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석한길,Seok, Han-Gil 한국재료학회 1998 한국재료학회지 Vol.8 No.4
구미와 일본에서는 균열이 실린더벽을 과통하므로서 발생되는 일부누설로 인하여 실린더가 불안전 파괴가 이루어진 후 급속파단으로 전개되는 판당전 누설(Leak Before Break, LBB)를 전제로 한 구조건전성의 확인 시험연구가 널리 수행되고 있다. 본고에서는 Gs-C25 실린더의 구조건전성을 LBB개념의 도입과 파괴역할을 이용하여 평가하였다. 내부압력 80bar일때의 실린더에서 응력확대계수 계산은 구조물의응력확대계수가 극단적으로 큰 디멘젼을 지닌 측균열인 경우에서만 재료의 인성계수 $K_{lc}$ /와 $K_{eff}$ 에 도달된다는 것을 나타내었으며, 반면에 원주균열은 파괴 인성치 $K_{lc-}$ 와 $K_{eff-}$ 값까지는 어떠한 경우에도 도달되지 않았다. 구조물의 국부적인 취성파괴는 균열을 함유한 누설로 유도되는 범위에서, "$K_{1}$ 구조물$\geq$$K_{lc}$ 및 $K_{eff}$ "의 조건을 만족시에만 발생되며, 이는 축균열이 원주균열보다 훨씬 더 위험하다는 것을 증명한다.는 것을 증명한다.
석한길 三陟大學校 産業科學技術硏究所 2004 産業科學技術硏究論文集 Vol.9 No.1
In this study, productivity elevation of horizontal fillet welding process using the auto carriage was investigated. And we studied micro-structures of grooves in various welding processes. Furthermore, it was performed the elasto-plastic finite element analysis in welding residual stress field to evaluate the fatigue strength of structure steel for bridge. Residual stress that happen on weld line direction affects greatly in weld zone fatigue strength because it is overlapped each other with external force. That is, if welding residual stresses is the bigger, fatigue strength is fallen.
석한길 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.5
For construction of I-beam steel structures, a fillet welding is one of the main manufacturing process. However, this welding process cause some problems associated with welding residual stress and welding deformation that are harmful to the safety of structures. Accordingly, this study clarified the creation mechanism of the welding deformation on I-beam steel structure from the experimental results given by the FEM method. To prevent or minimize the longitudinal bending deformation, first of all, a field supervision is necessary to observe the optimal groove design. Secondly, the welding order for cooling weld zone is needed.
석한길 三陟大學校 産業科學技術硏究院 2005 産業科學技術硏究論文集 Vol.10 No.-
We calculated optimum die angle theoretically according to elongation ratio and materials, and proved it by an experiment. This angle requires the minimum for actual work and can lower manufcture cost on its work. In order to make cold-worked carbon steels ductile, they are annealed at appropriate temperatures. And during annealing the changes on microstructure that occur can be subdivided into recovery, recrystallization and grain growth. The brittle fracture form is shown at 900 and 850℃ in the annealing test and bad mechanical properties (lower elongation ratio, lower tension strength and brittle fracture) are observed. Conclusively, 750 to 800℃ (hold time : 1 hour) is optimal as annealing temperature of this low carbon steel. And it is desirable to do air cooling about 550 to 300℃ .
H 빔 구조물의 T-Joint에서 용접조건에 따른 용접잔류응력의 영향
석한길 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.5
In the welding for the steel structure of H-beam with mild steel and 490N/$\textrm{mm}^2$ high tensile steel, we applied the fillet weld mostly and 6-8mm weld length(AISC-spec.). And a new developed metal-cored-wire is used in automatic welding as well as semi-automatic welding. In this study we have attempted to raise the welding productivity and to stabilize the quality on horizontal positions of fillet welding with the following items: - We improved the weld productivity using metal based cored wire with a high deposition rate in the steel structure of H-beam. - We tested the weldability and evaluated the quality of the weldmetal by horizontal fillet $CO_2$ welding. The process is carried out in combination with a special purpose metal-based FCW with excellent resistance to porosity and high welding speed. - We studied the micro structure of the weldmetal by the various welding conditions. - We studied the effect of welding residual stress by the welding conditions in T-joint. Therefore, it can be assured that more productive and superior quality of the weldmetal can be taken from this study results.
원용신,석한길 三陟大學校 産業科學技術硏究所 1999 産業科學技術硏究論文集 Vol.4 No.-
This paper discribes the test results on the heating and cooling temperature effects of the hot forming method in bending working of steel plate.
극한 상태에서 A490 고장력 볼트 세트의 체결 품질 연구
석한길(Han-Gil Suk),조인습(In-Seup Cho),홍현선(Hyeon-Sun Hong) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.1
This test focuses on the correlation between the lubrication, ductility and strength through the change of nut lubricant which decides joining angle for A490 bolt sets required in the AASHTO (American Association of State Highway & Transportation Officials). Because the lubrication of high tension bolt, nut, washer sets becomes an important factor to ductility and joining load, the quality improvement is required for improving reliability and securing enough lubrication of maker and user. This study examines the quality characteristics required in the specification through tests because only this standard specifies joining quality in the extreme conditions (as much about two times of the joining angle on site as normal condition). Moreover, this study is limited to the test on joining axial force required in the AASHTO for the three nut lubrication conditions of A490 bolt set. It is concluded that the nuts should be coated or waxed enough for the improvement of the joining axial force and ductility of bolts required in the standards. It is shown that in the case of plain high tension bolt sets, a rust preventing lubricative oil shall be applied and the torque coefficient value for A490 bolt sets should be maintained below 0.175.