• Tribology and Lubricants
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• v.39 no.5
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• pp.190-196
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• 2023

Anti-adhesion coatings are very important in the processing of adhesive materials such as optical clear adhesive (OCA) films. Choosing the appropriate release coating material for dies and tools can be quite challenging. Hydrophobic surface treatment is usually performed, and its performance is often estimated by the static water contact angle (CA). However, the relationship between the release performance and the CA is not well understood. In this study, the water CAs of surfaces coated with anti-adhesion materials and the peel strengths of the acrylic-based adhesive films are evaluated. STC5 and SUS304 are selected as the base materials. Base materials with different surface roughnesses are produced by hairline finishing, mirror-polishing, and end milling. Four fluoropolymer compounds, including a self-assembled monolayer, are selected to make the base surface hydrophobic. Static, advancing, and receding CAs are mostly increased due to the coating, but the CA hysteresis is found to increase or decrease depending on the coating material. The peel strengths all decreased after coating and are largely dependent on the coating material, with significantly lower values observed for fluorosilane and perfluoropolyether silane coatings. The peel strength is observed to correlate better with the static CA and advancing CA than with the receding CA or hysteresis. However, it is not possible to accurately predict the anti-adhesion performance based on water CA alone, as the peel strengths are not fully proportional to the CAs.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.121-126
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• 2005

Micro wires manufactured by the straightening process are used in the BT(Bio-Technology), IT(Information-Technology), NT(Nano-Technology). We have developed a novel wire straightener which uses the direct heating method(DHM) for straightening the micro wire and shearing device for burr-less cutting. In this study, we confirm the tendency of micro wire after the shearing process. It is impossible to remove the burr in the shearing process. However, the embodiment of minimum burr size after the shearing process is the best in-process method. In order to minimize the burr size, we have accomplished the various experiment condition such as the U-groove, the effect of the counter punch, the shear angle, clearance.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.323-328
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• 2001

Supersonic coaxial, axisymmetric, jets issuing from various kinds of dual coaxial nozzles were experimentally investigated. Four different kinds of coaxial, dual nozzles were employed to characterize the major features of the supersonic, coaxial, dual jets. Two convergent-divergent supersonic nozzles with an impinging angle in the jet axis of the annular jets were designed to have the Mach number 2.0 and used to compare the coaxial jet flows with those discharging from two sonic nozzles. The primary pressure ratio was changed in the range from 4.0 to 10.0 and the assistant jet ratio from 1.0 to 4.0. The results obtained show that the assistant jets from the annular nozzle affect the coaxial jet flows and an increase of both the primary jet pressure ratio and assistant jet pressure ratio produces longer supersonic length of the dual, coaxial jet.

• Journal of Welding and Joining
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• v.6 no.3
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• pp.37-42
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• 1988

The Hole Drilling Method(HDM) is widely used to measure residual stresses in the welded structures. The purpose of this study is to evaluate the accuracy fo measuring residual stresses when drilling the hole by Air-abrasive Jet machine(AJM). Simulated residual stresses wre introduced by applying known stresses to steel bars. These known streses were then compared with measured stresses relaxed from hole drilling. the obtained results are summarized as follows; 1) It was possible to obtain well defined holes with the nozzle designed for this study. 2) If the hole shape is not cylindrical, critical may occur. 3) In the uniaxial strain field, the measurement error of the maximum principal stress was within .+-.10 percent. The orientation angle of the maximum principal stress was within 8.deg. from the given directioin. 4) meausrements were made varying hole depths. Little or no change of stresses occurs since holse were drilled more than the depth of the 0.6 times diameter. 5) The air-abrasive jet machining for drilling holse does not cause appreciable apparent stresses which si critical to measure residual stresses.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.211-219
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• 2000

This paper simulated surface grinding process with statistically simulated grinding wheel topography, considering ridge formation phenomenon when grain scratch workpiece. Wheel grain is modeled as hybrid sphere and cone. Grinding wheel characteristic was evaluated with stylus by expanding the scanning region of the profilometer from a straight line to a plane. Each grain's diameter and semi-angle are assumed as normal distribution, each grain's protrusion height from wheel plane is assumed gamma distribution. So grinding wheel is simulated with grain's position randomly distributed without overlapping. Ground surface is 3-dimensionally simulated considering ridge formation of workpiece by each grain's cutting, and then surface profile and surface roughness parameters are compared with real ground workpiece.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.51-60
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• 2006

At new constructing national road, a cutting slope was surveyed and gotten face mapping for three months. The slope is composed of gray phyllite and coaly slate which is the Chang-ri Formation, Okcheon system. The slope angle is 40 degree and the direction is NNE. The attitude of schistosity is $260^{\circ}/45^{\circ}$. So the slope direction is nearly parallel to the schistosity. This is the reason that the slope is very unstable. On the other hand, the very unstable slope is caused by the direction of the schistosity and the slope. First month the coaly slate was slided through the schistosity plane about 10cm. However, three months late the displacement was 2m maximum.

• Journal of the Korean Ceramic Society
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• v.19 no.1
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• pp.24-34
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• 1982

The effect of the several variables on wetting of AISIB1113 steel by molten glass was studied by Sessible-drop method. Experimental variables were temperature, firing atmospheres, Fe2O3 addition to the sealing glass and steel surface conditions. The degree of wetting in terms of contact angles between molten glass and metal tested at different test conditions was analyzed by using Young's equation. The results showed that contact angles in H2 atmosphere in the glass metal systems were high but in N2 atmosphere, were small for studied glass metal systems. Especially, when the glass drop was in contact with oxidized steel in N2 atmosphere, The best adherence with contact angle of approximately 9°was obtained. In the case of Fe2O3 addition in glass contact angles subtantially increased due to the increase of surface tension of glass. Wetting phenomena were also discussed under the basis of these experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.8
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• pp.185-193
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• 2003

The modular self-wiping co-rotating twin screw extruder (SWCOR) has become the most important of twin screw machines. Screw design is one of the most important factors in determining performance of screw extruder. The screw flight and screw channel geometry of SWCOR is determined by the screw diameter, centerline distance, helix angle, and flights number. The maximum allowable throughput rate on a twin screw extruder is determined by a combination of free volume and available specific torque. In this paper we designed geometrical parameters of extruder screw and presented optimal specific torque value in K=1.55, and then developed screw design program for the screw cutting by the use of JAVA API in the twin screw extruder.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.29-32
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• 2008

Dental high-speed air turbine handpieces have been used as a dental cutting tool in clinical dentistry for over 50 years, yet little study has been reported on their flow and performance analysis. Therefore it is necessary to investigate turbine for the performance improvements of an air turbine handpiece. This paper presents pressure on turbine rotor and flow analysis in air turbine handpiece using CFD (computational fluid dynamics). Characteristics on each flow and pressure for four various reflection angles of turbine rotor are presented, and then performance change is analyzed about air turbine handpieces by CFD results.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.122-127
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• 2004

The purpose of this study is to introduce the standard of the durability and evaluation method for paper shredder. The major evaluation criteria include shredding capability, shredding blade (or cutter) hardness and edge roughness, and durability. Due to the difficulties in assessing the durability directly, performance deterioration of the shredder was assessed by measuring the torque variation along with the variation in shredded chip size and load, thereby proposing the indirect method of assessing the paper shredder durability.