• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.488-492
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• 2011

Heat-treatable Al-Mg-Si-Cu alloy sheets, which are expected to have a growing demand, were fabricated by Cross rolling to improve their formability. The mechanical properties and texture of the sheets after the final annealing process were investigated by a tensile test, EBSD and XRD analysis. The grain size of the cross-rolled sheets was remarkably decreased compared to conventional rolled sheets, and the R-value of the cross-rolled sheets was notably increased by about one and a half times that of the conventional rolled sheet. Cube{001}<100> and cubic system orientations were strongly developed in conventional rolled sheets. However, randomized textures were formed in the cross-rolled sheets without specific texture. It is thought that much shear deformation was induced during the cross rolling. The results show that the cross rolling method is effective for improving the R-value of aluminum alloys sheets and their grain refinement. As a result, it is considered that cross rolling is effective for improving formability.

• Korean Journal of Materials Research
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• v.31 no.5
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• pp.245-254
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• 2021

Wire arc additive manufacturing (WAAM) is being considered as a technology to replace the conventional manufacturing process of titanium alloys. However, coarse β grains, which can extend through several deposited materials, result in strong textures and anisotropy. As a solution, we study the plastic deformation effects of ultrasonic needle peening (UNP) on the microstructure. UNP treated materials deform plastically and the dislocation density increases. Fine α+α' grains with low aspect ratio are observed in the UNP treated specimens. UNP treated WAAM Ti-6Al-4V alloys have higher strength and lower elongation than those characteristics of WAAM Ti-6Al-4V alloys. Due to UNP treatment, the z-axis directional specimens exhibit a greater effect of reducing elongation than do the x-axis directional specimens. The UNP treatment produces fine grains in proportion to the number of times UNP is performed, thereby increasing strength. UNP processes produce a large number of dislocations in the WAAM Ti-6Al-4V alloys, with the most dislocations being formed at the surface.

• Advances in concrete construction
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• v.13 no.3
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• pp.265-279
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• 2022

The roughness of substrate concrete interfaces before new concrete placement has a major effect on the interface bond behaviour. However, there are challenges associated with the consistency of the final roughness interface prepared using conventional roughness preparation methods which influences the interface bond performance. In this study, five quantitative interface roughness textures with different roughness tooth angles, depths, and tooth distribution were created to ensure consistency of interface roughness and to evaluate the bond behaviour at a precast and new concrete interface using the splitting tensile test, slant shear test, and double-shear test. In addition, smooth interface specimens and two separate the pitting interface roughness were also utilized. Obtained results indicate that the quantitative roughness has a very limited effect on the interface tensile bond strength if no extra micro-roughness or bonding agent is added at the interface. The roughness method however causes enhanced shear bond strength at the interface. Increased tooth depth improved both the tensile and shear bond strength of the interfaces, while the tooth distribution mainly influenced the shear bond strength. Major failure modes of the test specimens include interface failure, splitting cracks, and sliding failure, and are influenced by the tooth depth and tooth distribution. Furthermore, the interface properties were obtained and presented while a comparison between the different testing methods, in terms of bond strength, was performed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.663-676
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• 1996

Physical properties and textural parameters of thirty-five piston tore samples recovered from the southeastern coast of Korea (Korea Strait), were investigated using the autopycnometer. The physical properties (porosity, water content, wet bulk density, dry bulk density, gram density, and void ratio) were measured at rather uniform intervals along each core. Sediment texture (grain size, sand, silt, and clay contents) was also measured at the same subbottom depth. The measured and calculated results are; mean grain size $0.57\~8.09\phi(average:3.67\phi)$, porosity $26\~81\%\;(average:\;55\%)$, water content $16.7\~61.4\%(average:\;31.6\%)$, wet bulk density $1.37\~2.18g/cm^3\;(average:\;1.85g/cm^3)$, dry bulk density $2.55\~3.11g/cm^3\;(average:\;2.35g/cm^3)$, grain density $2.40\~3.10g/cm^3\;(average:\;2.85g/cm^3)$, and void ratio $0.56\~2.54$ (average: 0.94). The sediment texture generally coincides well with the bathymetry indicating the influence of Pleistocene-Holocene sea level changes. Also the contours of physical properties are closely related to the sediment texture. Fluctuation of physical properties are similar to the textural variation. It seems that sediment texture is a significant factor in determining physical property in this study area.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.3
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• pp.353-359
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• 2012

