• 동력기계공학회지
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• 제17권6호
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• pp.73-78
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• 2013

A Small-size axial fan(SSAF) has widely been utilized to circulate a cooling air in a refrigerator, etc. Generally, the aerodynamic performance of SSAF is strongly dependent upon the depth between SSAF and bellmouth, and it includes axial, partially stalled, mostly stalled and radial flow regions according to the flow coefficient. In this study, four kinds of bellmouth depths were considered to analyze the aerodynamic performance of SSAF. As a bellmouth depth increases, a maximum flowrate decreases, but a maximum static pressure increases. Also, stall region includes an inflection point in all aerodynamic performance curves. Finally, a static pressure efficiency shows the maximum value of 37%.

• 한국공작기계학회논문집
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• 제11권5호
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• pp.88-92
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• 2002

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also, it was able to evaluate with the formula, $HV^2$/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location 2~4mm apart from the center in the condition of $90^{\circ}$ of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W'shape.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.798-801
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• 2001

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also it was able to evaluate with the formula, HV2/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location, 2~4mm apart from the center in the condition of 90$^{\circ}$of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W' shape.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.220-228
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• 1999

The machining accuracy has been improved with the development of NC machine tools and cutting tools. However, it is difficult to obtain a high degree of accuracy when machining deep pocket with long end mill, since machining accuracy is mainly dependant on the stiffness of the cutting tool. To improve surface accuracy in machining deep pocket using end mill, the performance by down cut and up cut is compared theoretically and experimentally. To verify usefulness of up milling, various experiments were carried out. As a result, it is found that up milling produce more accurate surface than down milling in machining deep pocket. For effective application of up milling, various values in helix angle, number of teeth, radial depth of cut and axial depth of cut are applied in experiment.

• 한국정밀공학회지
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• 제20권8호
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• pp.213-220
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• 2003

By the localization of electro-chemical dissolution region, we succeeded in a few micrometer size hole drilling on stainless steel with the radial machining gap of about 1 ${\mu}{\textrm}{m}$. Tens of nanosecond duration voltage pulses were applied between WC micro-shaft and stainless steel in the 0.1 M $H_2SO_4$ solution. Pt balance electrode was used to drill the high aspect ratio micro-hole without generation of Cr oxide layer on the machined surface. The effects of applied voltage, pulse duration, and pulse period on localization distance were investigated according to machining time. We suggested the taper reduction technique especially brought up on blind-hole machining. High quality micro-holes with 8 ${\mu}m$ diameter with 20 ${\mu}m$ depth and 12 ${\mu}m$ diameter with 100 ${\mu}m$ depth were drilled on 304 stainless steel foil. The various hole shapes were also produced including stepped holes and taper free holes.

• 한국추진공학회지
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• 제10권4호
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• pp.34-39
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• 2006

두께가 얇고 길이가 긴 튜브 제품을 생산하기 위한 방법으로 유동성형 공정이 많이 이용되고 있으며 이는 다른 가공방법에 비해 성형력이 작고 유동성형에 의해 가공된 제품의 기계적인 강도가 우수하기 때문이다. 특히 유동성형은 로켓 모터 케이스, 연소기, 유압 실린더 그리고 고압용기 등과 같은 고정밀도의 두께가 얇은 실린더 제품을 생산하기 위한 적합한 공정이다. 본 논문에서는 3개의 롤러를 가지는 전후방 유동성형에 대한 유한요소해석을 통해 가공깊이와 가공속도가 성형력에 미치는 영향을 살펴보았다. 다양한 가공깊이와 가공속도 조건에서 얻어진 전후방 유동성형에서의 축방향과 반경방향의 성형력을 비교하였다.

• 한국기계가공학회지
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• 제2권3호
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• pp.20-25
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• 2003

The End-milling has been widely used in the industrial world because it is effective to cutting working with various shape. Recently the end-milling is demanded the high-precise technique with good surface roughness and rapid manufacturing time for precision machine and electronic elements. The cutting working of end-milling such as, cutting direction, revolution of spindle, feed rate and depth of cut have an effect on optimum surface roughness. This study was carried out to decide the working condition for optimum surface roughness and rapid manufacturing time by design of experiment and ANOVA. From the results of this study, the optimum working condition for end milling is upward cutting in cutting direction, 600rpm in revolution of spindle, 240mm/mm in feed rate, 2mm in axial depth of cut and 0 25mm in radial depth of cut. The design of experiment has become an useful method to select optimum working condition mend-milling.

• 물과 미래
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• 제22권2호
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• pp.201-211
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• 1989

인접계측지점의 상관성을 이용하여 결측지점의 자료를 보완한 다음, 다중상관 기법에 의하여 총강우량의 호우곡면을 구성한다. 구성된 호우 곡면에서 주기성분을 분리하여 호우잔차를 발생시키는데, 이중 프리에 해석을 이용했다. 각 강우에 잔차성분들은 균질등방성이라고 가정하여 이에 대응하는 자기 상관 함수를 조사하엿다. 실용성을 보완하기 위해서 경험치와 비교하였다. 모든 강우에 대한 정규상관 함수의 계수는 비슷한 양상을 보였다. 위의 결과를 사용하여 한강유역에 내린 강우의 공간분포를 나타내는 환상스펙트럼 분포함수를 추정하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1121-1126
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• 2003

Strength evaluation was carried out for the fillet and oil hole of crankshaft of medium speed diesel HiMSEN engine to verify initial concept design. Alternating torque obtained from torsional vibration analysis and radial force due to firing pressure were applied. It was assumed that the maximum alternating torque and radial force occur simultaneously. Weak points in view of fatigue are proceeding fillet and crank pin fillet area and the minimum normalized fatigue safety factor is 1.17 at crank pin fillet. The fatigue strength of the oil hole was evaluated to verify the effect of the surface roughness of the oil hole. As results, the specific level of the inner surface roughness and the polishing depth of the oil hole for sufficient fatigue strength was suggested. The maximum stress value and stress distribution at the inner surface of the oil hole can be easily estimated at initial design stage by the newly developed method.

• 대한토목학회논문집
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• 제28권4B호
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• pp.413-419
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• 2008

본 연구에서는, 바닥의 수심이 반경의 임의 차수의 제곱 꼴로 표현되는 다양한 형태의 축 대칭 지형 위를 통과하는 장파의 해석해를 유도하였다. 첫 번째 지형은 둔덕 위에 원기둥 모양의 섬이 있는 경우이며 두 번째는 원형의 섬이 있는 경우이다. 해를 구하기 위하여 변수 분리법, Taylor 급수전개법 및 Frobenius 급수법을 사용하였다. 유도된 해석해를 기존에 유도된 해석해와 비교를 하여 그 정확성을 검증 하였다. 또한, 입사파의 주기, 둔덕의 반지름 및 차수를 가지는 경우에 대하여 분석하였다.