• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.109-123
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• 1996

A series of quasi-static crushing tests were carried out on thin-walled square tube specimens with axial and/or circumferential stiffeners including unstiffened specimens. The effective crushing length and mean crushing strength of the test specimens were investigated. Using the equivalent plate thickness approach, a simplified analytical model for predicting the mean crushing strength of stiffened square tubes has been developed.

• Tuberculosis and Respiratory Diseases
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• v.40 no.4
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• pp.449-453
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• 1993

A 64-year-old male was admitted due to abruptly developed, severe dyspnea via local clinic. He had been a heavy smoker and alcoholic for a long time. Chest PA showed huge haziness in right upper lung field. Sputum culture for bacteriology was positive for Klebsiella pneumoniae. Immediately, appropriate antibiotics were administered and artificial ventilation was started. On 40th hospital day, simple chest roentgenogram taken due to sudden aggravated dyspnea showed marked hyperlucency in right upper lung field, suggestive of rupture of abscess cavity and resultant pneumothorax. At that time, chest tube was inserted but air leakage from the chest tube persisted. Chest CT scan taken after chest tube insertion showed the tube inserted into a thin-walled cavity in the above lesion. on 84th hospital day, right upper lobectomy with decortication was performed. Pathologically, cavittary lung abscess was diagnosed on the findings of partial re-epithelialization of ciliated columnar epithelium with severe pulmonary vascular occlusion and extensive fibrous pleural adhesions.

• International Journal of Automotive Technology
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• v.6 no.5
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• pp.519-527
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• 2005

Recently, weight reduction of vehicles has been of great interest and consequently the use of low-density materials in the automotive industry is increasing every year. However, the substitution of one material for another is not simple because it accompanies several problems, for example, weakness in the strength and stiffness and difficulty in the joining. To overcome these problems, the structure of the automobile redesigned totoally. Aluminum spaceframe is rapidly being adopted as a body structure for accommodating lightness, stiffness and strength requirement. In aluminum spaceframe manufacturing, it is often required to join aluminum tube. However, there are few suitable methods for joining aluminum tube, so that much interest has been focused on testing suitable joining methods. Joining by electromagnetic forming (EMF) can be useful method in joining aluminum tube, which offers some advantages compared with the conventional joining methods. In this paper, joining by EMF was investigated as a pre-study for applying an automotive spaceframe. Finite element simulations and strength tests were performed to analyze the influence of geometric parameters on joint strength. Based on these results, configurations of axial joint and torque joint were suggested and guidelines for designing EMF joint were established.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.16-25
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• 2016

In severe loss of coolant accidents (LOCA), similar to those experienced at Fukushima Daiichi and Three Mile Island Unit 1, the zirconiumalloy fuel claddingmaterials are rapidlyheateddue to nuclear decay heating and rapid exothermic oxidation of zirconium with steam. This heating causes the cladding to rapidly react with steam, lose strength, burst or collapse, and generate large quantities of hydrogen gas. Although maintaining core cooling remains the highest priority in accident management, an accident tolerant fuel (ATF) design may extend coping and recovery time for operators to restore emergency power, and cooling, and achieve safe shutdown. An ATF is required to possess high resistance to steam oxidation to reduce hydrogen generation and sufficient mechanical strength to maintain fuel rod integrity and core coolability. The initiative undertaken by Electric Power Research Institute (EPRI) is to demonstrate the feasibility of developing an ATF cladding with capability to maintain its integrity in $1,200-1,500^{\circ}C$ steam for at least 24 hours. This ATF cladding utilizes thin-walled Mo-alloys coated with oxidation-resistant surface layers. The basic design consists of a thin-walled Mo alloy structural tube with a metallurgically bonded, oxidation-resistant outer layer. Two options are being investigated: a commercially available iron, chromium, and aluminum alloy with excellent high temperature oxidation resistance, and a Zr alloy with demonstratedcorrosionresistance.Asthese composite claddings will incorporate either no Zr, or thin Zr outer layers, hydrogen generation under severe LOCA conditions will be greatly reduced. Key technical challenges and uncertainties specific to Moalloy fuel cladding include: economic core design, industrial scale fabricability, radiation embrittlement, and corrosion and oxidation resistance during normal operation, transients, and severe accidents. Progress in each aspect has been made and key results are discussed in this document. In addition to assisting plants in meeting Light Water Reactor (LWR) challenges, accident-tolerant Mo-based cladding technologies are expected to be applicable for use in high-temperature helium and molten salt reactor designs, as well as nonnuclear high temperature applications.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.379-382
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• 2006

