• Laser Solutions
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• v.4 no.2
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• pp.13-19
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• 2001

When a high-power laser beam is irradiated on the surface of material, it is well known that a cavity, called a keyhole induced by the pressure action of the vapor plume, is generated in the molten material. This paper describes the interaction between a pulsed CO$_2$ laser beam and water. The laser-beam is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. Experimental results show that the depth of laser-beam penetration is limited by hydrodynamic instability. The instability of the surface cavity can be understood by the capillary instability of a hollow jet. Theoretical computation of the steady keyhole shape has been performed. modifying the model suggested by Andrews et al. (1976). The model predicts the qualitative behavior of the keyhole but significantly underestimates the average diameter.

• Journal of Korean Association for Spatial Structures
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• v.22 no.3
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• pp.65-72
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• 2022

A typical low and medium-sized neighborhood living facility in reinforced concrete building secures a high floor and pursues an efficient module plan(long span). Accordingly, research on the development of new hybrid beams that can innovatively reduce labor costs such as on-site installation and assembly while securing strength and rigidity is ongoing. In order to verify the structural performance of the U-flanged truss composite beam with newly developed shape, Experiments with various variables are required. Based on the results, this study is to evaluate the strength of U-flanged truss hybrid beam through the flexural strength of the Korea Design Code and experimental values. It was evaluated that nominal flexural strength was 110% to 135% higher than the experimental value.

• Steel and Composite Structures
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• v.25 no.5
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• pp.593-601
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• 2017

Carbon Fiber Reinforced Polymer (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been done on steel beams and steel columns. No independent study, to the researcher's knowledge, has studied the effect of CFRP strengthening on steel beam-columns, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel beam-columns. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel beam-columns, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine the ultimate load of SHS steel beam-columns, ten specimens, eight of which were strengthened with the different coverage length and with one and two CFRP layers, with two types of section (Type A and B) were analyzed. ANSYS was used to analyze the SHS steel beam-columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel beam-columns. The results also showed that the coverage length, the number of layers, and the location of CFRP composites were effective in increasing the ultimate load of the SHS steel beam-columns.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4310-4321
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• 2022

The concept of dense granular-flow target (DGT) for the China Initiative Accelerator Driven Subcritical system (CiADS) is an attractive choice for high heat removal ability, low chemical toxicity, and radiotoxicity. A wobbling hollow beam is proposed to enhance the homogeneity of temperature rise of flowing particles in beam-target coupling zone. In this paper, the design procedure of target and beam parameters was discussed firstly. Then we simulated the heat deposition and transfer of the scanning beam in DGT to study the effect of beam parameters. The results show the flux density of proton beam plays a crucial role in the distribution of temperature rise while the contributions from scanning frequency heat transfer are also obvious. Moreover, heat transfer in transversal directions is insignificant, resulting in a low heat flux towards the sidewalls of DGT. This work not only contributes to the design of DGT, but also beneficial for understanding the beam-target coupling in porous materials.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.159-160
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• 2012

• Proceedings of the Optical Society of Korea Conference
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• 2007.02a
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• pp.127-128
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• 2007

• Journal of Korean Association for Spatial Structures
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• v.8 no.1
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• pp.89-97
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• 2008

The object of this paper is to evaluate on behavior the experimentally of beam-to-column joints for modular steel frame with the hollow structural steel section to LEB C-shape. Beam-to-column joints carried out test on the joint shape bracket-type and welded-type to consideration which the joints for modular steel frame was capacity, deformation and failure mode. Test of results, the beam-column joints decided to the lateral buckling strength in LEB C-shape regardless of joint-shape and joint failure. The strength & stiffness for joints increase as the bracket-thickness. The results from theory of lateral buckling are compared to the experimental results. The ratio of experimental results to theory value is $0.83{\sim}0.95$ in the case of bracket-type and welded-type of $0.87{\sim}0.9$, indicating an accurate and safe estimation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.2
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• pp.175-182
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• 2012

In this paper we are concerned with the performance of structural stability of torsion in square cross section of a beam with holes. The critical load is defined as the smallest load at which the equilibrium of the structure fails to be stable as the load is slowly increased from zero. The beams subjected to torsion are frequently encountered in general structures and these forces influence to the stability of structure. The boundary element method is found to be very efficient and accurate for the analysis of torsion problems including complex boundary conditions with respect to its simplicity and generality. In this paper, it is required to derive the boundary element formulation for torsion problem and integrate directly on the discrete boundary. To investigate the validity of the developed computer program, three distinctly solid cross-sections which are elliptical, rectangular and triangular one are analyzed, and comparisons are made with analytical approaches where these can also be used.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.10a
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• pp.68-75
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• 1995

In recent year, column member is used for square hollow section(5.H.5) and beam member is used for H-section. But 5.H.5 column has vulnerability because of low flexural stiffness between column and beam connection joints. To reinforce this vulnerability, 5.H.5 column filled with concrete and concrete slab connection compounded with H-beam is developed in many ways. In this paper, modelling of predicting behavior of various types of connections is studied using finite element method. k order to simulate the actual behavior, a three-dimensional modelling is used. A simple efficient contact algorithm with a new gap element is employed to simulate the interaction between 5.H.5 column and concrete, The modelling result$ are compared with the experimental results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.126-133
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• 2017

This report investigates the stress distribution according to the location and shape change of the circular hole for the lightweight design of the cross beam of a railway passenger car and studies the lightweight design. To design a lightweight cross beam with a circular hole, we selected the non-circular crossbeam as a basic model, examined the stress distribution and displacement by position and determined the location, shape, size and quantity of the hole for light weight. We analyzed the effects of the position and shape of the hole on the maximum equivalent stress and displacement. The influencing factors were set as the design parameters, and the stress value was examined according to the variation of each variable. By considering the stress value according to the change of each variable and selecting the design parameter with the narrowest scattering value of the stress at each position of the hollow cross beam with various hole positions and shapes, we studied a cross beam with a circle hole under identical load condition to have an equal stress distribution to that of a non-circular cross beam.