• Design & Manufacturing
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• v.16 no.4
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• pp.17-23
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• 2022

Recently, several studies are being conducted to achieve a curvature of 180° or more for the edge of the display glass. The thermocompression molding process is applied to the manufacture of curved glass, and high hardness G5 graphite is used as the mold material to withstand the impact applied to the mold. G5 graphite has high hardness and strong brittleness, which makes tool wear and surface damage easy during machining. Therefore, the demand for diamond-coated tools with good mechanical properties is increasing in the G5 machining field. In this study, the optimal cutting conditions and machinability of a nanodiamond (NCD) coated ball end mill being developed by a tool manufacturer were analyzed and evaluated. For this purpose, the same test was performed on the microdiamond (MCD) coated ball end mill and compared together. In summary, the machinability of MCD and NCD coated tools showed better cutting performance at a cutting speed of 282 m/min, a feed rate of 1,400 mm/min, and a radial depth of cut of 0.08 to 0.1 mm.

• Korean Journal of Metals and Materials
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• v.47 no.9
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• pp.580-585
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• 2009

The effects of shear speed and tip height on the high speed shear test of Sn-3.0wt.%Ag-0.5wt.%Cu ball joints were investigated. Solder balls of $450{\mu}m$ in diameter were reflowed at $245^{\circ}C$ on a FR4 PCB (Printed Circuit Board) in order to obtain a sample for the high-speed shear test. The UBM was comprised of Cu/Ni/Au, and the shear speed and tip height varied from 0.5 to 3.0 m/s, and from 10 to $135{\mu}m$, respectively. According to the experimental results, faster shear speed enhanced the shear strength of the solder joints, regardless of the tip height. The fraction of ductile (solder) fracture decreased when the shearing speed was raised from 0.5 to 3.0 m/s. With an increasing tip height from 10 to 50 and $135{\mu}m$, the fracture mode changed from pad lift to mixed (ductile and brittle) and ductile fracture, respectively, while the shearing energy also increased in the same order. The shear energy had a proportional relationship with the fraction of the solder fracture.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.335-342
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• 2003

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to from the oxide layer and the characteristics of the oxide layer formation are investigated. AISI 52100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4 ${\mu}{\textrm}{m}$ in coating thickness. AISI 1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.109-116
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to form the oxide layer and the characteristics of the oxide layer formation are investigated. AIS152100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4um in coating thickness. AISI1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in ambient for forming oxide layer on the contact parts and in nitride environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

• Korean Journal of Materials Research
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• v.21 no.6
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• pp.299-302
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• 2011

[ $WO_3$ ]powders were ball-milled with an alumina ball for 0-72 hours. $In_2O_3$ doped $WO_3$ was prepared by soaking ball-milled $WO_3$ in an $InCl_3$ solution. The mixed powder was annealed at $700^{\circ}C$ for 30 min in an air atmosphere. A paste for screen-printing the thick film was prepared by mixing the $WO_3$:In2O3 powders with ${\alpha}$-terpinol and glycerol. $In_2O_3$ doped $WO_3$ thick films were fabricated into a gas sensor by a screen-printing method on alumina substrates. The structural properties of the $WO_3$:$InO_3$ thick films were a monoclinic phase with a (002) dominant orientation. The particle size of the $WO_3$:$InO_3$ decreased with the ball-milling time. The sensing characteristics of the $In_2O_3$ doped $WO_3$ were investigated by measuring the electrical resistance of each sensor in the test-box. The highest sensitivity to 5 ppm $CH_4$ gas and 5 ppm $CH_3CH_2CH_3$ gas was observed in the ball-milled $WO_3$:$InO_3$ gas sensors at 48 hours. The response time of $WO_3$:$In_2O_3$ gas sensors was 7 seconds and recovery time was 9 seconds for the methane gas.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.65-70
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• 2008

The mechanical shear strength of BGA(Ball Grid Array) solder joints under high impact loading was investigated. The Sn-37Pb solder balls with a diameter of $500{\mu}m$ were placed on the pads of FR-4 substrates with ENIG(Electroless Nickel Immersion Gold) surface treatment and reflowed. For the High Temperature Storage(HTS) test, the samples were aged a constant testing temperature of $120^{\circ}C$ for up to 250h. After the HTS test, high speed shear tests with various shear speed of 0.01, 0.1, 1, 3 m/s were conducted. $Ni_3Sn_4$ intermetallic compound(IMC) layer was observed at the solder/Ni-P interface and thickness of IMC was increased with aging process. The shear strength increased with increasing shear speed. The fracture surfaces of solder joints showed various fracture modes dependent on shear speed and aging time. Fracture mode was changed from ductile fracture to brittle fracture with increasing shear speed.

