• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.216-219
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• 1996

Polytetrafluoroethylene is very suitable for insulation materials because of it's high thermal and chemical stability, high electrical resistance and low loss factor. But almost all kinds of pure fluoroplastic cannot endure long time in the high temperature arc environment breaking high voltage and current In this study, inorganic materials such as BN, TiO$_2$ and Al$_2$O$_3$ were filled in the polytetrafluoroethylene to improve arc resistance. The electrical properties, arc resistant properties and light reflectance of the composites were investigated.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.58-65
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• 1999

The effect of specimen thickness on fatigue crack growth rate was studied. The objective of the present study is to investigate the effect of specimen thickness on the fatigue crack growth behavior at various stress intensity factor ranges and also the variation of material restance to fatigue crack growth. The fatigue crack growth resistance was treated as a spatial stochastic process, which varies randomly on the crack path, Compact tension specimens with a LT orientation for structural steel were used. All testing was done at a constant stress intensity level. The experimental data were analyzed for the size effect to determine the Weibull distributions of the material resistance.

• Journal of the Korean Solar Energy Society
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• v.33 no.3
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• pp.51-57
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• 2013

Metal curtain wall systems are widely used in high-rise commercial and residential buildings. While aluminum is the most frequent used frame material, steel framing is also reemerging as a high-performance material in glazed curtain walls due to less thermal conductivity and design flexibility. The purpose of this study is to evaluate thermal performance of a steel frame curtain wall system by comparing with a aluminum frame curtain wall system. The thermal transmittance was measured according to KS 2278, and condensation resistance was calculated by the test results according to KS F 2295. The steel framing test specimen showed lower thermal transmittance and temperature descending factor compared to the aluminum framing test specimen.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.573-576
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• 2000

The physical, electrical and piezoresitive characteristics of CrN(chromium nitride) thin-films on silicon substrates have been investigated for use as strain gauges. The thin-film depositions have been carried out by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(5∼25 %)Na$_2$). The deposited CrN thin-films with thickness of 3577${\AA}$ and annealing conditions(300$^{\circ}C$, 48 hr) in Ar-10 % N$_2$deposition atmosphere have been selected as the ideal piezoresistive material for the strain gauges. Under optimum conditions, the CrN thin-films for the strain gauges is obtained a high electrical resistivity, $\rho$=1147.65 ${\mu}$$\Omega$cm, a low temperature coefficient of resistance, TCR=-186 ppm/$^{\circ}C$ and a high temporal stability with a good longitudinal gauge factor, GF=11.17.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.200-206
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• 2006

An electric power efficiency of electrodeless fluorescent lamp depens on a big relative property of gas, gas pressure, lamp formation, ingredients of magnetic substance and shape and action frequency etc. in lamp. We used magnetic substance that opens self-examination material of electrodeless fluorescent lamp antenna. We used Mn-Zn type as the Ferrite. We have examined resistance, impedance and Q-factor's frequency characteristic by ferrite. Coil turns were changed from 13 to 15 turns to recognize brightness change of lamp by winding number. Optical equipment (LS-100) was used to measure brightness. We could know Q-factor's difference according to material is important part of antenna design. When an electrodeless fluorescent lamp was made using T company's PE22, it showed the highest brightness. As number of winding is increased the brightness increased, and starting characteristic became good.

• Journal of the Korean Society of Safety
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• v.30 no.1
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• pp.66-71
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• 2015

Safety, resilience and comfort of pedestrian were assessed by the British Pendulum Test and SB/GB factor test at 8 kinds of sidewalk pavement. Sidewalk paving materials were normal concrete, porous concrete, concrete block, soil concrete, asphalt, rubber chip/resin mixture, wood chip/resin mixture and floor tile. In addition, a survey was conducted to investigate the perception of pedestrians on the sidewalk paving material. As a result, while the skid resistance value was measured in the most 60BPN above, the floor tile showed a low value of about 30BPN. The ratios of SB factor to GB factor of the elastic pavements(rubber/resin mixture and wood chip/resin mixture) appeared to be relatively large when compared with those of the conventional sidewalks. The survey showed that respondents perceived as more safe and comfortable elastic pavements compared to conventional pavements. Approximately 50% of respondents answered that hardened soil pavement was the most environmentally friendly.

