• Structural Engineering and Mechanics
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• v.87 no.5
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• pp.419-429
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• 2023

This study conducts numerical analyses of a thin-walled composite cylinder under axial compression and internal pressure of 10 kPa. Numerical vibration correlation technique and nonlinear postbuckling analyses are conducted using the nonlinear finite element analysis program, ABAQUS. The single perturbation load approach and measured imperfection data are used to represent the geometric initial imperfection of thin-walled composite cylinder. The buckling knockdown factors are derived using present initial imperfection and analysis methods under axial compression without and with the internal pressure. Furthermore, the buckling knockdown factors are compared with the buckling test and computation time are calculated. In this study, derived buckling knockdown factors in present study have difference within 10% as compared with the buckling test. It is shown that nonlinear postbuckling analysis can derive relatively accurate buckling knockdown factor of present thin-walled cylinders, however, numerical vibration correlation technique derives reasonable buckling knockdown factors compared with buckling test. Therefore, this study shows that numerical vibration correlation technique can also be considered as an effective numerical method with 21~91% reduced computation time than nonlinear postbuckling analysis for the derivation of buckling knockdown factors of present composite cylinders.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.331-349
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• 2011

This study investigates the use of a vibration correlation technique (VCT) to identify the buckling load of a rectangular thin plate. It is proposed that the buckling load can be determined experimentally using the natural frequencies of plates under tensile loading. A set of rectangular plates was tested for natural frequencies using an impact test method. Aluminum and stainless steel specimens with CCCC, CCCF and CFCF boundary conditions were included in the experiment. The measured buckling load was determined from the plot of the square of a measured natural frequency versus an in-plane load. The buckling loads from the measured vibration data match the numerical solutions very well. For specimens with well-defined boundary conditions, the average percentage difference between buckling loads from VCT and numerical solutions is -0.18% with a standard deviation of 5.05%. The proposed technique using vibration data in the tensile loading region has proven to be an accurate and reliable method which might be used to identify the buckling load of plates. Unlike other static methods, this correlation approach does not require drawing lines in the pre-buckling and post-buckling regions; thus, bias in data interpretation is avoided.

• Structural Engineering and Mechanics
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• v.57 no.3
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• pp.543-567
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• 2016

This study attempts to address the buckling and free vibration characteristics of an isotropic cylindrical panel subjected to non-uniform temperature rise using numerical approach. Finite element analysis has been used in the present study. The approach involves three parts, in the first part non-uniform temperature field is obtained using heat transfer analysis, in the second part, the stress field is computed under the thermal load using static condition and, the last part, the buckling and pre-stressed modal analysis are carried out to compute critical buckling temperature as well as natural frequencies and associated mode shapes. In the present study, the effect of non-uniform temperature field, heat sink temperatures and in-plane boundary constraints are considered. The relation between buckling temperature under uniform and non-uniform temperature fields has been established. Results revealed that decrease (Case (ii)) type temperature variation field influences the fundamental buckling mode shape significantly. Further, it is observed that natural frequencies under free vibration state, decreases as temperature increases. However, the reduction is significantly higher for the lowest natural frequency. It is also found that, with an increase in temperature, nodal and anti-nodal positions of free vibration mode shapes is shifting towards the location where the intensity of the heat source is high and structural stiffness is low.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.56-63
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• 2004

Exact solutions are presented for the free vibration and buckling of rectangular plates haying two opposite edges ( x=0 and a) simply supported and the other two ( y=0 and b) clamped, with the simply supported edges subjected to a linearly varying normal stress $\sigma$$_{x}$=- $N_{0}$[1-a(y/b)]/h, where h is the plate thickness. By assuming the transverse displacement ( w) to vary as sin(m$\pi$x/a), the governing partial differential equation of motion is reduced to an ordinary differential equation in y with variable coefficients. for which an exact solution is obtained as a power series (the method of Frobenius). Applying the clamped boundary conditions at y=0 and byields the frequency determinant. Buckling loads arise as the frequencies approach zero. A careful study of the convergence of the power series is made. Buckling loads are determined for loading parameters a= 0, 0.5, 1, 1.5. 2, for which a=2 is a pure in-plane bending moment. Comparisons are made with published buckling loads for a= 0, 1, 2 obtained by the method of integration of the differential equation (a=0) or the method of energy (a=1, 2). Novel results are presented for the free vibration frequencies of rectangular plates with aspect ratios a/b =0.5, 1, 2 when a=2, with load intensities $N_{0}$ / $N_{cr}$ =0, 0.5, 0.8, 0.95, 1. where $N_{cr}$ is the critical buckling load of the plate. Contour plots of buckling and free vibration mode shapes ate also shown.shown.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.2
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• pp.75-82
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• 2022

Nondestructive method to predict buckling load for the propellant tank of launch vehicle should be evaluated. Vibration correlation technique can predict the global buckling load of unstiffened cylindrical structure with geometric initial imperfection using correlation of natural frequency and compressive load from compressive test below the buckling load. In this study, vibration and buckling tests of a thin metal unstiffened propellant tank model subjected to internal pressure and compressive loads were performed and the test results were used for VCT to predict global buckling load. For the vibration test of thin structure, non-contact excitation method using a speaker was used. The response was measured with piezoelectric polymer(PVDF) sensor. Prediction results of VCT were compared with the measured buckling load in the test and the nondestructive global buckling load prediction method was verified.

