• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.360-364
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• 2001

본 논문에서는 최근의 진화적 구조최적화(ESO) 전략을 회전축의 형상최적화에 적용하였으며, 각 계산 스텝마다 단위 유한요소의 크기를 변경함으로써 기존의 방법보다 빠르고 정확한 최적형상에 수렴하는 새로운 방법을 제시하였다. 축요소의 직경을 시스템 설계변수로 하였으며, 축중량의 감소, 공진배율(Q-factor)의 감소 및 충분한 위험속도의 분리여유를 갖도록 목적함수를 설정하였다. 불평형응답 및 굽힙응력의 구속조건을 부가하였으며, 목적함수에 대한 설계변수의 감도해석을 수행하였다. 전동기축계에 대한 적용 결과로부터 주파수와 동적 구속조건하의 로터베어링 시스템에 대한 축 형상 최적화에 ESO법이 효과적으로 이용될 수 있음을 확인하였다.

• Journal of KSNVE
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• v.9 no.3
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• pp.570-576
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• 1999

This paper presents numerical and experimental results of modal parameter identification in a generator stator frame for 500 MW fossil power plants. A commercial finite element analysis S/W was employed for modal analysis. The generator is excited by alternating electromagnetic forces, mainly of 120 Hz in 60 Hz machines, due to magnetic field and electric current in windings. It is necessary to verify that the stator frame has adequate frequency margin from the excitation frequency to avoid possible resonance when operating. Thus, frequency margin required for the stator frame is established using the numerical and experimental results. The results show that the stator frame meets the frequency-margin requirements. Also, results of modal analysis for design modification in order to reduce weights of the stator frame without deteriorating vibration characteristics are presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.225-226
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• 2010

ISO 22266-1 issued in May 2009 provides guidelines for applying shaft torsional vibration criteria, under normal operating conditions, for the coupled shaft system and long blades of a turbine generator set. In case that a turbine generator vendor do not meet the separation margin of torsional natural frequencies in the technical specifications of the purchaser, this standard can present the reasonable and objective criteria about torsional vibration which both purchaser and supplier can agree on, while ensuring the integrity of turbine generator. This paper describes the application case of ISO 22266-1 for the establishment of torsinal vibration criteria under retrofitting the turbine generator of 'U' nuclear power plant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.253-259
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• 1997

씨일의 마모에 따른 터빈펌프의 동적거동을 고찰하기 위해서 10단 터빈펌프를 대상으로 유한요소법에 의한 동특성 해석을 수행하였다. 베어링과 씨일의 동적계수를 회전속도의 하수로 계산하였으며, 이를 동적거동해석에 적용하였다. 해석결과 씨일들은 그 간극이 커질수록 강성 및 감쇠계수가 크게 떨어지고 누설량이 급격히 늘어남을 확인하였다. 따라서 1차 위험속도(1st Critical Speed) 이하에서 충분한 분리여유(Seperation Margine)를 가지고 정상운전되도록 설계된 터빈펌프라 할지라도 장기적 사용시 마모가 진전됨에 따라 계의 1차 위험속도가 변하여 운전속도에 접근할 수 있으며, 아울러 이 때 씨일의 감쇠가 크게 줄어들어 급격한 진동의 증가를 가져올 수 있음을 보였다.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.6
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• pp.78-85
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• 2007

In this study, we performed finite element analysis for the design of a medical centrifuge and two-types of centrifuge were compared with each other. The types of centrifuge are 2-arm straight type and 3-arm type. Structural analysis was done with respect to the change of the rotational speed of the rotor of a centrifuge. When the rotor of centrifuge was rotated, the von Mises stress of 2-arm straight type-rotor was compared with the von Mises stress of 3-arm type. The margin of safety was estimated from the result. We found the critical speed of centrifuge from the campbell diagram by modal analysis.