• Journal of Welding and Joining
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• v.20 no.2
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• pp.116-124
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• 2002

The fatigue life is predicted on tensile-shear spot weldment made from Al-Mg alloy sheet with thickness of 0.8mm using Mitchell's method and uniform material law by $B{\ddot{a}}umel$ and Seeger based on local strain approach. The fatigue properties of critical HAZ region are estimated from the tensile property using simple hardness method. To predict the fatigue life of spot weldment, the local stresses and strains at the potential critical region are estimated by Neuber's rule. The predicted fatigue life based on uniform material law using HAZ's material properties provides good results within a factor of 3, conservatively.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.1
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• pp.62-70
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• 2007

The development of new materials that are light-weight, yet high in strength has become vital to the machinery, aircraft and auto industries. However, there are a lot of problems with developing such materials that require expensive tools, and a great deal of time and effort. Therefore, the improvement of fatigue strength and fatigue life are mainly focused on by adopting residual stress. The fatigue crack growth rate of the Shot-peened material was lower than that of the Un-peened material. And in stage I, threshold stress intensity factor of the shot-peen processed material is high in critical parts unlike the Un-peened material. Also, fatigue crack growth exponent and number of cycle of the Shot-peened material was higher than that of the Un-peened material. That is concluded from effect of da/dN. And Fatigue life shows more improvement in the Shot-peened material than in the Un-peened material. And compressive residual stress of surface on the Shot-peen processed operate resistance force of fatigue crack propagation.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.196-202
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• 2004

The development of new materials with light weight and high strength has become vital to the machinery, aircraft and auto industries. However, there are a lot of problems with developing such materials that require expensive tools, and a great deal of time and effort. Therefore, the improvement of fatigue strength and fatigue life are mainly focused on adopting residual stress(in this thesis). The compressive residual stress was imposed on the surface according to each shot velocity(57, 70, 83, 96 m/sec) based on Shot-peening, which is the method of improving fatigue life and strength. By using the methods mentioned above, the following conclusions have been drawn. 1. The fatigue crack growth rate(da/dN) of the Shot-peened material was lower than that of the Un-peened material. And in stage I, ΔKth, the threshold stress intensity factor, of the shot-peen processed material is high in critical parts unlike the Un-peened material. Also m, fatigue crack growth exponent and number of cycle of the Shot-peened material was higher than that of the Un-peened material. That is concluded from effect of da/dN. 2. Fatigue life shows more improvement in the Shot-peened material than in the Un-peened material. And compressive residual stress of surface on the Shot-peen processed operate resistance force of fatigue crack propagation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.200-203
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• 2003

A study on the arc resistance and light reflectance of PTFE (polytetrafluoroethylene) nozzle for circuit breaker is presented. PTFE has been used widely as a material for circuit breaker nozzle. PTFE has excellent electrical resistivity, high melt viscosity, chemical inertness, heat resistance and low loss factor. PTFE melts at $327\;^{\circ}C$ but the viscosity is very high above the melting point. In the arcing environment in a circuit breaker, the fraction of the power is emitted out of the arc and reaches the nozzle wall by radiation, causing ablation at the surface and in the depth of the wall. Some fraction of the radiation power emitted out of the arc directly break up the chemical bonds at the surface while some fraction of the radiation power penetrates into the wall, heats up the material to evaporation temperature and causes damages deeper inside the volume of the nozzle. In this paper, some fillers that have endurance in the high temperature arc environment were added into PTFE. Adding some fillers into PTFE was expected to be efficient in improving the endurability against radiation. The light reflectance and arc resistance of PTFE composites were investigated.