• Transactions of Materials Processing
• /
• v.25 no.1
• /
• pp.43-48
• /
• 2016

H-beams are generally produced by hot rolling composed of a Break Down Mill (BDM) and a Finishing Mill (FM). The goal of the current study was to develop BDM rolling of H300ｘ300 beams from blooms slit from slabs. In order to manufacture H300ｘ300 beams, the caliber design and the pass schedule of BDM rolling were proposed for a bloom instead of a beam blank. The proposed BDM caliber design and pass schedule were tested using FE-simulation and pilot tests. For the major shape dimensions, such as flange width, web height, web thickness, as well as BDM rolling loads, a comparative analysis between the FE-simulation and the pilot rolling tests was conducted. The results of FEM analysis and pilot rolling tests showed good consistency. Moreover, BDM rolling loads were predicted to be in the range of allowable rolling loads. It was concluded that the designed BDM rolling is suitable for implementation within current manufacturing capacity.

• Nuclear Engineering and Technology
• /
• v.43 no.5
• /
• pp.421-428
• /
• 2011

The out-of-pile mechanical performance and microstructure of recrystallized Zr-1.5 Nb-S alloy was investigated. The strength of the recrystallized Zr-1.5Nb-O-S alloys was observed to increase with the addition of sulfur over a wide temperature range, from room temperature up to $300^{\circ}C$. A yield drop and stress serrations due to dynamic strain were observed at room temperature and $300^{\circ}C$. Wavy and curved dislocations and loosely knit tangles were observed after strained to 0.07 at room temperature, suggesting that cross slip is easier. At $300^{\circ}C$, however, dislocations were observed to be straight and aligned along the slip plane, suggesting that cross slip is rather difficult. At $300^{\circ}C$, oxygen atoms are likely to exert a drag force on moving dislocations, intensifying the dynamic strain aging effect. Oxygen atoms segregated at partial dislocations of a screw dislocation with the edge component may hinder the cross slip, resulting in the rather straight dislocations distributed on the major slip planes. Recrystallized Zr-Nb-S alloys exhibited ductile fracture surfaces, supporting the beneficial effect of sulfur in zirconium alloys. Oxidation resistance in air was also found to be improved with the addition of sulfur in Zr-1.5 Nb-O alloys.

• Journal of the Korean Society for Railway
• /
• v.8 no.3
• /
• pp.222-227
• /
• 2005

This study investigates the change of the temperature and mechanical properties of the braking disk for the railway vehicle. The average temperature is measured about $100^{\circ}C$ and the maximum temperature is measured over $200^{\circ}C$ by non-contact sensor from Seoul to Chun-an. As a result of measuring, we determine the temperature of test(tensile and J-integral) at $20^{\circ}C,\;100^{\circ}C,\;200^{\circ}C$ and $300^{\circ}C$. In the test, the material values are decreased by the increasing of the temperature. But ratio of decreasing is the largest at $200^{\circ}C$, the tensile test value is decreased about $10\%$ and the J-integral test value is decreased $30\%$. The mechanical properties of this material are mostly changed at $200^{\circ}C$.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.298-300
• /
• 1998

The superconducting magnetic energy storage (SMES) system which has characteristics of high efficiency and rapid response is a way to maximize a utility's generation and transmission capacity. But SMES is required for much capital and operating cost. Therefore, It is important to determine the optimal size of SMES for constructing and operating. In this paper, we proposed a method of determinating an optimal size of a large scale of SMES for energy storage and a small scale of SMES for stabilizing power system.

• Journal of Powder Materials
• /
• v.20 no.5
• /
• pp.376-381
• /
• 2013

Spherical Ti-6Al-4V powders in the size range of 250 and 300 ${\mu}m$ were uniformly doped with nano-sized hydroxyapatite (HAp) powders by Spex milling process. A single pulse of 0.75-2.0 kJ/0.7 g of the Ti-6Al-4V powders doped with HAp from 300 mF capacitor was applied to produce fully porous and porous-surfaced Ti-6Al-4V implant compact by electro-discharge-sintering (EDS). The solid core was automatically formed in the center of the compact after discharge and porous layer consisted of particles connected in three dimensions by necks. The solid core increased with an increase in input energy. The compressive yield strength was in a range of 41 to 215 MPa and significantly depended on input energy. X-ray photoelectron spectroscopy and energy dispersive x-ray spectrometer were used to investigate the surface characteristics of the Ti-6Al-4V compact. Ti and O were the main constituents, with smaller amount of Ca and P. It was thus concluded that the porous-surfaced Ti-6Al-4V implant compacts doped with HAp can be efficiently produced by manipulating the milling and electro-discharge-sintering processes.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.3
• /
• pp.583-597
• /
• 1998

The purpose of this study was to evaluate temperature change occurred in enamel, dentin and pulp due to the heat from cavity prepration with laser. We made three models had different cavity depth: cavity depth of model A was 3.52mm, model B was 2.32mm, model C was 1.16mm. We irradiated cavity base with thermal capacity of $30J,100J,300J/cm^2s$ during few seconds and studied the change of temperature in tooth during 10 seconds, and estimated change of thermal capacity by different irradiated site and exposure time. At $300J/cm^2$ irradiation for 2 seconds, the temperature of irradiated surface was elevated fast according to irradiated thermal energy during 1 second. In proportion to continuous exposure time, temperature elevated slowly. The surface temperature was $1370^{\circ}C$. After discontinue of thermal irradiation, the heat of irradiated surface was diffused in dentin and pulp and the greatest temperature was made. The greatest temperature was disappeared within 10 seconds The greatest temperature of the inner part of model brought about very severe change by different depth. Temperature in pulp was raised by the greater irradiated energy density and exposure time.

• Composites Research
• /
• v.23 no.6
• /
• pp.14-18
• /
• 2010

Among the factors that threaten spacecraft, Micrometeoroid and Orbital Space Debris(MMOD) cause damage to spacecraft and impact velocity is about 8~70km/s. Nowadays, various Whipple Shield are studied and applied to protect spacecraft. As the materials used to Shielding System, aluminum is usually used but composite is also used increasingly. So this study compared characteristics of hypervelocity impact of Aluminum and composites through finite element analysis. The Projectile was a spherical shape using Aluminum 2017-T4, and aluminum plate was using Aluminum 6061-T6, CFRP plate was using T300/5208. Initial impact velocity of projectile was 1km/s. As a result, kinematic energy of projectile decreased to about 64J and about 63J for aluminum plate and CFRP plate, respectively after impact. Although both results is almost same about the absorption of impact energy, you can think the CFRP has good ballistic characteristic, because CFRP is lighter about 1.7 times compared with density of aluminum.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2008.11a
• /
• pp.299-300
• /
• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2013.05a
• /
• pp.299-300
• /
• 2013

• Communications of the Korean Mathematical Society
• /
• v.10 no.1
• /
• pp.23-26
• /
• 1995

Throughout this paper R will always denote an integral domain with the quotient field K. Let A denote the polynomial ring R[x], I be an ideal of $A, I_K = I \otimes_R K$ and $J = I_K \cap A$.