The identification of effective root zone would clarify dynamics of plant available water and soil water balance. Using the relationship between soil properties and electrical resistivity (ER) the purpose of this research is to identify soil zone affected by a plant root activity using electrical resistivity tomography (ERT) technique. Four plastic containers were prepared for two different soil textures (clay and sandy loam) and one container for each texture was selected for planting four corn seedlings (Zea mays L.) and the others were prepared for the blank. For ERT monitoring, we prepared 0.8 m plastic sticks with 17 electrodes installed with 5 cm space. The Ministing (AGI Inc., Texas) instrument for electrical resistivity measurement and semi-auto converter of electrode arrangement were set up for dipole-dipole array. During 2 months of the corns growing, ERT monitoring was made 3 to 4 days after the irrigation practice. Despite of the same amount water supplied into soils, two textures showed very different apparent resistivity values due to different clay content. The apparent electrical resistivity is consistently lower in clay loam comparing to sandy loam soil implying that plant root does not significantly alter the overall trend of resistivity. When plant root system, however, is active both soils with plants showed 2-7 times higher electrical resistivity and higher coefficient variation than soils without plant, implying the effect of root system on the resistivity, in which may caused by. This result suggests plant root activities regulating the soil water dynamics mainly control the variation of electrical resistivity over soil textural difference. Therefore the identification of water uptake zone would highly be correlated to plant root activities, thus ERT will be feasible approach to identify spatial characteristics of a plant root activity.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.105-116
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• 2017

The purpose of this study is to provide the information on genesis of obsidian occurring in the southwestern part of Ulleung Island, Korea, and to discuss its implications for volcanic activity through volcanological and mineralogical properties of obsidian. Obsidian occurs locally at the lower part of the Gombawi welded tuff, showing various complex textures and flow banding. Though obsidian is mostly homogeneous, it is closely associated with alkali feldspar phenocrysts, reddish tuff, and greyish trachyte fragments. The obsidian occurs as wavy, lenticular blocks or lamination composed of fragments. Cooling fractures developed on obsidian glass are characterized by perlitic cracks, orbicular or spherical cracks, indicating that obsidian rapidly quenched to form an amorphous silica-rich phase. It is evident that hydration took place preferentially at the outer rim relative to the core of obsidian, forming alteration rinds. The glassy matrix of obsidian includes euhedral alkali feldspars, diopside, biotite, ilmenite, and iron oxides. Microlites in glassy obsidian are composed mainly of alkali feldspars and ilmenite. Quantitative analysis by EPMA on the obsidian glass part shows trachytic composition with high iron content of 3 wt.%. Accordingly, obsidian formed with complex textures under a rapid cooling condition on surface ground, with slight rheomorphism. Such results might be induced by collapse of lava dome or caldera, which produced the block-and-ash flow deposit and the transportation into valley while keeping high temperatures.

• Korean Journal of Food Science and Technology
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• v.28 no.4
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• pp.668-672
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• 1996

Four low fat ground beef groups containing 10% fat plus 0, 5, 10 and 20% additional cooked old rice and a control ground beef containing 30% fat were prepared. Various sensory characteristics and instrumental textures were measured in order to determine the acceptability of low fat ground beef and to find out the most appropriate level of addition of cooked old rice as a fat replacer. Ground beef containg 10% fat had higher flavor and firmness scores than any other ground beef groups. Ground beef with 10% fat plus 5% cooked old rice had higher flavor, particle size, firmness and overall acceptability scores but lower juiciness and tenderness scores than ground beef with higher amount of cooked old rice (10 and 20%) and ground beef with 30% fat. Ground beef containing 10% fat plus 10 and 20% cooked old rice had higher juiciness, tenderness, particle size and overall acceptability scores but lower flavor and firmness scores than any other ground beef groups. Ground beef with 30% fat had higher flavor, juiciness, tenderness and firmness scores but lower particle size and overall acceptability scores. Conclusively, ground beef with the fat content reduced to 10% plus 5 or 10% additional cooked old rice as fat replacer still possessed the desirable sensory and instrumental texture properties.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.3
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• pp.249-255
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• 1995

