• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.267-267
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• 2004

엔드밀은 산업현장에서 정밀 금형과 다이 제조 시 넓게 사용되는 절삭 공구이며 공작기계의 향상에 따라 많은 발전을 거듭해 왔다 공작기계의 고속화에 따라 공작기계의 측면에서는 강성 증가, 열변형의 억제와 동적 안정성의 개선 및 응답성 개선을 통하여 정밀도를 향상시키고 이송속도와 절삭속도의 증가를 통해 생산성을 증대시키고 있으며 공구의 측면에서는 새로운 재종 및 코팅기법의 개발을 통해 공구수명의 향상을 달성하고 있다. 또한 공구형상의 최적화를 통해 동적 안정성을 확보하고 가공 정밀도를 개선하고자 하는 다양한 시도가 이루어지고 있다.(중략)

• 한국산학기술학회논문지
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• 제16권2호
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• pp.940-946
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• 2015

선삭작업에서 가공 여유각 변경은 가공특성을 변화시킨다. 본 연구에서는 피삭재로 기계구조용탄소강, 크롬믈리브텐강, 스테인리스강을 선택하여 정해진 가공조건으로 재질들의 특색이 어떻게 변화하는지 나타내었다. 피삭재의 재질별 표면거칠기를 알아보기 위하여 촉침식 표면 거칠기 측정기로 측정한 결과 인장강도가 높은 피삭재가 표면거칠기 값이 좋게 나왔다. 또한, 가공 이송속도 0.07 mm/rev와 0.10 mm/rev를 비교하였을 경우, 0.07mm/rev일 때가 재질과 관계없이 표면거칠기가 매우 좋게 나타났다. 선삭 여유각 변경에 따른 표면거칠기를 종합하여 분석하여 보면 3가지 재질 모두 $0.9^{\circ}$일 때 가장 좋은 거칠기 값을 보였으며 $0.3^{\circ}$일 때 가장 나쁜 거칠기 값을 보였다.

• 동력기계공학회지
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• 제21권1호
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• pp.70-79
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• 2017

The output power of turbine is greatly affected by the losses generated within the passage. In order to develop a better turbine or loss models, an experimental study was conducted using a linear cascade experimental apparatus. The total pressure loss and flow structures were measured at two cross-sectional planes located downstream of blade row. Measurement was conducted in a steady state for the several different locations of the blade row along the rotational direction. The blade row moved by 20 % of the pitch, and tip clearance was varied from 2% to 8%. Axial-type blades were used and its blade chord was 200mm. A square nozzle was applied and its size was $200mm{\times}200mm$. The experiment was conducted at a Reynolds number of $3{\times}10^5$ based on the chord. Nozzle flow angle sets to $65^{\circ}$ based on the axial direction and the solidity of blade row was 1.38. From the experimental results, the total pressure loss was greatly varied in the receding region than in the entering region. The flow properties within the blade passage were strongly changed according to the location of blade row.

• Journal of Biosystems Engineering
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• 제29권5호
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• pp.425-432
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• 2004

In harvesting rice and barley using combine, the inclination of the body caused by the irregular surface condition of the field and the soil sinking from the unbalanced weight during the grain collection used to make harvesting operation difficult and even impossible. To overcome such a problem hydraulic system far automatic and manual leveling control of a combine has been developed. The system was composed of the combine body and the hydraulic level control system mounted on it. The maximum height of ground clearance was set up to be 290mm. And the limit angle of the leveling control was set up to be $\pm7^{\circ}$. The proposed controller and hydraulic system was implemented to the prototype combine. The prototype combine was designed and built as a separable structure with the body and the track of it. This paper shows results of a specification and design testing with the hydraulic level control system far body of combine.

• 한국농공학회지
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• 제17권4호
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• pp.3970-3979
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• 1975

On account of the development of the high speed internal combustion engines, several methods for increasing burning velocity has been investigated lately. Installation of a squash area on a cylinder head is one of the simple and practical method to induce the strong tubulant flow of air-fuel mixtureinto a combustion chamber. In this study, a four-stroke engine used for agricultural purpose was tested as an experimental model. A mathematical model of the squash velocity was derived, and also, several characteristics of the squash phenomena during the motoring of the engine used as a modelwere investigated. The results obtained were as follows: (1) Mathematical model of squash velocity was established and cheked (2) Squaash velocity and engine speed were found to be proportional to the squash area while they were inversely proportional to the squash width. (3) Squash velocity and crank angle at which the squash velocity become its peak were influenced by the magnitude of squash clearance: increase of squash clearance made squash velocity reduced acd made the peak of the squash velocity for from the top dead center and (4) When the squash area is divided in small areas baving unit width along the squash section, squash velocity at each unit width was proportional to the magnitude of the squash distance covered by the unit width.

