• Transactions of Materials Processing
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• v.14 no.6 s.78
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• pp.559-564
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• 2005

INCONEL 718, nickel based superalloy, has good formability, high strength, excellent corrosion resistance and mechanical properties at high temperature. Owing to theses attractive properties, it is utilized in applications such as combustion system, turbine engines and nuclear reactors. In such applications, components are typically required to be tolerant of high stress impact loading. This may cause material degradation and lead to catastrophic failure during service operation. Accurate understanding of material's mechanical properties with various strain rates is required in order to guarantee the reliability of structural parts made of INCONEL 718. This paper is concerned with the dynamic material properties of the INCONEL 718 at various strain rates. The dynamic response of the INCONEL 718 at the intermediate strain rate is obtained from the high speed tensile test and at the high strain rate is from the split Hopkinson pressure bar test. The effect of the strain rate on dynamic flow stress, work hardening characteristics, strain rate sensitivity and elongation to the failure is evaluated with the experimental results. Experimental results from both the quasi-static and the high strain rate up to 5000/sec are interpolated in order to construct the Johnson-Cook model as the constitutive relation that should be applied to simulate and design the structural parts made of rNCONEL 718.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.283-288
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• 2021

A tungsten material using a pressure sintering process and a titanium sintering additive was prepared to evaluate the microstructure, and mechanical properties of flexural strength and hardness. In addition, the reliability on each hardness data was evaluated by analyzing the distribution of the hardness of the tungsten material using the Weibull probability distribution. In particular, the optimal manufacturing conditions were analyzed by analyzing the correlation between the sintering temperature and the mechanical properties of the tungsten sintered body. Although the sintering density of the tungsten material was hardly changed up to 1700 ℃, but it was increased at 1800 ℃. The hardness of the tungsten sintered material increased as the sintering temperature increased, and in particular, the tungsten material sintered at 1800 ℃ showed a high hardness value of about 1790 Hv. It showed relatively excellent flexural strength at a sintering temperature of 1800 ℃.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.17 no.2
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• pp.109-118
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• 2021

In the periodic surveillance material test for the spacer component of fuel channel assembly in CANDU, a microstructural characterization analysis is required in addition to the mechanical property evaluation test. In this study, detailed microstructure analysis and simple mechanical property evaluation of archive spacer parts were conducted to indirectly support the surveillance test and assist in the study of spacer material degradation. We investigated the microstructural characteristics of the spacer garter spring coil through comparative analysis with the plate material. The main microstructure characteristics of the garter spring coil X-750 are represented by the fine grain size distribution, the ordering phase distribution developed inside the matrix, the high dislocation density inside the grains, and the arrangement of coarse carbides. In addition, the yield strength of the garter spring coil X-750 was indirectly evaluated to be approximately 1 GPa. We also established an analytical method to elucidate the microstructural evolution of the radioactive spacer garter spring coil X-750 based on Canadian research experiences. Finally, we confirmed the measurement technique for helium bubble formation through TEM examination on the helium implanted X-750 material.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.172-176
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• 2000

Solid solutions of Ti$_{0.5}$Zr$_{0.5}$B$_2$were successfully synthesized and densified simultaneously from elemental reactants by the use of a field-activated, pressure-assisted synthesis method. The method involves the application of an electric current and mechanical pressure across reactant compacts to achieve combustion synthesis. Dense solid solutions with relative densities of up to 99% were produced and characterized by XRD, SEM, and EPMA methods. With a maximum measured temperature of 145$0^{\circ}C$ under a load of 86 MPa for 30 min, the desired dense solid solution wad synthesized.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.37-42
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• 1997

This paper describes result of experiment of parameters affecting the micro hole drilling time, kind of assisting gas and it's pressure. The result reveals that parameter value of 0.08J, 20Hz, dwell time of 300 microseconds can be a good machining condition to make micro hole diameter range of 50-70${\mu}{\textrm}{m}$, Assistant gas such air, O2, Ar, N2 was adapted. Assistant gas of air makes heat affected zone enlarge due to burning of material, also it makes hole irregular and damage because of refusion stick to caused by chemical reaction with Al2O3 ceramic material. O2(99.9%) has good characteristic to get good drilling and smooth surface on pressure of 0.2kgf/$\textrm{cm}^2$, but it is expensive. Ar, N2 makes material burn and crack severely and proved to be an appropriate but, Ar was better than N2.

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.39-44
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• 2018

Dust explosions are occurring in a variety of industries. A dust explosion caused by a specific energy generates huge amount of energy in the ignition and releases decomposition gas. Damages can be increased since this released decomposition gas can cause second and subsequent explosions. In this study, the goal was to obtain practical information on what could affect the explosion by comparing the characteristics of two kinds of dusts with completely different chemical properties. Three kinds of dusts were measured and evaluated for explosion pressure, dust explosion index, explosion limit and minimum ignition energy. It is possible to grasp the characteristics of each dust and use it as useful accident prevention data in the production of raw material powder.

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.8-8
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• 2004

• Journal of the Korean Society of Safety
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• v.13 no.1
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• pp.19-25
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• 1998

In this study, proper injection molding condition has been studied through stress relaxation tests in order to experimentally investigate the effect of the condition on softening of mold product, using specimens produced under the different conditions according to the recommendation of resin manufactures. As a result, softening of the specimens was found to be strongly influenced by material melting temperature. The specimen with higher material melting temperature is found to have lower softening. However, softening of the specimen with lower mold temperature has an decrement, compared with other specimens. In particular, specimen with notch is influenced by mold temperature. The softening increase with higher injection speed and pressure. Finally in order to improve softening, material melting temperature, injection speed and injection pressure were found to be increased with low mold temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.902-907
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• 2003

In this paper, the ITO thin film, which is considered as one of the most currently used material for the high performance transparent conducting films for the PDP cell, was made in a parallel-plate, capacitively coupled DC magnetron sputtering system. Some electrical and optical properties of ITO films were investigated and discussed on the basis of glow discharge characteristics. The optimized thin film fabricating conditions of Ar gas pressure and substrate temperature were derived from the Paschen curve and glow discharge characteristics. The maximum transmittance of 89.61 % in the visible region and optical band gap of 3.89 eV and resistivity of 1.67${\times}$10$\^$-3/ $\Omega$-cm were obtained under the conditions of 300 C of substrate temperature and 10∼15 mtorr of pressure, which corresponds nearly to that of Paschen minimum.

• Ceramist
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• v.22 no.1
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• pp.4-16
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• 2019

Recently, wearable sensors have received considerable attention in a variety of research fields and industries as the importance of wearable healthcare systems, soft robotics and bio-integrated devices increased. However, expensive and complex processes are hindering the commercialization of wearable sensors. Nanoparticle presents some of solutions to these problems as its adjustable for processability and tunable properties. In this paper, the recent development of nanoparticle based pressure and strain sensors was reviewed, and a discussion on their strategies to overcome the conventional limitation and operating principles is presented.