• 연구논문집
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• s.28
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• pp.193-207
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• 1998

Fully dense THCN) based carbonitride ceramics were fabricated by pressureless sintering. During sintering, solid solutions were formed from the ceramic ingredients. The ceramics exhibited microvickers hardness of 1560-2050kgf/mm2, fracture toughness of 3.0-5.4 MPa $m^(1/2)$, and three point flexural strength of 645-1072 MPa. Some of the ceramics were shaped in a cutting tool, and the cutting performance was evaluated. In case of cutting SCM440 alloy steel, the ceramics showed better performance than the commercially available alumina-titanium carbide ceramic cutting tool. Considering the excellent productivity of pressureless sintering compared with other densification methods and their cutting performance, this new class of ceramics are very promising for wear resistant applications.

• Corrosion Science and Technology
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• v.15 no.5
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• pp.203-208
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• 2016

DC potential drop technique was employed during the slow strain rate tests to study the hot salt stress corrosion crack (HSSCC) initiation at 300 and $400^{\circ}C$. Threshold stresses for HSSCC initiation were found to about 88 % of the yield strength at both temperatures, but the time from crack initiation to final failure (${\Delta}t_{scc}$) decreased significantly with temperature, which reflects larger tendency for brittle fracture and secondary cracking. The brittle fracture features consisted of transgranular cracking through the primary ${\alpha}$ grain and discontinuous faceted cracking through the transformed ${\beta}$ grains.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.759-760
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• 2006

Ti-6Al-4V has low specific gravity, high corrosion resistance and superior mechanical properties but it is very difficult to control oxygen content in MIM process. It is necessary to use powders with coarse particle size to decrease oxygen content of powders, so feedstocks with poor fluidity and sintered bodies with lower density are obtained in such cases. Fine titanium hydride-dehydride powders were blended with atomized powders to accomplish higher fluidity and sintered density. Sintered bodies had higher sintered density and mechanical properties equivalent to those of wrought materials by controlling oxygen content less than 0.35mass%.

• Journal of the Ergonomics Society of Korea
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• v.16 no.2
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• pp.83-100
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• 1997

The Human Sensory Feedback Laboratory, park of the Armstrong Laboratory at Wright-Patterson Air Force Base, Ohio, is involved in the development and evaluation of systems that provide sensory feedback to the human operator in telerobotic and virtual environment applications. Specific projects underway in the laboratory are primarily concerned with the information provided by force and vibrotactile feedback to the operator in dextrous manipulation tasks. Four specific research projects are described in the present report. These include : 1) experiments evaluating a 30-element fingertip display, which employs a titanium-nickel shape memory alloy actuator design to provide vibrotactile feedback about object shape and surface texture ; 2) of a fingertip force-feedback display for 3-dimensional information about object shape and suface texture ; 3) use of a force- feedback joystic to provide "force tunnel" information in pilot pursuit tracking tasks ; and 4) evaluations of a 7 degree-of-freedom exoskeleton used to control a robotic arm. Both basic and applied research questions are discussed.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.3 s.22
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• pp.51-55
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• 2005

In this paper, a near net shape technology using superplasticity and diffusion bonding characteristics was presented for application to various components of aircraft and missiles. Due to these special characteristics of some aerospace alloys, it is possible to produce complex components to shape very near final dimension with enhanced design freedom, reduced material usage, and overall saving of weight and cost. The high pressure vessel for a space launcher was fabricated with Ti-6Al-4V alloy by superplastic forming and diffusion bonding process and the failure characteristics are compared with conventionally fabricated vessel spin formed and TIG welded. The structural integrity of the superplastic forming and diffusion bonding process was successfully demonstrated.

• Journal of Surface Science and Engineering
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• v.37 no.1
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• pp.58-63
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• 2004

The oxidation behavior of Ti-Nb alloys was studied in dry atmosphere. After vacuum arc melting and hot rolling treatment, Ti-Nb alloys were oxidized at $450^{\circ}C$∼$750^{\circ}C$. The oxidation behaviors between matrix and oxide scale were analyzed by SEM, XPS and XRD. Ti-Nb alloys had higher oxidation resistance than pure Ti at $750^{\circ}C$. XPS analysis of oxide film revealed that $TiO_2$ oxide was formed on the top of surface. The weight gains during the oxidation increase rapidly at temperature above $600^{\circ}C$ which obey the parabolic law.

• Journal of Surface Science and Engineering
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• v.29 no.5
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• pp.424-429
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• 1996

Thin films of Ti-Ni alloy were formed by sputtering under various Ar gas pressures and r. f. powers to investigate the optimum sputtering conditions and to demonstrate their shape memory effect. The composition and structure of the films were examined by electron micro-probe analysis and scanning electron microscope. These films were annealed in order to crystallize them. The mechanical property of the annealed films was evaluated by a conventional bending test. The transformation tmeperatures were determined by differential scanning calorimetry. The shape memory behaviour was examined quantiatatively by changing in sample temperature under various constant loads. It was found that the Ar gas pressure had a critical effect on the mechanical property of the thin film,s although the r.f. power also affected it. The films formed at a high Ar gas pressure were too brittle to be bent successfully. However, the films formed at a low Ar gas pressur could be bent and their shape memory behavior was found to be comparable with that of bulk Ti-Ni alloys.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1207-1214
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• 2011

Design of 500W class UMGT(Ultra Micro Gas Turbine) for power generation is conducted. Basic design parameters are obtained by cycle analysis. Off-design performances are predicted by 1D aerodynamic design and 1D performance analysis of compressor and turbine. 3D impellers are designed and 3D performance analysis is carried out to predict the performance characteristics of UMGT. 1D and 3D performance analysis show similar results. Structure analysis is conducted to select materials. Titanium Alloy is proposed for structural stability.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.298-302
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• 2011

티타늄 용접부는 수소취성과 잔류응력에 대한 영향을 최소화 하기 위해 용접 후 잔류응력 제거 열처리 작업을 수행하고 있다. 하지만, 현재 항공 분야에 널리 사용하고 있는 규격에 따라 열처리 온도가 다양하게 설정되어 있어 현장에 적용하기에는 어려움이 있다. 이에 규격 별로 대표하고 있는 열처리 조건을 선정하여 열처리 조건에 따른 용접부에 대한 잔류응력, 잔류수소량을 확인하였고, 용접부에 대한 강도와 충격 인성을 확인하였다.

• Journal of Digestive Cancer Research
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• v.10 no.2
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• pp.92-98
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• 2022

Self-expandable metal stent (SEMS) is effective for biliary drainage, especially in pancreaticobiliary cancer. The mechanical properties, material, and design of SEMS are important in preventing recurrent biliary obstruction and complication. Radial and chronic expansion forces play roles in preventing stent migration and collapse. Complications, such as stent impaction, cholecystitis, and pancreatitis, were related to the axial force. The nickel-titanium alloy shows more flexibility, conformability, and optimal axial force compared to previously used stainless steel. Additionally, the stent structure affected the mechanical properties of SEMS. Therefore, understanding the mechanical properties, material, and design of SEMS will provide the best outcome for biliary drainage, as well as better SEMS development.