• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.749-752
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• 2002

In this study, we carried out the finite element analysis about screw that is the weakest part of the centrifuge for sewage management. Structural analysis was done with respect to the change of outer radius and thickness of screw blade and screw with sewage discharge hole. If the area of circular hole is equal to that of extended holes, maximum equivalent stress was compared between hole and extended hole. Centrifugal force on account of rotation of 4000 rpm was applied the screw. The results are as follows : 1 . When the larger radius and thickness of screw blade was used, the higher maximum equivalent stress is occurred. 2. When the larger radius of sewage discharge hale was used, the higher maximum equivalent stress is occurred. 3. When the longer parallel part length of extended hole was used, the higher maximum equivalent stress is occurred. 4. If the extended hole with the same discharging area which circular hole uses, the maximum equivalent stress is lower.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.131-134
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• 2004

The hub hole is usually formed with a stretch flanging process followed by a blanking process of a hole. Since the hole is made by blanking, the blanked surface is so rough that the formability in the region is rather poor. The emerging task is to identify the formability of the blanked region in the forming simulation and to relate the criterion to the real forming process by experiments. In this paper, the blanked region of a hole surface is modeled by a defected-edge finite element for stretch flanging simulation. The analysis deals with the level of defect in the blanked region in order to identify the formability in the real process. The analysis provides the formability depending on the level of defect and seeks the way to match the level of defect to that of the real surface. The approach makes the analysis possible to deal with the formability of the high strength steel and predict the fracture at the hole surface during the stretch flanging simulation.

• 대한기계학회논문집B
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• 제25권7호
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• pp.933-943
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• 2001

Using a semi-circled blunt body model, the geometrical effects of injection hole on the turbine blade leading edge film cooling are investigated. The film cooling characteristics of two shaped holes (laterally- and streamwise-diffused holes) and three cylindrical holes with different lateral injection angles, 30°, 45°, 60°, respectively, are compared with those of cylindrical hole with no lateral injection angle experimentally and numerically. Kidney vortices, which decrease the adiabatic film cooling effectiveness, appear on downstream of the cylindrical hole with no lateral injection angle. At downstream of the two shaped holes have better film cooling characteristics than the cylindrical one. Instead of kidney vortices, single vortex appears on downstream of injection holes with lateral injection angle. The adiabatic film cooling effectiveness is symmetrically distributed along the lateral direction downstream of the cylindrical hole with no lateral injection angle. But, at downstream of the cylindrical holes with lateral injection angle, the distribution of adiabatic film cooling effectiveness in the lateral direction shows asymmetric nature and high adiabatic film cooling effectiveness regions are more widely distributed than those of the cylindrical hole with no lateral injection angle. As the blowing ratio increases, also, the effects of hole shapes and injection angles increase.

• 한국분무공학회지
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• 제19권4호
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• pp.216-220
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• 2014

This paper presents effect of nozzle hole number on atomization characteristic of DME fuel spray using three different type of injector having the hole number of 6, 7 and 8. For this study, PDPA(phase Doppler particle analyzer) experiment was performed in terms of $T_{ASOE}$ under various injection pressure. To compare general trend of atomization characteristic, the law data were ensemble averaged based on $T_{eng}$ of 0.2 ms. Results showed that the droplet diameter in terms of SMD(Sauter Mean Diameter) was reduced as increase in injection pressure. Increasing the number of hole lead to reduce in droplet diameter, but no significant reduction in diameter was observed between hole number of 7 and that of 8. In addition, increasing the number of hole resulted in decrease in droplet velocity which is considered as the effect of reduction in spray momentum due to decreasing of fuel quantity per each hole.

