• 한국정밀공학회지
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• 제25권6호
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• pp.47-54
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• 2008

Fitting process carried out in the automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that heats gear to a suitable range under the tempering temperature and squeezes it toward the outer diameter of shaft. Its stress depends on the yield strength of gear. Press fitting is a method that generally squeezes gear toward that of shaft at room temperature by a press. Another method heats warmly gear and safely squeezes it toward that of shaft. Warm shrink fitting process for the automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by this process produced dimensional changes in both the outer diameter and profile of the gear. So that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of warm shrink fitting process, in which design parameters are involved; contact pressure according to fitting interference between outer diameter of shaft and inner diameter of gear, fitting temperature, and profile tolerance of gear. In this study, an closed form equation to predict contact pressure and fitting load was proposed in order to develop an optimization technique of the warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, that is, thermal-structural coupled field analysis. Actual loads measured in the field was in good agreements with the results obtained by the theoretical and finite element analysis.

• 한국해양학회지
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• 제6권1호
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• pp.49-55
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• 1971

1969년 10월에 완성된 남강 다목점 댐과 방수로가 준공되어 1969년에 7회, 1970년에 3회 합계 10회에 걸쳐 1,359 $10^{6}$㎥ 이상의 담수를 진주만으로 방수하였다. 방수 속도는 최고 약 3,770㎥/sec 에 이르렀으며 1회 누적 방수량은 최고 4.50 $10^{6}$㎥ 이상에 달하였다. 이 결과 방수로 하류부와 연결되는 사천만 북부에서는 5kt 이상의 빠른 유속이 해저의 토사를 이동시켜 간석지와 해저의 지형을 변동시켰다. 양식장 시설물과 패류를 매몰, 유실 시키는 원인이 되었다. 하구 현상이 일어 났으며 2중조가 관측되었다. 어구의 파손, 발장의 도괴 및 어선의 조업 불능 등으로 피해가 막심하였다. 방수후 진주만의 염분은 급격히 하강하였으며 특히 사천만 에서는 밀물때에도 5 이하의 이상저염분수가 분포하였다. 현저한 조경이 이루어졌으며 반조석 주기에 4.6 에서 30 로 약 25 이상의 염분 급변이 있었다. 이와같은 염분의 저하와 급변은 동해역의 굴, 바지락 등 패류를 폐사시키고 멸치, 문어 등을 만외로 추방하는 원인이 되었으며, 내유 어군의 접근을 방해하였다. 염분의 저하는 해수의 밀도와 삼투압 환경을 급변 시키는 원인이 되었고, 투명도가 낮은 혼탁한 물덩이는 광선의 투입을 방해하여 광합성 작용을 억제할 것이다.

• 수산해양기술연구
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• 제50권3호
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• pp.233-243
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• 2014

The difference of mooring tension by type of buoy was investigated in the circulating water channel and the wave tank for deducting the most stable buoy from the current and the wave condition. 5 types of buoy made up of short cylinder laid vertically (CL-V), short cylinder laid horizontally (CL-H), capsule (CS), sphere (SP) and long cylinder (CL-L) were used for experiments. A mooring line and a weight were connected with each buoy. A tensile gauge was installed between a mooring line and a weight. All buoy's mooring tension was measured at the same time for the wave test with periods of 1.5~3.0 sec and wave heights of 0.1~0.3 m, and the current test with flow speeds of 0.2~1.0 m/sec. As a result, the order of tension value in the wave test was CL-H > CL-V > SP > CS > CL-L. In the current test CL-V and CL-H were recorded in the largest tension value, whereas SP has the smallest tension value. So it seems that SP buoy is the most effective in the location affected by fast current. CS is predicted to be suitable for a location that influence of wave is important more than that of current if practical use in the field is considered. And it was found that the difference of mooring tension among buoys in wave is related to the product of the cross sectional area and the drag coefficient for the buoy's bottom side in high wave height. The factor for the current condition was not found. But it was supposed to be related to complex factors like a dimension and a shape by buoy's posture to flow.

• 항공우주기술
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• 제7권1호
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• pp.15-23
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• 2008

본 논문은 항우연에서 운용 중에 있는 축소 로터 시험장치(General Small-scaled Rotor Test System, GSRTS)에 대한 구조 안전성 확보를 위한 구조해석 수행 결과를 제시하고 있다. 프루드(froude) 축소 및 마하(mach) 축소 시험을 수행하고, 관절형 및 무힌지 로터 등 다양한 로터 시스템 적용을 위해서는 시험장치의 안전성 확보와 운용상의 능력 범위를 확인하기 위해 로터 운용 조건에서 나오는 기준하중을 이용하여 구조 안전계수를 산출하였다. 특히, 구동계통(drive system)은 베어링 및 기어, 축 등으로 구성되어 있어 운용상의 안전성 확보가 우선적으로 요구되는 필수 항목이다. 구조해석은 구동계통의 기본 부품의 형상 및 재료 물성치를 이용하여 해석적 방법으로 구하였다. 본 로터 시험장치는 설계된 안전계수 안에서 운용을 해야 하며, 향후 KUH 축소 품동모델 시험을 적용할 때도 하중계산을 통해서 시험시 운용조건의 범위를 정해야한다.

