• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.110-113
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• 2004

Aluminum and CFRP tube is light-weight material representatively but collapse mechanism is different under axial loading. Aluminum tube absorbs energy by stable plastic deformation under axialloading. While CFRP(Carbon Fiber Reinforced Plastics)tube absorb synergy by unstable brittle failure but its specific strength and stiffness is higher than that of aluminum tube. In this study, for complement of detect and synergy effect by combination with the advantages of each member, the axialcollapsetests were performed for combined aluminum CFRP tubes which are composed of aluminum tubes wrapped with CFRP out side aluminum square tubes. Collapsecharacteristics were analyzed for combined square tubes which have different CFRP orientation angle and thickness. Test results were compared with that of aluminum tubes and CFRP tubes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.397-400
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• 2004

The direct extrusion with porthole die can produce condenser tube which has the competitive power in costs and qualities compared with the existing conform extrusion. In general, porthole die extrusion has a great advantage in the forming that produces the hollow sections difficult to produce by conventional extrusion with a mandrel on the stem. Especially, condenser tube manufactured by porthole die belongs to sophisticated part and demands tighter dimension tolerance and higher surface finish than any other part. In order to confirm the general of porthole die extrusion, we perform the 3D FE analysis of hot porthole extrusion in non-steady state by using DEFORM 3D and investigate a pattern of elastic deformation for porthole die through the stress analysis using ANSYS 5.5 during extrusion process.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.15-20
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• 1997

This paper presents the experimental study of the non-contact temperature measurement for the shadow mask of cathode ray tube using InSb sensor. At present, High resolution of CRT(Cathode Ray Tube) is needed broadly; therefore, the measurement of temperature distribution of shadow mask in CRT during operation is important to analyze the thermal deformation of shadow mask. Most of the studies could not measure the temperature distribution of shadow mask precisely. We studied the temperature dis- tribution of shadow mask using InSb photo sensor for 17" cathode ray tube (CRT). Experiments using ther- mocouple are performed to validate the results of non-contact measurement. The results agree well with those results of non-contact method using InSb sensor.nsor.

• Journal of KSNVE
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• v.5 no.3
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• pp.373-383
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• 1995

From the viewpoint of the structural design, the principal problem of the heat exchanger is the potentiality of structural instabilities due to the fluid loading effect during operations. Excessive fluid loading may give rise to permanent deformation of tube and would enentually result in collapse of heat exchanger, which would cause an obstruction of the fluid flow in the narrow channels. In this study, a fluid-structural interaction model was developed to investigate analtically the vibration characteristics of thin rectangular tube used in the heat exchanger. The model consists of two flat plates separated by fluid. The effects of the fluid in the tube was stuided. For analyses, the natural frequency coefficients of the model were investigated for the plate aspect ratios, channel heights, and boundary conditions. As conclusions, the natural frequency coefficients of the tube is found to be affected largely by the fluid loading and the channel heights.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.4
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• pp.24-31
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• 1988

The Upper Bound Solution has been used to investigate the effect of the various parameters on the floating-plug tube-drawing precess. A kinematically admissible velocity field considering the change of the tube thickness is proposed for the deformation process. Taking into account the position of the plug in the deforming region, shear energy at entrance and exit, friction energy on contact area, homogeneous energy are calculated. The theoretical values in proposed velocity field are good agreement with experimental values, It is investigated that the tube thickness in the deforming region is changed slightly toward minimization of deforming energy and then the drawing stress in lower than the crawing stress in the velocity field that the tube thickness is uniform.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.2
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• pp.26-33
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• 2005

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effect of process variables such as gap height, relative gap width and die comer radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.168-175
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• 2003

In this paper, the tube forming by radial-forward extrusion is analyzed by numerical simulation and experiments. The paper discusses the effects of process variables such as gap height, relative gap width and die corner radius on tube forming. The influence of deformation patterns of flange in radial extrusion on forward extrusion for tube forming is investigated and summarized in terms of the maximum forming force and hardness variations along the extrusion path. Furthermore the external defects are shown experimentally during the forming operation. Based on finite element analysis in conjunction with experimental test in Al alloy, analysis is performed for important parameter combination in order to reduce forming defects. Eventually, the process parameters for safe forming are suggested in order to reduce the forming defects.

• 연구논문집
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• s.30
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• pp.121-128
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• 2000

The failed tube received for this study has been used for approximately 10 year at $330^{\circ}C$ in a steam production boiler tube was fractured in the transversed direction to tube length, and fracture mode was typically intergranulas type without the plastic deformation. The fracture surface was covered by the oxide scale formed from the intermal high pressure steam at high temperature. The microstructure was not nearly thermal-degraded during the service. From this result, we can conclude that the oxide film was proferentialy formed into the grainboundary and this grainboundary oxide film was brittle-fractured by the thermal stress in the longitudinal direction to the tube brittle intergranular fracture mode.

• Advances in nano research
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• v.10 no.5
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• pp.493-507
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• 2021

This article focused on studying the buckling behavior of two-dimensional functionally graded (2D-FG) nanosize tubes, including porosity based on first shear deformation and higher-order theory of tube. The nano-scale tube is simulated based on the nonlocal gradient strain theory, and the general equations and boundary conditions are derived using Hamilton's principle for the Zhang-Fu's tube model (as higher-order theory) and Timoshenko beam theory. Finally, the derived equations are solved using a numerical method for both simply-supported and clamped boundary conditions. The parametric study is performed to study the effects of different parameters such as axial and radial FG power indexes, porosity parameter, nonlocal gradient strain parameters on the buckling behavior of di-dimensional functionally graded porous tube.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.199-210
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• 1995

We could say that the concrete filled steel tube structure is superior in the vlew of various structure properties as to promote improvement of structural capacity to dtmonstrate heterogeneous material properties interdependently. The compressive strength is increased by putting to tri axial stress because lateral expansion of concrete 1s confined by the steel tube, when concrete conflned by steel tube fall under centric axial load. Also, it have an advantage that decreasr of load carrying capacity 1s small, not occuring section deficiency due to protect falling piienornonon by co~nprrssion fallurc of concrete. So this study investigated for structural behaviors yroprrtiex of concwir. confined by steel tube throughout a series of experlmerit with kcy parxncter, such as diameter-to-thickness(D / t) ratio, strength of concrete as a study on properties of structural behaviors of confined concrete confined by circular steel tube( tri axial stress). Frorn the expcrment results, the obtained results, are surnrnarised as foliow. (1) The restraint effect of concrete by steel tube was presented significantly as the D /t ratio of steel tube and the strength of filled concrete decrease, and the confined concrete by circular steel tube was increased respectively twice as much as 4-7 in deformation capacity at the ultimate strength ,compared with those of non-confined concrete, so expected to increase flexible effect of concrete. (2) The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint coefficient of concrete were proposed.