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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.
MR 댐퍼의 제작과 Bingham 모델의 매개변수 추정
이건명(Gun-Myung Lee),박문수(Mun-Soo Park) 한국기계가공학회 2014 한국기계가공학회지 Vol.13 No.6
Small MR dampers with a simple structure were designed and manufactured. The Bingham model was used to represent the dynamic characteristics of the damper, and the parameters of the model were estimated from experimental data which were obtained by harmonic tests. The value of the estimated yield shear force remains positive when no electric current is applied, and it increases slowly with the current. The estimated viscous damping coefficient has a value close to zero when no electric current is applied, and it increases almost linearly with the current.
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.
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.
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.