• Steel and Composite Structures
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• v.17 no.6
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• pp.867-890
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• 2014

This paper deals with the geometric nonlinear bending analysis of laminated composite stiffened plates subjected to uniform transverse loading. The eight-noded degenerated shell element and three-noded degenerated curved beam element with five degrees of freedom per node are adopted in the present analysis to model the plate and stiffeners respectively. The Green-Lagrange strain displacement relationship is adopted and the total Lagrangian approach is taken in the formulation. The convergence study of the present formulation is carried out first and the results are compared with the results published in the literature. The stiffener element is reformulated taking the torsional rigidity in an efficient manner. The effects of lamination angle, depth of stiffener and number of layers, on the bending response of the composite stiffened plates are considered and the results are discussed.

• Steel and Composite Structures
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• v.28 no.1
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• pp.25-37
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• 2018

For the first time, the parametric instability characteristics of tow-steered variable stiffness composite laminated (VSCL) cylindrical panels is investigated using B-spline finite strip method (FSM). The panel is considered containing geometrical defects including cutout and delamination. The material properties are assumed to vary along the panel axial length of any lamina according to a linear fiber-orientation variation. A uniformly distributed inplane longitudinal loading varies harmoni-cally with time is considered. The instability load frequency regions corresponding to the assumed in-plane parametric load-ing is derived using the Bolotin's first order approximation through an energy approach. In order to demonstrate the capabili-ties of the developed formulation in predicting stability behavior of the thin-walled VSCL structures, some representative results are obtained and compared with those in the literature wherever available. It is shown that the B-spline FSM is a proper tool for extracting the stability boundaries of perforated delaminated VSCL panels.

• Structural Engineering and Mechanics
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• v.41 no.5
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• pp.605-615
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• 2012

In this paper, guided circumferential wave propagating in an orthotropic viscoelastic cylindrical curved plate subjected to traction-free conditions is investigated in the frame of the Kelvin-Voight viscoelastic theory. The obtained three wave equations are decoupled into two groups, Lamb-like wave and SH wave. They are separately solved by the Legendre polynomial series approach. The availability of the method is confirmed through the comparison with the published data of the SH wave for a viscoelastic flat plate. The dispersion curves and attenuation curves for the carbon fiber and prepreg cylindrical plates are illustrated and the viscous effect on dispersion curves is shown. The influences of the ratio of radius to thickness are analyzed.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.37-43
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• 2019

This paper studies application of modified couple stress theory and first order shear deformation theory to magneto-electro-mechanical vibration analysis of three-layered size-dependent curved beam. The curved beam is resting on Pasternak's foundation and is subjected to mechanical, magnetic and electrical loads. Size dependency is accounted by employing a small scale parameter based on modified couple stress theory. The magneto-electro-mechanical preloads are accounted in governing equations to obtain natural frequencies in terms of initial magneto-electro-mechanical loads. The analytical approach is applied to investigate the effect of some important parameters such as opening angle, initial electric and magnetic potentials, small scale parameter, and some geometric dimensionless parameters and direct and shear parameters of elastic foundation on the magneto-electro-elastic vibration responses.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.1
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• pp.38-48
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• 2007

In this paper, we propose an image-based method for modeling 3D objects with curved surfaces based on the NURBS (Non-Uniform Rational B-Splines) representation. Starting from a few calibrated images, the user specifies the corresponding curves by means of an interactive user interface. Then, the 3D curves are reconstructed using stereo reconstruction. In order to fit the curves easily using the interactive user interface, NURBS curves and surfaces are employed. The proposed surface modeling techniques include surface building methods such as bilinear surfaces, ruled surfaces, generalized cylinders, and surfaces of revolution. In addition to these methods, we also propose various advanced surface modeling techniques, including skinned surfaces, swept surfaces, and boundary patches. Based on these surface modeling techniques, it is possible to build various types of 3D shape models with textured curved surfaces without much effort. Also, it is possible to reconstruct more realistic surfaces by using proposed view-dependent texture acquisition algorithm. Constructed 3D shape model with curves and curved surfaces can be exported in VRML format, making it possible to be used in different 3D graphics softwares.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.41-49
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• 1993

This paper presents a geometrically non-linear and elastoplastic F.E. formulation using a total Lagrangian approach for the two dimensional isoparametric curved beam elements. The beam element is derived by using plane stress elements. The basic element geometry is constructed using the coordinates of the nodes on the element center line and the nodal point normals. The element displacement field is described using two translations of the node on the center line and a rotation about the axes normal to the plane containing the center line of the element. The layered approach is used for the elastoplastic analysis of the plane framed structure with the arbitrary cross section. The iterative load or displacement incremental method for non-linear finite element analysis of the frame structure is used. Numerical examples are presented to demonstrate the behavior and the accuracy of the proposed beam element for geometric and elastoplastic non-linear applications. Comparisons made with present theory and other published data show that tilt' beam element products accurate results with good convergence characteristics.

• Korean Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.76-83
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• 1996

A three dimensional FE mesh generation scheme based on mapping approach is proposed in this study. A volume in Eucledian space is represented by composite hyperpatches which are piecewise cubic functions in parameters u, v, w. A key idea in the proposed approach is that I sampled grid data points lying only on the boundary surfaces are needed for the shape representation. Inner points which are necessary to form a hyperpatch are internally generated by Coons patches. This approach is most appropriate for the shapes which are compositions of hexahedronlike shapes and also severely curved.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.10
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• pp.109-116
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• 2007

Focused ion beams are a potential tool for micro/nano structure fabrication while several problems still have to be overcome. Redeposition of sputtered atoms limits the accurate fabrication of micro/nano structures. The challenge lies in accurately controlling the focused ion beam to fabricate various arbitrary curved shapes. In this paper a basic approach for the focused ion beam induced direct fabricate of fundamental features is presented. This approach is based on the topography simulation which naturally considers the redeposition of sputtered atoms and sputtered yield changes. Fundamental features such as trapezoidal, circular and triangular were fabricated with this approach using single or multiple pass box milling. The beam diameter(FWHM) and maximum current density are 68 nm and $0.8 A/cm^2$, respectively. The experimental investigations show that the fabricated shape is well suited for the pre-designed fundamental features. The characteristics of ion beam induced direct fabrication and shape formation will be discussed.

• Journal of Korean Neurosurgical Society
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• v.40 no.1
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• pp.22-27
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• 2006

Objective : The purpose of this study is to investigate the clinical results of anterior and posterior stabilization by one stage posterolateral approach for the unstable fracture of thoracolumbar and lumbar spine. Methods : By posterolateral approach with curved skin incision, unilateral facet and pedicle were removed. Through this route, corpectomy was performed, and then this space was replaced with mesh cage filled up with autologous bone graft. Both side pedicle screw fixation was followed to upper and lower levels. Results : Six of seven patients of this study showed neurological improvement. The other one patient showed no neurological change. One patient had postoperative infection, another patient had postoperative kyphosis. The other patient had epidural hematoma on operation site after surgery. And all patinets on this study made to have spinal stability except one patient happened postoperative kyphosis. Conclusion : In the unstable fracture of thoracolumbar and lumbar spine, one stage anterior and posterior stabilization and fusion by posterolateral approach seems to be an effective procedure, if we have more care and supplementation.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.1205-1206
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• 2008

In the conventional floating display system some image distortions might be occurred in the floating image plane, in which a flat screen has been mostly used for providing an adequate input image plane. In this paper, as a new approach to alleviate image distortion problem in a floating display system, a curved screen is suggested by through some computer simulation using an optics design program of Light Tools.