• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.1
• /
• pp.73-82
• /
• 2017

In Korea, previous certification of water supply infrastructure was mainly focused on economical and physical aspects. Recently, hygienic safety of water supply service has become a sensitive and important issue to our people for evaluating the water quality with growth of economy and education system. According on water quality in 497 Korean water supply facilities, pH values in the supplied water have ranged between 5.8-8.5. However, little is known about metal leachability at the pH conditions observed in the real water supply systems because a fixed pH condition (pH 7.0) has been used in the current standard method, 'Hygienic Safety Testing Method', in water supply. In this work, we examined the effects on heavy metal leachability with pH differences in the water supply pipes which are typically used in Korea. As a result, the amounts of metal leachability were tended to increase when pH levels were decreased. Especially at pH 5.8, Cu leachability from Cu pipes was found to exceed the public health standard level even after applying a normalization factor (NF) given by the current Korea standard method. The Cr and Cu leached from stainless steel pipes, Cd, Pb, Cu, and Zn from Cu-based pipe fittings, and Zn from Zn-based pipe fittings were exceeded the Korean hygienic safety standards while, after applying the NF, concentrations of the leached metals were satisfied with the current Korean standard. The findings from this work provide implications on the needs of reforming the current hygienic safety standard methodology.

• Journal of the Society of Disaster Information
• /
• v.18 no.3
• /
• pp.542-549
• /
• 2022

Purpose: Pipes are widely used as applied devices in many industrial fields such as machinery, electronics, electricity, and plants, and are also widely used in safety-related fields such as firefighting and chemistry. With the diversification of products, the importance of technology in the piping field is also increasing. In particular, when changing the existing copper pipe to stainless steel, it is necessary to evaluate safety and flow characteristics through structural analysis or flow analysis. Method: This study investigated the structural stability of the 6.35 and 15.88 socket models, which are integrated insert type connectors developed by a company, using FEM. For structural analysis, HyperMesh as pre-processor, HYPER VIEW as post-processor, and LS-DYNA as solver were used. Result: In the case of 6.35 socket, the maximum stresses at hook, holder and hinge were 95.02MPa, 19.59MPa and 44.01MPa, respectively, and in case of 15.88 socket, it was 127.7 MPa, 40.09MPa and 45.23MPa, respectively. Conclusion: Comparing the stress distribution of the two socket models, the stress in the 15.88 socket, which has a relatively large outer diameter, appears to be large overall, but it is significantly lower than the yield stress of each material, indicating that there is no problem in structural safety in both models.

• Journal of the Korean Institute of Gas
• /
• v.26 no.6
• /
• pp.16-23
• /
• 2022

In this study, characteristics of effect on hydrogen gas was investigated to hydrogen embrittlement by disk and tensile tests. The developed and commercial alloy was fabricated to a plate material made from an alloy ingot. The prepared materials were processed in the form of a disk to measure rupture pressure by hydrogen and helium gas at a rate of 0.1 to 1,000 bar/min. In the hydrogen pre-charged tensile test, a specimen was hydrogenated using an anode charging method, and the yield strength, ultimate tensile strength, elongation, and reduction in area rate were carried by a strain rate test. Also, the microstructure was observed to the fracture surface of the tensile test specimen. As a result, the developed materials satisfied endurable hydrogen embrittlement, and the fractured surface showed a brittleness fracture surface with a depth of several ㎛, but dimple due to ductile fracture could be observed.

• Composites Research
• /
• v.36 no.1
• /
• pp.37-41
• /
• 2023

The treated water inside the ballast electrolytic cell creates a highly alkaline atmosphere due to hydroxide generated at the DSA(Dimension Stable Anode) electrode during electrolysis. In this study, a composite material that can replace the weakness of the PE-coated steel pipe used in the existing ballast pipe was prepared. The test samples are BRE(Basalt fiber reinforced epoxy), BRP(Basalt fiber reinforced unsaturated polyester), GRE(Glass fiber reinforced epoxy), and GRP(Glass fiber reinforced unsaturated polyester). And then it was immersed in NaOH for 720 hours. The friction test of each specimen was conducted. The Friction coefficient analysis according to material friction depth and interfacial adhesion behavior between resin and fiber were analyzed. As a result, the mechanism of interfacial separation between resin and fiber could be analyzed. In the case of the unsaturated polyester resin with low interfacial bonding strength the longer the immersion time in the alkaline solution, the faster the internal deterioration caused by the deterioration that started from the surface, resulting in a decrease in the friction coefficient. It is hoped that this study will help to understand the degradation behavior of composite materials immersed in various chemical solutions such as NaOH, acid, and sodium hypochlorite in the future.