• 한국유체기계학회 논문집
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• 제13권6호
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• pp.5-12
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• 2010

Comparative study on the flow measurement by 5-hole and 7-hole probes was conducted in a linear cascade with tip clearances of 2.3%, 3.1%, and 4.4% of the blade span. Calibration range of the 5-hole and the 7-hole probes were ${\pm}25$ and ${\pm}50$ degrees, respectively. Results show that the secondary flow and total pressure loss measured by the 5e-hole and 7-hole probes were similar at small tip clearance cases. However, at the tip clearance of 3.1% and 4.4% of the blade span cases, flow angles exceeding the calibration range of the 5-hole probe were observed. Because of the wider calibration range, larger flow angle by strong leakage vortex could be measured by the 7-hole probe.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1671-1677
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• 2001

Cracks at mechanical fastener holes usually nucleate as elliptical comer cracks at the faying surface of the mechanical joints and grow as elliptical arc through cracks. The weight function method for elliptical arc through cracks at mechanical fastener holes has been developed and verified in the part I of this study. In part H, applying the weight function method, the effects of the amount of clearance on the mixed-mode stress intensity (actors are investigated and the change of crack shape is predicted from the analysis for various crack shapes. The stress intensity factors leer inclined crack are analyzed and critical angle at which mode I stress intensity factor becomes maximum is determined.

• 설비공학논문집
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• 제13권2호
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• pp.134-143
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• 2001

This paper presents the characteristics of flank and tip seal leakage in a scroll compressor for air-conditioners with R-22 under actual operating conditions. It is well known that the leakage has significant effect on the performance of the scroll compressor. Experiments were performed by using indirect method for measuring mass flow rate passing through flank and tip seal under actual operating conditions, In addition, an analytical model for tip seal leakage was developed to investigate tangential and radial leakage observed at grooves and contact points of tip seals. For low oil concentration, theoretical results were compared with experimental data to verify the analytical model. As a result, leakages through flank and tip seal parts were evaluated as afunction of pressure ratio, orbiting angle, discharge pressure, tip clearance, and leakage point. It was also found that the tip seal leakage was considerable even though the tip seal provided adequate sealing effect.

• 대한교통학회지
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• 제28권1호
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• pp.97-105
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• 2010

교차로에서 신호시간 변경 시 교차로를 벗어나지 못한 차량과 대향 차량, 교차로 횡단보도의 보행자(자전거)와의 충돌을 피하기 위하여 황색신호와 별도로 전전색신호를 운영하고 있다. 외국은 전적색신호 운영이 교통사고에 미치는 영향을 분석해 오고 있다. 반면 국내의 경우에는 이와 같은 유사한 연구가 미흡한 실정이다. 본 연구에서는 국내에서 운영되는 전적색신호가 교통사고에 어떠한 영향을 미치는 지를 가설검정 통하여 평가하였다. 전적색신호를 도입한 교차로 10개소에 대하여 전 후 사고율을 분석하였다. 95% 유의 수준에서 비모수 검정을 실시한 결과 전적색신호의 도입은 교차로 안전성을 향상시키는 것으로 분석되었다. 이는 전적색신호가 신호변경 중에 교차로에 남아 있는 차량의 정리와 미리 진입하는 차량을 통제함으로써 교차로내의 직각충돌사고를 감소시켰기 때문으로 분석된다.

• 한국소음진동공학회논문집
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• 제12권9호
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• pp.717-724
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• 2002

In this study, a numerical analysis for the piston secondary dynamics of small refrigeration reciprocating compressors is performed. In general, the length of cylinder in this class of compressors is shortened to diminish the frictional losses of the piston-cylinder system. So, the contacting length between piston and cylinder wall is in variable with the rotating crank angle around the BDC of the reciprocating piston. In the problem formulation of the piston dynamics, the change in bearing length of the piston and all corresponding forces and moments are considered in order to determine the piston trajectory, velocity and acceleration at each step. A Newton-Raphson procedure was employed in solving the secondary dynamic equations of the piston. The developed computer program can be used to calculate the entire piston trajectory and the hydrodynamic force and moment as functions of crank angle under compressor running conditions. The results explored the effects of the radial clearance, lubricant viscosity, length of the cylinder wall, and pin location on the stability of the piston.