• 대한기계학회논문집B
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• 제25권2호
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• pp.235-243
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• 2001

This paper describes a design study of the cylindrical multi-hole premixed burner to be used for condensing gas boiler which can raise performance and reduce NOx emission. In this study, specifications of the multi-hole burner (hole diameters and arrangement) are investigated using model flat burners in terms of flame stability, and combustion characteristics for stability and NOx emission are examined for cylindrical multi-hole burner. As a result, the equivalence ratio for optimum operation condition of the cylindrical burner is around 0.72(0.7∼0.75). In this condition, turn-down ratio becomes 3 : 1 at least which is suitable for proportional control. The NOx and CO emission is less than 40ppm and 25ppm(0$_2$0% basis), respectively. This burner can be applied LPG as well as NG because there is no difference for stable combustion region.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.120-123
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• 2004

The bending phenomenon has been known to be occurred by the difference of velocity at the die exit. The difference of velocity at the die exit section can be obtained by the different velocity of billets inside die chamber after passing the multi-hole container. The curvature can be controlled by the two variables, the one of them is the different velocity of billets through the multi-hole container, the other is the difference of hole diameter. The bending phenomenon during extruding using four billets can be obtained by the difference of hole diameters in the multi-hole container or by the difference of relative velocity of billet inserted in the container. As results of DEFORM-3D analysis, it can be shown that bending can be obtained during extruding by the difference of relative velocity of two billets or by the difference of hole diameter, and the amount of curvature is increased by the difference of velocity and diameter. According to the shape of products, the curvature of rectangular section is bigger than the curvature of regular square section. And, it is estimated that, because the stress on the welding line is much higher than yield stress of material, the bonding of four billets can be obtained.

• 한국항공우주학회지
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• 제48권4호
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• pp.243-254
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• 2020

한국 전통 지연은 장방형으로 그 가운데 방구멍을 가진 특이한 형태를 갖고 있다. FLUENT 코드를 사용하여, 가로세로비 1:1.5인 한국 전통 지연에 작용하는 공기역학적 힘들을 수치적으로 계산하였다. 다양한 직경의 방구멍에 대하여 연의 비행을 시뮬레이션하여, 방구멍의 역할과 방구멍 크기에 따른 영향을 조사하였다. 방구멍은 연싸움에서 연실의 빠른 되감기로 인한 장력의 급격한 상승을 완화시켜 주는 역할을 함으로써, 연실을 더 빨리 되감을 수 있게 한다. 방구멍의 적절한 직경은 가로 폭의 1/3이다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.1125-1132
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• 2009

The theory and a probe of the pilot hole wall deformation method, which is a 3-dimensional stress measurement method based on the stress relief principle, were developed. A pilot hole is drilled from the bottom of a borehole and the stress measurement probe is inserted into the pilot hole. The borehole is advanced as the overcoring and the changes in the radius of the pilot hole in three directions and in the axial lengths between the borehole bottom and the pilot hole wall along four axial lines are measured by cantilever type-displacement sensors. The differences between the displacements by the elastic stress analysis and those measured by using the probe were within 3% in the uniaxial compression test of an acrylic resin plate having a hole.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권1호
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• pp.45-53
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• 2013

In this paper, we analyze the failure mechanism of the washer pump to find what is the failure cause in the road environment. The statistics show the field common failure mode is inner corrosion. The failure mechanism is assumed that the inner part of washer pump is corroded due to inflow of moisture through vent hole. To prevent the failure, we can think a method that is covering the vent hole. In general, the vent hole is designed to play an important role in an automobile parts. So, we need to prove the vent hole is not necessary. The first purpose of this paper is to make sure that the vent hole does not affect the durability of washer pump using the analysis of operating condition. The second purpose is to compare the durability properties if the vent hole is covered.

• 화약ㆍ발파
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• 제32권3호
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• pp.10-17
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• 2014

본 연구에서는 2자유면을 가진 암반의 장공발파 시 천공간격과 뇌관의 기폭시차에 따라 발생되는 내부주변형률의 변화를 확인하기 위하여 Visual FEA 유한요소 프로그램으로 해석 암반의 단면을 모델링하여 인접공균열권 내의 주요 절점에서 최대주변형률을 분석하였다. 결과적으로, 장공발파 시 천공간격이 좁고 기폭시차가 길수록 인접공 균열권 내에 미치는 최대주변형률 값이 크게 나타났고, 장약장 내 폭약의 기폭 위치에 따라 최대 주변형률의 차이를 보였다.