• The Journal of the Petrological Society of Korea
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• v.27 no.4
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• pp.185-194
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• 2018

The basaltic rocks of Daljeon-ri columnar joint (Natural Monuments # 415) and Noeseongsan Noerok site (Natural Monuments # 547) were analysed in order to understand basalt types of two areas. The basaltic rocks of the Pohang Daljeon-ri columnar joint show a typical porphyritic texture containing phenocrysts (olivine and clinopyroxene) and groundmasses composed of clinopyroxene, plagioclase, and opaque minerals,. In contrast, basaltic rocks of Noeseongsan Noerok are characterized by fine-grained groundmass with large phenocrysts of plagioclase. Other analysis such as magnetic susceptibility, X-ray diffraction and X-ray fluorescence also support the petrological differences of two basalt rocks. The Daljeon-ri basaltic rocks are plotted on phonotephrite volcanic rocks of alkaline series in TAS(total alkali silica), and on within plate basalt in Zr-Ti diagram. The Noeseongsan basalts, on the other hand, are plotted on basaltic andesite to andesite of sub-alkaline series in TAS, and on volcanic arc basalt in Zr-Ti diagram. These results indicate that the original mantle materials between two basalt rocks were different each other, which probably originated from the change of a tectonic setting in the southeastern Korean peninsula during the Miocene.

• The Journal of the Petrological Society of Korea
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• v.14 no.4 s.42
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• pp.212-225
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• 2005

This study has been designed to elucidate the morphology of Jisagae columnar joints and the petrography and petrochemistry of Daepodong basalt in Jeju Island, distributed along the 3.5 km-long coast from Seongcheonpo to Weolpyeongdong. Colonnade of the Jisagae columnar joint typically occurs within the upper part of a flow and consists of relatively well-formed basalt columns. Most columns are straight with parallel sides and diameters from 100 cm to 205 cm, $130\~139\;cm$ in maximum. Length of the columns extends up to 20 m. Most columns tend to have 6 or 5 sides but sometimes they have as few as $3\~4$ or as many as 7 or 8 sides. The Daepodong basalt consists of plagioclase, olivine, orthopyroxene, clinopyroxene, ilmenite and magnetite. Plagioclase is labradorite, clinopyroxene is augite, orthopyroxene is bronzite and olivine is chrysolite and hyalosiderite. The Daepodong basalt shows porphyritic texture with matrix of mainly intersetal texture. The Daepodong basalt is plotted into alkali rock series on the TAS diagram. The tectonic setting of the Daepodong basalt represents within plate environment.

• Journal of the Korean earth science society
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• v.39 no.6
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• pp.575-592
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• 2018

This study investigates the formation mechanism of columnar joints at the Sanin Kaigan Geopark in Japan based on its morphology, rock type and igneous structure. Columnar joints distribute to five areas of three prefectures. That is, Kyogasaki, Byobuiwa, Tateiwa and Kyugenkado in Kyotango area of Kyoto prefecture; Genbudo and Kinumaki Shrine in Toyooka City of Hyogo prefecture; Yoroinosode, Takanosushima, Mini-Yoroinosode in Kamicho Town of Hyogo prefecture; Miooshima and Nagasakihana, Shitaara Domon, Kuzakuishi, Moroyose dyke in Shinonsencho Town of Hyogo prefecture; Shirawara dyke in Iwamicho Town in Tottori prefecture. Igneous structures are divided into three types: lava flow, sill and dyke. Lithologies are divided into five types including basalt, andesite, dacite, rhyolite, and quartz porphyry. Lava flow shows colonnade and entablature. However, entablature is not seen in the sills and dykes in the area. Although the polygons of columnar joint vary from tetragon to octagon, hexagon is most frequently found. The width of colonnades ranges from 10cm to 1m, but their size does not correlate with its $SiO_2$ contents. Meanwhile, their size and morphology at single site are comparatively uniform.

• The Journal of the Petrological Society of Korea
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• v.18 no.3
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• pp.195-209
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• 2009

Juwangsan area($107.4km^2$) has been designated as the twelfth National Park in 1976, because it has magnificent aspect and seasonally spectacular landscapes. Juwang valley($9,177.5m^2$) has been designated as Noted Scenery No. 11 in 2003, because it has the same topographical landscape as rock domes, rock cliffs, caves, waterfalls and plunge pools. The most spectacular landscapes are exhibited in the densely welded zone of the Juwangsan Tuff. The rock cliffs generated from vertical joints in the densely welded zone, in which there are the same many rock cliffs as Geupsudae, Haksodae, Sinseondae, Mangwoldae, Giam and Byeongpungbawi, three caves such as Juwanggul, Mujanggul and Yeonhwagul in the cliff. The cliffs and caves are landscapes that were generated from vertical joints in the densely welded zone, and the rock domes and waterfalls are landscapes of erosional vertical joint planes in the zone. The vertical joints are columnar joints formed during cooling of the Juwangsan Tuff. Therefore the topographical features cause the cooling columnar joints that are vertically intersected in the densely welded zone of the Juwangsan Tuff.

