• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.677-684
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• 2006

An ejector is a fluid transfer device to be used for mixing of fluids, maintaining vacuum, and overcoming a poor suction condition. To date, most ejectors have been made from the casting process. which is time-consuming and high-cost process. Therefore, a new production method of ejectors is desired if any. In this experimental study, we proposed a new type ejector manufactured from the commercial fitting materials and the welding process, which is equipped with an orifice type nozzle. The proposed ejector has a good integrity compared with the conventional ejector because the fittings have manufactured by forging and they have more strength than the casting materials. Furthermore we adopted a multi-opening orifice type nozzle for improving a suction capacity and compared with a single-opening orifice type nozzle. From the experimental results. we confirmed that the multi-opening nozzle had a food suction capacity than the single-opening nozzle and the proposed new type ejector showed higher vacuum than the conventional type ejector in non-load condition. These improved characteristics suggests that a new type ejector by using the commercial fittings opens the feasibility to be adopted in various industry fields and that the increased suction capacity can be achieved by altering the nozzle design of a conventional ejector.

• Journal of the Korean Institute of Gas
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• v.4 no.4 s.12
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• pp.6-12
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• 2000

We have developed a new split tee which can be used to effectively branch into a main gas steel pipelines without losing any gas pressure or having to shut down a line. The split tee has been designed considering the locations of branch connection to the pipelines. Therefore, we could keep the depth of buried pipelines which used to be the problem of the conventional split tees. Test results of the developed split tee showed that the performance of the tightness, hydraulic strength, sealing, welding, bending, and compatibility were excellent. The application of the split tee can provide the advantage of eliminating cost and time, and easy field pipeline coatings.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.79-81
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• 2005

Bridges constructed recently are preferred to have long spans and simple structure details considering not only the function as bridge but scenic beauty, maintenance, construction term and life cycle cost, etc. Therefore, they require high performance steels like extra-thick plate steels and TMCP steels. A TMCP steel produced by themo-mechanical control process is now spot lighted due to the weldability for less carbon equivalent. It improved at strength and toughness in microstructure. Recently, the SM570-TMC steel which is a high strength TMCP steel whose tensile strength is 600MPa has been developed and applied to steel structures. But, for the application of this steel to steel structures, it is necessary to elucidate not only the material characteristics but also the mechanical characteristic of welded joints. In this study, the characteristics of residual stresses in welded joints of SM570-TMC steel were studied through the three-dimensional thermal elastic-plastic analyses on the basis of mechanical properties at high temperatures obtained from the elevated temperature tensile test.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.3
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• pp.195-203
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• 2002

In the engine room and the aft part areas of the ship, there exist so many tank structures contacting with fresh water or sea water or oil. If these structures exhibit excessive vibrations during the sea trials, it takes a lot of cost, time and effort to improve vibration situation because the reinforcement work requires emptying the fluid out of the tanks, additional welding and special painting. It is therefore very important to predict a precise vibration characteristics of the tank structures at the design stage, however it is not easy to estimate vibration characteristics of the structures because of difficulties for accurate evaluation of the added (or virtual) mass effect due to the fluid inside the tank. In this paper, numerical and experimental approaches have been performed to present same fundamental data necessary for anti-vibration design of tank structures contacting with fluid, by investigating vibration behaviors of rectangular tank structure for various water depths.

• Corrosion Science and Technology
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• v.16 no.2
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• pp.85-89
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• 2017

One of the most challenging issues in the oil and gas industry is corrosion assessment and management in subsea structures or equipment. At present, almost all steel pipelines are sensitive to corrosion in harsh working environments, particularly in salty water and sulphur ingress media. Nowadays, the most commonly practiced solution for a damaged steel pipe is to entirely remove the pipe, to remove only a localized damaged section and then replace it with a new one, or to cover it with a steel patch through welding, respectively. Numerous literatures have shown that fiber-reinforced polymer-based composites can be effectively used for steel pipe repairs. Considerable research has also been carried out on the repair of corroded and gouged pipes incorporated with hybrid natural fiber-reinforced composite wraps. Currently, further research in the field should focus on enhanced use of the lesser and highly explored hybrid-biocomposite material for the development in corrosion prevention. A hybrid-biocomposite material from renewable resource based derivatives is cost-effective, abundantly available, biodegradable, and an environmentally benign alternative for corrosion prevention. The aim of this article is to provide a comprehensive review and to bridge the gap by developing a new hybrid-biocomposite with superhydrophobic surfaces.

