• 한국자동차공학회논문집
• /
• 제2권2호
• /
• pp.95-102
• /
• 1994

Aluminum sheet application to automobile body panels has now become an important objective to meet the requirements of automobile weight reduction. As the Mg content in Al-Mg based alloys increased up to 7.19%, the strength and elongation increased. For instance. Al-7.19Mg alloy had a high strength of 305MPa and a high elongation of 35%. A study was also made to investigate the interrelation between grain size and tensile properties with varying the contents of Mg, Ti and Zr elements and annealing conditions. The yield stress decreased as the grain size increased, which increased the uniform elongation. The strain hardening exponents n increased as the Mg content increased, which depended on the increasing difficulties of the cross slip of dislocation.

• 한국표면공학회지
• /
• 제34권3호
• /
• pp.247-257
• /
• 2001

In an effort to improve the dent resistance of exterior body panels at a reduced steel thickness, the bake hardenable steels added Ti or Nb with tensile strength of 35Kgf/$\textrm{mm}^2$ were investigated. The bake hardenability increased with the annealing temperature and solute carbon content. Bake hardening of 3 to 5Kgf/$\textrm{mm}^2$ was obtained in steels with a controlled solute carbon concentration range from 6 to 10ppm. The galvannealing temperature and time had little influence on the bake hardenability. The Fe-Zn alloying reaction of 35Kgf/$\textrm{mm}^2$ BH steel was remarkably retarded due to a 0.07%P addition. The optimum galvannealing temperatures of 35Kgf/$\textrm{mm}^2$ BH steel were ranged from 520 to 56$0^{\circ}C$ in view of the Fe content and powdering resistance. The cross-section and planar views of the galvannealed coatings to characterize morphology development were discussed.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
• /
• pp.748-752
• /
• 2004

The Hydrogenated amorphous carbon (a-C:H) thin films are deposited to fabricate suppored layer on silicon substrate with a closed field unbalanced magnetron(CFUBM) sputtering system. This study focuses on the characteristic of Diamond like carbon (DLC) films and Pb(Zr,Ti)$O_3$ (PZT) films for membrane structure. The deposition rate and the surface roughness of DLC fims decrease with DC bias voltage. hardness is 26 GPa at -200 V. Interface of DLC/Si and Pt/DLC layers was excellent.

• 대한기계학회논문집A
• /
• 제24권10호
• /
• pp.2420-2427
• /
• 2000

In contacting between surface, there is wear and the generation of wear particles. The particles contained in the lubricating oil carry detailed and important information about the condition monitoring of the machine. Therefore, This paper was undertaken for Ferrography system of wear debris generated from lubricated moving machine surface. The lubricating wear test was performed under different experimental conditions using the Falex wear test of Pin and V-Block type by Ti(C,N) coated. It was shown from the test results that wear particle concentration(WPC) ; wear severity Index(IS) and size\distribution have come out all the higher value by increases sliding friction time. By the Ferrogram a thin leaf wear debris as well as ball and plate type wear particles was observed.

• 한국공작기계학회논문집
• /
• 제17권1호
• /
• pp.16-20
• /
• 2008

This paper presents the construction of micro tool clamping device using a Ni-Ti shape memory alloy(SMA) ring. Clamping force of the device is produced by elastic force of the SMA reverted to its original shape in normal temperature. Phase transformation of the SMA was realized by temperature control using a peltier element. Prototype of the SMA tool clamping device was fabricated and examined its clamping force and clamping/unclamping operation.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2004년도 추계학술대회논문집
• /
• pp.203-206
• /
• 2004

Copper-based bulk amorphous alloy composite was synthesized by using the copper-coated $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ amorphous powder which was obtained by argon gas atomization. The amorphous powder having a super-cooled liquid region of 53 K was coated by crystalline copper by electroless coating. The consolidation was carried out by manufacturing performs and by the subsequent warm extrusion at 743 K. During the compression test at the room temperature, the composite containing a large fraction of crystalline copper displayed a larger plastic strain after yielding. FEM simulation revealed change in fracture modes in the composites depending on the amount of crystalline copper in the composites.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 추계학술대회 논문집
• /
• pp.16-21
• /
• 2002

The high speed machining center(HMC) has been widely applied to manufacture a die and trial product in many machine industry. Because the evaluation fer the HMC is not sufficiently performed and the efficient cutting conditions aren't selected, a great loss has been caused in the cost aspect. In this study, the need of preliminary running time and unstable spindle speed is presented from the analysis of acceleration in idling. The Machinability fur the TiAlN coated flat end mill and STD11( $H_{R}$C60) is evaluated from the trends of tool wear and cutting force according to cutting conditions and slenderness ratio and a low response of tool dynamometer in high speed is proved. The resonance spindle speed is identified through the tool wear and natural frequency test.t.

• 한국초전도ㆍ저온공학회논문지
• /
• 제18권2호
• /
• pp.37-41
• /
• 2016

This paper presents the developed quench analysis code and protection circuit design for a superconducting magnet system of 28GHz electron cyclotron resonance (ECR) ion source. The superconducting magnet is composed of a hexapole magnet and four solenoid magnets located outside of the hexapole one. All magnets are wound with NbTi composite wire and impregnated by epoxy. By using the developed characteristic analysis code, the normal zone resistance, decaying current and temperature rising can be estimated during quench. Also, the stored magnetic energy is successfully consumed from the series resistor of the designed protection circuit. The analytical results are compared with the experimental results to verify the developed quench analysis code and protection circuit.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제11C권2호
• /
• pp.18-22
• /
• 2001

The thin films of high permitivity in ferroelectric materials using a capacitor are applied to DRAMs and FRAMs. (Ba, Sr)TiO$_3$ thin as ferroelectric materials were prepared by the sol-gel method and made by spin-coating on the Pt/Sio$_2$/Si substrate at 4,000 [rpm] for 10 seconds. The structural characteristics of the surface were analyzed by fractal dimension. The thickness of BST ceramics thin films was about 260∼280 [nm]. The property of the leakage current was stable with 10-9∼10-11[A] when the applied voltage was 0∼3[V]. BST thin films ha low leakage current properties when fractal dimension was low and a coating area was high.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 춘계학술대회 논문집
• /
• pp.344-349
• /
• 2001

This paper was to investigate of a adhesiveness for the plasma sprayed coating materials did salt spray by acoustic emission method in tensile loadings. The powders used for the coating were nickel aluminum composite powder Ni-4,5wt.%Al and titanium dioxide powder Ti02. These powders were coated on a carbon steel S45C by plasma spray method. The salt solution was a 5% NaCl and the salt spray times were 2, 5 and 10 hours respectively. The salt solution penetrated into the surface of the substrate through pore of the coating layer built in the process of plasma spay. Corrosion productions formed on the surface of substrate. The adhesiveness between the substrate and the coating layer is weaken by corrosion and the exfoliation initiated chiefly at the corrosion surface of the substrate. The AE events and energy of the corroded coating specimens decreased as the salt spray times increased.