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RISS 인기검색어
- 검색키워드
- 주제어 : Natural frequency loci veering (검색결과 6 건)
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Simple vibration model for the design of a vertical axis wind turbine
Hyung Hee Kim,Yutaek Oh,Hong Hee Yoo 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2
Wind turbines are widely used these days as one of renewable energy sources. In this paper, a dynamic model of a vertical axis wind turbine is developed by considering coupling effects among shaft bending, shaft torsion, shaft tension, rotor tension and rotor bending. The modal characteristics of the vertical axis wind turbine were obtained by using the dynamic model. The accuracy of the proposed model was first validated by comparing its numerical results to those obtained with a commercial program. Then, the effects of key design parameters such as shaft length, shaft diameter and rotor cross section area on the modal characteristics of the wind turbine were investigated. The natural frequency loci veering phenomena occurred when those parameters varied. The loci veering phenomena were associated with the mode shape switch between shaft bending and rotor bending, which should be carefully examined to improve the vibration quality of the wind turbine. The main contribution of this study is to propose a simple vibration model by which the effects of various design parameters on the modal characteristics of the vertical axis wind turbine can be investigated. Some design guidelines related to the vibration performance are also suggested.
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Mode localization and veering of natural frequency loci in two circular plates coupled with a fluid
Jeong, Kyeong-Hoon Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.6
An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.
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Vibration Analysis of Rotating Composite Cantilever Plates
Kim, Sung-Kyun,Yoo, Hong-Hee The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.3
A modeling method for the vibration analysis of rotating composite cantilever plates is presented in this paper. The coupling effects between inplane motions and the bending motion are considered and explicit mass and stiffness matrices are derived for the modal analysis. Numerical results are obtained and some of them are compared to those of a commercial program to confirm the accuracy of the present method. Numerical results show that the coupling effects become important only when laminates are stacked up unsymmetrically. Incidentally, natural frequencies loci veering, loci crossing, and associated mode shape variations are observed.
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Vibration Analysis of Cantilever Plates Undergoing Translationally Accelerated Motion
Yoo, Hong-Hee,Kim, Sung-Kyun The Korean Society of Mechanical Engineers 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.4
This paper presents a modeling method for the vibration analysis of translationally accelerated cantilever plates. An accurate dynamic modeling method, which was introduced in the previous study, is employed to obtain the equations of motion for the vibration analysis. Dimensionless parameters are identified to generalize the conclusions from numerical results. The effects of the dimensionless parameters on the natural frequencies and mode shapes are investigated. Particularly, the magnitude of critical acceleration which causes the dynamic buckling of the structure is calculated. Incidentally, the natural frequency loci veering phenomena are observed and discussed.
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Dynamic analysis of an axially moving robot manipulator supported by bearings
김재원,정진태 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7
In this study, a robot manipulator is modelled as a cantilever beam, which moves in an axial direction, has a lumped mass at the end, and is supported by intermediate springs. Considering the tip mass and intermediate springs in the modeling, we derive the equations of motion in which the rigid-body motion is coupled with the flexible motions, and then analyze the transverse vibrations of the beam. Furthermore, we study the tip mass effects on the natural frequencies and the corresponding mode shapes. The natural frequency loci veering is analyzed for variations in the tip mass and the spring position/stiffness. In addition, we investigate the exchange and localization of modes around these veering regions as well as the parameter effects on the mode shapes. Using a Short-time Fourier transform (STFT), the relationship between the dynamic characteristics and dynamic responses are described. It is found that the dynamic characteristics of the beam are dependent on the veering distance. It is also shown via dynamic responses that the mode exchanges occur when a veering distance is close.
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임홍석,유홍희 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.10
A modeling method for the dynamic characteristic analysis of a translationally accelerated trapezoidal cantilever plate is presented in this paper. The equations of motion for the plate are derived and transformed into a dimensionless form. The effects of the inclination angles and the acceleration on the vibration characteristics of the plate are investigated. Incidentally, natural frequency loci veering and associated mode shape variations are observed and discussed.
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