• Advances in Computational Design
• /
• v.7 no.1
• /
• pp.69-79
• /
• 2022

In this research, the aeroelastic instability of a tail section manufactured from aluminum isotropic material with different shell thickness investigated. For this purpose, the two degrees of freedom flutter analytical approach are used, which is accompanied with simulation by finite element analysis. Using finite element analysis, the geometry parameters such as the center of mass, the aerodynamic center and the shear center are determined. Also, by simulation of finite element method, the bending and torsional stiffnesses for various thickness of the airfoil section are determined. Furthermore, using Lagrange's methods the equations of motion are derived and modal frequency and critical torsional/bending modes are discussed. The results show that with increasing the thickness of the isotropic airfoil section, the flutter and divergence speeds increased. Compared of the obtained results with other research, indicates a good agreement and reliability of this method.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2004.10a
• /
• pp.220-223
• /
• 2004

The weight reduction of carbody structures is of great concern in developing high speed tilting train for the normal operation of tilting system. The use of composite materials for the carbody structures has many advantages due to their excellent material properties. In this paper, finite element analysis was conducted to analysis and design the composite structure of Tilting Train eXpress(TTX). According to JIS E 7105, static load tests were performed and the structural safety of the composite carbody structure was verified by conducting finite element analysis of the model to which reinforcing frame are added in the composite carbody structure. In addition, modal analysis was conducted to estimate the natural frequency of a train.

• Smart Structures and Systems
• /
• v.24 no.5
• /
• pp.631-639
• /
• 2019

Finite element analysis is one of the important methods to study the structural performance. Due to the simplification, discretization and error of structural parameters, numerical model errors always exist. Besides, structural characteristics may also change because of material aging, structural damage, etc., making the initial finite element model cannot simulate the operational response of the structure accurately. Based on Bayesian methods, the initial model can be updated to obtain a more accurate numerical model. This paper presents the work on the field test, modal identification and model updating of a Chinese reinforced concrete pagoda. Based on the ambient vibration test, the acceleration response of the structure under operational environment was collected. The first six translational modes of the structure were identified by the enhanced frequency domain decomposition method. The initial finite element model of the pagoda was established, and the elastic modulus of columns, beams and slabs were selected as model parameters to be updated. Assuming the error between the measured mode and the calculated one follows a Gaussian distribution, the posterior probability density function (PDF) of the parameter to be updated is obtained and the uncertainty is quantitatively evaluated based on the Bayesian statistical theory and the Metropolis-Hastings algorithm, and then the optimal values of model parameters can be obtained. The results show that the difference between the calculated frequency of the finite element model and the measured one is reduced, and the modal correlation of the mode shape is improved. The updated numerical model can be used to evaluate the safety of the structure as a benchmark model for structural health monitoring (SHM).

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.10
• /
• pp.1211-1222
• /
• 2011

It is necessary to use prestressed modal analysis to calculate the modal frequencies and mode shapes of a prestressed structure such as a spinning blade, a preloaded structure, or a thermally deformed pipe, because the prestress effect sometimes causes significant changes in the frequencies and mode shapes. When the finite element model under consideration has a very large number of degrees of freedom, repeated prestressed modal analyses for investigating the prestress effects might become too computationally expensive to finish within a reasonable design-process time. To alleviate these computational difficulties, a Krylov subspace-based model order reduction, which reduces the number of degrees of freedom of the original finite element model and speeds up the necessary prestressed modal analysis with the reduced order models (ROMs), is presented. The numerical process for the moment-matching model reduction is performed directly on the full order models (FOMs) (modeled in ANSYS) by the Arnoldi process. To demonstrate the advantages of this approach for performing prestressed modal analysis, the prestressed wheel and the compressor impeller under their high-speed rotation are considered as examples.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.570-575
• /
• 2002

Servo performance of a disk drive is greatly affected by the mechanical resonance frequencies of the head gimbal assembly (HSA). It is important factor to allow broader bandwidths for servo system in improving overall drive performance. In this paper, an optimal design for ODD suspension is attempted to increase resonance frequencies in tracking direction. Initial model was designed and the design parameter was defined to the model. The mode frequency variation for the change of design parameter was observed by modal analysis using the finite element method(FEM). The sensitivity matrix was calculated from the observed data and so through sensitivity analysis, an optimized ODD suspension was designed to have the higher resonant frequency than the initial model.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.6
• /
• pp.130-141
• /
• 2000

The virbration characteristics of a passenger car steering column are studied by using a modal test and a finite element (FE) analysis. To verify the FE model and the results, an experiment using the impact exciting method is performed. Two types of the steering column in this study are considered as follows; (ⅰ) the non-tilt type steering column and (ⅱ) the upper-tilt type steering column. The experimental results are compared with those o the FE analysis, and it ti shown that the results agree with each other. The effects of various design parameters such as the bracket thickness, the column diameter on the natural frequencies are also investigated by FE analysis.

• Journal of Industrial Technology
• /
• v.27 no.A
• /
• pp.47-53
• /
• 2007

A theoretical model based on Rayleigh-Ritz method is proposed to predict the resonance frequency of a W/T(Wind Turbine) tower structure supported by guy cables. In order to verify the validity of the theoretical model, a reduced W/T tower system is manufactured and tested. Frequency response and mode data are determined by modal testing and finite element analysis is performed to calculate the natural frequency of the tower model. Numerical and experimental results are compared with those by the theoretical analysis. Parametric study by the theoretical model shows how the cable tension and cable elasticity influence the resonance frequency of the W/T tower structure. Finally, vibration response under various rotating speed is investigated to examine the possibility of severe resonance.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.348-354
• /
• 1999

An AC traction motor was developed, of which the rotor core has an unique structure, made of multi-layered silicon steel plates which were shrink-fitted to a shart. the equivalenet material properties were estimated with a newly proposed efficient method, based on the correlation between finite element analysis results and modal testing. A general rotordynamic analysis for the rotor with the equivalent material properties was carried out to evaluate the structural integrity of the virtually built-up motor.

• Structural Engineering and Mechanics
• /
• v.73 no.1
• /
• pp.27-35
• /
• 2020

In rail industry, noise reduction is a concern to decrease environmental pollution. The current study focuses on rail damper modeling and improvement of the model through validation with experimental results. Accurate modeling and simulation of rail dampers, specifically tuned rail dampers with layers interconnected by bolt joints, shall enable objective-oriented improvement of their design. In this work, to improve the damper model cone pressure theory is applied in the FE model and the sensitivity analysis is then applied to gradually improve the FE model. The improved model yields higher Modal Assurance Criterion (MAC) values and lower frequencies deviation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.840-845
• /
• 2004

Development of the linear motors is recently required to control a high-speed and high-resolution in the high-integrated and speed process industry. This paper presents vibration analyses as well as measurement standards of the newly developed linear motors through analyzing the vibration characteristics of the advanced products. Vibration experiments are conducted for identifying vibration level during operation. They are also included in the modal test to analyze dynamic characteristics. Analytic data using Finite Element Method (FEM) are compared with the results of the modal. The FEM and experiments make it possible to understand these characteristics. Further, through computer simulation for the behavior of moving part to be vibration source, the best acceleration pattern of moving part movement can be verified to achieve effective moving part positioning and reduce the vibration due to moving part movement.