• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.1
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• pp.79-88
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• 2002

13%Cr martensitic stainless steel has been used mainly with a material for fish pre-processing machinery. However, it has not very nice cutting section because of little of the carbon content. Therefore, SUS420J2 steel that contents 0.3%C with high-strength in spite of the rust is used with a material for fish pre-processing machinery. However, studies on the corrosion characteristics of SUS420J2 steel are relatively rare. Especially, the corrosion phenomenon may cause serious degradation because the fish pre-processing machinery is exposed always to seawater environment. In this paper, the immersion corrosion test was carried out at seawater environment (pH=7.52) on SUS420J2 steel specimens that have various post-treatment conditions and its corrosion characteristics were evaluated. From test results, the specimens such as base metal, vacuum heat treatment, electrolytic polishing and tempering after quenching tend somewhat sensitive from the corrosion. In the case of vacuum heat treatment specimen of continuous immersion during 360 days, the weight loss ratio was high about seven times when compared with the different specimens. On the contrary, SUS420J2 steel specimen that has the heat treatment of tempering after quenching and the electrolytic polishing was less sensitive from the corrosion, and the weight loss ratio was very low.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.322-327
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• 2020

An Armor Piercing Fin Stabilized Discarding Sabot (APFSDS), which penetrates and sabotages the target by physical energy, consists of a general penetrator using Depleted Uranium (DU) or Tungsten Heavy Alloy (THA) but THA is preferable because of manufacturing and environmental issues. On a THA penetrator, the penetration performance is determined mainly by self-sharpening depending on the hardness and toughness of materials. In particular, the tensile strength and impact strength work as key factors. The correlation coefficient for the penetration performance of the tensile strength was 0.721 and the impact strength was -0.599. The improved penetration performance by additional heat treatment was proven experimentally. Therefore, maintaining elongation over 9 % and tensile strength over 123 kg/㎟ is desirable, and the impact strength should be less than 6.8 kg·m/㎠ for good penetration performance.

• Geotechnical Engineering
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• v.12 no.2
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• pp.33-42
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• 1996

The weathering of mudrock in the Pohang area is mainly caused by slaking and swelling when the mudrock is absorbed with water. In this regard, this paper chows the results of chemical analysis and the identification of rock-forming minerals from XRD. It also compares the slaking and swelling characteristics of mudrocks sampled from 3 different sites. The chief rock -forming minerals are the quartz, and the several types of clay minerals. The slake durability indices are ranged from 71% to 96%, and these values are closely related to the liquid limit of the powdered nock specimen. In a similar manner to the slaking characteristics the greatest values of the swelling pressure and the swelling strain were measured from the mudrock specimen with the highest value of liquid limit. The greatest measured values of the swelling pressure and the swelling strain are 9.4 kg 1 cm2 and 33.5% respectively. The residual sheer strength of mudrock decreases as the number of wet -diy cycles increases, and the residual strength at 5 cycles are measured to c,=0.24kg/cm2 and p,=28$^{\circ}$. The lowest residual strength is measured at the fresh rock -rock contact surface in the moist condition of which values are cr: 0 and n,: 21.5$^{\circ}$.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.629-632
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• 2008

In the concrete repairing industry, it's very significant to apply adequate repair materials and construction method in order to extend service life of deteriorated concrete structure efficiently. also, adequate diagnosis of deteriorated structure's status should be involved. This paper describes an investigation of bond strength of polymer modified mortar applied both old deteriorated concrete surface substrate and well cured new concretes. The purpose of this investigation is comparing how much the tensile bond strength on construction site is different from laboratory test results. in the results of investigation, most of sample tested in laboratory is in compliance with KS F 4042's specification. and most of results of construction site are not in compliance with the specification cause of low tensile strength of concrete's surface.

• Applied Chemistry for Engineering
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• v.23 no.2
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• pp.210-216
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• 2012

For the recycling of rapid-cooled steel slag, various specimens were prepared with the various replacement ratios of the rapid-cooled steel slag and the addition ratios of polymer binders. The physical properties of these specimens were then investigated by absorption test, compressive strength test, flexural strength test and hot water resistance test, and the pore and the micro-structure analysis was performed using scanning electron microscope. Results showed that the flexural strength increased with the increase of rapid-cooled steel slag and polymer binder, but the compressive strength showed a maximum strength at a certain proportion. By the hot water resistance test, compressive strength and flexural strength decreased remarkably and the total pore volume increased but the pore diameter decreased. SEM observation of the structure before the hot water resistance test revealed a very compact infusion of structure but the decomposition or thermal degradation appeared in polymer binders when observed after the hot water resistance test.