The flow forming has been used to produce long thin walled tube parts, with reduced forming force and enhanced mechanical and surface quality for a good finished part, compared with other method formed parts. Especially, the flow forming is suitable for making high precision thin walled cylinders, such as rocket motor cases, combustion chamber, hydraulic cylinders and high-pressure vessels and so on. In this paper, finite element analysis of three-roller forward and backward flow forming for combustion chamber is carried out to study efforts of forming depth and feed rate on forming force. The axial and radial forming forces of forward flow forming on several forming depth and feed rate conditions are compared with those of backward flow forming.

• Steel and Composite Structures
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• v.23 no.4
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• pp.453-464
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• 2017

The square tubed-reinforced concrete (TRC) column is a kind of special concrete-filled steel tube (CFST) columns, in which the outer thin-walled steel tube does not pass through the beam-column joint, so that the longitudinal steel reinforcing bars in the RC beam are continuous through the connection zone. However, there is a possible decrease of the axial bearing capacity at the TRC column to RC beam connection due to the discontinuity of the column tube, which is a concern to engineers. 24 connections and 7 square TRC columns were tested under axial compression. The primary parameters considered in the tests are: (1) connection location (corner, exterior and interior); (2) dimensions of RC beam cross section; (3) RC beam type (with or without horizontal haunches); (4) tube type (with or without stiffening ribs). The test results show that all specimens have relatively high load-carrying capacity and satisfactory ductility. With a proper design, the connections exhibit higher axial resistance and better ductility performance than the TRC column. The feasibility of this type of connections is verified.

• Steel and Composite Structures
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• v.43 no.6
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• pp.689-706
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• 2022

Thin-walled square concrete-filled double steel tubular (CFDST) columns composed of the inner circular tube filled with concrete can be used to carry the large axial loads or strengthen existing CFST columns in composite constructions. This paper reports an experimental program carried out on short square CFDST columns loaded concentrically. The influences of important column parameters on the post-buckling performance of such columns are investigated. Test results exhibit that the inner circular tube significantly improves the ultimate loads and the ductility of such columns compared to conventional concrete-filled steel tubular (CFST) and double-skin CFST (DCFST) columns with an inner void. A mathematical model developed is used to simulate the ultimate strengths and load-strain curves of such columns loaded axially. Furthermore, the ultimate strengths of such columns are predicted using existing codified design models for conventional CFST columns as well as the formulas proposed by previous researchers and compared against a large database comprising 500 CFDST columns. Lastly, an accurate artificial neural network model is developed for the practical applications of such columns under axial loading.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.297-300
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• 2009

The roll forming process is often used to manufacture long, thin-walled products such as a pipe. The final cross-section is a comparatively simple open-channel, a closed tube section or a complex profile with several bends. In recent years, that process is often applied to the bumper beam in the automotive industries. In this study, a optimal Center Floor Cross Member manufacturing technology, model deign and proper roll-pass sequences can be suggested by forming number of roll-pass and bending angle, and also effects of the process parameters on the final shape formed by roll forming defects were evaluated.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.5
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• pp.119-127
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• 1998

Assuming that the static loaded square tube and the dynamic loaded one have no difference in their characteristics of the crush distance, the theoretical mean dynamic crush load was calculated with respect to the impact speed considering the strain rate sensitivity of the material. The ratio of dynamic to static mean crush load was predicted with previous results. The theoretical analysis was compared with the experimental results of aluminum square tubes axially loaded dynamically.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.35-39
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• 1985

The closed form of the stiffness matrix is derived in terms of closed forms of intergrals for analyses of plane frame members containing linerly tapered members with the cross section of thin-walled tube. The series expansion forms of these are also developed to study the errors in the closed form of the stiffness matrix. The useful limits of the closed form of integrals are defined in terms of the relative taper.