• Journal of Advanced Marine Engineering and Technology
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• v.38 no.8
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• pp.968-973
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• 2014

Aluminum anode of marine growth prevention system for ship is installed in seachest or sea water strainer. The Al anode is connected to a control panel that feeds a current to the anode. The dissolved ions produced by the anode are transferred in sea water, spreads through the sea water pipe system and creates a protective film in the pipelines. Thereby, corrosion in pipeline system significantly is reduced. In application on condition as a steel ship, the big accident can be caused by the corrosion. Accordingly, in this research, we evaluated influence of applied current and flow velocity on electrochemical characteristics of Al anode for marine growth prevention system (MGPS). Based on the results of the erosion-cavitation experiments, cavitation rate increased greatly until 120 min. of the experimental time and decreased a little at the point of 180 min. where pit grew and merging occurred but showed a tendency of steadily increasing consumption rates. Based on the results of the Tafel analysis, compared to static states, corrosion current densities show a rapidly increasing tendency when flow occurred.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.4
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• pp.93-100
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• 2007

The flow velocity distribution at inlet and exit of Diesel Particulate Filter(DPF) by fabricating L-shape connector with the DPF was measured using a Pitot-tube and 2-D transverse machine. An adaptor designed for making the Pitot tube probe access to the inlet and exit of the DPF was connected with the inlet and exit flange of the DPF, respectively. The Pitot tube which was mounted in the 2-D positioning machine could access to the inlet and exit of the DPF through the rectangular window of the adaptor. The L-shape connector in the DPF inlet has a flow guide which is a perforated steel pipe. The flow velocity distribution at the inlet of the DPF showed a chaotic velocity distribution which is different from that with a diffuser type connector. The velocity distribution at the exit of the DPF showed a crown shape which is similar to that of the diffuser type connector. The velocity distribution at the exit of DPF showed different patterns according to the air flow rate.

• Structural Monitoring and Maintenance
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• v.3 no.3
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• pp.297-314
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• 2016

As the study of internal corrosion of pipeline need a large number of experiments as well as long time, so there is a need for new computational technique to expand the spectrum of the results and to save time. The present work represents a new non-destructive evaluation (NDE) technique for detecting the internal corrosion inside pipeline by evaluating the dielectric properties of steel pipe at room temperature by using electrical capacitance sensor (ECS), then predict the effect of pipeline environment temperature (${\theta}$) on the corrosion rates by designing an efficient artificial neural network (ANN) architecture. ECS consists of number of electrodes mounted on the outer surface of pipeline, the sensor shape, electrode configuration, and the number of electrodes that comprise three key elements of two dimensional capacitance sensors are illustrated. The variation in the dielectric signatures was employed to design electrical capacitance sensor (ECS) with high sensitivity to detect such defects. The rules of 24-electrode sensor parameters such as capacitance, capacitance change, and change rate of capacitance are discussed by ANSYS and MATLAB, which are combined to simulate sensor characteristic. A feed-forward neural network (FFNN) structure are applied, trained and tested to predict the finite element (FE) results of corrosion rates under room temperature, and then used the trained FFNN to predict corrosion rates at different temperature using MATLAB neural network toolbox. The FE results are in excellent agreement with an FFNN results, thus validating the accuracy and reliability of the proposed technique and leads to better understanding of the corrosion mechanism under different pipeline environmental temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.2
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• pp.127-136
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• 1990

Air-solid bed has been known to be an effective heat transfer augmentation device which could be applied to heat exchangers. In this study, pressure drop and heat transfer characteristics of vertical annular fluidized bed heat exchanger with air flowing through were studied experimentally. The experiments was conducted to calculate overall heat transfer coefficient on fluidized bed heat exchangers immersed single vertical tube and investigate minimum fluidized velocity in fluidized bed of alumina beads and steel balls. The influence of flow direction, particle diameter, the heights of static bed and air mass fluidizing velocity has been examined. The experimental results showed the optimum operating condition and effective static bed height for fluidized bed heat exchangers. For the same power loss, comparisions of heat transfer effect between the fluidized bed heat exchanger and the single phase forced convetion heat exchanger indicate that both miniaturization of heat exchanger and heat transfer augmentation at low flow velocity are possible by application of the air-solid to heat exchangers.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.37-42
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• 2000

