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이건명(Gun-Myung Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Some characteristics of the sensitivities of the eigenvalues for beams have been found in the paper. For<br/> cantilever beams and simply supported beams, the sensitivities of the eigenvalues to the stiffness correction<br/> factor of one element are equal and opposite to the sensitivities to the mass correction factor of the<br/> symmetrically positioned element. The relationship means that to increase stiffness in one element has the<br/> same effects on the eigenvalues as to decrease mass by the same proportion in the symmetrically positioned<br/> element. For beams with other boundary conditions, however, the relationship does not hold.
이건명(Gun-Myung Lee),주영호(Young-Ho Ju),박문수(Mun-Soo Park) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.10
The responses of a bridge due to a moving vehicle are obtained analytically by modeling a vehicle as a constant point force. From the results it is found that the responses after a vehicle leaves the bridge become very small for some speeds of a vehicle. When a vehicle is modeled as a two dof system for a more accurate analysis, the same phenomenon is observed while the roughness of the bridge is small. Determining the fundamental frequency of a bridge so that one of the above speeds coincides with a frequent speed of vehicles, the responses of a bridge can be minimized.
Updating of Finite Element Models Including Damping
이건명(Lee, Gun-Myung),주영호(Ju, Young-Ho),박문수(Park, Mun-Soo) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.12
Finite element models are updated in two stages in this paper. In the first stage, damping is neglected, and mass and stiffness matrices of a finite element model are updated using an optimization technique. The objective function for optimization consists of natural frequencies and mode shapes obtained from experimental modal testing data and finite element analysis. In the second stage, damping is considered with the mass and stiffness matrices fixed. A damping matrix is estimated assuming a proportional damping system. Then the damping matrix is adjusted using an optimization process so that the difference between the analytical and measured frequency response functions becomes minimum. This procedure of model updating has been applied to a simulated system and an experimental cantilever beam.
고성능 회전형 미분탄 분리장치의 효과에 관한 실험적 연구
이건명(Gun Myung Lee),하종광(Jong Kwang Ha),이익형(Ik Hyung Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
If the fineness of pulverized coal is increased in the coal-fired stations, unburned carbon in ash shall be reduced and combustion efficiency shall be improved. Especially, In connection with the environmental protection issue recently, the reduction of NOx is a secondary advantage. So, this study was conducted in the pilot scale pulverizer model and drop tube furnace that the used of static and dynamic classifier for the high performance effect of rotating pulverized coal separator. The results of the experiment showed that the amount of pulverized coal passing 200 mesh of the pulverizer with dynamic classifier was higher than that of the pulverizer with static classifier. Also unburned carbon in ash and NOx emission were reduced. Additionally, In case of the pulverizer with dynamic classifier, the power consumption and pressure loss were decreased than that of the pulverizer with static classifier based on the same fineness level.
이건명(Gun-Myung Lee),김경주(Kyung-Ju Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping. In the second stage, a damping matrix is updated with the mass and stiffness matrices fixed, and several methods may be used. A method to estimate a damping matrix for this purpose is proposed in this paper. In the method a damping matrix is estimated from the impedance matrix which is the inverse of the FRF matrix. Only one low or one column of the FRF matrix is measured, and modal parameters such as natural frequencies, damping ratios, and residues are estimated by performing a modal analysis of the measured FRFs. Next, unmeasured FRFs are synthesized using the estimated modal parameters and a full FRF matrix is obtained. This procedure to obtain a full FRF matrix saves time and effort to measure FRFs and can help overcome a drawback of the damping estimation method using an impedance matrix.
이건명(Gun-Myung Lee),박문수(Mun-Soo Park) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.6
등하중지지대는 플랜트의 배관을 지지하는 장치로서 열팽창으로 인하여 배관이 움직이더라도 배관에 일정한 힘을 제공하는 역할을 한다. 본 논문에서는 등하중지지대의 캠 윤곽을 설계하는 방법을 제안하였다. 캠의 윤곽은 캠의 기하학적 관계식, 부하 튜브의 힘 평형식, 보조스프링의 압축력과 캠의 회전각 사이의 관계식, 그리고 캠의 모멘트 평형식을 만족하여야 함을 보였고, 이 방정식들을 연립하여 푸는 계산 과정을 제안하였다. 이 계산 과정을 사용하여 요구하는 조건을 만족하는 등하중지지대의 캠을 설계하였다. A constant hanger is a device for supporting pipes in plants. It supplies a constant force to a supporting pipe even if the pipe moves because of thermal expansion. In this paper, we propose a method for designing the contour of a cam for a constant hanger. It has been shown that the contour of a cam must satisfy the geometrical relation of the cam, the force balance equation for the load tube, the relation between the side spring compression and the cam rotation angle, and the moment balance equation for the cam. A calculation procedure to solve these equations simultaneously is proposed, and a constant hanger is designed successfully.
이건명(Gun Myung Lee),하종광(Jong Kwang Ha),안상택(Sang Taek Ahn),이익형(Ik Hyung Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
Three-dimensional experimental analysis was conducted in the pulverizer simplified isothermal model.<br/> The experiment model was constructed on a 1/3.5 scale of 500MW pulverizer. The purpose of this study is to<br/> investigate the effect of design parameters on the pulverized coal separator efficiency. Where used pulverized<br/> coal separator design parameters are guide vane angle, static classifier angle, dynamic classifier rpm. Taguchi<br/> method was used to find the effective design parameters related to pulverized coal separator efficiency. The<br/> results of the experiment showed that guide vane angle and dynamic classifier rpm were the design key<br/> parameters. In addition to the total number of experiment cases were reduced by Taguchi method.
Approximate Response of a Non-linear Vibration Isolation System Using the Harmonic Balance Method
Gun-Myung Lee(이건명) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.6
A non-linear vibration isolation system which is composed of a non-linear spring and a linear damper was proposed in past research. When the support of the isolation system is excited harmonically, the response component of the isolation system mass at the excitation frequency has been calculated approximately using the harmonic balance method. The response was approximated by a single mode, and the result was compared with a numerical result which is assumed as an accurate one. Next, the response was approximated by two modes, and the result was compared with the former one.