• Advances in nano research
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• v.9 no.2
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• pp.91-104
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• 2020

The bending, stability (buckling) and vibration response of nano sized beams is presented in this study based on the Eringen's nonlocal elasticity theory in conjunction with the Euler-Bernoulli beam theory. For this purpose, the bending, buckling and vibration problem of Euler-Bernoulli nanobeams are developed and solved on the basis of nonlocal elasticity theory. The effects of various parameters such as nonlocal parameter e₀a, length of beam L, mode number n, distributed load q and cross-section on the bending, buckling and vibration behaviors of carbon nanotubes idealized as Euler-Bernoulli nanobeam is investigated. The transverse deflections, maximum transverse deflections, vibrational frequency and buckling load values of carbon nanotubes are given in tables and graphs.

• Structural Engineering and Mechanics
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• v.59 no.6
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• pp.1055-1070
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• 2016

The aim of this experimental study is to investigate the free vibration and buckling behaviors of hybrid composite beams having different span lengths and orientation angles subjected to different impact energy levels. The impact energies are applied in range from 10 J to 30 J. Free vibration and buckling behaviors of intact and impacted hybrid composite beams are compared with each other for different span lengths, orientation angles and impact levels. In free vibration analysis, the first three modes of hybrid beams are considered and natural frequencies are normalized. It is seen that first and second modes are mostly affected with increasing impact energy level. Also, the fundamental natural frequency is mostly affected with the usage of mold that have 40 mm span length (SP40). Moreover, as the impact energy increases, the normalized critical buckling loads decrease gradually for $0^{\circ}$ and $30^{\circ}$ oriented hybrid beams but they fluctuate for the other beams.

• Structural Engineering and Mechanics
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• v.74 no.2
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• pp.175-187
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• 2020

The theories having been developed thus far account for higher-order variation of transverse shear strain through the depth of the beam and satisfy the stress-free boundary conditions on the top and bottom surfaces of the beam. A shear correction factor, therefore, is not required. In this paper, the effect of surface on the axial buckling and free vibration of nanobeams is studied using various refined higher-order shear deformation beam theories. Furthermore, these theories have strong similarities with Euler-Bernoulli beam theory in aspects such as equations of motion, boundary conditions, and expressions of the resultant stress. The equations of motion and boundary conditions were derived from Hamilton's principle. The resultant system of ordinary differential equations was solved analytically. The effects of the nanobeam length-to-thickness ratio, thickness, and modes on the buckling and free vibration of the nanobeams were also investigated. Finally, it was found that the buckling and free vibration behavior of a nanobeam is size-dependent and that surface effects and surface energy produce significant effects by increasing the ratio of surface area to bulk at nano-scale. The results indicated that surface effects influence the buckling and free vibration performance of nanobeams and that increasing the length-to-thickness increases the buckling and free vibration in various higher-order shear deformation beam theories. This study can assist in measuring the mechanical properties of nanobeams accurately and designing nanobeam-based devices and systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.756-759
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• 2001

The purpose of this paper is to investigate the buckling and dynamic characteristics for the cylindrical shell under shear loading. To do this, a vibration model tests and analyses and static buckling analyses were performed for the reduced scale model of nuclear reactor vessel. From the results of vibration modal analysis with the pre-shear displacement loads, it is known that the beam vibration mode is not affected by the shear displacement, however shell vibration modes are significantly affected by it. As the pre-shear displacement increases to the critical buckling displacement, the 1st shell vibration frequency in greatly reduces and approaches to zero value.

• Steel and Composite Structures
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• v.21 no.1
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• pp.37-55
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• 2016

In this study, the influence of centrally placed circular and square cutouts on vibration and buckling characteristics of different ply-oriented laminated panels under the action of compressive and/or tensile types of non-uniform in-plane edge loads are investigated. The panels are inspected under the action of uniaxial compression, uniaxial tension and biaxial, compression-tension, loading configurations. Furthermore, the effects of different degrees of edge restraints and panel aspect ratios are also addressed in this work. Towards this, a nine-node heterosis plate element has been adopted which includes the effect of shear deformation and rotary inertia. According to the results, the tensile buckling loads are higher than that of compressive buckling loads. However, the tensile buckling load continuously reduces with the increased cutout sizes irrespective of ply-orientations. This is also true for compressive buckling loads except for some particular ply-orientations with higher sized cutouts.