• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.47-58
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• 2004

Steel Pipelines were located in hillside and mountain areas where landslides occurred during the Northridge earthquake. This paper describes the investigations that were performed to identify and locate the different types of steel pipeline construction in the system using GIS (Geographical Information System). The paper explores the damage correlations of steel pipelines with PGV (peak ground velocity) and investigates the areas subjected to the landslide effects during the Northridge earthquake. One noticeable finding is that the repair rates for steel distribution pipelines after the Northridge earthquake are higher than those of CI (cast iron) pipelines. The relatively high susceptibility of steel piping to damage during the Northridge earthquake may be explained in part by utility practices, such as using steel pipe for the highest internal pressures, and increased susceptibility to corrosion also appears to play a role in steel pipeline performance.

• Steel and Composite Structures
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• v.38 no.6
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• pp.691-703
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• 2021

In this study, experiments were conducted to evaluate the flexural performance of prestressed hybrid wide flange (PHWF) beams with hollowed steel webs. A total of four PHWF beams were fabricated, where the width and spacing of the steel webs and the presence of cast-in-place (CIP) concrete were set as the main test parameters, and their flexural behavior and crack patterns, and the longitudinal strain distribution in a section with respect to the width and spacing of the steel webs were analyzed in detail. The experiment results showed that, as the ratio of the width to the spacing of the steel webs decreased, the flexural stiffness and strength of the PHWF beams without CIP concrete decreased. In addition, in the case of composite PHWF beam with CIP concrete, fully composite behavior between the precast concrete and the CIP concrete was achieved through the embedded steel member. Finite element analyses were performed for the PHWF beams considering the bond properties between the hollowed steel webs and concrete, and nonlinear flexural analyses were also conducted reflecting the pre-compressive strains introduced only into the bottom flange. From the comparison of the test and analysis results, it was confirmed that the analysis models proposed in this study well evaluated the flexural behavior of PHWF beams with and without CIP concrete.

• Corrosion Science and Technology
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• v.18 no.6
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• pp.258-266
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• 2019

The objective of this study was to evaluate corrosion resistance of additive manufactured 316L stainless steel and alloy 625 powders widely used in corrosion resistance alloys of marine industry in comparison with cast alloys. Directed Energy Deposition (DED) method was used in this work for sample production. DED parameter adjustment was also studied for optimum manufacturing and for minimizing the influence of defects on corrosion property. Additive manufactured alloys showed lower corrosion resistance in seawater compared to cast alloys. The reason for the degradation of anti-corrosion property was speculated to be due to loss of microstructural integrity intrinsic to the additive manufacturing process. Application of heat treatment with various conditions after DED was attempted. The effect of heat treatments was analyzed with a microstructure study. It was found that 316L and alloy 625 produced by the DED process could recover their expected corrosion resistance when heat treated at 1200 ℃.

• Journal of Powder Materials
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• v.9 no.3
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• pp.189-198
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• 2002

In this work, transient liquid phase (TLP) bonding of Ni-Cr heat resisted cast alloy (HP) was investigated. And also the behaviors of the solid particles distributed in the interlayer during TLP bonding were investigated. The MBF-60 and solid particles (Ni, Fe, and $Al_2O_3$ powders respectively) added MBF-60 which will be a liquid phase coexisting with solid particles at the bonding temperature were used as insert metal. The effective and sound bonding was possible by spark plasma sinter-bonding due to the differences of electric resistance between base metal and liquid insert layer which creates high temperature region. During the isothermal solidification, $Al_2O_3$ particles and solid particles of liquid phase sintered insert metal have shown no growth, while Ni and Fe particles grow rapidly. In this TLP bonding using the MBF-60 and distributed Fe, Ni particles as insert materials, the whole isothermal solidification process was dominated by the growth rate of the solid particles distributed in the interlayer.

• Journal of the Korean Society for Precision Engineering
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• v.2 no.3
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• pp.28-40
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• 1985

In this study, to check up on the effect of the components of cutting resistance upon friction between drill and inside wall of hole in drilling, the experiment was performed with individual specimen of carbon steel, cast iron, aluminium alloy under various cutting conditions: depth of hole, cutting speed, feed rate, shape and material of specimen. On the basis of the experimental results, the following conclusions are drawn; 1. The components of cutting resis- tance were increased in proportion to the increase of depth of hole owing to frictional resistance of drill margin and chip-jamming. 2. As feed rates increase, torque and thrust were increased. When comparing to the increasing rate for these components respecitively, thrust is higher tendency than torque. 3. As drill diameter increase, torque and thrust were increased. When comparing to the increasing rate for these components respectively, torque is higher tendency than thrust. 4. In the case of torque, the frictional resistance between drill margin and inside wall of drilled hole accounts for about 20 percent of carbon steel, 14 of cast iron, 10 aluminium alloy in drilling. But the effect of thrust force could be negligible. 5. Comparison between the theoretical and experimental results showed a close agreement so far as depth of hole is about three times of drill diameter. But there was a wide difference between them beyond the rane of three times, because of characteristics of the drilling process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.337-343
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• 2017

