 고찰하고자 한다.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.12 no.2
• /
• pp.100-106
• /
• 2013

Stainless steel has some excellent properties as the material for the mechanical component. Purpose of this study is carried out to obtain mirror surface on the surperfinishing of stainless steel with high efficiency. To achieve this, we have conducted a series of polishing experiment for stainless steel using abrasive film from the perspective of oscillation speed, the rotational speed of workpiece, contact roller hardness, contact pressure and feed rate. Abrasive film used this study is a micro-finishing film and a lapping film. Furthermore, the polishing characteristics and efficiency of stainless steel is discussed through measuring optimal polishing time and surface roughness. From the obtained results, it was confirmed that efficient superfinishing conditions and polishing characteristic of Stainless steel can be determined.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.4 no.2
• /
• pp.73-82
• /
• 2000

본연구의 목적은 반복하중을 받는 철근콘크리트 교량 교각의 비선형 이력거동을 해석적으로 예측하는 것이다 이를 위해서 반복적인 횡하중이 작용하는 경우에 실험결과와 일치하는 교각의 하중-변위 이력곡선을 도출하고자 수정된 trilinar 이력거동모델을 이용하였다 철근과 콘크리트의 비선형 거동특성과 각 하중단계에 따른 교각의 중립축을 구하여 소성힌지부의 모멘트와 변형률을 구하고 반복하중하에서의 강성의 변화를 해석적으로 모형화하기 위하여 각기 다른 강성을 갖는 5가지 지선을 갖춘 형태의 이력거동모델식을 제안하였다 본 연구에서는 실험적으로 구한 하중-변위 이력곡선을 이용하여 축하중비 주철근비 및 구속철근비에 따른 강도감소지수와 강성감소지수의 영향을 회귀분석을 이용하여 일반식으로 제안하였다 새로운 이력거동 해석 모델을 프로그램 SARCF III에 적용함으로써 기존 철근콘크리트 교각에 강도 및 강성감소 현상을 정확하게 예측하였다

• 전기의세계
• /
• v.15 no.1
• /
• pp.1-13
• /
• 1966

The harmonic components of a current in the power system have been known to be harmful to the sound operation of the system. Their occurrence is mainly due to the nonlinear characteristics of magnetic materials which are used in the system. This paper has, therefore, numerically analyze the harmonics from the relation between the magnetic characteristic curve and the harmonic components of a current in the R-L-C circuit. It also has suggested a new method of calculating the magnitudes and phase angles of the harmonic components by means of approximate formulas derived here. The method is expected to apply to the determination of harmonics-limiting conditions in case of the design of such power equipments as transformer, reactor and so on.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.929-931
• /
• 2004

Recently, there are growing demands for permanent magnet(PM) type stepping motor that greater mechanical output, smaller size. Especially, the PM type stepping motor with claw-poles is preferred solution for many small electronics position determination devices since it is small in size, low cost. But, the design of the PM type stepping motor with claw-poles is very difficult because it has a magnetic 3-D shape. This paper deals with a study of the miniaturization of the PM type stepping motor with claw-poles. We investigate the characteristic of the actual model using the equivalent magnetic circuit method and 3-D FE analysis.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.4B no.3
• /
• pp.114-121
• /
• 2004

Switched reluctance motors have received much attention as a driving means for various industrial applications because they have simple construction, low cost and high efficiency. Nevertheless, the requirements of drive converters make it difficult to lower the overall system cost as compared with the DC motor application. Single phase switched reluctance motors (SPSRMs) provide a solution to the high cost problem since the number of switching power devices can be reduced and consequently the trials for application are increased. However, research involving SPSRMs, especially in the area of design work, is insufficient. This paper introduces a novel design methodology of single phase SRM. The design work for SPSRM comprises the determination of many variables such as stator and rotor pole arc as well as on, off and so on. Managing all variable combinations leads to lengthy computation time and a fault in the design process. For that reason, a reliable technique and brief procedure term are required in SPSRM design.

• Proceedings of the KIEE Conference
• /
• 2004.05b
• /
• pp.169-172
• /
• 2004

The tower footing resistance is an extremely important parameter in the determination of lightning flashover. For the reduction of back flashover faults, power utility companies have had a concern to decrease the footing resistance. There are two manufactures of the conductivity concrete materials in Korea. In this paper, we investigated possibility of soil pollution due to the conductivity concrete materials. Also, we analyzed on the reduction characteristics of footing resistance of those.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.4
• /
• pp.601-611
• /
• 2010

Currently, a life cycle cost estimates(LCCE) is the most important factor in weapon system acquisition process. However, operation and maintenance(O&M) cost related studies are insufficient from the previous literature survey. O&M cost consists of various cost factors such a man power, maintenance and direct & indirect support costs. We have known that spare-parts cost is a key factor in the O&M cost. In this paper, we developed the spare-parts cost estimating relationships(CERs) of fixed-wing aircraft and armored vehicle weapon systems which include 4 historical cost drivers ; system acquisition cost, deterioration rate, localization rate, mission characteristic. Furthermore, we proposed the application methodologies that O&M cost estimating, total life cycle cost estimating and determination of the economic life using the spare-parts CERs.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1261-1263
• /
• 2005

The micro permanent magnet(PM) type stewing motor preferred solution for many small electronics position determination devices since it is small in size. Thus, there are growing demands for PM type stepping motor that greater mechanical output, smaller size. But, the design of the it, having high performance and small size is very difficult because of its complex mechanical structure. This paper deals with a development of the newly structured micro PM type stepping motor with claw-poles. We introduced the small-sized PM type stepping motor that has new structure and analyzed the magnetic characteristic of it versus general type model using 3-D finite element analysis(FEA).

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.585-588
• /
• 2005

The dissolution characteristic of metal shows the different tendency according to the applied electrical potential, the kind of electrolyte and pH value, etc. In the micro electrochemical machining (ECM), unfavorable oxide/passive layer formation and overall corrosion of electrodes must be prevented. The anodic polarization curve of nickel has distinct three dissolution regions, i.e. two active regions and the transpassive dissolution region. In this paper, the stable electrode potentials of workpiece and tool were determined in sulfuric acid and hydrochloric acid solution, respectively. In each solution, different machining property was shown and possible electrochemical reactions were discussed. On the basis of this experiment, the methodology to obtain the proper electrode potential was suggested.