• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.614-618
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• 2018

The changes in the mechanical properties according to the width of the tool shoulder, rotation speed and moving speed in friction stir welding (FSW) are evaluated using Al 6061-T6. The results indicated that the tensile strength value increases with increasing rotation speed. The higher the moving speed of the tool shoulder, the lower the tensile strength, regardless of the tool type. A higher tensile strength value was generally obtained with a tool shoulder diameter of 12mm (TSD12) than with 8mm. When the moving and rotation speeds exceed a limiting value, a stabilization stage is reached, in which (the tool shoulder diameter?) no longer affects the material properties. At a tool shoulder diameter of 8mm (TSD8), the material properties are decreased and the mixture of material in the welding area is incomplete in comparison with the tool type of TSD12. The tensile strength value is decreased at a rotation speed of 1500 rpm. As a result, a rotation speed higher than the threshold value is needed in order for and the transition temperature to be reached, which allows the complete mixing of the material in the welding area.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.681-689
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• 2020

This paper presents methods and results of both flight test examining roll angle estimation performance of slowly rolling munition forced to spin in the air, and fabricating a replica of guided munition. Guided munition was deployed from multi rotor type UAV mother ship whose altitude and velocity was conveyed to it as initial state. Flight test scenario is composed of a sequence of munition drop(deployment), munition spin, roll angle estimation and stabilization. Munition was deployed from mother ship at around 200m high with horizontal velocity of 15m/s, and was made spun using internal reaction wheel. Performance analysis on roll angle estimation is provided in comparison with commercial aerospace graded GPS/INS. Moreover, several mechanisms that rotates munition using reaction wheel, and actual product that realizes one of them are introduced.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.84-91
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• 2017

The dynamic characteristics of a ducted fan in hovering condition were investigated. The section properties of the fan blade were calculated, and a simulation model was developed according to the rotor system components. Dynamic analyses were conducted relative to the rotational speed and the collective pitch. The proposed ducted fan system showed less aero-elastic instability within the designated operating ranges. To verify the analytical approach, a rotating test stand of the ducted fan was set up. A functional test of the assembly was carried out to determine the kinematics and interference between components. The non-rotating and rotating normal frequencies were measured by excitation of the collective pitch using hydraulic actuators. The results indicated a correlation between the test equipment and the simulation model.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.776-782
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• 2003

This paper describes a newly developed double squirrel cage induction motor in which the rotor is located outside the stator. The outside rotor type brushless dc motor has been used for VTR's head drum and PC's cooling fan, but this kind of induction motor has not been developed yet. The parameters of outside rotor type induction motor were measured from the locked rotor test and no load test. It is possible to determine the parameters which are presented in the steady-state equivalent-circuit of the outside rotor type induction motor. Load test of induction motor was carried out using a dynamometer. For the characteristics of torque, efficiency, power factor and output. the developed double squirrel cage induction motor is compared with the ordinary induction motor It is believed that the results of this paper can be used for the development of the outside rotor type induction motor.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1747-1749
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• 2003

발전기 회전자 권선에 종종 발생하는 층간단락 현상을 찾아내는 진단기법에는 크게 두가지가 있으며, 정지중 진단기법인 분담전압 시험과 운전중 진단기법인 flux probe 시험이다. 본 논문에서는 서인천복합화력발전소 #2 스팀터빈 발전기에 대하여 분담전압 및 flux probe 시험을 시행하여 회전자 권선의 건전성을 확인하고, 그 결과를 상호 비교, 분석하여 정지중 및 운전중 진단기법의 신뢰성을 평가하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.149-152
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• 2008

A slinger combustor which can be applied to micro turbojet engine has been developed with the combustor rig test. A rotating fuel injector with high speed rpm was designed, manufactured and tested to apply into slinger combustor through spray test and adequate droplet size and spray distribution were achieved. The CFD was used to analyze internal flow of the combustor. We found out that the combustor shows 11.2% of pressure loss and 99.8% of combustion efficiency at full combustor rig test.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.692_693
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• 2009

본 논문은 초전도 플라이휠 에너지 저장장치(Superconductor Flywheel Energy Storage System : SFES)의 고속회전 시험을 통하여 휠의 진동 특성을 평가 하였다. 초전도 베어링(Superconductor Magnetic Bearing : SMB)은 동작시키기 않고 플라이휠의 외부 외란이나 예측하지 못한 진동을 억제할 수 있도록 설치된 전자석 댐퍼(Electric Magnetic Damper : EMD) 만을 이용해 휠을 부양하고 고속회전 시험을 수행하였다. 이를 통하여 플라이휠의 고속 회전 운전영역에서 EMD는 충분한 진동억제 능력을 보임을 확인 하였다.