• Journal of the Korean Geotechnical Society
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• v.24 no.4
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• pp.15-21
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• 2008

Long term changes of hydraulic properties and tensile strength of natural fiber drain (NFD) are analyzed and compared with those of intact NFD's. NFD was buried in distilled water, two types of seawater and clay soils obtained in southern and western parts of Korea, Kwang-Yang and Si-hwa. Specimens are taken out in 0, 3, 9 and 18 month intervals, and durability tests of the NFD are performed. Hydraulic conductivity of the NFD samples decreased compared with that of intact NFD samples, because clay particles easily passed to coarsened mesh of filters and clogged the porous stone below and reduced hydraulic conductivity. Tensile strength of drains from the soil bucket is reduced larger than those in the seawater and the distilled water. Strength reduction was higher in summer than winter.

• The Journal of Engineering Geology
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• v.34 no.1
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• pp.25-38
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• 2024

Laboratory tests of accelerated artificial weathering compared the effects of seawater and acidified distilled water on rock weathering. The experiments simulated chemical and physical weathering of five different types of volcanic rock by applying 45 freeze-thaw cycles using seawater and acidified distilled water (pH 3), both at 70℃. The physical properties and uniaxial compressive strength (UCS) of the rocks were measured after 15 and 45 cycles of artificial weathering. Most of degradation of physical properties appeared within the first 15 cycles, and acidified distilled water had a greater effect than seawater. Analysis of variance (ANOVA) statistically evaluated the differences in UCS of the different rock types during the tests. The rate of UCS reduction after 45 cycles was similar across the samples, being independent of the rock type and the trend of changes in physical properties. In contrast to the changes in the physical properties, the UCS was more affected by seawater than by acidified distilled water.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1153-1163
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• 2013

Bonded concrete overlay is a favorable maintenance method since the material properties are similar to existing concrete pavements. In addition, bonded concrete overlay has advantage of structural performance based on being bonded together, both for the overlay layer and the existing pavement which perform as one monolithic layer. Therefore, it is important to have a suitable bond strength criteria for long term performance of bonded concrete overlay. This study aimed to investigate the affecting of bond strength on various bond characteristics, and to compare the bond strength between direct tensile test and indirect tensile test due to various conditions such as overlay materials, compressive and flexure strength of existing pavement, and deterioration status of existing pavement. As a result of this study, bond strength occurred by both of direct and indirect tensile test due to monotonic load is highly correlated such as coefficient of determination of 0.75 and P-value of 0.002. However, bond strength by indirect tensile test was relatively higher than bond strength by direct tensile test. It was known that correlation between direct and indirect tensile test was possible to use the characteristics analysis of bond fatigue behavior based on bond strength due to cyclic load which can simulate real field behavior of bonded concrete overlay.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.1
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• pp.62-69
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• 2023

For the nuclear power concrete plant structures in the UAE, it is necessary to consider the deterioration from high sulfate ions in the atmosphere and high chloride ions from the coast. In this study, two strength grade concrete mixture (40 MPa and 27 MPa) and two curing/diffusion temperatures (20 ℃ and 50 ℃) were considered for evaluating the temperature effects on diffusion and strength due to high average temperature above 38 ℃ a year in UAE. When the initial curing temperature was high, the compressive strength increased in high-temperature curing to 7 days, but the strength slightly increased in the 20 ℃ curing condition at 28 days. Regarding diffusion test, unlike the compressive test results, reduced chloride diffusion coefficients were evaluated both in 40 MPa and 27 MPa grade at 28 days. In the case of 91 days of curing, an increase in diffusivity due to high temperature and a decrease in diffusivity due to age effect occur simultaneously. Compared to the results of the curing and diffusion tests at 20 ℃ and 28 days, when the curing and diffusion tests were conducted at 50 ℃ in 91 days, the diffusion coefficients decreased to 76.2 % in 40 MPa grade and 85.4 % in 37 MPa grade with increasing curing period, respectively.

• Journal of Conservation Science
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• v.34 no.3
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• pp.195-209
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• 2018

In this study, the characteristics of various raw hairs used for traditional Korean brushes were examined; further, the characteristics and deterioration patterns of Korean, Chinese, and Japanese brushes were compared, with a quantitative evaluation to assess the brush performance. The tensile strength was generally found to be higher with a greater fiber thickness. Among the hairs examined, the back and flank hair of goat was more damaged than that in other parts, and the tensile strength was low. Higher elasticity of the brush made with hair of high cysteine content was measured. Owing to deterioration by use of the brushes, artificial drying brushes had a higher yellowness index and lower tensile strength than natural drying brushes. Further, it was confirmed that brushes with good absorbency exhibited good consistency, but not good elasticity. Thus, the performance of the brush can be influenced by the kind of material used and the brush usage pattern. In addition, it is possible to identify the material science characteristics of brushes which have been produced only by experience; therefore, the results of this study could provide basic data for manufacturing brushes employed in conservation treatment, in the future.