• The Korean Journal of Zoology
• /
• v.26 no.2
• /
• pp.135-153
• /
• 1983

Studies of fouling organisms in Deukryang Bay in 1981 showed that amphipod crustaceans comprised the most abundant zoological group. Three tubicolous gammaridean amphipods, Jassa falcata (Montagu, 1808) Corophium acherusicum (Costa, 1857) and Ericthonius brasiliensis (Dana, 1853) were described. They formed great masses of silty tubes attached to plastic and cement experimental plates. The ecological aspects of these fouling organisms have been also discussed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.06a
• /
• pp.89-95
• /
• 2001

The fretting wear characteristics of Zircaloy-4 tube at room and high temperature were Investigated experimentally. In this study, the number of cycles, slip amplitude and temperature were selected as main factors of fretting wear. The results of this research showed that the wear volume Increased with the Increase of slip amplitudes and the number of cycles but decreased with temperature and the coefficient of friction were observed different tendency between room and high temperature. According to SEM(EDS) only gross slip were observed on the surface of both specimens and compacted oxide were on worn surfaces. XRO patterns showed that the crystallization of ZrO$_2$ were observed on the worn surface at high temperature. The fretting wear were Investigated due to oxidation and accumulation of plastic flow.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.1
• /
• pp.83-89
• /
• 2004

Flare nut is an important Part that used to joint a brake tube-end in automobiles. It was made of SWCH 10A by machining. But we studied to make it by metal forming. The main focus of this paper is to investigate an optimal forging processes for flare nut using the DEFORM$^{TM}$-3D. commercially available finite element code and tests. Actually an explicit finite element analysis of the flare nut forging processes has been carried out to predict an optimal shape of the flare nut and its results were reflected in the tests of the forging processes design for flare nut. The simulation results which had obtained from finite element analysis were contributed to the forging processes design for flare nut. An optimal shape of nave nut showed agreements with test results. Furthermore. this paper should contribute to a development of the forging process for a variety of parts.s.

• Journal of Korean Association for Spatial Structures
• /
• v.22 no.3
• /
• pp.73-80
• /
• 2022

Unlike the CFT retrofit method, The EPFT retrofit method, which fills the steel tube with engineering plastic, does not require a separate concrete forming work and is a lightweight seismic Retrofit Method. In this study, an prototype model of the EPFT was proposed, and to analyze the seismic performance, an independent specimens and a reinforced concrete column were fabricated to conduct a seismic performance test. As a result of loading test of the independent specimens, the strength was increased compared to the steel tube column without internal filling, and the ductility ratio did not significantly increase due to the falling off of the weld. As a result of loading test of the concrete reinforcement specimen, the strength, ductility ratio, and energy dissipation were increased, and the number of cracks by loading step decreased compared to the non-reinforced specimen.

• Archives of Plastic Surgery
• /
• v.33 no.5
• /
• pp.627-631
• /
• 2006

Purpose: Ischial region is common site of pressure sore as well as greater trochanteric area. In general, ischial pressure sore associated with a large subcutaneous bursa often requires radical surgical treatment. The authors performed sclerotherapy using absolute ethanol which was considered as an alternative in treating recurrent ischial pressure sore. Methods: From may 2005 to February 2006, 11 ischial pressure sore patients were treated sclerotherapy using absolute ethanol. The authors performed sclerotherapy using absolute ethanol in 11 patients in whom the ischial sore has recurred despite of multiple radical surgical treatment. The patients' original disorders were spinal cord injury in 9 patients, cerebral palsy in 1 patient and giant cell tumor in thoracic vertebrae 1 patient. Results: Recurrence of pressure sore was not found in any patient during the follow-up period. The swap of the bursa taken before the surgery was germ cultured and compared with the discharge from an end of the inserted drain tube. The germ cultured results after the surgery were tested negative in all patients. Conclusion: This method involves causing the bursa to become scarred and closing it up by sterilizing, fixing, and denaturing by the pharmacologic effect of absolute ethanol instead of surgical excision of the bursa. We felt that aforementioned treatment modality may be considered as an alternative in treating recurrent ischial pressure sore.

• Steel and Composite Structures
• /
• v.15 no.6
• /
• pp.679-703
• /
• 2013

This paper presents experimental investigations of the fundamental behavior of concrete filled steel tube (CFT) beam-columns under fire loading. A total of thirteen specimens were tested to determine the axial force-moment-curvature-temperature behavior of CFT beam-columns. The experimental approach involved the use of: (a) innovative heating and control equipment to apply thermal loading and (b) digital image correlation with close-range photogrammetry to measure the deformations (e.g., curvature) of the heated region. Each specimen was sequentially subjected to: (i) constant axial loading; (ii) thermal loading in the expected plastic hinge region following the ASTM E119 temperature-time T-t curve; and (iii) monotonically increasing flexural loading. The effects of various parameters on the strength and stiffness of CFT beam-columns were evaluated. The parameters considered were the steel tube width, width-tothickness ratio, concrete strength, maximum surface temperature of the steel tube, and the axial load level on the composite CFT section. The experimental results provide knowledge of the fundamental behavior of composite CFT beam-columns, and can be used to calibrate analytical models or macro finite element models developed for predicting behavior of CFT members and frames under fire loading.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.06a
• /
• pp.45-48
• /
• 2006

