• 한국분무공학회지
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• 제26권4호
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• pp.197-203
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• 2021

In gasoline direct injection injectors, cavitation can be generated inside the hole because of their high injection pressure. In this paper, the effects of cavitation development in injector were investigated depending on the various hole drilling angles were investigated by a numerical method. In order to verify the internal flow model, injection rate and injection quantity of individual holes were measured. The BOSCH long tube method was used to measure the injection rate. As a result, even if the hole diameters were the same, the discharge coefficient differed by up to 10% depending on the hole angle. Moreover, if the hole drilling angle became greater than 30°, the area coefficient and the discharge coefficient decreased as the nozzle outlet was blocked due to cavitation.

• 소성∙가공
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• 제16권3호
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• pp.157-162
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• 2007

The hydropiercing process gives a lot of advantages to the tube hydroforming such as cost reduction and high productivity. However it has a drawback, the amount of deflection around the hole is bigger than that of conventional die piercing process. The deflection can cause the problem at the assembly process of stamped parts and hydroformed part. Therefore the reduction of deflection is one of the most important issues for hydropiercing process. In this study, the deflection around hydropierced hole was investigated by experiment. As a result of investigation, the amount of deflection is influenced by the internal pressure, the material thickness' and the size of hole. Especially the hole size is most influencing factor on the deflection around the hydropierced hole.

• 한국가구학회지
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• 제19권3호
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• pp.211-218
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• 2008

This experiment was carried out to investigate the effect of internal holes on the bending strength of PB. The diameters of holes are 0mm to 13mm. The locations of holes are 1/8 to 4/5 point horizontally from sample end and are 1/5 to 4/5 vertically from sample surface, the numbers of holes are 1 to 4 pcs. In the size of internal holes, the bending strengths of PB were decreased significantly with the increase of diameter of holes, and the relationship between diameters(D) of holes and bending strength (${\sigma}_b$) of PB was ${\sigma}_b=-11D+168.8$ ($r^2=-0.99^{**}$). The effects of hole-locations and hole-numbers on the bending strengths of PB were large. and so they should be considered as major factors for the jointing design of PB.

• 한국추진공학회지
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• 제7권2호
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• pp.15-22
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• 2003

본 연구에서는 2차원 압축성 Navier-Stokes 방정식을 사용하여 $30^{\cire}$ 경사진 터빈익의 냉각구를 통한 유출계수를 예측하였다. 내/외부 유동이 유출계수에 미치는 영향을 알아보기 위하여 외부유동만 존재하는 경우, 내부유동만 존재하는 경우 그리고 내/외부 유동이 없는 3가지 경우에 대하여 수치해석을 수행하였으며. 실험결과와 비교하였다. 본 연구의 수치해석결과는 유출계수를 잘 예측하였으며, 외부유동은 유출계수를 감소시키고, 내부유동은 냉각구내에서의 전압손실과 경계층의 영향을 감소시켜 특정 구간에서 유출계수를 증가시킨다는 것을 알았다.

• Smart Structures and Systems
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• 제22권6호
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• pp.675-687
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• 2018

In the previous studies on the porous rock strength the effect of pore number and its diameter is not explicitly defined. In this paper crack initiation, propagation and coalescence in Brazilian model disc containing a single cylindrical hole and or multiple holes have been studied numerically using PFC3D. In model with internal hole, the ratio of hole diameter to model diameter was varied between 0.03, 0.17, 0.25, 0.33, and 0.42. In model with multiple hole number of holes was different in various model, i.e., one hole, two holes, three holes, four holes, five holes, six holes, seven holes, eight holes and nine holes. Diameter of these holes was 5 mm, 10 mm and 12 mm. The pre-holed Brazilian discs are numerically tested under Brazilian test. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured. The mechanism of cracks propagation in the wall of the ring type specimens is also studied. In the case of multi-hole Brazilian disc, the cracks propagation and b cracks coalescence are also investigated. The results shows that breaking of the pre-holed disc specimens is due to the propagation of radially induced tensile cracks initiated from the surface of the central hole and propagating toward the direction of diametrical loading. In the case of disc specimens with multiple holes, the cracks propagation and cracks coalescence may occur simultaneously in the breaking process of model under diametrical compressive loading. Finally the results shows that the failure stress and crack initiation stress decreases by increasing the hole diameter. Also, the failure stress decreases by increasing the number of hole which mobilized in failure. The results of these simulations were comprised with other experimental and numerical test results. It has been shown that the numerical and experimental results are in good agreement with each other.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.359-362
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• 2006