• Journal of Korean Society of Transportation
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• v.15 no.1
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• pp.129-156
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• 1997

8차로 고속도로에서 중앙분리대와 길 어깨에 의해 측방 여유폭이 제공되는 외측차 로(1.4차로)와 측방 여유폭이 제공되지 않는 내측차로 (2.3차로)에서 나타나는 운전자의 횡 방향 주행특성을 4개 지점에서 비디오 촬영하여 분석한 결과는 다음과 같다. (1) 차량의 횡 방향 주행궤적은 차로의 중심으로부터 주행방향의 좌측으로 이격된 주행 행태를 보이고 있 으며 이는 운전석의 위치에 의한 영향으로 판단된다. (2) 차량의 병행 주행시 외측 차로의 중심 이격 거리는 평균 0.38m이고 내측차로의 중심 이격 거리는 평균 0.34m로 나타났으며 T-test 겨로가 내측 차로와 외측 차로의 주행 이격 거리는 신뢰도 95%에서 상이한 것으로 나타났다. (3) 외측 차로의 주행궤적간 이격 거리는 평균 3.90m이고 내측 차로의 주행궤적 간 이격 거리는 평균 3.54m로서 내측 차로의 주행궤적간 이격 거리는 외측 차로의 주행궤 적간 이격 거리보다 0.36m 작다. 특히 내측 차로의 주행궤적간 이격 거리는 내측 차로간 차로 중심간 간격인 3.6m 보다 0.1m 작은 것으로 나타났다. (4) 내측차로 확장 대안으로 기존 도로폭 유지안 (3.5m, 3.7m, 3.5m)과 기존 도로폭 확장안 (3.6m, 3.7m, 3.7m, 3.6m)을 고려할 수 있으며 두 대안의 비교·분석결과 경제적 영향을 고려할 때 기존 도로폭 유지안이 우수한 것으로 분석되었다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.267-273
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• 2013

Recently, turbine-generators have been replaced for the integrity reinforcement and the efficiency improvement, also, the blade's failures of LP turbines due to torsional vibration have been reported. Excessive torsional vibrations can result in failures of components. The severity of torsional oscillations and stress depends upon the separation margin between the excitation frequencies and torsional natural frequencies. Therefore it is needed to measure the torsional natural frequencies after replacement of the components to conform the separation margin of torsional natural frequencies. In this study torsional vibration measurements were performed after LP turbine and generator replacement and the torsional natural frequencies for the turbine-generator train were calculated to evaluate the effects of generator replacement on torsional natural frequencies of turbine-generator train. It is expected that these evaluation results will be used effectively to identify the root causes of torsional vibration problems.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.91-95
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• 2011

This paper deals with the detail rotordynamic analysis for the assembly rotor composed of turbine wheel, turbine shaft, connecting arbor, and flange & spindle in order to perform the spin test of turbocharger turbine. Prior to rotordynamic analysis, the 1st spin test was performed but the test was failed by excess vibration in the neighborhood rated speed. It is the reason for this fail that the separation margin between the rated speed and critical speed is not enough, confirmed by rotordynamic analysis results. Since then, the dimension of turbine shaft was modified and the critical speeds were again reviewed for modified assmebly rotor. In results, the separation margin between the rated speed and critical speed is over 20% and then the 2nd spin test was performed successfully. In preparing spin test for turbine, compressor wheels and etc., the geometry design of connecting arbor and dimension of rough machining should be reviewed by considering rotordynamic results, and the separation margin should be enough for successful spin test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.900-907
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• 2013

Payload fairing(PLF) protects satellites and related equipment from the external environment. They are separated before the satellite separation. Payload fairing made of composite sandwich materials due to their considerable bending stiffness and strength-to-weight ratio. Payload fairing have compression, shear and bending load during the flight. In this study, To check the strength of PLF and connected part, structural test of PLF accomplished using an actuator and a fixture. Purpose of structural test is to verify the strength of PLF in force of separation spring and combination structural load applied. Test result shows that the PLF have an acceptable margin of safety for the combination structural load and force of separation spring.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.3
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• pp.249-256
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• 1999

The conventional robot manipulability is decomposed into linear manipulability and angular manipulability so that they may be analysed and visualized in easy way even in the case of 3 dimensional task space with 6 variables. After the Jacobian matrix is decomposed into linear part and angular part, constraint on joint velocities is transformed into linear task velocity and angular task velocity through the decomposed Jacobian matrices. Under the assumption of redundant robot manipulators, several optimization problems which utilize the redundancy are formulated to be solved by linear programming technique or sequential quadratic programming technique. After deriving the solutions of the optimization problems, we give graphical interpretations for the solutions.