유한 원통셸의 큰 끝단 종진동을 발생시키는 감쇠파에 대한 분석 연구

길현권,Kil, Hyun-Gwon 한국음향학회 2011 韓國音響學會誌 Vol.30 No.7

진동하는 원통셸에서는 파동의 크기를 유지하며 전파하는 진행파 (굽힘파, 종파, 전단파)와 전파함에 따라서 파동의 크기가 지수 함수적으로 급격히 감쇠하며 소멸되어가는 감쇠파가 발생한다. 감쇠파의 영향은 일반적으로 가진 지점 혹은 구조물의 끝단 지점 부근에 국한되어 작게 발생되게 된다. 그러나 원통셸의 경우 상당히 큰 감쇠파가 발생할 수 있으며, 이러한 감쇠파로 인하여 종진동이 끝단 부근에서 상당히 크게 발생하는 현상이 일어날 수 있다. 이러한 현상은 저자의 유한 원통셸의 종진동 측정 실험 논문에서 관찰되었으며, 본 논문에서는 이러한 큰 감쇠파에 의한 원통셸의 끝단 종진동 현상을 해석적으로 분석하였다. 원통셸의 진동해석을 위하여서는 파동 전파 방법을 활용하였으며, 해석 결과를 실험 결과와 비교함으로써 진동하는 원통셸의 끝단에서 모드 변환 (굽힘파와 감쇠파간의 변환)에 의하여 상당히 큰 감쇠파가 발생할 수 있음을 보였다. 또한 감쇠파의 영향은 원통셸 끝단의 큰 종진동을 발생시키며, 원통셸 전체 길이의 1/3 지점까지도 영향을 줄 수 있음을 보였다. Propagating waves (flexural, longitudinal and shear waves) travelling with constant amplitudes and evanescent waves decaying exponentially are generated on a cylindrical shell. Evanescent waves are generally generated in the vicinity of an vibration excitation point and near ends of the shell. But the evanescent waves can generates strong axial vibration at the ends of the cylindrical shell. The strong end axial vibration due to those evanescent waves has been observed in an author's previous paper dealing with measurements of the in-plane axial vibration of a finite cylindrical shell. In this paper the strong end axial vibration due to the evanescent waves has been theoretically analyzed. In order to analyze the vibration of the cylindrical shell, wave propagation approach has been implemented. Comparison between theoretical and experimental results for the axial vibration of the shell showed that the strong evanescent wave can be generated due to mode conversion (conversion from flexural wave to evanescent wave) at the ends of cylindrical shell. It also showed that the evanescent wave can generate the strong axial vibration near the ends of the cylindrical shell and that it can have effect even on 1/3 of the total length of the shell.

링 보강 원통셸의 고유진동수 최적화에 관한 연구

장진건(Jin-Geon Chang),이영신(Young-Shin Lee),양태호(Tae-Ho Yang) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.3

보강 원통셸의 기본 고유 진동수를 최적화하기 위해서, 보강재의 개수를 1 개에서 5 개까지 보강된 원통셸에 대한 시뮬레이션을 수행하였다. 고유 진동수에 대한 최적화를 시뮬레이션하기 위해서 ANSYS 11.0 을 사용하였다. 최적화 방법으로 Subproblem Approximation Method 를 이용하였다. 최적화의 설계 함수로는 T-형 링 보강재의 기하형상이며, 제한 함수로는 보강에 따른 추가 부피가 10 % 이내로 제한하였다. 목적함수는 기본 고유진동수를 최대화하는 것이다. 최적 설계에 대한 성능 지표는 비보강 원통셸과 보강원통셸의 고유진동수와 부피의 비로서 정의하였다. 최적 성능 지수는 3 개의 보강재를 사용한 원통셸에서 나타났다. For the optimization of the fundamental natural frequency of stiffened cylindrical shells, simulations were performed for cylindrical shells that were stiffened with between one and five ring stiffeners. ANSYS 11.0 was used to simulate the optimization for the natural frequency. The Subproblem Approximation Method was applied as the optimization method. The design function of the optimization was the geometry of the T-shaped ring stiffener, and the constraint function was the maximum additional volume, constrained to a 10% increase. The objective function of the optimization was chosen to maximize the fundamental natural frequency. The performance index for optimal design was defined as the ratio of the natural frequency to the volume of the unstiffened and stiffened shells. The optimal performance index was obtained for the shell stiffened with three rings.

비선형 최소제곱법을 이용한 점탄성 감쇠를 갖는 원통셸의 실험진동해석

민천홍(CHEON-HONG MIN),박한일(HAN-IL PARK),배수룡(SOO-RYONG BAE) 한국해양공학회 2008 韓國海洋工學會誌 Vol.22 No.3

It is a recent trend for advanced ships and submarines to incorporate composite structureswith viscoelastically damping material. Much research has been done on curve-fitting techniquesto identify vibration characteristic parameters such as natural frequencies, modal damping ratios, and mode shapes of the composite structure. In this study, an advanced technique for accurately determining vibration characteristic of a circular cylindrical shell-attached viscoelastically damping material is used, based on a multi-degree of freedom (MDOF) curve-fitting method. First, an initial value is obtained by using a linear least square method. Next,sung the initial value, the exact model parameters of the composite circular cylindrical shell are obtained by using a nonlinear least square method. Results show computation time is greatly decreased and accurate results are obtained by the MDOF curve-fitting method.