The boiler tubes and steam Pipes operating both at high temperature and pressure for a long period of time in a power plant are degraded by creep because of internal pressure. So, the remaining life of a component is evaluated by the creep rupture strength. Although the conventional method to evaluate the creep damage is widely used, it has some disadvantages such as requires large size specimen and long employed to evaluate the correlation between fracture toughness and evaluation time. Recently, new method so called "small lunch test' is used to evaluate degradation of creep. In this study, a conventional creep test and a small punch test are conducted using 2.25Cr-1Mo steel which is mainly used for the boiler tubes and steam pipes in power plant. The creep life, approximately 1,500 hrs, is determined by conventional method under a severe condition then specimens for a small Punch test are obtained after certain time intervals such as 1/4, 1/2 and 3/4 of final rupture time, respectively.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.453-458
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• 2001

Pipelines have the highest capacity and are the safest and the least environmentally disruptive way for gas or oil transmission. Recently, failures due to corrosion defects have become of major concern in maintaining pipeline integrity. A number of solutions have been developed for the assessment of remaining strength of corroded pipelines. However, these solutions are known to be dependent on material properties and pipeline geometries. In this paper, a Fitness-For-Purpose type limit load solution for corroded gas pipelines made of the X65 steel is proposed. For this purpose, a series of burst tests with various types of corrosion defects are performed. Finite element simulations are carried out to derive an appropriate failure criterion. And then, further, extensive finite element analyses are performed to obtain the FFP type limit load solution for corroded X65 gas pipelines as a function of defect depth, length and pipeline geometry. And also, a window based computer program far the assessment of corrosion defect, which is named as COPAP(COrroded Pipeline Assessment Program) has been developed on the basis of proposed limit load solution.

• Journal of Welding and Joining
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• v.23 no.2
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• pp.66-74
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• 2005

API(American Petroleum Institute) steel, as a line pipe material, requires the enhanced mechanical and chemical properties with the environmental severity. Especially, the weld part(weld metal and heat affected zone) is an important region for the safety. However, the study for the behavior of microstructure and toughness in multi-pass welding is seldom. In this study, the relationship between the microstructure and toughness of welds with several welding, bending and heat-treatment conditions was examined. In particular, HIC property in the weld metal was evaluated. The microstructure and toughness in multi-passed HAZ seemed to be determined by the final welding thermal cycle and the low toughness was attributed to the MA constituents formed in the intercritically reheated region. The weld metal showed very low toughness and it was not improved by the change in bending and heat treatment conditions. Additionally, the cracks are observed in the weld metal. from these results, it was found that the choice of welding wire/flux is very important.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.202-208
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• 1997

The component materials threatened by cavitation include ship propellers as well as turbine runners, pump impellers, pipe lines and radiators. Today it is known that cavitation damage takes place on many other components including on the coding water side of the cylinder liners of diesel engines. Cavitation erosion - corrosion implies damage to materials due to the shock pressure or shock wave that results when bubbles form and collapse at a metal surface within a liquid. To suppress cavitation erosion as well as cavitation erosion - corrosion to hydraulic equipment, innovations such as the improvement in the geometric design of the equipment or the selection of suitably resistant construction materials are necessary. In this study, we investigated that the cavitation erosion - corrosion damage under vibratory cavitation can be reduced by adding of side now velocity to the cavitation bubble group in order to eliminate bubbles formed in sea water environment.

• Journal of Welding and Joining
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• v.19 no.4
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• pp.391-398
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• 2001

MIAB welding method uses a rotating arc as its heat source and is known to be efficient in pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. This paper is concerned with the experiment of initial stage for process control, monitoring for weld quality, and the design of coil system which is efficient of flux generation and concentration. A coil system for the generation of magnetic flux was designed and constructed. Magnetic flux density and arc rotating behavior are important factors in MIAB welding, so the relations between these factors and process parameters were investigated. Various experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The magnetic flux density is increased by increasing exciting current and decreasing gap size. The maximum of arc rotating frequency is affected by exciting current and gap size. However, the variations of arc rotating frequency during welding and then the melting process are mainly influenced by welding current. Thus, it is considered that the results of this study can be used as important data on the monitoring for weld quality and the design of efficient coil system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.495-496
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• 2014

The suction method is the substructure installation using the water pressure difference generated by discharging water inside the pile by the pumping operation, after the intrusion by the self-weights of a large hollow steel pipe or a concrete structure. It is known as the low-noise and low-vibration method against the general pile driven method and eco-friendly, also. Most current design and safety assessment of the support structure and considering only the static load, however, the importance of dynamic behavior becomes magnified as the size of wind power generator increases. This study measures the natural frequency of the suction pile prototype about the penetration depth as a part of basic research and analyzed the interaction between the soil and the structure.