This study was conducted to investigate the effects of some soil conditioners, such as polyacrylamide(PAM), polyvinylalcohol(PVA) and Bitumen emulsion, on aggregate formation and stability, wetting angle, sorptivity and penetrability of the soil with different textures : sand, sandy loam, loam and clay loam. A pot experiment was carried out to find out the effect of treatment on the germination and growth of lettuce with three textures : sand, sandy loam and silt loam. Soil aggregates larger than 2mm in untreated soils at dry condition were naught in sand, 45% in sandy loam, 80% in loam and 90% in clay loam. Treatments of soil conditioners tended to increase the occurrence of soil aggregate larger than 2mm, which were 20~25% in sand, 55~75% sandy loam, but not affected greatly aggragate occurence in loam and clay loam. The aggregate instability was decreased by the soil conditioner treatment. The wetting angles of the soils were greatly changed by hydrophobic of Bitumen, but those were changed slightly by PVA and PAM application. The sorptivity and penetrability data indicated that the effects of different materials on these parameters differed depending upon soil texture. Application of PVA and PAM were no effect exceptive in sand. Application of Bitumen revealed that water movement was not showed in all soils. The germination rate, root weight and top plant weight of lettuce were increased in all soils by PAM treatment as compared to untreated soils. Particularly the greater effect was occurred in sand soil than in sandy loam and silt loam. PAM increased greatly the moisture content and air phase of soils.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.67 no.4
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• pp.296-304
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• 2022

To maximize the medicinal properties of bellflower root (Platycodi radix), its growth and development according to soil texture were investigated using four types of soil: masato (decomposed granite), soil mix, loamy sand, and sandy loam. Saponin content was measured. With regard to bellflower root growth depending on soil texture, its growth was better in the order of loamy sand > sandy loam > soil mix > masato in the above-ground part, and loamy sand > soil mix > sandy loam > masato in the underground part in the order. The average content of general ingredients were 77.3% water, 2.6% crude fat, 3.2% crude flour, 6.0% crude protein, and 10.9% carbohydrates. With respect to saponin analysis of bellflower roots, the saponin content regarding platycodin D, platycodin D3, polygalacin D, and deapioplatycodin D were higher in the order of 282.4, 104.7, 29.1, 19.1 mg/100 g, respectively. The content of organic matter and phosphoric acid was high in soil mix and sandy loam, and platycodin D3 showed similar levels in all soil types. As a result, the soil mix is considered most suitable in terms of yield and component levels, however, it is the most expensive type. As a replacement, sandy loam was adequate in terms of fresh weight related to yield and highest saponin content.

• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.21-27
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• 2005

Tensile properties and hardness of nickel electroform from chloride-free nickel sulfamate electrolyte at 50℃ and PH 4.5 were investigated. Current density varied from 20 to 60 mA/㎠. The deposit thicknesses were 360, 480 and 980 ㎛. It was found in 480 ㎛ thick electroform that highest tensile and yield strengths and hardness of 83.7 ksi, 53.6 ksi and 216 DPH, respectively were obtained at a current density of 40 mA/㎠ and they were slightly decreased at 20 and 60 mA/㎠. However the ductility was lowest of 7.9% at 40 mA/㎠. Such a high strength and low ductility at 40 mA/㎠ seems to be related to the narrower columnar structure than those of other current densities. All the deposits exhibited pronounced necking behavior. Tensile strength, yield strength and ductility increased as the nickel electroform thickens. Initial strong (200) texture developed on stainless steel mandrel decreased and (111) and (220) textures increased as deposit thickness increased, whereas (200) texture was preferred as the current density increased.