두꺼운 복합재료 회전원판의 동적 특성

구교남(Kyo-Nam Koo) 한국항공우주학회 2016 韓國航空宇宙學會誌 Vol.44 No.8

두꺼운 복합재료 회전원판은 경량화와 고속화가 요구되는 터빈 디스크, 플라이휠 등에 다양한 기계요소도 활용되고 있다. 본 연구에서는 회전속도가 두꺼운 복합재료 원판의 동적특성에 미치는 영향을 살펴보았다. 이를 위해 두꺼운 복합재료 회전원판의 동적 운동방정식을 유도하고 유한요소 정식화를 수행하였다. 등방성 원판, 원주강화 복합재료 원판, 그리고 반경강화 복합재료 원판에 대한 수치해석을 수행하였다. 횡전단변형과 회전관성의 고려는 원판이 회전할 때에도 고유진동수를 감소시킬 뿐만 아니라 임계속도를 낮추는 역할을 한다. 원판의 회전속도가 증가함에 따라 횡전단변형과 회전관성 효과가 감소한다는 이전의 연구결과와는 달리 탄성계수의 이방성, 두께비, 모우드에 따라 그 효과가 감소 또는 증가할 수 있는 것으로 나타났다. Thick composite disks are utilized in the fast-rotating machines such as turbine disks, flywheels, and so on. The effects of rotating speed on the dynamic characteristics of thick composite disks are deeply studied in this paper. The dynamic governing equations of a rotating composite disk including transverse shear and rotary inertia are derived and then formulated into the finite element equation. Isotropic, circumferentially reinforced disk, and radially reinforced disk are selected for the numerical analysis. The inclusion of the transverse shear and rotary inertia into the governing equation of the rotating disks makes the natural frequency reduced as well as the critical speed. The present results show that the rotation of a thick disk may not reduce the effect of transverse shear and rotary inertia depending on anisotropy, thickness ratio and mode, unlike the results reported in other studies.

압전 패치 가진에 의한 탄성 원판의 진동 분포

안병호,김진오 대한기계학회 2023 大韓機械學會論文集A Vol.47 No.2

This study presents the vibration response of an elastic disc that is harmonically excited by a piezoelectric circular patch in an ultrasonic sensor structure. The ultrasonic sensor employed is composed of an elastic disc coupled with a cylindrical wall and attached by a small piezoelectric circular patch. The response equation was theoretically obtained by considering axially symmetric bending moment excitations for the elastic disc with a fixed boundary. The vibration response distribution of the elastic disc coupled with a cylindrical wall was analyzed using finite element analysis to enhance the theoretical result. Experiments were performed to confirm the response distribution in an enlarged specimen of the ultrasonic sensor structure. The theoretical and experimental results were compared and the radius ratio with maximum amplitude was confirmed. The vibration distribution obtained could be used for analyzing the acoustic characteristics of ultrasound radiating from an ultrasonic sensor for distance measurement. 본 논문은 초음파 센서 구조에서 원형 압전 패치의 조화 가진에 의한 탄성 원판의 진동 응답을 다룬다. 탄성 원판이 원통벽과 결합되고 작은 원형 압전 패치가 부착된 초음파 센서를 대상으로 한다. 둘레가 고정되어 있는 탄성 원판에 대하여 축 대칭 굽힘 모멘트 가진을 고려하여 응답 식을 이론적으로 구하였다. 원통벽과 결합된 탄성 원판의 진동 응답 분포를 유한요소 해석하여 이론적 결과를 보강하였다. 초음파 센서 구조의 확대 모형에서 실험을 하여 응답 분포를 확인하였다. 이론 및 실험의 진동 응답 분포 결과를 비교하였고 최대 진폭을 갖는 반지름 비율을 확인하였다. 거리측정용 초음파 센서의 음향 특성 해석에 사용할 진동 분포를 확보하였다.

