• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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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)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.940-946
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• 2015

The turning clearance angle changes the machining characteristics. In this study, three workpiece materials, machine structural carbon steel, chrome-molybdenum steel and stainless steel, were examined. The experiments revealed how the features of selected materials changed when they were processed with machining operation. To find the surface roughness of workpiece materials, the workpiece materials, which have a higher tensile strength, showed a much better surface roughness in the surface roughness tester. Moreover, the process feed rate was compared between 0.07 mm/rev and 0.10 mm/rev. When the process feed rate was 0.07 mm/rev, the surface roughness has superior results without reference to the quality of the materials. According to this research on the turning clearance angle, the best roughness value was observed when the quality of the materials were $0.9^{\circ}$, whereas the worst roughness was observed when quality of the materials was $0.3^{\circ}$.

• Journal of Power System Engineering
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• v.21 no.1
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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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• v.29 no.5 s.106
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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.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.4
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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.

• The KSFM Journal of Fluid Machinery
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• v.13 no.6
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.2
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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.

• Journal of Korean Society of Transportation
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• v.28 no.1
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• pp.97-105
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• 2010

An All-red clearance interval(AR) has been operating with amber signal in order to avoid collision between vehicles which cannot come out of the intersections, vehicles coming in from the opposite direction, and pedestrians(bicycles) on the crosswalk during the signal conversion time at the intersections. Foreign nations have been analyzing AR's influences of traffic accidents. On the other hand, the similar research has not been conducted in the country. The objective of this paper, therefore, is to analyze the safety at the intersections with respect to the installation of AR through the hypothesis test. A before-and-after analysis has been performed for 10 intersections where applied AR. From the 95% of significance level, the results of Non-parametric Test show that the installation of AR improves a safety at the intersections. The results indicates that AR discharges vehicles passing through the intersections and control entering vehicles at the intersections.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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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.