Recently, the use of tubular hydroforming technology has seen increased usage and increased consideration for wide range of tubular automotive applications. In manufacturing hydroformed parts, bending and pre-forming operations are often required prior to the hydroforming process. Higher bending quality of bent tubes is crucial for the successful hydroforming operation because most of plastic strains and wall thinning at the extrados of bend area occur in the bending operation. Springback is also observed due to elastic recovery of tube material after bending. Proper correction of springback is required not only to well place the bent tube into a hydroforming die cavity but also to avoid pinching when the upper die is brought down to closing position. Therefore, prediction of springback at early development stage is one of the key factors to produce high quality hydroformed parts. In this study, a variety of bending experiments has been carried out to investigate springback amount under change in bending angle and material boosting. Throughout the experimental approach, springback characteristics of bent tubes are quantified according to the change in various bending parameters, and a mathematical model to predict correction amount of springback to a given bend angle is found.

• Nuclear Engineering and Technology
• /
• v.32 no.5
• /
• pp.465-476
• /
• 2000

In a nuclear power plant, steam generator tubes cover a major portion of the primary pressure-retaining boundary. Thus very conservative approaches have been taken in the light of steam generator tube integrity According to the present criteria, tubes wall-thinned in excess of 40% should be plugged whatever causes are. However, many analytical and experimental results have shown that no safety problems exist even with thickness reductions greater than 40%. The present criterion was developed about twenty years ago when wear and pitting were dominant causes for steam generator tube degradation. And it is based on tubes with single cracks regardless of the fact that the appearance of multiple cracks is more common in general. The objective of this study is to review the conservatism of the present plugging criteria of steam generator tubes and to propose a new coalescence model for two adjacent through-wall cracks existing in steam generator tubes. Using the existing failure models and experimental results, we reviewed the conservatism of the present plugging criteria. In order to verify the usefulness of the proposed new coalescence model, we performed finite element analysis and some parametric studies. Then, we developed a coalescence evaluation diagram.

• Transactions of Materials Processing
• /
• v.14 no.6 s.78
• /
• pp.527-532
• /
• 2005

Among the failure modes which can occur in tube hydroforming such as wrinkling, bursting or buckling, the bursting by local instability under excessive tensile stresses is irrecoverable phenomenon. Thus, the accurate prediction of bursting condition plays an important role in producing the successfully hydroformed part without any defects. As the classical forming limit criteria, strain-based forming limit diagram (FLD) has widely used to predict the failure in sheet metal forming. However, it is known that the FLD is extremely dependant on strain path throughout the forming process. Furthermore, The application of FLD to hydroforming process, where strain path is no longer linear throughout forming process, may lead to misunderstanding for fracture initiation. In this work, stress-based forming limit diagram (FLSD), which is strain path-independent and more general, was applied to prediction of forming limit in tube hydroforming. Combined with the analytical FLSD determined from plastic instability theory, finite element analyses were carried out to find out the state of stresses during hydroforming operation, and then FLSD is utilized as forming limit criterion. In addition, the approach is verified by a series of bulge tests in view of bursting pressure and shows a good agreement. Consequently, it is shown that the approach proposed in this paper will provide a feasible method to satisfy the increasing practical demands for judging the forming severity in hydroforming processes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.05a
• /
• pp.92-96
• /
• 2005

Among the failure modes which can be occurred in tube hydroforming such as wrinkling, bursting or buckling, the bursting by local instability under excessive tensile stresses is irrecoverable phenomenon. Thus, the accurate prediction of bursting condition plays an important role in producing the successfully hydroformed part without any defects. As the classical forming limit criteria, strain-based forming limit diagram has widely used to predict the failure in sheet metal forming. However, it is known that the FLD is extremely dependant on strain path throughout the forming process. Furthermore, the path-dependent limitation of FLD makes the application to hydroforming process, where strain path is no longer linear throughout forming process, more careful. In this work, stress-based forming limit diagram (FLSD), which is strain path-independent and more general, was applied to prediction of forming limit in tube hydroforming. Combined with the analytical FLSD determined from plastic instability theory, finite element analyses were carried out to find out Ihe state of stresses during hydroforming operation, and then FLSD is utilized as forming limit criterion. In addition, the approach is verified with a series of bulge tests in view of bursting pressure and shows a good agreement. Consequently, it is shown that the approach proposed in this paper will provide a feasible method to satisfy the increasing practical demands for judging the farming severity in hydroforming processes.