• Corrosion Science and Technology
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• v.14 no.2
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• pp.47-53
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• 2015

Recently, the bending process is greatly applied to fabricate the pipe line. Bending process can reduce welding joints and then decrease the number of inspection. Thus, the maintenance cost will be reduced. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. By this thermal process, corrosion properties and microstructure can be affected. This work focused on the effect of induction heating bending process on the properties of ASME SA106 Gr. C low carbon steel pipes. Microstructure analysis, hardness measurements, and immersion corrosion test were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. Hardness was measured using a Rockwell B scale. Induction heat bending process has influenced upon the size and distribution of ferrite and pearlite phases which were transformed into finer structure than those of base metal. Even though the fine microstructure, every bent area showed a little lower hardness than that of base metal. It is considered that softening by the bending process may be arisen. Except of I2, intrados area, the others showed a similar corrosion rate to that of base metal. But even relatively high rate of intrados area was very low and acceptable. Therefore, it is judged that induction heat bending process didn't affect boric acid corrosion behaviour of carbon steel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4398-4404
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• 2015

Stainless steel sheets are widely used as the structural material for dynamic machine structures, These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding, For fatigue design of gas welded joints such as various type joint. It is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. Thus in this paper, ${\Delta}P-N_f$ curves were obtained by fatigue tests. and, ${\Delta}P-N_f$ curves were rearranged in the ${\Delta}{\sigma}-N_f$ relation with the hot spot stresses at the gas welded joints. Using these results, the accelerated life test(ALT) is conducted. From the experiment results, an life prediction model is derived and factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.126-133
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• 2004

MRE-1 Dual Thruster Module(DTM), which will be used in KOMPSAT(Korea Multi-Purpose Satellite), can provide reliable and cost-effective means for attitude and maneuvering control system. Thruster heat shield, one of the main components of DTM, is designed to prevent the critical radiative heat exchange between thruster and satellite during firing. To overcome the manufacturing difficulties, a electroforming process is preferred to classical welding process. In this case, an inner diameter of a new shield will be decreased a little due to the change of manufacturing process. Therefore, the interference problem between thruster nozzle and heat shield is investigated through structural analysis and their results are described in this paper.

• Steel and Composite Structures
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• v.33 no.6
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• pp.823-836
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• 2019

Spiral welded tubes (SWTs) are fabricated by helically bending a steel plate and welding the resulting abutting edges. The cost-effectiveness of concrete-filled steel tube (CFST) columns can be enhanced by utilising such SWTs rather than the more conventional longitudinal seam welded tubes. Even though the steel-concrete interface bond strength of such concrete-filled spiral-welded steel tubes (CF-SWSTs) is an important consideration in relation to ensuring composite behaviour of such elements, especially at connections, it has not been investigated in detail to date. CF-SWSTs warrant separate consideration of their bond behaviour to CFSTs of other tube types due to the distinct weld seam geometry and fabrication induced surface imperfection patterns of SWTs. To address this research gap, axial push-out tests on forty CF-SWSTs were carried out where the effects of tube material, outside diameter (D), outside diameter to wall thickness (D/t), length of the steel-concrete interface (L) and concrete strength grade (f'_c) were investigated. D, D/t and L/D values in the range 102-305 mm, 51-152.5 and 1.8-5.9 were considered while two nominal concrete grades, 20 MPa and 50 MPa, were used for the tests. The test results showed that the push-out bond strengths of CF-SWSTs of both mild-steel and stainless-steel were either similar to or greater than those of comparable CFSTs of other tube types. The bond strengths obtained experimentally for the tested CF-SWSTs, irrespective of the tube material type, were found to be well predicted by the guidelines contained in AISC-360.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.3
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• pp.246-253
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• 2014

Liquid natural gas is stored and transported inside cargo tank which is made of specially designed cryogenic materials such as 9% Ni steel, Al5083-O alloy and SUS304 and so on. The materials have to keep excellent ductile characteristics under the cryogenic environment, down to -163oC, in order to avoid the catastrophic sudden brittle fracture during the operation condition. High manganese steel is considered to be the promising alternative material that can replace the commonly used materials mentioned above owing to its cost effectiveness. In line with this industrial need, the mechanical properties of the high manganese steel under both room and cryogenic environment were investigated in this study focused on its tensile and fatigue behavior. In terms of the tensile strength, the ultimate tensile strength of the base material of the high manganese steel was comparable to the existing cryogenic materials, but it turned out to be undermatched one when welding is involved in. The fatigue strength of the high manganese steel under room temperature was as good as other cryogenic materials, but under cryogenic environment, slightly less than others though better than Al 5083-O alloy.