• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.188-193
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• 2005

To provide the various machining materials with excellent quality and dimensional accuracy, high -speed machining is very useful tool as one of the most effective rapid manufacturing processes. However, high-speed machining is not suitable for microscale thin-walled structures because of the lack of the structure stiffness to resist the cutting force. A new method which is able to make a very thin-walled structure rapidly will be proposed in this paper. This method is composed two processes, high-speed machining and filling process. Strong workholding force comes out of the solidification of filling materials. Low-melting point metal alloys are used in order to minimize the thermal effect during phase change and to hold arbitrary shape thin-walled structures quickly during high-speed machining. To verify the usefulness of this method, we will show some applications, for examples thin -wall cylinders and hemispherical shells, and compare the experimental results to analyze the dimensional accuracy of typical parts of the structures.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.238-246
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• 2000

In this paper, an optimization method of thin walled beam structures is proposed, Stiffnesses of a thin walled beam are characterized by the thickness of thin plates and the shape of the typical section of the beam. Explicit formula for section properties such as area, area moment of inertia, and torsional constants are derived using the response surface method. The explicit formula can be used for the optimal design of a structural system which consists of complicated thin walled beams. A vehicle structural system is optimized to demonstrate the proposed method.

• Steel and Composite Structures
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• v.2 no.3
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• pp.223-236
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• 2002

An analytical procedure based on the transfer matrix method to estimate not only the natural frequencies but also vibration mode shapes of the thin-walled members composed of interconnected cylindrical shell panels is presented. The transfer matrix is derived from the differential equations for the cylindrical shell panels. The point matrix relating the state vectors between consecutive shell panels are used to allow the transfer procedures over the cross section of the members. As a result, the interactions between the shell panels of the cross sections of the members can be considered. Although the transfer matrix method is naturally a solution procedure for the one-dimensional problems, this method is well applied to thin-walled members by introducing the trigonometric series into the governing equations of the problem. The natural frequencies and vibration mode shapes of the thin-walled members composed of number of interconnected cylindrical shell panels are observed in this analysis. In addition, the effects of the number of shell panels on the natural frequencies and vibration mode shapes are also examined.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2E
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• pp.63-70
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• 2002

In this paper, an optimization technique for thin walled beams of vehicle body structure is proposed. Stiffness of thin walled beam structure is characterized by the thickness and typical section shape of the beam structure. Approximate functions for the section properties such as area, area moment of inertia, and torsional constant are derived by using the response surface method. The approximate functions can be used for the optimal design of the vehicle body that consists of complicated thin walled beams. A passenger car body structure is optimized to demonstrate the proposed technique.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.113-118
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• 2008

This paper presents a flexural-torsional analysis of thin-walled open-section composite beams. A general geometrically nonlinear model for thin-walled composite beams and general laminate stacking sequences is given by using systematic variational formulation based on the classical lamination theory. The nonlinear algebraic equations of present theory are linearized and solved by means of an incremental Newton-Raphson method. Based on the analytical model, a displacement-based one-dimensional finite element model is developed to formulate the problem. Numerical results are obtained for thin-walled composite beams under general loadings, addressing the effects of fiber angle, laminate stacking sequence and loading parameters.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.358-365
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• 2000

For the general case of loading conditions and boundary conditions, it is very difficult to obtain closed form solutions for buckling loads and natural frequencies of thin-walled structures because its behaviour is very complex due to the coupling effect of bending and torsional behaviour. In consequence, most of previous finite element formulations are introduce approximate displacement fields to use shape functions as Hermitian polynomials, and so on. The Purpose of this study is to presents a consistent derivation of exact dynamic stiffness matrices of thin-walled straight beams, to be used ill tile free vibration analysis, in which almost types of boundary conditions are exist An exact dynamic element stiffness matrix is established from governing equations for a uniform beam element of nonsymmetric thin-walled cross section. This numerical technique is accomplished via a generalized linear eigenvalue problem by introducing 14 displacement parameters and a system of linear algebraic equations with complex matrices. The natural frequency is evaluated for the thin-walled straight beam structure, and the results are compared with analytic solutions in order to verify the accuracy of this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2191-2201
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• 2000

End effects due to sectional deformations of thin-walled beams with closed cross section are analysed by a one-dimensional theory. In particular, end effects associated with warping (out of plane m otion) and distortion (in plane motion) are investigated. The exact solutions as a vector form are newly derived to reveal slowly-decaying nature of the end effects in a thin-walled beam loaded by a couple. Several examples of thin-walled beams under various loading conditions indicate that the local end effect zone due to warping and distortion is approximately ten times the typical beam width.

• Steel and Composite Structures
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• v.1 no.1
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• pp.75-96
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• 2001

Actual buckling curves are always characterised by the erosion of ideal buckling curves. In case of compact sections this erosion is due to the imperfections, while for thin-walled members, a supplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach- Erosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise the instability behaviour of thin-walled members. The present state-of-art paper describes the theoretical background of this method and the applications to cold-formed steel sections in compression and bending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation. The ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members, and the paper provides significant results on this line.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.369-376
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• 2000

For the general loading condition and boundary condition, it is very difficult to obtain closed-form solutions for buckling loads and natural frequencies of thin-walled structures because its behaviour is very complex due to the coupling effect of bending and torsional behaviour. Consequently most of previous finite element formulations introduced approximate displacement fields using shape functions as Hermitian polynomials, isoparametric interpoation function, and so on. The purpose of this study is to calculate the exact displacement field of a thin-walled straight beam element with the non-symmetric cross section and present a consistent derivation of the exact dynamic stiffness matrix. An exact dynamic element stiffness matrix is established from Vlasov's coupled differential equations for a uniform beam element of non-symmetric thin-walled cross section. This numerical technique is accomplished via a generalized linear eigenvalue problem by introducing 14 displacement parameters and a system of linear algebraic equations with complex matrices. The natural frequencies are evaluated for the non-symmetric thin-walled straight beam structure, and the results are compared with available solutions in order to verify validity and accuracy of the proposed procedures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.385-392
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• 2002

Derivation procedures of exact elastic element stiffness matrix of thin-walled curved beams are rigorously presented for the static analysis. An exact elastic element stiffness matrix is established from governing equations for a uniform curved beam element with nonsymmetric thin-walled cross section. First this numerical technique is accomplished via a generalized linear eigenvalue problem by introducing 14 displacement parameters and a system of linear algebraic equations with complex matrices. Thus, the displacement functions of displacement parameters are exactly derived and finally exact stiffness matrices are determined using member force-displacement relationships. The displacement and normal stress of the section are evaluated and compared with thin-walled straight and curved beam element or results of the analysis using shell elements for the thin-walled curved beam structure in order to demonstrate the validity of this study.