• Journal of Life Science
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• v.15 no.4 s.71
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• pp.584-589
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• 2005

To investigate factors affecting the removal of phosphorus from the practical wastewater in the F-STEP PROCESS using a loess ball and Chromobacterium WS 2-14, first, the loess ball size and calcining temperature, initial pH, initial phosphorus concentration, working temperature, and aeration were studied. A $2\~4mm$ of loess ball made at $960^{\circ}C$ of calcining temperature was the most suitable one for the removal of phosphorus. When the initial pH was increased from 3.0 to 6.0, the removal efficiency of phosphorus was increased. Especially, at 6.0 of initial pH, the maximum removal efficiency of phosphorus was $88.7\%$. The maximum removal efficiency of phosphorous was gained, 1.8mg/h when the initial concentration of phosphorous was 5.0mg/1. When the operating temperature was $30^{\circ}C$, the maximum removal efficiency of phosphorus was obtained. In the case of aeration, when it was increased from 0.5 to 5.0L/min, the removal efficiency of phosphorus was increased. On the other hand, above 7.0 L/min, the removal efficiency of phosphorus did not increased. Using the optimum operation conditions, pilot tests for the effective removal efficiency of phosphorus were carried out for 65 days. The average removal efficiency of phosphorus was $92.0\%$. The average removal efficiency of COD, BOD, and SS were 77.1, 74.2, and $86.4\%$, respectively. from the results, it can be concluded that F-STEP PROCESS using loess ball might be useful process for phosphorus removal.

• Tribology and Lubricants
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• v.25 no.4
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• pp.217-224
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• 2009

In this study, friction tests were carried out in order to investigate the friction behavior of textured surface in unlubricated state using ball-on-disk type apparatus. Test specimens were SUJ2 bearing steel ball and SM45C steel disk. Square arrays of circular micro-dimples were created on the surface of disk specimen by Nd:YAG Laser. Friction tests were performed for the disk specimen with various micro-dimple parameters and was also conducted for the variation of normal loads and relative velocities. The results showed that fiction coefficient of textured surface was lower than that of non-textured surface and the deeper depth of micro-dimple was, the lower friction coefficient obtained at the same diameter of micro-dimple in unlubricated state. Area density of micro-dimple had an effect on the friction coefficient. It was also found that friction coefficient generally decreased with the increase of normal load and relative velocity.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.243-252
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• 2019

Recently, as the utilization of underground space increases, the demand for underground excavation increases. In this study, the concrete mixture with a new material was used to develop and evaluate the stability of the CS-H wall that can greatly minimize the problems of existing wall and minimize the impact of ground depression and surrounding ground that may occur in the future for excavation of over 30 m deep in urban areas. The fiber reinforcement formulation of steel fibers, synthetic fibers, and glass fibers, along with fine aggregate parts of PS-ball and ferronickel, were mixed. The Mixture ratios were determined by conducting slump test compresive strength test, modulus of elastic test, flexural strength test, splitting tensile strength test and conductivity test. As a result of the test, the steel fiber mixture showed very good results compared to other reference values in all items, and it is considered to be the most suitable for the CS-H wall to be developed.

• Horticultural Science & Technology
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• v.33 no.5
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• pp.789-795
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• 2015

The new garden chrysanthemum (Dendranthema grandiflorum Ramat.) cultivar 'Nuri Ball' was developed at Yesan Chrysanthemum Experiment Station of Chungcheongnam-do Agricultural Research and Extension Services in 2011. 'Nuri Ball' was bred through a cross between the '02-145-01' line as the female parent with yellow flower color and '02-04-32' as the male plant with white flower color in 2004. Three years of adaptation trials were conducted from 2006 to 2009 under natural conditions. This study compared the external shape type with that of 'White Miri' and conducted ploidy and RAPD (Random amplified polymorphic DNA) marker analyses. These tests showed that 'Nuri Ball' cultivar has its own characteristics compared with the control 'White Miri'. 'Nuri Ball' was a shrub type variety with semi-double flowers of 4.0 cm in width with white petals. It could produce 1025.2 flowers per plant in autumn. Compared with the control 'White Miri', 'Nuri Ball' was similar in terms of shape and color of flowers, but was different in flower size and number. The natural flowering time of 'Nuri Ball' was late September. It had very vigorous growth and an early budding plant. 'Nuri Ball' was demonstrated to be a new cultivar based on ploidy test and RAPD analysis. 'Nuri Ball' is intended for use as a bed chrysanthemum and expected to contribute to farm incomes in landscaping.