• 한국기계가공학회지
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• 제20권12호
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• pp.44-53
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• 2021

As environmental issues have emerged worldwide, emission gas regulations have been strengthened. In the construction machinery sector, studies have been actively conducted to utilize the power source of electric motors owing to the increasing demand for zero emissions. In this study, the gear specifications of an electric axle for construction machinery were selected by considering the specifications of the motor, gear tooth contact pattern, and face load factor. The gear strength evaluation was performed at the system level using the simulation model. The bending and contact strength of the spiral bevel gears and the bending strength of the planetary gear set showed a safety factor of 1 or more. However, the contact strength of the planetary gear set showed a safety factor of 0.92. Conservative results were derived by performing the analysis under the rated load condition of the motor. However, the ratio of the equivalent torque to the rated torque of the motor was 45% or less, hence, it was determined that no difficulties should arise regarding the durability of the axle.

• 한국기계가공학회지
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• 제18권6호
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• pp.91-97
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• 2019

Rotating machining unit is a revolutionary product that can process worm shaft or spiral shaft with fast and precise, a rotary type cutting tool, which is attached to automatic lathe and processes spiral groove on outer circumference of round bar. In this work, a study on micro tooth shape modification method of driving gear train in the rotating machining unit was presented. To observe the effect on power transmission characteristics of the driving gear pair, visualize the gear meshing condition and the load distribution on the gear teeth by using the professional gear train analysis program RomaxDesigner. By comparing the repeated analysis results, the effect of micro tooth shape modification on power transmission characteristics on driving gear can be summarized. The optimized gears were fabricated and measured by precision tester as a validation in this research.

• 항공우주시스템공학회지
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• 제13권4호
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• pp.66-73
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• 2019

본 연구에서는 항공기 플랩 제어를 위한 선형 구동기의 기본 설계에 대한 구조 안전성을 평가하였다. 다물체 동역학 분석을 통해 선형 구동기의 기계적 운동을 이해하였고, 접촉 하중을 산출하여 유한요소해석 기반의 구조 분석에 적용하였다. 구조 분석에서는 선형 구동기의 설계 속도 조건에 대한 열, 정적 거동을 검토하였고, 구조적 안전성을 평가하였다. 또한 모드 해석을 수행하여 동적 거동을 분석하였다. 분석 결과, 모터가 225 rpm으로 작동 시 구동 로드는 약 5 mm/s로 병진 운동하였고, 기어 간 최대 32.83 N의 접촉 하중이 발생하였다. 한편, 최대 열 응력과 정 응력은 철의 항복강도의 약 1.57%, 78%로 발생하였고, 각 부품은 서로의 공진 주파수를 회피하였다. 따라서 제안된 선형 구동기의 기본설계는 구조적으로 안전하며, 공진에 대해 안정적임을 밝혔다.

• 한국기계가공학회지
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• 제18권4호
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• pp.93-99
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• 2019

A cross drilling/milling Unit is an important mechanical part which is widely used in many kinds of machining tool, and various gear trains with good accuracy and reliability features are widely used in power transmission systems. A study on a novel power transmission optimization method for driving gear trains in cross drilling/milling units is presented in this paper. A commercial program for gear system simulation, Romax Designer, was used in this research to intuitively observe the gear meshing and the load distribution conditions on the gear teeth. We obtained the optimal modification value through comparing the results of repeated experiments. For validation, optimized gears were fabricated and then measured with a precision tester.

• 농업과학연구
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• 제47권4호
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• pp.1135-1145
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• 2020

The purpose of this study was to compare and analyze the emissions of SOx and NH3 for a 78 kW class agricultural tractor during agricultural operations. A real-time monitoring system was constructed for measuring the load data. The field test was conducted during plow and rotary tillage. The working conditions were selected with the transmission gears in M3 Low and M2 High for the plow tillage and L3 High and L3 Low for the rotary tillage. The engine torque and fuel consumption were measured using controller area network (CAN) communication, and the emissions of SOx and NH3 were calculated based on the fuel consumption. As a result of the field tests, the engine torque was higher for the plow tillage than for the rotary tillage. As the gear stage was increased, the engine torque became higher. The emissions of SOx and NH3 were higher for the plow tillage than for the rotary tillage because the fuel consumption increased. Moreover, the emissions of SOx and NH3 tended to be more distributed for the rotary tillage than for the plow tillage. To develop an emission factor for agricultural machinery, it is important to measure reliable emission data during agricultural operations. In a future study, we will collect various emission data using a portable emission measurement system during agricultural operations.

• 디지털융복합연구
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• 제18권12호
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• pp.543-548
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• 2020

본 연구는 다중의 동력장치를 이용하여 다수의 객체를 움직이는 키네틱 디자인작품을 제작하면서 다수의 객체를 소수의 동력장치를 이용하여 다수의 동력장치를 이용한 것 같은 다양한 움직임을 구현할 수 있게 하는 것이 목적이다. 다수의 객체를 다양하게 움직이기 위해선 다수의 동력장치를 사용하여 움직임을 나타내는 것이 일반적인 방법이나 이렇게 하면 객체만큼의 많은 동력장치를 이용해야 하며 과다한 동력장치 사용으로 비용의 상승과 작품무게가 증가하게 된다. 많은 동력장치를 움직이기 위한 많은 전력 소모를 하게 된다. 이에 소수의 동력장치로 다수의 객체를 다양한 움직임을 통해 제어할 수 있는 메커니즘을 작품에 적용하여 실험하였다. 메커니즘을 이용해 다수의 객체를 움직이면 작품의 무게와 전력 소모량을 현저하게 줄일 수 있었다. 또한, 캠의 위치와 모양을 변경한 캠샤프트 구조의 이용과 베벨기어의 이용을 통해 객체의 행과 열을 늘려 다양한 움직임을 표현할 수 있었다. 본 연구를 통해 키네틱 디자인 작품을 제작하는 많은 디자이너에게 다수의 객체를 제어하는 하나의 또 다른 방법을 제시하게 된다.