In this paper, hole expanding tests are carried out in order to identify the effect of the hole process condition on the hole expanding ratio. Specimens with two different hole conditions are prepared: one is produced with punching process; and the other is reamed after punching to get smoother hole surface. The experimental results show that the facture mechanism and the hole expanding ratio are quite different with respect to the hole condition. The hole expanding ratio of a punched specimen is much smaller than that of a reamed one due to the difference of surface roughness and internal defects. For the thorough investigation of those effects, tensile tests of a specimen with a hole are performed. The fracture strain is obtained with different hole conditions and a finite element analysis of the hole flanging process carried out. The experimental results are confirmed and reevaluated by finite element analysis of the hole flanging process with ductile fracture criterion proposed.

• 한국분무공학회지
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• 제7권1호
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• pp.36-42
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• 2002

The objective of this investigation was to obtain an excellent spray at the low injection pressure. When cavitation occurred in the nozzle hole the atomization of the liquid jet enhanced considerably. In this experiments, a acrylic nozzle which was installed the gap and installed the bypass in the nozzle hole was used to enhance the atomization of the liquid jet at the few injection pressure. The liquid flow in the nozzle hole was photographed by a transmitted light using a micro flash. The spray angle was measured by macroscope images of PMAS and the Sauter mean diameter was measured by PDA system. The pressure of the notate hole was measured by pressure transducer. It was found that enhanced atomization of the liquid jet at the low injection pressure was obtained by installing the gap and the bypass at the single hole nozzle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3497-3500
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• 2007

The internal structure is subjected to dynamic analysis due to the structural integrity. The internal structure shall be installed in the vertical hole call IR1 of reactor core. In order to verify the deflection of the internal structure, the mode and response spectrum analysis of the internal structure was performed. The natural frequency of the internal structure is 11.6 Hz(mode 1 and 2) and deflections of the internal structure are less than values of allowable design (3.2 mm).

• 한국CDE학회논문집
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• 제22권1호
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• pp.59-69
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• 2017

Internal capacity of a refrigerator is an important indicator for design and purchasing criteria. The components facing the internal space may have holes or gaps between parts. In traditional way, design engineers manually remodeled the parts to fill the holes and the gaps for enclosed boundary of the internal space. Then they calculated internal volume by subtracting the assembly of parts from its enclosing volume. However, filling holes and gaps is not an automated process requiring a plenty of labor and time. In this research, we have developed a voxel-based method to estimate the internal volume of a refrigerator automatically. It starts transforming all components facing the interior space into voxels and fills all holes and gaps automatically by the developed hole-filling algorithm to form a completely closed boundary of the assembly. Then, it identifies the boundary voxels that are facing to the internal voxels with any part of the component. After getting the intersection points between the boundary voxels and the surfaces of components, it generates the boundary surface of triangular facets with the intersection points. Finally, it estimates the internal volume by adding volume of each tetrahedron composed of a triangle of boundary surface and an arbitrary point.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1155-1160
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• 1991

Active part mating algorithm using 6-axis force sensor data for the assembly automation and/or teletobotics is presented and experimented. Parts to be mated are cylindrical and have no chamfers. There are basically two modes. One is the normal mode with only a positional error, the other is the tilted mode with an orientational error in addition to a positional error. The used algorithm distinguishes a contact external to the hole from that of internal to the hole in order to perform part-mating in spite of the relative tilt between the hole and the peg.