• 동력기계공학회지
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• 제17권2호
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• pp.46-55
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• 2013

In this paper, the computational algorithm for free vibration analysis of an axisymmetric cylindrical shell is formulated by the Sylvester-transfer stiffness coefficient method (S-TSCM) which combines the Sylvester's inertia theorem and the transfer stiffness coefficient method. After the computational programs for obtaining the natural frequencies and natural modes of the axisymmetric cylindrical shell are made by the S-TSCM and the finite element method (FEM), the computational results which are natural frequencies, natural modes, and computational times by both methods are compared. From the computational results, we can confirm that S-TSCM has the reliability in the free vibration analysis of the axisymmetric cylindrical shell and is superior to FEM in the viewpoint of computational times.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.448-453
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• 2002

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.

• Structural Engineering and Mechanics
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• 제18권3호
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• pp.303-314
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• 2004

An artificial neural network (ANN) application is presented for flexural and axial vibration analysis of elastic beams with various support conditions. The first three natural frequencies of beams are obtained using multi layer neural network based back-propagation error learning algorithm. The natural frequencies of beams are calculated for six different boundary conditions via direct solution of governing differential equations of beams and Rayleigh's approximate method. The training of the network has been made using these data only flexural vibration case. The trained neural network, however, had been tested for cantilever beam (C-F), and both end free (F-F) in case the axial vibration, and clamped-clamped (C-C), and Guided-Pinned (G-P) support condition in case the flexural vibrations which were not included in the training set. The results found by using artificial neural network are sufficiently close to the theoretical results. It has been demonstrated that the artificial neural network approach applied in this study is highly successful for the purposes of free vibration analysis of elastic beams.

• 한국공간구조학회논문집
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• 제17권1호
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• pp.93-100
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• 2017

With increasing number construction of high-rise building which has about 40 to 60 floors there have been many kinds of problem which related with usage from vibration. To predict response acceleration, it is important to assess correct natural frequency. However, due to the noise of MEMS sensor, it is difficult to measure dynamic characteristic such as natural frequency when measuring ambient vibration using MEMS sensor within cell phone. Therefore, a comparative analysis on vibration measuring applications was performed after measuring ambient vibration of 2 skyscrappers which have height between 133.5~244.3m that are located in Seoul and Observation tower using I-jishin APP with noise reduction function of MEMS sensor in order to verify the effectiveness of low noise type vibration measurement APP.

• Structural Engineering and Mechanics
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• 제77권5호
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• pp.601-612
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• 2021

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1347-1354
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• 2005

The free vibration characteristics of Al cantilever square plates with a brass inclusion were analyzed experimentally and numerically The experimentally obtained natural frequencies and mode shapes were compared with the FEM analysis results. The impulse exciting method was used for experiment and ANSYS software package was used for FEM analysis. The natural frequencies obtained iron experiment and numerical analysis matched within $0\%$. It was found that the natural frequencies of the Al cantilever square plates with a brass inclusion decrease as the size of inclusion increases. For the third mode shape, comparing the nodal line of the Al plate and the Al plate with a inclusion, the mode shape showed the reversed quadratic curve. The natural frequencies of inclusion plate were decreased as the location of inclusion moves from the clamped edge to the tree edge.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.114-121
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• 2010

As a vehicle speed increases, more vibration energy is transmitted from chassis to a driver. Current isolation system for the driver's seat by damping control can reduce the transmitted vibration energy near resonance area. But in higher frequency region than natural frequency multiplied by $\sqrt{2}$, the vibration energy transmitted to the driver has a tendency to be increased. Therefore, the method by natural frequency reduction of the system is preferred to increase the effectiveness of the anti-vibration. However, the natural frequency could not be freely reduced due to the nature of the isolation system structure. A new passive suspension system to reduce the natural frequency is proposed. The theoretical analysis and experimental results show better vibration attenuation compared with the current isolation system.

• Steel and Composite Structures
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• 제31권6호
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• pp.591-600
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• 2019

Based on the energy-variational principle, a coupling vibration analysis model of high-speed railway simply supported beam bridge-track structure system (HSRBTS) was established by considering the effect of shear deformation. The vibration differential equation and natural boundary conditions of HSRBTS were derived by considering the interlayer slip effect. Then, an analytic calculation method for the natural vibration frequency of this system was obtained. By taking two simply supported beam bridges of high-speed railway of 24 m and 32 m in span as examples, ANSYS and MIDAS finite-element numerical calculation methods were compared with the analytic method established in this paper. The calculation results show that two of them agree well with each other, validating the analytic method reported in this paper. The analytic method established in this study was used to evaluate the natural vibration characteristics of HSRBTS under different interlayer stiffness and length of rails at different subgrade sections. The results show that the vertical interlayer compressive stiffness had a great influence on the high-order natural vibration frequency of HSRBTS, and the effect of longitudinal interlayer slip stiffness on the natural vibration frequency of HSRBTS could be ignored. Under different vertical interlayer stiffness conditions, the subgrade section of HSRBTS has a critical rail length, and the critical length of rail at subgrade section decreases with the increase in vertical interlayer compressive stiffness.

• 한국정밀공학회지
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• 제21권8호
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• pp.120-128
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• 2004

The impulse between launch vehicle and atmosphere can generate a lot of noise and vibration during the process of launching a satellite. Structurally, the electronic equipment of a satellite consists of an aluminum case containing PCB. Each PCB has resistors and IC. Noise and vibration of the wide frequency band are transferred to the inside of fairing, subsequently creating vibration of the electronic equipment of the satellite. In this situation, random vibration can cause malfunctioning of the electronic equipment of the device. Furthermore, when the frequency of random vibration meets with natural frequency of PCB, fatigue fracture may occur in the part of solder joint. The launching environment, thus, needs to be carefully considered when designing the electronic equipment of a satellite. In general, the safety of the electronic equipment is supposed to be related to the natural frequency, shapes of mode and dynamic deflection of PCB in the electronic equipment. Structural vibration analysis of PCB and its electronic components can be performed using either FEM or vibration test. In this study, the natural frequency and dynamic deflection of PCB are measured by FEM, and the safety of the electronic components of PCB is evaluated according to the results. This study presents a unique method for finite element modeling and analysis of PCB and its electronic components. The results of FEA are verified by vibration test. The method proposed herein may be applicable to various designs ranging from the electronic equipments of a satellite to home electronics.

• 로봇학회논문지
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• 제11권2호
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• pp.73-82
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• 2016

This paper focuses on the vibration analysis of planar cable-driven parallel robots on their configurations. Despite of many advantages of the cable robots, elasticity of the cables may cause the vibration at the existence of external disturbance, resulting in deterioration of positioning accuracy. According to the vibration theory, having high first order natural frequency can prevent resonance with low frequency disturbance from the surrounding environment. A series of simulations showed that choosing frame / end-effector shape and cable connection method affects robots' natural frequency. For the precise simulation, the cables are modeled as linear springs and axial vibration of cables is mainly considered. Aspect ratios of the frame and end-effector are defined as non-dimensional parameters while their areas are fixed. It was shown that vibration analysis guides to design a planar cable robot in terms of high capacity to reduce vibration.