• Composites Research
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• v.27 no.2
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• pp.37-41
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• 2014

Fiber reinforced composite materials have outstanding specific strength and specific stiffness. So the use of composite materials increases in various kinds of industrial fields including sports goods such as bicycles. Composite materials are used to make structural parts with various kinds of shapes. Specially, rectangular composite tubes are used to make a few of composite bicycle frames, but there has been a few of research on this issue. Rectangular composite tubes are designed to have appropriate radius of curvature and endure bending and torsional loads. In this research, nine kinds of rectangular composite tubes having aspect ratios 1:1, 1:1.5, 1:2 and radius of curvatures R5, R10, R15 were fabricated. The carbon fiber reinforced composite material was used to make tubes having same cross sectional areas. The stacking sequence of tubes is $[0/90/{\pm}45]s$. Experimental evaluation was accomplished to apply bending and torsional load to the tubes. Experimental results show that bending and torsional characteristics depend on radius of curvature and aspect ratio of rectangular composite tubes.

• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.1
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• pp.176-182
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• 2000

$360^{\circ}$ bending of Ti-6Al-4V large-diameter seamless tube(62.37 mm $OD {\times} 4.40mm$ wall thickness) has been achieved at room temperature without heating. The bending process comprised two steps : the first step is $360^{\circ}$ bending by an uniquely designed rotary bender allowing spring back, which is subsequently eliminated by the second or finishing step which comprised repeated bending processes by powered three roll bender, In odor to prevent collapse of tube during bending, Cerro $Tru^{TM}$(Trade name of a non-ferrous low melting point alloy)has been employed as a filler metal. The resultant ovality(out of roundness) obtained was 1.28%, as compared with 6~8% without applying Cerro $Tru^{TM}$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.10
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• pp.1053-1061
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• 2015

This paper discusses the analysis of the curl deformation behavior when a dynamic force is applied to a tearing tube installed on a flat die to predict the energy absorption capacity and deformation behavior. The deformation of the tips of the curling strips was obtained when the curl tips and tube body are in contact with each other, and a formula describing the energy dissipation rate caused by the deformation of the curl tips is proposed. To improve this formula, we focused on the variation of the curl radius and the reduced thickness of the tube. A formula describing the mean curl radius is proposed and verified using the curl radius measurement data of collision test specimens. These improved formulas are added to the theoretical model previously proposed by Huang et al. and verified from the collision test results of a tearing tube.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.524-530
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• 2003

This paper presents a new model on deformation characteristics of cylindrical tubes under pure bending. The model is based on the upper bound method that minimizes total strain energy of a system. It does not assume inextensibility condition. Geometric relations and displacement fields are derived by analysis of deformation behaviors of elastic tubes. Simulations are calculated using numerical optimization and integration techniques. The results give information about cross-sectional deformation of cylindrical tubes. Simulation results are compared with available data in literatures, which show that this method predicts deformation characteristics of tube bending process.

• Journal of the Korea Institute of Military Science and Technology
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• v.3 no.1
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• pp.231-236
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• 2000

The wall thickness of the Ti-6Al-4V Large-Diameter Seamless Tube, which is supposed to be a very important parameter in a system design, was measured during $360^{\circ}$ cold bending processes. The factors or processes affecting the wall thickness include 1) primary bending, 2)secondary or finishing step of the $360^{\circ}$ bending, 3)cleaning processes in CERO TRUTM(CT)process. But thinning effects of the wall thickness during the cleaning processes are negligible compared to those during the formers. The variations in the percentages of the change in wall thickness were found to be from -14% to +16%.

• Composites Research
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• v.29 no.6
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• pp.358-362
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• 2016

Mechanical properties of static and dynamic behavior became important since the use of conical composite tubes in large structures such as aerospace, planes, and submarines as well as leisure goods such as bicycle frames, fishing rods, and golf shafts. In the past, the mechanical property prediction model for static behavior was studied using vibration, bending, and buckling. But there is a need to study how fiber orientation error affects mechanical properties of conical composite structure because the model assumes constant fiber orientation angle. The purpose of this study is to derive an equation that can predict the static behavior of conical composite tube for bicycle frames by considering fiber orientation error with respect to various design parameters.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.10a
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• pp.261-266
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• 1998

In this study, crush characteristics of thin-walled rectangular tube is investigated. The stiffness of the element is obtained from analytical moment-rotation relationship and approximated load-deflection relationship of thin-walled rectangular tube. A computer program is developed for the large deformation analysis of frame. An incremental displacement method is used in the program and at each incremental stage, the stiffness matrix of the total structure is checked with the state each element for bending and compression.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.244-247
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• 2009

Hydroformed parts have higher dimensional accuracy, structural strength, and dimensional repeatability. Particularly in the automotive industry, manufacturing of parts with complex shapes from tubular materials sometimes requires one or more pre-forming operations such as bending before the hydroforming process. The pre-bending process is an important factor for successful hydroforming in the case where the perimeter of the blank is nearly the same as that of final product. The bendability of a tube depends on the parameters such as the bending radius, variation of the diameter, thickness, hardness. This study shows the analysis of bending through the stainless steel tubes bent to rotary draw bending machine.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.493-494
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.97-98
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• 2008