• Journal of Welding and Joining
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• v.18 no.1
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• pp.91-96
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• 2000

Characteristics of the weld defect, such as a blowhole and a pit in lap-jointed fillet Co₂ welds of Zn-coated steel sheet were studied in order to make clear the sequence of the blowhole formation during welding. Main conclusions obtained are as follows: 1) Blowhole, wormhole and pit were found in fillet welds, although the optimum welding condition of 200A-23V-100cm/min was applied. 2) Zn was only detected at the solidification boundary at the early stage of the blowhole formation. 3) Most of the blowholes was started to form at lap-joint by the Zn vapor. With increasing of the Zn vapor and its pressure, the blowhole was develope to th bed surface until the completion of weld solidification. 4) The behavior of the blowhole in growth was similar to that of the columnar dendrite during welding.

• Journal of The Geomorphological Association of Korea
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• v.19 no.1
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• pp.83-97
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• 2012

Slopes of Seoseokdea~ Jangbuljae, at Mt. Moodeung, appears repeatedly the cliffs are mostly greater than $70^{\circ}$, and the planations maintain around $5^{\circ}$ in general. They studied the creation of development environments, cryoplanation are mainly facing the southwest. It is assumed that rock falling had been wostly occurred under a periglacial environment through jointing due to repeated freezing and thawing. Planation at the bottom of Columnar joint are described structural benches. Movement precesses of planation matrix are solifluction or jelifluction. The result of age determination of the slopes in Jangbuljae tells that the upper part of Ibseokdae has been remaining exposed to the land surface from 110,000 year ago. The blocks in the bottom part has been exposed to the surface around 10,000 year ago while Jangbuljae has been exposed to the surface about 50,000 year ago. It was assumed that they moved to the current location since being separated from columnar joint after exposure to the surface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.12-21
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• 2022

Directed energy deposition (DED) was adopted as a metal additive manufacturing method to develop a mold for the hot stamping process. The test piece was machined from Heatvar laminate material, and results were obtained through microstructure and defect observations, as well as hardness, tensile strength, and joint strength tests. 1) Spherical pores and irregular-shaped cavities were observed as lamination defects, and columnar dendrites formed in the structure, which tended to become coarse upon heat treatment. 2) The hardness of the heat-treated material (480HV) was slightly lower than that of the non-heat-treated material (500HV). 3) In the tensile test, the maximum tensile stress and strain of the heat-treated material were 1392 MPa and 15%, respectively, which were slightly higher than the values of 1381 MPa and 13%, respectively, for the non-heat-treated material. 4) In the case of the early final fracture in the tensile test, in most cases, pores or irregularly shaped cavities were observed at the fracture surface or near the surface. 5) In the joint strength test, most of the specimens finally fractured in the laminated metal area, and the fracture surface was intragranular. In addition, dimples formed over the entire area on the fracture surface of the fractured specimen after sufficient elongation.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.61-67
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• 2015

The application of SS400 carbon steel and AISI430 ferritic stainless steel joint has been increased in industries because of the advantage of both metals was able to increase the service lifetime of the important structures. Therefore, a fusion welding process that could produce a sound weld and good joint properties should be optimized. This research is aimed to weld a butt joint of SS400 carbon steel and AISI430 ferritic stainless steel using Gas Metal Arc Welding (GMAW) welding process and to study the effects of welding parameters on joint properties. The experimental results were concluded as follows. The optimized welding parameter that produced the tensile strength of 448 MPa was the welding current of 110A, the welding speed of 400 mm/min and the mixed gas of $80%Ar+20%CO_2$. Increase of the welding current affected to increase and decrease the tensile strength of the joint, respectively. Lower welding current produced the incomplete bonding of the metals and indicated the low tensile strength. Microstructure investigation of the welded joint showed a columnar grain in the weld metal and a coarse grain in the heat affected zone (HAZ). The unknown hard precipitated phases were also found at the grain boundaries of the weld metal and HAZ. The hardness profile did not show the difference of the hardness on the joint that was welded by various welding currents but the hardness of the weld metal was higher than that of the other location.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.

• Journal of the Korean earth science society
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• v.42 no.2
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• pp.185-194
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• 2021

A lava dome and sheet lava flow can be observed at the seashore of Aewol, Jeju island. The cylindrical lobes are characterized by a concentric structure consisting of a massive core and radial joints. Columnar joints with different thickness between the upper and lower parts are developed in the sheet lava flow around the rock salt field in Goeomri. The upper part of the columnar joints is uneven in shape, and has a diameter of 120-150 cm. The lower part of the columnar joints is hexagonal and pentagonal in shape, and has a diameter of about 60 cm. The cylindrical lobes can be divided into two groups based on size and shape. One is a megalobe, with a semicircular outline and a maximum diameter of 30 m. The other is a circular lobe with a diameter of less than 10 m. The columns in the radial joints have hexagonal and pentagonal cross sections and gradually increasing diameter, outward from the core, to a size of 80-120 cm at the rim. The concentric structure observed in the cylindrical lavas is attributable to a combination of four factors. The first is a circular crack caused by the decrease of the temperature and density difference between the inside and outside of the cylindrical lava flow. The second is a concentric chisel mark of the radial joints, which formed at the same time as the radial joints. The third is a flow band, which is a trace left in a round passage when lava flows through. The fourth is a vesicular band formed in a cave by gas bubbles escaping from the lava flow.