• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.902-909
• /
• 2006

In this study, three-dimensional rotordynamic analyses have been conducted using equivalent beam, hybrid and fun three-dimensional models. The Present computational method is based on the general finite element method with rotating gyroscopic effects of a rotor system. General purpose commercial finite element code, SAMCEF which includes practical rotordynamics module with various types of rotor analysis methods and bearing elements is applied. For the purpose of numerical verification, comparison study for a benchmark rotor model with support bearings is performed first. Detailed finite element models based on three different modeling concepts are constructed and then computational analyses are conducted for the realistic and complex three-dimensional rotor system. The results for rotor stability and mass unbalance response are presented and compared with the experimental vibration test conducted in this study.

• Journal of KSNVE
• /
• v.9 no.4
• /
• pp.703-713
• /
• 1999

A side mirror is an important safety tool with which the driver can observe objects out of sight. This paper presents an organized design technology for the side mirror of improved vibration characteristics. Resonance response to forced vibration is critical to observability through the mirror to be designed. This study aims at the reduction of vibration level by the modification of mirror structures and consequent effects are predicted by computer simulations. We used a three-dimensional solid modeling and the modal and frequency analysis ; Pro/Engineer is used as a solid modeler; Pro/Mechanica for vibration analysis. The simulation results are compared with those obtained in experiemnts to check the validity by the three-dimensional modeling. The design technique of side mirror has been established and found to be effective in vibration analysis of redesigned parts.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.9 no.5
• /
• pp.1107-1112
• /
• 2008

Since vibration properties of a building structure were not easy to find out through a test, it was very difficult to in advance evaluate an influence of earthquake or other excitations on the building structure. However, currently, along with the development of the vibration analysis technique, it is possible to predict the structural performances of the buildings. The prediction of the vibration properties of the building structure has mainly employed a two-dimensional plane analysis so far, but not a three-dimensional analysis. The two-dimensional plane analysis encounters a reliability problem when the building is asymmetrical. This study has performed a three-dimensional modeling and vibration analysis on residential buildings when a subway passes below.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.2 s.119
• /
• pp.105-113
• /
• 2007

In this study, three-dimensional rotordynamic analyses have been conducted using equivalent beam, hybrid and full three-dimensional models. The present computational method is based on the general finite element method with rotating gyroscopic effects of the rotor system. General purpose commercial finite element code, SAMCEF which includes practical rotordynamics module with various types of rotor analysis tools and bearing elements is applied. For the purpose of numerical verification, comparison study for a benchmark rotor model with support bearings is performed first. Detailed finite element models based on three different modeling concepts are constructed and then computational analyses are conducted for the realistic and complex three-dimensional rotor system. The results for rotor stability and mass unbalance response are presented and compared with the experimental vibration test data conducted herein.

• Journal of KSNVE
• /
• v.9 no.1
• /
• pp.206-213
• /
• 1999

In the beam-like ship vibration analysis. three-dimensional correction factor(J-factor) can be calculated by considering the three-dimensional effect of the two-dimensional added mass. However, existing method is time-consuming with low accuracy in respect of global vibration analyses for vessels with large breadth. In this paper, to improve the demerit of the previous method, a new method of the beam-like ship vibration analysis is introduced In this method. the three-dimensional fluid added mass of surrounding water is calculated directly by solving the velocity potential problem using the Boundary Element Method (BEM). Then the three-dimensional added mass is evaluated as the lumped mass for each strip. Also, the beam-like ship vibration analysis for the structural beam model if performed with the lumped mass considered. It was verified that this new method is useful for the beam-like ship vibration analysis by comparing results obtained from both the existing method and the new method with experimental measurements for the open top container model.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.4 s.97
• /
• pp.457-464
• /
• 2005

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, complete (not truncated) conical shells of revolution, Unlike conventional shell theories, which are mathematically two-dimensional (2-D). the present method is based upon the 3-D dynamic equations of elasticity. Displacement components $u_{r},\;u_{z},\;and\;u_{\theta}$ in the radial, axial, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in , and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the conical shells are formulated, the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of theconical shells. Novel numerical results are presented for thick, complete conical shells of revolution based upon the 3-D theory. Comparisons are also made between the frequencies from the present 3-D Ritz method and a 2-D thin shell theory.

• Journal of Digital Contents Society
• /
• v.11 no.2
• /
• pp.117-122
• /
• 2010

This is a study on the analysis of vibration mode of a laser doppler. We measure the vibration mode of a doppler and analyze each component, and want to estimate three dimensional properties from 2-dimensional data. The vibration mode relies on a range detector that uses a distance sensor. Since the outputs are determined by the measured distance, we want to study how 3-dimensional vibration mode is generated from 2-dimensional ones. The study will include the patterns of generating a 3-dimensional vibration mode as well as the relationship between the distance and the vibration mode.

• Steel and Composite Structures
• /
• v.26 no.5
• /
• pp.649-662
• /
• 2018

In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of sandwich sectorial plates with multiwalled carbon nanotube-(MWCNT)-reinforced composite core are considered. Modified Halpin-Tsai equation is used to evaluate the Young's modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. In this paper, free vibration of thick functionally graded sandwich annular sectorial plates with simply supported radial edges and different circular edge conditions including simply supported-clamped, clamped-clamped, and free-clamped is investigated. A semi-analytical approach composed of two-dimensional differential quadrature method and series solution are adopted to solve the equations of motion. The material properties change continuously through the core thickness of the plate, which can vary according to a power-law, exponentially, or any other formulations in this direction. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated sectorial plates.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.10 s.115
• /
• pp.1024-1035
• /
• 2006

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, complete (circumferentially closed), circular rings with an elliptical or circular cross-section. Displacement components $u_r,\;u_\theta\;and\;u_z$ in the radial, circumferential, and axial directions, respectively, are taken to be periodic in ${\theta}$ and in time, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the circular rings are formulated, and upper bound values of the frequencies are obtained by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four-digit exactitude is demonstrated for the first five frequencies of the rings. Novel numerical results are presented for the circular rings having an elliptical cross-section based upon 3-D theory. Comparisons are also made between the frequencies from the present 3-D Ritz method and ones obtained from thin and thick ring theories, experiments, and another 3-D method.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.3
• /
• pp.228-235
• /
• 2002

Two kinds of experimental modal analyses have been performed on a radial tire for passenger car under fixed axle. One is the modal analysis to obtain three-dimensional modes of tire using accelerometers and the other is the one to identify cavity resonance frequency using a pressure sensor. From the first analysis, we have obtained three-dimensional natural modes and their decomposed 3-D modes in each direction, which make it possible to grasp the features of the modes that cannot be identified in the conventional 2-D modes and to classify the vibrationall modes into symmetric, non-symmetric, and antisymmetric modes in a simple way by using the experimental results. From the second experimental analysis, the cavity resonance frequency is found. Coomparing the results of the two analyses, we have Identified the three-dimensional mode of the cavity resonance. We also haute shown that natural frequencies of structural vibration depends on inflation Pressure while the cavity resonance does not.