• Wind and Structures
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• v.8 no.1
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• pp.35-48
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• 2005

Wind loading is very important in structural design of large-span single-layer reticulated shell structures. In this paper, a geometrically nonlinear wind-induced vibration analysis strategy for large-span single-layer reticulated shell structures based on the nonlinear finite element method is introduced. According to this strategy, a computation program has been developed. With the information of the wind pressure distribution measured simultaneously in the wind tunnel, nonlinear dynamic analysis, including dynamic instability analysis, for the wind-induced vibration of a single-layer reticulated shell is conducted as an example to investigate the efficiency of the strategy. Finally, suggestions are given for dynamic wind-resistant analysis of single-layer reticulated shells.

• Ocean and Polar Research
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• v.25 no.1
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• pp.1-7
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• 2003

The purpose of this study was to determine changes in the growth rates and the degree of shell bioerosion exhibited by endolithic organisms of the Japanese scallop family, Patinopecten (Mizuhopecten) yessoensis, on the coast of Furugelm Island (Peter the Great Bay, northwest of East Sea = Sea of Japan) over the last three decades. The areas studied are affected by lumen (Tumangang) River run-off, which is enriched by organic matter and polluting agents. It was found that the linear growth rates of the Japanese scallops living along the coasts of Furugelm Island have decreased over the last three decades. The degree of bioerosion of scallop shells has significantly increased for the same period. These phenomena may be explained by a gradual increase in bottom sediment silting, organic enrichment and pollution of the areas being studied. It was found that the degree of scallop shell bioerosion increased with the scallop's age. At present, In each age group, the shells of the scallops sampled from the muddy sand showed greater erosion than the shells of individuals collected from the sandy substrate.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.2
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• pp.47-54
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• 2012

In this study, composite laminate cantilever type cylindrical shells with edge-stiffeners are analyzed. A versatile 4-node flat shell element which is useful for the analysis of shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. Two models by load conditions are considered. Load type A and B are loaded by point load at the free edge and line load respectively. A various parameter examples are presented to obtain proper stiffened length and stiffened thickness of edge-stiffeners. It is shown that the thickness of shell can be reduced minimum 30% by appropriate edge-stiffeners.

• Transactions of Materials Processing
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• v.7 no.4
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• pp.393-399
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• 1998

For minimizing wall thickness thinning of circular shells, a new stamping technology, the deep draw-ing process combined with ironing is approached and investigated. The design requirements for the deep drawing shells are to keep the optimum wall thickness with max. 10 percent thickness thinning of the initial blank thickness, to make uniform thickness strain distribution for the wall of circular shell and to improve the shape accuracy for the roundness and concentricity. In order to check the validity and effectiveness of proposed work, a sample process design is applied to a circular shell needed for a 4multi-stepped deep drawing. Through experiments, the variations of the thickness strain distribution in each drawing process are observed. Also a series of experiments are performed to investigate optimum process variables such as the geometry of tooling, radius and drawing rate. In particular, the advantage of current approach with ironing is shown in contrast to the conventional deep drawing process. From the results of proposed method, the optimum value of process variables are obtained, which contribute more uniform thickness strain distribution and better quality in the drawn product.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4E
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• pp.45-51
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• 2001

This paper examines the dispersion relation governing the wave propagation on cylindrical shells. The assumption of thin shells allows the dispersion relation to be separated into three relations related to the propagation of flexural waves and two types of membrane waves. Those relations are used to identify the characteristics of the wave number curves. The dispersion relation provides two and three closed wave number curves below and above the ring frequency. Above the ring frequency three wave number curves are clearly identified to be those of flexural, shear and longitudinal waves, respectively. Below the ring frequency, the characteristics of two wave number curves are identified with dependence of the direction of wave propagation.

• Structural Engineering and Mechanics
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• v.13 no.6
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• pp.695-711
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• 2002

Here, the dynamic response characteristics of thick cross-ply laminated composite cylindrical shells are studied using a higher-order displacement model. The formulation accounts for the nonlinear variation of the in-plane and transverse displacements through the thickness, and abrupt discontinuity in slope of the in-plane displacements at any interface. The effect of inplane and rotary inertia terms is included. The analysis is carried out using finite element approach. The influences of various terms in the higher-order displacement field on the free vibrations, and transient dynamic response characteristics of cylindrical composite shells subjected to thermal and mechanical loads are analyzed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.160-165
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• 2008

Fluid loading of a vibrating cylindrical shell can change natural frequencies and vibration magnitudes of the shell and a vibrating cylindrical shell can also change acoustic pressure of fluid. The vibroacoustics of fluid-filled cylindrical shells need the coupled solution of Helmholtz equation and governing equation of a cylindrical shell with boundary conditions. This paper proposed the wall impedance of fluid-filled axisymmetric cylindrical shells, focusing on the inner fluid/shell interaction. To propose the impedance, shell displacements used the linear combination of in vacuo shell modes. Acoustic pressure prediction of fluid used Kirchchoff-Helmholtz Integral equation with Green function of the plane mode. For the demonstration of the proposed results, numerical applications on mufflers were conducted.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.524-528
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• 2010

In this study, the structure and properties of waste oyster shell and its phosphorus removal efficiency were investigated. Waste oyster shells are troublesome environmental waste in the coastal region where the oysters are produced. Waste oyster shells were pyrolyzed by bench-scale rotary kiln for its activation. It shows maximum 76% of phosphorus removal efficiency for the municipal wastewater and livestock wastewater. We found that the activated oyster shells can be used as a phosphorus removal agent with the consideration of high efficiency, easy processing, and cost effectiveness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1802-1812
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• 2001

The theoretical method is developed to investigate the effects of ring stiffeners on free vibration characteristics and transient response for the ring stiffened composite cylindrical shells subjected to the impulse pressure Loading. In the theoretical procedure, the Love's thin shell theory combined with the discrete stiffener theory to consider the ring stiffening effect is adopted to formulate the theoretical model. The concentric or eccentric ring stiffeners are laminated with composite and have the uniform rectangular cross section. The modal analysis technique is used to develop the analytical solutions of the transient problem. The analysis is based on an expansion of the loads, displacements in the double Fourier series that satisfy the boundary conditions. The effect of stiffener's eccentricity, number, size, and position on transient response of the shells is examined. The results are verified by comparison with FEM results.

• 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.