원판의 비선형 비대칭 강제진동응답

여명환,이원경 한국소음진동공학회 2001 한국소음진동공학회 논문집 Vol.11 No.4

An investigation into asymmetric vibrations of a clamped circular place under a harmonic excitation is made. We examine a primary resonance. in which the frequency of excitation is near the natural frequency of an asymmetric mode of the plate. We found not only a response haying the form of standing wave but also one having the form of traveling wave, which was not observed by Sridhar, Mook and ${Nayfeh}^{(1)}$

테두리가 보강된 회전 원판의 반-유한요소해석

구교남(Koo, Kyo-Nam) 한국소음진동공학회 2009 한국소음진동공학회 논문집 Vol.19 No.5

In order to increase the critical speed of rotating disks of which functional material could not be changed such as in optical and magnetic data storage disks, a new disk with a rim reinforced by composite material is proposed and its concept is verified by numerical analysis. Stress distributions are found for the rotating disk composed of two annular disks of which materials are isotropic inside and orthotropic outside. Dynamic equation is formulated in order to calculate the natural frequency and critical speed. For the solution of lateral vibration, a rotational symmertry condition is applied along circumferential direction and a finite element interpolation with Hermite polynomial is performed along the radial direction to obtain a proper solution. According to the results, reinforcing a disk at rim makes critical speeds drastically increased, and induces a buckling phenomenon in mode (0,0) which occurs over the lowest critical speed.

다양한 경계조건에서 원판이 결합된 원통 셸의 고유진동 해석

임정식,손동성 한국소음진동공학회 1998 소음 진동 Vol.8 No.5

A theoretical formulation for the analysis of free vibration of a cylindrical shell with a circular plate attached at an arbitrary axial position of the shell under various kinds of boundary conditions was derived and programed to get the numerical results for natural frequencies and mode shapes of the combined system. The boundary conditions of the shell to be considered here are clamped-free, clamped-simply supported, both ends clamped and both ends simply supported. The frequencies and mode shapes from theoretical calculation were compared with those of commercial finite element code, ANSYS. The results showed good agreement with those of ANSYS in frequencies and mode shapes. The program will contribute to the design optimization of a shell/plate combined system through the analysis of natural frequencies and mode shapes for the system.

독립좌표연성법을 이용한 편심 된 원형 구멍을 갖는 원판의 자유진동해석

허석(Heo, Seok),곽문규(Kwak, Moon-K.) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.6

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.

환형평판과 원판으로 구성된 유체용기의 고유진동 해석

정경훈(Jeong, Kyeong-Hoon),김종인(Kim, Jong-In),박진석(Park, Jin-Seok) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.8

An analytical method for the hydroelastic vibration of a vessel composed of an upper annular plate and a lower circular plate is developed by the Rayleigh-Ritz method. The two plates are clamped along a rigid cylindrical vessel wall. It is assumed that the fluid bounded by a rigid cylindrical vessel is incompressible and non-viscous. The wet mode shape of the plates is assumed as a combination of the dry mode shapes of the plates. The fluid motion is described by using the fluid displacement potential and determined by using the compatibility conditions along the fluid interface with the plate. Minimizing the Rayleigh quotient based on the energy conservation gives an eigenvalue problem. It is found that the theoretical results can predict well the fluid-coupled natural frequencies comparing with the finite element analysis result

원형 압전 패치 가진에 의한 탄성 원판의 진동 분포

안병호(Byeong Ho An),김진오(Jin Oh Kim) 한국소음진동공학회 2019 한국소음진동공학회 학술대회논문집 Vol.2019 No.10

극직교 이방성 회전원판의 진동해석 및 임계속도, II

구교남(Koo, Kyo-Nam) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.3

This paper (Part II) provides the application results of the method presented in a companion paper (Part I) where the dynamic equation for rotating polar orthotropic disk is formulated and its solution method is considered. The natural frequencies and critical speed of polycarbonate CD are calculated to validate the present method and are shown to by very accurate. The critical speeds of typical GFRP and CFRP CD's are computed by aligning the fibers in radial and circumferential directions. The radially reinforced CFRP CD is shown to have the five times higher critical speed than that of the polycarbonate CD. The natural frequencies and critical speeds of disks with various elastic modulus ratios are obtained. The results show that the radially reinforced disk is more effective in increasing critical speed than the circumferentially reinforced disk.

극직교 이방성 회전원판의 진동해석 및 임계속도 I

구교남(Koo, Kyo-Nam) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.2

Rotating annular disks are widely used in data storage devices such as CDs, DVDs(digital versatile disks), and HDs(hard disks). Higher data transfer rate in data storage disks could not be achieved by polycarbonate disks in the present market. The problem can be solved by applying the fiber-reinforce composite materials to the disks. In this paper, an application of composite materials to rotating disks is proposed to increase the critical speed. Dynamic equation is formulated in order to calculate the natural frequency and critical speed for rotating composite disks by the Galerkin method. The orthogonal functions are used in series solution. A companion paper(Part II) presents and discusses the numerical results of vibration analysis and critical speed for rotating polar orthotropic disk using the formulation and solution method given in this paper (Part I).