• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.851-856
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• 2016

In this paper, the free vibration characteristics of longitudinally corrugated cylindrical shells is investigated by the theoretical analysis. The equivalent homogenization model is adapted to investigate the overall mechanical behavior of these corrugated shells. The corrugated element can be represented as an orthotropic material. Both the effective extensional and flexural stiffness of this equivalent orthotropic material are considered in the analysis. To demonstrate the validity of the proposed theoretical approach, the theoretical results are compared with those from 3D finite element analysis using ANSYS commercial code. Some numerical results are presented to check the effect of the geometric properties.

• Earthquakes and Structures
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• v.18 no.6
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• pp.743-752
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• 2020

The phenomenon of reflection and transmission of plane waves at an interface between fluid half space and orthotropic piezothermoelastic solid half-space with two-temperature has been investigated. Energy ratios of various reflected and transmitted waves are computed with the use of amplitude ratios. The law of conservation of energy across the interface has been justified. It is found that the energy ratios are the functions of angle of incidence, frequency of independent wave and depend on the different piezothermoelastic material. A piezothermoelastic material has been considered which is in welded contact with water. Variations of energy ratios corresponding to the reflected waves and transmitted waves are computed and shown graphically for the two different models. A particular reduced case of interest is also discussed.

• Journal of Biosystems Engineering
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• v.27 no.6
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• pp.557-564
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• 2002

Corrugated board is an efficient low-cost structure material fur the boxes that are widely used for transporting, storing and distributing goods. Corrugated board is also considered as an orthotropic because the principal material directions are the same as in paperboard. The purpose of this study was to elucidate the principal design parameters of ventilating box through the FEA on the various types of ventilating hole. From the viewpoint of the stress distribution and stress level, the optimum pattern and location of the ventilating hole were vertically oblong, and symmetry position with a short distance to the right and left from the center of front and rear panel. And, the optimum location and pattern of hand hole were a short distance to the top from the center of both side panels, and modified shape to increase the radius of curvature of both side in horizontal oblong. In general, the optimum pattern and location of both the ventilating hole and hand hole based on the FEM analysis were well verified by experimental investigation. It is suggested that decrease in compressive strength of the box could be minimized in the same ventilating hole area under the condition of the length of major axis of ventilating hole is less than 1/4 of box length, the ratio of minor axis/major axis is 113.5∼l/2.5, and number of the ventilating holes is even and symmetrical.

• Steel and Composite Structures
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• v.17 no.4
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• pp.453-470
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• 2014

This article is the result of an investigation on the influence of a Pasternak elastic foundation on the stability of exponentially graded (EG) cylindrical shells under hydrostatic pressure, based on the first-order shear deformation theory (FOSDT) considering the shear stresses. The shear stresses shape function is distributed parabolic manner through the shell thickness. The governing equations of EG orthotropic cylindrical shells resting on the Pasternak elastic foundation on the basis of FOSDT are derived in the framework of Donnell-type shell theory. The novelty of present work is to achieve closed-form solutions for critical hydrostatic pressures of EG orthotropic cylindrical shells resting on Pasternak elastic foundation based on FOSDT. The expressions for critical hydrostatic pressures of EG orthotropic cylindrical shells with and without an elastic foundation based on CST are obtained, in special cases. Finally, the effects of Pasternak foundation, shear stresses, orthotropy and heterogeneity on critical hydrostatic pressures, based on FOSDT are investigated.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.377-386
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• 2019

Flexible composite propellers have a relatively large deformation under heavy loading conditions. Thus, it is necessary to accurately predict the deformation of the blade through a fluid-structure interaction analysis. In this work, we present an LST-FEM method to predict the deformation of a flexible composite propeller. Here, we adopt an FEM solver called OOFEM to carry out a structural analysis with an orthotropic linear elastic composite material. In addition, we examine the influence of the lamination direction on the deformation of the flexible composite propeller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.539-540
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• 2008

• KCI Concrete Journal
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• v.13 no.1
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• pp.19-25
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• 2001

Based on the orthotropic hypoelasticity formulation, a constitutive material model of concrete taking account of triaxial stress state is presented. In this model, the ultimate strength surface of concrete in triaxial stress space is described by the Hsieh's four-parameter surface. On the other hand, the different ultimate strength surface of concrete in strain space is proposed in order to account for increasing ductility in high confinement pressure. Compressive ascending and descending behavior of concrete is considered. Concrete cracking behavior is considered as a smeared crack model, and after cracking, the tensile strain-softening behavior and the shear mechanism of cracked concrete are considered. The proposed constitutive model of concrete is compared with some results obtained from tests under the states of uniaxial, biaxial, and triaxial stresses. In triaxial compressive tests, the peak compressive stress from the predicted results agrees well with the experimental results, and ductility response under high confining pressure matches well the experimental result. The reinforcing bars embedded in concrete are considered as an isoparametric line element which could be easily incorporated into the isoparametric solid element of concrete, and the average stress - average strain relationship of the bar embedded in concrete is considered. From numerical examples for a reinforced concrete simple beam and a structural beam type member, the stress state of concrete in the vicinity of talc critical region is investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.758-769
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• 1986

A general analytical procedure is developed for evaluating the free vibration characteristics of orthotropic and laminated composite circular cylindrical shells. The solution is obtained through a direct solution procedure with axial mode displacements presented as simple Fourier series expressions. On the basis of the various thin shell theories most commonly used, the frequency equation is derived and is expressed in a unified form. The present analysis can deal with shells which are made of an arbitrary number of bonded layers each with a different thickness and different elastic orthotropic properties, and have classical boundary conditions of any kind. Several examples are shown with the consideration of the effects of fiber orientations and boundary conditions as well as different shell geometries and material properties. To verify the validity and accuracy of this analysis, the results are compared with the experimental and analytical results of other workers. Agreement among the various results is found to be fairly good.

• Structural Engineering and Mechanics
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• v.18 no.3
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• pp.377-388
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• 2004

Based on the basic equations of elasticity, free-edge effects on stresses in cross-ply laminated plates are found by using the state space method. The laminates are subjected to uniaxial-uniform extension plate, which is a typical example of general plane strain problem. The study takes into account material constants of all individual material layers and the state equation of a laminate is solved analytically in the through thickness direction. By this approach, a composite plate may be composed of an arbitrary number of orthotropic layers, each of which may have different material properties and thickness. The solution provides a continuous displacement and inter-laminar stress fields across all material interfaces and an approxiamte prediction to the singularity of stresses occurring in the boundary layer region of a free-edge. Numerical solutions are obtained and compared with the results obtained from an alternative numerical method.

• Structural Engineering and Mechanics
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• v.37 no.5
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• pp.529-542
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• 2011

Three dimensional solutions for free vibrations analysis of functionally graded fiber reinforced cylindrical panel are presented, using differential quadrature method (DQM). The orthotropic panel is simply supported at the edges and is assumed to have an arbitrary variation of reinforcement volume fraction in the radial direction. Suitable displacement functions that identically satisfy the simply supported boundary condition are used to reduce the equilibrium equations to a set of coupled ordinary differential equations with variable coefficients, which can be solved by differential quadrature method to obtain natural frequencies. The main contribution of this work is presenting useful results for continuous grading of fiber reinforcement in the thickness direction of a cylindrical panel and comparison with similar discrete laminate composite ones. Results indicate that significant improvement is found in natural frequency of a functionally graded fiber reinforced composite panel due to the reduction in spatial mismatch of material properties.