The laser cladding process on structural steel (SCM440) and gray cast iron (GC250) substrates with Co-based powder (Stellite 12) was studied. A diode laser (2 kW) was used as a heat source, and the powder was supplied by a disc rotary powder feeder. The relationship between the laser cladding process and the cross-sectional analysis of coating was examined based on coating shape and microstructure. Additionally, the microhardness was measured to confirm the mechanical property improvements. As a result, proper laser cladding conditions were selected through this study and verified by cross-sectional analysis. In addition, the evaluation process for laser cladding feasibility was conducted on the selected materials.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.55-63
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• 2001

Friction and wear properties of brake friction materials containing different metal fibers (Al, Cu or Steel fibers) were investigated using a pad-on-disk type friction tester. Two different materials(gray iron and Al-MMC)) were used for disks rubbing against the friction materials. Results from ambient temperature tests revealed that the friction material containing Cu fibers sliding against cast iron disk showed a distinct negative ${\mu}$-ν (friction coefficient vs. sliding velocity) relation implying possible stick-slip generation at low speed. The negative ${\mu}$-ν relation was not observed when the Cu-containing friction materials were rubbed against the. Al-MMC counter surface. As applied loads increased, friction materials showed higher friction coefficients comparatively. Friction materials slid against cast iron disks exhibited higher friction coefficients than Al-MMC disks during high temperature tests. On the other hand, high temperature test results suggested that copper fibers in the friction material improved fade resistance and the steel fibers were not compatible with Al-MMC disks showing severe material transfer and erratic friction behavior during sliding at elevated temperatures.

• Composites Research
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• v.33 no.5
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• pp.251-255
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• 2020

In this study, TiC ceramic particulate reinforced steel composites was fabricated using a liquid pressing infiltration process. Studies were conducted on microstructure analysis and basic physical properties such as hardness and corrosion characteristics in salt water environment for comparison with commercial nodular cast iron. As a result of comparison of corrosion characteristics in a salt water environment, both corrosion potential and corrosion current density were lower than that of ductile graphite cast iron. The lower calculated corrosion rate confirms that the TiC-Fe metal composite has superior corrosion resistance than the cast iron.

• Journal of Korean Society of Steel Construction
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• v.27 no.1
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• pp.87-97
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• 2015

In this study, an experimental study was performed to evaluate the concrete breakout strength of cast-in-place(CIP) anchors in cracked concrete under static shear loading. The CIP anchors involved in this study were 30mm in diameter with an edge distance of 150mm and an embedment length of 240mm. The experiment was carried out for two specimens in uncracked concrete and three specimens in cracked concrete orthogonal and parallel to the direction of shear loading, respectively. Compared to the uncracked concrete specimen, cracked specimen orthogonal to the direction of shear loading showed no reduction in the concrete breakout strength and that parallel to the load direction about 91% strength which corresponds to 84% of uncracked concrete strength defined in ACI 318-11. Therefore, the experimental results showed smaller decrease in the shear resistance of CIP anchors in cracked concrete than that specified in ACI code which account for 71% strength of uncracked concrete in cracked concrete.

• Journal of Korean Society of Steel Construction
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• v.30 no.2
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• pp.67-76
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• 2018

An experimental study was conducted to evaluate the breakout strength of stirrup-reinforced cast-in anchors under dynamic shear loadings. The shear loadings were applied in the manner specified in the ACI 355.2 and ETAG 001 for the seismic qualification tests. Test specimens were fabricated with M36 anchor (edge distance, 180mm) reinforced with D10 stirrups (spacing, 100mm). The specimens reached almost the breakout strength and thereafter fracture of anchor occurred. Additional tests with M42 anchor (edge distance, 160mm) reinforced with D6 bars (spacing, 100mm) were also conducted. The experimental results showed that the dynamic shear strength was not less than the static resistance. Based on the test results, it was shown that ACI 318 and ETAG 001 specifications estimate the breakout strength of stirrup-reinforced anchors conservatively as more reinforcement is provided.