원통셸의 진동 데이터에 대한 파수해석을 위한 공간신호처리 방법의 응용 연구

길현권(Kil, Hyun-Gwon),이찬(Lee, Chan) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.9

The vibration of a cylindrical shell is generated due to elastic waves propagating on the shell. Those elastic waves include propagating waves such as flexural, longitudinal and shear waves. Those also include non-propagating decaying waves, i.e. evanescent waves. In order to separate contributions of each type of waves to the data for the vibration of the cylindrical shell, spatial signal processing techniques for wavenumber analysis are investigated in this paper. Those techniques include Fast Fourier transform(FFT) algorithm, Extended Prony method and Overdetermined Modified Extended Prony method(OMEP). Those techniques have been applied to identify the waves from simulated vibration signals with various signal-to-noise ratios. Futhermore, the experimental data for in-plane vibration of the cylindrical shell has been processed with those techniques to identify propagating waves(longitudinal, shear and flexural waves) and evanescent waves.

원통셸의 수치 해석 진동에 대한 파동 분리

吉賢權 수원대학교 2006 論文集 Vol.24 No.-

Vibration of cylindrical shells are generated by elastic waves propagating on the vibrating cylindrical shells. The propagating elastic waves include out-of-plane waves and in-plane waves. The out-of-plane waves correspond to flexural waves and the in-plane waves correspond to longitudinal waves and shear waves. In order to understand vibration characteristics and sound radiation characteristics, it is required to separate contributions of the structural vibration by out-of-plane waves and in-plane waves. In this paper, the Fourier analysis and Prony method have been implemented to separate the contribution of the simulated structural vibration of by the out-of-plane waves and the in-plane waves.

비틀림 및 횡압럭을 받고 있는 복합재 원통쉘의 좌굴

한병기,이성희,유택인,Han, Byeong-Gi,Lee, Seong-Hui,Yu, Taek-In 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.5

The problem ofinstability of laminated circular cylindrical shell under the action of torsio or lateral pressure is investigated. The analysis is based on the Sander's theory for finite deformations of thin shell. The buckling is elastic for thin compoisite shell nad the geometry is assumed to be free of initial imperfections. The equilibrium equations are obrained by usitn the p[erturbation technique. Solution procedure is based on the Galerkin mehtod. The computer program for numerical results is made for several stacking sequence, length-to-radius ratio, and radius-to-thickness ratio. The numerical results of buckling load are present.

유체로 채워진 삼중 원통셸의 해석적 진동 특성 평가

지용관,이영신 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.2

The free vibration characteristics of the triple cylindrical shells filled with fluid are investigated. The triple cylindrical shells are filled with compressible fluid. The boundary condition is clamped at both ends. Analytical method is developed to evaluate natural frequencies of triple cylindrical shells using Sanders' shell theory and courier series expansion by Stokes' transformation. Their results are compared with those of finite element method to verify the validation of the method developed. The modal characteristics of shells filled with fluid at region 1, 2 and 3 are evaluated.

신경회로망을 이용한 원통셸의 충격하중 추론에 관한 연구

명창문,이영신 한국소음진동공학회 2001 한국소음진동공학회 논문집 Vol.11 No.9

A study on the structural analysis of the composite laminated cylindrical shell which has simply supported boundary conditions at both ends, was performed. The results were used into the neural networks. Neural networks identify the load characteristics of the composite shells. Momentum Backpropagation which the learning rate can be varied was developed. Input patterns consist of strains at 9 side points which is divided equally. Output layers are the load characteristics. Developed program was used for the training. The training with variable learning rate was converged close to real oad characteristics. Inverse engineering can be applicable to the composite laminated cylindrical shells with developed neural networks.

종동력을 받는 원통셸의 동적 안정성에 관한 연구

김현순,김지환 한국소음진동공학회 1998 소음 진동 Vol.8 No.2

The dynamic instability of cylindrical shell with clamped-free boundary condition subjected to constant follower force or $P_0 + P_1cos {\Omega}_t$ type pulsating follower force is analyzed. The motion of shell is modeled using the shell theory considering rotary inertia and shear deformation, and analyzed with finite element method. In case of constant follower force, the changes of eigenvalues dependent on the magnitude of applied load are investigated and the critical loads are obtained. In case pulsating follower force, instability regions of exicitation frequency are obtained by modal transform with right and left modal matrix and by multiple scales method. The effects of thickness ratio and aspect ratio on the instability of shell are studied.

길이방향으로 주름진 원통셸의 진동 해석

김영완(Young-Wann Kim) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.7

In this paper, the free vibration characteristics of longitudinally corrugated cylindrical shells is investigated by the theoretical analysis. The equivalent homogenization model is adapted to investigate the overall mechanical behavior of these corrugated shells. The corrugated element can be represented as an orthotropic material. Both the effective extensional and flexural stiffness of this equivalent orthotropic material are considered in the analysis. To demonstrate the validity of the proposed theoretical approach, the theoretical results are compared with those from 3D finite element analysis using ANSYS commercial code. Some numerical results are presented to check the effect of the geometric properties.