• Aerospace Engineering and Technology
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• v.3 no.2
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• pp.217-228
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• 2004

This paper presents the rotating test techniques and the results of the roating test of the small-scaled hingeless rotor system with composite paddle blades in hover and forward flight conditions. The small-scaled rotor system was designed using froude-scaled properties of full scale rotor system. Metal flexures and composite flexures were made as hub flexures by the same dynamic properties of rotor system. The rotating tests of hingeless rotor system installed in GSRTS at KARI were carried out to get lead-lag damping ratios and aerodynamic loads of the hingeless rotor system. MBA(Moving Block Analysis) technique was used for the estimation of lead-lag damping ratio. 6-components balance was installed between hub and main shaft and straingauges on blades were instrumented for the measurements of aerodynamic loads of rotor system. Tests were performed on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.46-52
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• 2006

Techniques used for thrust vector control in rocket motors are mainly classified nozzles installed mechanical interference on the expansive region of nozzle(such as jet tabs and jet vanes) and movable nozzles(such as ball&socket and flexible seal). Using the numerical analysis and cold-flow test, this paper evaluates the performance of supersonic nozzle with asymmetric entrance shape when the test nozzle, especially ball&socket, is tilted. Numerical result shows that the effect of the asymmetric entrance shape on the flow field is suddenly diminished at the nozzle throat and downstream is mostly free from the effect of asymmetric entrance shape. Although the calculated thrust and lateral force are less than those of cold-flow test, two results show a fairly good agreement. But the cold-flow test results indicate the effective angles calculated from measured forces are not agreement with the geometric angles.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.223-229
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• 2002

패드엔팬을 이용하여 물 공급량, 팬 회전속도의 변화에 따른 온실 냉방효과 시험한 결과를 요약하면 다음과 같다. 가. 패드에 흐르는 물 공급량별로 일중 11:00-16:00경에 물 공급량이 분당 60$\ell$이상 공급하면 8.0~9.5$^{\circ}C$의 온도차를 낼 수 있으며, 팬을 1170rpm으로 회전시킬 경우 6.0~9.$0^{\circ}C$의 온도차를 낼 수 있었다. 나. 온실과 팬출구 공기의 온도차는 일중 14:30~16:00 경에 60$\ell$이상의 물을 패드에 공급하는 경우 6.0~7.8$^{\circ}C$ 온도 강하 효과가 있고 팬을 1170rpm으로 회전시킬 경우에는 외기온 28$^{\circ}C$일 때 3$0^{\circ}C$이하로 온도를 강하시킬 수 있었다. 다. 패드에 흘리는 물의량을 60 $\ell$/min 이상을 공급하여 주면 30분당 20~28$\ell$의 물을 증발시킬 수 있다. 배출팬 회전속도가 1170rpm일 경우에 30분당 20~30$\ell$의 물을 증발시키는 것으로 나타났다. 라. 본시험에 사용된 패드엔팬의 흡.배기의 엔탈피변화는 8:30이전에는 흡기가 배기보다 온도가 낮아 엔탈피가 양(+)의 값을 나타났고, 8:30 이후에는 흡기가 배기 보다 온도가 높아 -2.0~-4.OkJ/kg의 엔탈피 차만큼 냉각효과가 있었으며, 냉방효율을 65~80% 수준으로 나타났다. 마. 본시험결과로 패드엔팬의 냉기 공급방식만 개선된다면 이동식인 박스형 패드엔팬도 냉방장치로 사용 가능할 것으로 판단된다.