• Journal of Korean Society of Steel Construction
• /
• v.25 no.1
• /
• pp.35-45
• /
• 2013

The concrete-filled tube column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. It suggests that pipe should be produced by welding two sides together where two shapes are joined after a channel is pre-welded onto the three sides in order to form an internal diaphragm. The upper diaphragm of the connection used the horizontal plate and the lower diaphragm used the Vertical plate. This research performed 6 monotonic tension experiments describing the connection upside and downside in order to evaluate the structural capability of the offered connection. And the cyclic loading experiment was performed about 2 T-Type column to beam connections. As to the experimental result edge cutting geometry, there was no big effect. An increase in the number of holes of the plate ultimate strength was increased by 5% and The thickness of the plate increases, the maximum strength was increased by 4%. T-Type connections until it reaches the plastic moment showed a stable behavior.

• Analytical Science and Technology
• /
• v.5 no.1
• /
• pp.143-152
• /
• 1992

Corrosion resistances in various acids and high temperature oxidation properties have been investigated for the Ni-base superalloy KM 1557. Corrosion tests were performed in $H_2SO_4$, HCl, $HNO_3$, $H_3PO_4$ and $CH_3COOH$. Oxidation tests were carried out in air for 20 and 110hrs at $900^{\circ}C$, $950^{\circ}C$ and $1050^{\circ}C$. Hot corrosion tests were done in salt bath of 75% $Na_2SO_4-25%$ NaCl at $900^{\circ}C$ for 20hrs. After the tests, the samples were observed by optical microscopy and analysed by EPMA and X-ray mapping in order to investigate the distribution of composition. It was shown that corrosion resistances in various acids and hot salt bath were proven to be excellent. It was suggested that the amounts of oxides were determined mainly by the depth of internal and intergranular $Al_2O_3$ oxide layers.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.3
• /
• pp.625-639
• /
• 2018

This study is about the reinforcing type of reinforcement method which is reinforced in tunnel portal of tunnel with bad ground condition. Generally, it is known that the horizontal reinforcement method is more effective than the conventional reinforcement method. However, as a limitation of the tunnel construction technology, it is being constructed by the superposition reinforcement method. In recent years, high-strength large-diameter steel pipes and horizontally oriented longitudes (L = 30.0~50.0 m) construction technology have been developed. Therefore, it is required to study reinforcement method of tunnel portal reinforcement method. Therefore, 3-D numerical analysis (Midas GTS NX 3D) was performed by setting the reinforcement method (No reinforcement type, overlap reinforcement type and horizontal reinforcement type) and ground condition as parameters. As a result, it was considered that the reinforcement effect was the largest as the horizontal reinforcement type of the reinforcement method was the smallest in the displacement and the support material stress. Based on the results of the numerical analysis, horizontal steel pipe grouting was applied to the actual tunnel site. The displacement of the tunnel portal and the stress of the support material occurred within the allowable values and were considered to ensure sufficient stability.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.5
• /
• pp.252-261
• /
• 2017

This study examined the effect of heat treatment on the microstructure and mechanical properties of J55 line pipe steel. The experiments were carried out at under the following various conditions: austenization temperature($880^{\circ}C$, $910^{\circ}C$, $940^{\circ}C$), cooling methods(water quenching, oil quenching) and tempering temperature(none, $550^{\circ}C$, $650^{\circ}C$). The phase diagram and CCT curve were simulated based on the chemical composition of J55 steel to predict the microstructures. In the results, A1, A3 temperature decreased. As the austenization temperature increased, existing austenite grains grew exponentially which seriously degraded their mechanical properties. Various microstructures, including martensite, bainite, ferrite, and pearlite, developed in accordance with the heat treatments and were closely correlated with hardness, tensile strength and toughness. Martensite was formed after water quenching, but bainite and ferrite appeared after oil quenching. FeC precipitation formed and coarsened during tempering, which improved their toughness.

• Fire Science and Engineering
• /
• v.31 no.6
• /
• pp.33-39
• /
• 2017

Composite panel refers to the particular plywood produced in a way of stacking the different kinds of material in sandwich form and adhering them using adhesives and is widely used as building material for its constructability and cost efficiency. But as the surface is finished with steel plate, fire extinguishing agent cannot reach to the core material because of such steel plate on surface which causes the difficulties in suppressing the fire as well as in fire-fighting activities due to collapse. This study, to deal with such problem, is intended to set the fire pipe in core material to prevent the fire from spreading and in a bid to achieve this using minimized fire water, water supply test device was fabricated to estimate the required water flow of fire extinguisher and consequently, optimal water flow (0.5 L/min) was determined through a full-scale fire test.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.1
• /
• pp.190-198
• /
• 2018

In recent years, non-welded building hardware has been installed by bolt assembly is used. The non-welded building hardware method can reduce accidents caused by welding, and can be constructed by bolt assembly, which can reduce labor costs and shorten the construction period. However, there is a need for a method to compensate for the occurrence of buckling at the time of construction. The purpose of this study is to evaluate the behavior of joints between steel pipe and fastener and to evaluate the behavior of joints of non-welded and welded hardware frame. As a result, it was found that the foundation steel structure without welded joints was deformed to a rotation angle of member much larger than the allowable interlayer displacement angle 0.01 to 0.02 required according to the seismic load rating in the seismic load resistance system.