• Journal of Welding and Joining
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• v.22 no.2
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• pp.78-84
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• 2004

Effects of manganese and carbon on the HAZ microstructural evolution in 500㎫ grade titanium oxide steels were investigated. Microstructural evolution primarily depends on supercooling. When cooled at 3$^{\circ}C$/s in 0.15%C-1.5%Mn steel, grain boundary and Widmanst tten ferrite formed at 640 and 62$0^{\circ}C$, respectively, followed by competitive formation of acicular ferrite and upper bainite inside of grain at 58$0^{\circ}C$. With an increase of manganese, degree of supercooling increased while critical cooling rate for the formation of gain boundary ferrite decreased. Consequently, the amount of acicular ferrite in HAZ was decreased in 2.0%Mn after initial increase in 1.0 and 1.5%Mn. Therefore, optimum supercooling should be maintained to accelerate acicular ferrite formation in titanium oxide steels. Low carbon steel, 0.11%C-1.5%Mn, showed larger amount of acicular ferrite than higher carbon steel because of effectiveness of diffusionless transformation in low carbon steel.

• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.41-45
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• 2008

Effectsof carbon content on the weldability of B-containing 620 grade high Cr ferritic cast steels were investigated. Cast steel with lower carbon content of 0.07% showed lower HAZ hardness because of the formation of lower carbon martensite in HAZ. It also showed less solidification cracking susceptibility in weld metal because of the formation of delta ferrite. However, hot ductility showed no difference between cast steels with lower and higher carbon contents. Cast steel with lower carbon content showed greater HAZ softening after PWHT in the region heated between AC1 and AC3 because of its higher base metal hardness.

• Journal of Welding and Joining
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• v.26 no.2
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• pp.69-74
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• 2008

590MPa grade weldable steels were gas metal arc welded with flux cored wires. Welding parameters such as current, voltage, and speed were varied independently. Effects of each parameter on the strength and chemical composition of weld metal were investigated. Increase of voltage caused decrease of weld metal tensile strength due to the low recovery of alloying elements such as carbon and manganese. On the contrary, increase of current and speed resulted in increase of weld metal strength because of higher recovery of the alloying elements.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.183-185
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• 2005

In an attempt to optimize friction spot joining process of Mg alloys, effects of joining parameters such as rotating speed, plunging depth, and dwelling time on the joints properties were evaluated. Experimental tests were carried out for lap joined AZ31B-H24 sheets. A wide range of joining conditions could be applied to join Mg alloys without defects in the weld zone except for certain welding conditions with an insufficient heat input. The microstructures and hardness variations in the weld regions are discussed. For sound joints without defects, tensile shear strength of weld joints was higher approximately 116% than typical tensile shear strength of electrical resistance spot-welded joints for magnesium(Welding handbook, Vol 3, AWS).

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.322-324
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• 2007

Nd:YAG laser welding of AZ31B-H24 magnesium alloy was carried out using AZ61 filler wire(Mg-6wt%Al-1wt%Zn). Microstructure and mechanical properties of welded joint were examined by optical microscopy, scanning electronic microscopy(SEM), energy dispersive spectroscopy(EDS), electron probe micro analyzer(EPMA) and victors hardness, tensile test at the room and elevated temperature. Test results indicate that the specimens welded with AZ61 filler wire have better tensile strength, elongation and victors hardness at room temperature than those of welded without filler wire. However tensile strength are similar but elongation are quite different at elevated temperature.

• Proceedings of the Korean Society of Crop Science Conference
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• 2018.04a
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• pp.155-155
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• 2018

• Proceedings of the Korean Society of Crop Science Conference
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• 2018.04a
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• pp.192-192
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• 2018

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.01a
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• pp.77-80
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• 2012

태권도는 국제스포츠연맹 회원국수 10위를 자랑하며 올림픽 정식 종목으로 전 세계인의 사랑과 관심을 받아온 스포츠 종목이지만 영상분석을 통한 새로운 분야에선 관심을 받지 못하고 있는 실정이다. 따라서 이 논문에서는 컴퓨터 시뮬레이션의 기법을 활용하여, 태권도의 새로운 품새 동작을 창작하는데 활용할 수 있는 시뮬레이션 알고리즘을 제시한다. 또한 이 논문에서 제시한 알고리즘은 사용자가 원하는 환경에 따라 여러 가지 조건의 변화를 반영하고 그 각각의 결과를 보다 쉽게 얻을 수 있게 되어 있어서, 향후에 새로운 태권도 품새 개발과 표준화된 동작 모델 개발에 활용될 것으로 기대된다.

• Journal of Welding and Joining
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• v.20 no.3
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• pp.91-97
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• 2002

Variation of HAZ toughness of Ti-containing steel with nitrogen content was investigated and interpreted in terms of its microstructure and the amount of soluble nitrogen present. The amounts of Ti and Al combined in TiN and AlN, respectively, in HAZ at $1400^{\circ}C$ peak temperature were less than those in base plate; 55~88% in TiN and 21~28% in AlN, indicating the dissolution of nitrifies in HAZ. The calculated amounts of soluble nitrogen using the thermodynamic analysis showed a good agreement with the measured values in other experiment. Therefore, the analysis can be used to estimate the amount of soluble nitrogen in HAZ. Simulated HAZ toughness was influenced not only by its microstructure but also by the amount of soluble nitrogen present after the formation of BN during the cooling cycle of welding. It showed maximum value when the nitrogen content is in stoichiometric ratio with titanium content, showing that soluble nitrogen in HAZ is detrimental to its toughness.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.50-55
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• 2006

In an attempt to optimize friction spot joining process of Al alloys for automobiles, effects of joining parameters such as tool rotating speed, plunging depth, and joining time on the joints properties were investigated. A wide range of joining conditions could be applied to join Al alloys for automobile without defects in the weld zone except for certain welding conditions with a lower heat input. For sound joints without defects, tensile shear strength of joints was higher than acceptable criteria of tensile shear strength of resistance spot welded joints for aluminum.