• Journal of KSNVE
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• v.6 no.6
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• pp.819-825
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• 1996

Nonlinear dynamic characteristics of rubbing phenomenon in rotor dynamics are investigated experimentally and numerically. Rubbing phenomenon occurs when rotor contacts with stator during whirling and causes the large amplitude of vibration, high whirl frequencies, and possibly catastrophic failure. Rubbing has various types of forward whirl, backward rolling, backward slipping, and partial rub depending on the system parameters of rotating machinery and running speed. Experiments are performed for forward whirl and backward whirl. And numerical analysis are conducted to explain the changes between backward rolling and backward slipping. Experimental and numerical results show that the types of whirling motion depends on the friction coefficient between rotor and stator and the eccentricity of rotor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.6
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• pp.681-689
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• 2008

This paper is concerned with the free vibration analysis of a circular plate with an eccentric circular hole by the Independent coordinate coupling method(ICCM). It was proved in the previous study that the ICCM can accurately predict the natural frequencies and mode shapes of the annular plates and can also be used for the free vibration analysis of the simply-supported circular plate with an eccentric circular hole. In this study, the clamped and free boundary conditions were considered for the circular plate. The numerical results show that the ICCM can be used effectively for the free vibration problem of circular plate with an eccentric hole compared to the finite element method.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.251-259
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• 2001

본 논문은 직접 변위 설계법의 기본개념을 이용하여 비대칭 평면을 갖는 벽 식구조의 변위에 근거한 내진설계방법을 제안한다. 제안된 설계방법은 구조시스템의 각 벽체의 강도비와 강성비 및 목적 설계 변위를 결정하고, 직접 변위 설계법에 따라 설계하중은 구하는 과정으로 이루어진다. 탄성 영역에서는 강성 편심을, 비탄성 영역에서는 강도 편심을 주요한 설계변수로 사용하였다 성능에 기초한 내진설계의 개념에 따라 비대칭 평면을 갖는 구조물이 요구되는 성능 수준을 효과적으로 만족할 수 있도록 본 논문은 시스템의 비틀림 미케니즘과 각 벽체의 변형능력을 고려하였다. 제안된 설계방법을 이용하여 중진과 강진 지역에 대해 예제 구조물의 설계하중을 구하고, 최적의 설계방법을 제안하였다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1993.05a
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• pp.112-115
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• 1993

복사관을 이용한 가열방식은 복사관내에서 연료를 연소시킬 때 얻어지는 열이 관을 통하여 복사됨으로서 피가열물을 가열하는 방식으로서 분위기제어가 필요한 열처리로 등에 널리 사용되고 있다. 본 연구에서는 연속 소둔설비용으로서 저 NOx화 및 복사관의 표면온도를 상대적으로 균일하게 가열시키는 특성을 가진 버너의 개발을 위한 것으로서 실기규모 연소실험을 수행하였다. 연소실험은 기존버너 및 편심노즐버너에 대해서 수행하였으며 특히 개발실험용 버너의 실험과정에서는 새로 고안된 버너의 성능평가로부터 최적화에 이르기까지의 종합적인 실험을 수행하였다. 개발실험에 의해 편심노즐을 특징으로 하는 2단연소식 복사관버너를 고안하였으며 시제품버너의 성능실험결과 기존버너보다 NOx방출량에서 30%의 감소를 보여주었으며 복사관에서의 온도의 균일성이 향상되었음을 확인하였다.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2000.09a
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• pp.63-66
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• 2000

Stress variation due to size variation and the eccentricity of ring type tensile specimen was analyzed by FLAC program. To get the stable tensile strength the ratio of inner to outer ring diameter should be within a certain range. Diameter ratio of 0.3 was suggested to be adequate. It seemed to be difficult to determine the tensile strength because of stress distortion if eccentricity exceeded home limit. To limit the error in 10%, lateral and axial eccentricity was analyzed to be in the limits of 3% and 10%, respectively.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.587-591
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• 2011

To improve the performance of the control butterfly valve seals are used to eccentric shaft. In this case, vertical opening gas of the butterfly valve is non-symmetrical, which will change the flow pattern around the valve. In this study, the eccentric drive shaft of the butterfly valve to change flow characteristics are performed numerically. Flow pattern and pressure drop are investigated as the valve opening angle increases for a given mass flow rate. The valve flow coefficient is compared to the without eccentric shaft.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1721-1730
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• 2000

An eccentric degenerated shell element with geometric non-linearity for the precise and efficient analysis of stiffened shell structures is developed. To deal with the eccentricity, we define the e ccentric shell and the master shell that constitute one combined shell. It is assumed that the sections remain plane after deformation. The internal force vector and the tangent stiffness matrix based on the virtual work principle in the natural coordinate system are derived. To enhance the robustness of the element, assumed strain method for transverse shear and membrane strains is used. Through numerical experiments the effectiveness of the proposed element is demonstrated.

• The KSFM Journal of Fluid Machinery
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• v.4 no.2 s.11
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• pp.15-21
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• 2001

Basic equations and their solution procedure we derived for the analysis of an annular pump seal in which the rotor has a large static displacement from the centered position. The Bulk-flow is assumed for a control volume set in the seal clearance and the flow is assumed to be completely turbulent in axial and circumferential direction. Moody's wall-friction-factor formula is used for the calculation of wall shear stresses in the control volume. For the reaction force developed by the seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about an eccentric position. Flow variables are expanded by using Fourier series for the solution procedure. Integration of the resultant first-order pressure distribution along and around the seal defines the 12 elements of rotordynamic coefficients of the eccentric annular pump seal. The results of leakage and rotordynamic coefficients aye presented and compared with the Marquette's experimental results and the San Andres' theoretical analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.248-254
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• 1996

A disturbance rejection controller using eccentricity filtering and LQ control techniques is proposed to alleviate significantly the effect of roll eccentricity in multivariable cold-rolling processes. Fundamental problems such as process time delay inherent in exit thickness measurement and non-stationary characteristics of roll eccentricity signals can be overcome by the proposed control method. The filtered instantaneous estimate of roll eccentricity may be exploited to improve instantaneous estimate of the exit thickness variation based on roll force and roll gap mearsurements, and a feedforward compensator is augmented as a reference for a gaugemeter thickness estimator. And, LQ feedback controller is combined with eccentricity filter for the attenuation of the exit thickness variation due to the entry thickness variation. The simulation results show that eccentricity components have been significantly eliminated and simultaneously other distrubances also have been attenuated.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.956-963
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• 2001

The measurement of residual stresses by the hole-drilling method has been commonly used to evaluate residual stresses in structural members. In this method, eccentricity can usually occur between the hole center and rosette gage center. In this study, the error due to the hole eccentricity is predicted using the artificial neural network. The neural network has trained training examples of stress ratio, normalized eccentricity, off-centered direction and stress error using backpropagation loaming process. The prediction results of the error using the trained neural network are good agreement with FE analyzed ones.