• Corrosion Science and Technology
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• v.12 no.4
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• pp.179-184
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• 2013

Pipe wall thinning caused by erosion and corrosion can adversely affect the operation of aged nuclear power plants. Some injured workers owing to pipe rupture has been reported and power reduction caused by unexpected pipe damage has been occurred consistently. Therefore, it is important to develop erosion-corrosion damage prediction model and investigate its mechanisms. Especially, liquid droplet impingement erosion(LDIE) is regarded as the main issue of pipe wall thinning management. To investigate LDIE mechanism with corrosion environment, we developed erosion-corrosion damage simulation apparatus and its capability has been verified through the preliminary damage experiment of 6061-Al alloy. The apparatus design has been based on ASTM standard test method, G73-10, that use high-speed rotator and enable to simulate water hammering and droplet impingement. The preliminary test results showed mass loss of 3.2% in conditions of peripheral speed of 110m/s, droplet size of 1mm-diameter, and accumulated time of 3 hours. In this study, the apparatus design revealed feasibility of LDIE damage simulation and provided possibility of accelerated erosion-corrosion damage test by controlling water chemistry.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.259-270
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• 2002

A small granodiorite-quartz monzonitic stock containing sericitic and propylitic alteration assemblages hosts a Cu-W breccia-pipe deposit in the southeastern Cyeongsang basin. The mineralized breccia-pipe contains angular to subangular brecciated fragments of granitic rocks showing clast-supported textures. An assemblage of quartz, tourmalines, sulfide minerals (mainly chalcopyrite, arsenopyrite and pyrrhotite) and calcite was precipitated as a hydrothermal cement between the brecciated fragments. A tourmaline aureole surrounds the breccia pipe. Extensive tourmalinization of the granitic rocks near and within the pipe and no tourmalinization in the sedimentary and volcanic rocks. The tourmalines are marked by Fe-rich, black charcoal-like schorl (80 mol% schorl relative) nearer the schorl-dravite solid solution. The chemical changes in the hydrothermal fluid are reflected by variations in compositional Boning from cores to rims. They generally contain cores with low values of Fe/(Fe+Mg) and high values of Na/(Na+ca) relative to rims. This is because of an increase Fe and Ca contents toward rims. The main trend of these variations is a combination of the exchange vectors Ca(Fe, Mg) $(NaAl)_{- }$ $_1$ and $Fe^{3}^{+}$ $Al_{[-10]}$ $_1$ It is thought that boiling causes the loss of $H_2$ into the vapor phase resulting in the oxidation of Fe in the aqueous phase. pH of the melt would be one of important controlling factors for the tourmaline stability. The tourmalines could be precipitated when the system evolved to the acidic hydrothermal regime as most hydrothermal brines and acidic gases exsolved from the magma. The Ilgwang tourmaline crystallization is products of hypogene orthomagmatic hydrothermal processes that were strongly pipe-controlled.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1-6
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• 2004

In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective In this study, the intrinsic static/dynamic fracture toughness of Al 7175=T74 is evaluated from the apparent static/ dynamic toughness of notched specimen, The critical average stress fracture model is suggested to establish the relationship to predict the intrinsic fracture toughness from the apparent fracture toughness of a notched specimen. The critical average stress fracture model is established using the relation between the notch root radius and the effective distance calculated by finite element analysis. Also, effective distance is applied to estimate the failure criterion for the combustion pipe with notch. It is conclude that the true fracture toughness can be estimated from test results of apparent fracture toughness measured by using a notched specimen. Also, the effective distance can be used to evaluate the failure criterion of structure with notch.

• Structural Engineering and Mechanics
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• v.33 no.4
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• pp.503-527
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• 2009

This paper presents experimental results on the behaviour and ultimate load of fifteen pipes and six roof panels made of ferrocement. Additional results from three roof panels, carried out by others, are also compared with this research results. OPC cement, natural sand and galvanised iron wire mesh were used for the construction of 20 mm thick specimens. The pipe length was 2 m and roof panel length was 2.1 m. The main variables studied were the number of wire mesh layers which were 1, 2, 3, 4 and 6 layers, the inner pipe diameter which were 105, 210 and 315 mm, cross sectional shape of the panel which were channel and box sections and the depth of the edge beam which were 95 mm and 50 mm. All specimens were simply supported and tested for pure bending with test span of 600 mm at mid-span. Tests revealed that increasing the number of wire mesh layers increases the flexural strength and stiffness. Increasing the pipe diameter or depth of edge beam of the panel increases the cracking and ultimate moments. The change in the pipe diameter led to larger effect on ultimate moment than the effect of change in the number of wire mesh layers. The box section showed behaviour and strength similar to that of the channel with same depth and number of wire mesh layers.

• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.133-140
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• 2016

Most small weir installed in Korea is concrete solidated weir. Fixed weir causes stagnant flow, which leads to deposit sediment just upstream of weir. As time goes on, it would induce reduction of water storage capacity and invoke the serious water quality issues. Therefore, there has been a growing interest in movable weir. Especially, the flexible rubber weir is easy to install and possible to operate in extreme environments. However, even though this type can be flatable, it is also not free from sediment deposition problem. Thus, to enhance the ability of releasing deposition the bypass pipe was constructed underneath it. In this study the performance of its ability was examined with hydraulic model test. This bypass pipe was designed with 3 different dimensions to connect between each bottom of upstream and downstream of a weir, such as Type A, B, and C. The efficiency of drainage of deposition upstream was studied under two water of upstream and sediment heights. In addition, the ability of sediment emission through the bypass pipe after the pipe was blocked by debris like soil, vegetation et al. was examined by video monitoring. From this study, it was suggested a dimensionless equation which show the relationship of variable parameters and amount of emission sediment through bypass pipe. And it was found that the most significant factors on efficiency of releasing were elbow angle and discharge, and the ability of emission when the pipe was blocked was most highly influenced in tilting length.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4763-4768
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• 2014

Recently, aluminum pipes have been used instead of steel pipes for open and shut machines in vinyl housing because of its corrosion-resistance and light weight. In particular, the light weight is very useful for fitting and removal by human resources. On the other hand, an aluminum pipe is weak in winter because aluminum has a larger thermal expansion coefficient than steel. This study examined the freezing and bursting of aluminum pipes by numerical analysis. The mechanical-thermal deformation characteristics were analyzed under the condition of ice volumetric expansion in aluminum pipes reaching 50%. From numerical analysis, large stresses above the yield stress occurred in aluminum pipe after ice expanded in the net diameter immediately. In addition, the freezing and bursting of aluminum pipes was predicted around an ice volumetric expansion of 6 - 7% because the thickness of the aluminum pipe reached an aluminum elongation ratio of 17%. Therefore, it is recommended that aluminum pipes be sealed perfectly to prevent water flow in the pipe. These results suggest that it is very difficult to prevent freezing and bursting of aluminum pipes by water freezing in the pipe.

• Transactions of Materials Processing
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• v.21 no.2
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• pp.89-95
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• 2012

To examine the deformation characteristics of round aluminum pipe under biaxial compression, a horizontal biaxial compression die was fabricated. The change of material properties, punch load and deformation behavior were monitored in experiments using various compressive deformation rates in the range of 1mm/min.~400mm/min. The tensile and compressive strains were estimated from Vickers microhardness results. The punch load and deformation characteristic of the round aluminum pipes were found to change greatly at a deformation rate of about 200mm/min. The punch load decreased with increasing compressive deformation rate. Results of numerical simulation using Deform-2D were in good agreement with experimental results, and the measured hardness variation with the strain variation was predicted well by the simulation.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.463-468
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• 1997

This paper presents a theoretical approach of the instability criterion from stratified to nonstratified flow in horizontal pipe at cocurrent flow conditions. The new theoretical instability criterion for the stratified and nonstratified flow transition in horizontal pipe has been developed by hyperbolic equations in two-phase flow, Critical flow condition criterion and onset of slugging at cocurrent flow condition correspond to zero and imaginary characteristics which occur when the hyperbolicity of a stratified two-phase flow is broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al.[1] experimental data of pipes, it is shown that they are in good agreement with data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.915-922
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• 2006

Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around $-20^{\circ}C$, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with $N_2$ gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around $-20^{\circ}C$. It was observed that the gas loaded one had succeeded in chilling start-up operation.

• Ocean Systems Engineering
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• v.6 no.1
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• pp.99-115
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• 2016

In meeting the technical needs for deepwater conditions and overcoming the shortfalls of single-layer pipes for deepwater applications, pipe-in-pipe (PIP) systems have been developed. While, for PIP pipelines directly laid on the seabed or with partial embedment, one of the primary service risks is lateral buckling. The critical axial force is a key factor governing the global lateral buckling response that has been paid much more attention. It is influenced by global imperfections, submerged weight, stiffness, pipe-soil interaction characteristics, et al. In this study, Finite Element Models for imperfect PIP systems are established on the basis of 3D beam element and tube-to-tube element in Abaqus. A parameter study was conducted to investigate the effects of these parameters on the critical axial force and post-buckling forms. These parameters include structural parameters such as imperfections, clearance, and bulkhead spacing, pipe/soil interaction parameter, for instance, axial and lateral friction properties between pipeline and seabed, and load parameter submerged weight. Python as a programming language is been used to realize parametric modeling in Abaqus. Some conclusions are obtained which can provide a guide for the design of PIP pipelines.