• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.217-222
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• 2006

Large-scale model tests of welded tubular K-joints were carried out to observe the fatigue behavior of API 2W Gr.60 steel produced by POSCO. The fatigue crack behaviors for various loading conditions were measured and investigated around the critical joint sections. The experimental results have been verified with numerical approaches and also compared with the IIW, DnV RP-C203 and API RP 2A-WSD design curves. The hot spot stress method was applied in the study. The SCF factor for tubular K-joint was also obtained.

• 한국해양공학회지
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• 제22권2호
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• pp.58-64
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• 2008

Large-scale tests of welded tubular K-joint sunder balanced in-plane bending braces were carried out to observe the fatigue behavior of the API 2W Gr.60 steel plate produced by POSCO. Toe grinding and weld profiling were used to improve the fatigue life of a tubular K-joint. The effects of the steel grade and chord wall thickness on the fatigue life were also investigated. The present results were compared with the UK DEn design curve.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.32-33
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• 2003

The evaluation of HAZ toughness and cold crack susceptibility of 90mm thickness API 2W Grade 50 steel has been made in accordance with API RP 2Z as preproduction qualification test to be certified as il steel supplier from Shell International E & P. It was shown that the steel has superior HAZ toughness; CTOD value for CGHAZ more than 1.5mm at -10$^{\circ}C$, CVN absorbed energy more than 150J at -60$^{\circ}C$. Additionally, no generation of cold cracks was observed at 0.7kJ/mm even without preheating condition. These excellent results are due to the extremely low hardenability in HAZ of the steel.

• International Journal of Ocean System Engineering
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• 제2권3호
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• pp.160-169
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• 2012

Flux Cored Arc Welding (FCAW) is a common practice to join thick plates such as the structural members of large scale offshore structures and very large container ships. The objective of this study was to investigate the mechanical properties and variability of the fatigue crack initiation life in the flux cored arc welded API 2W Gr.50 steel joints typically applied to offshore structures with a focus on the effect of the materials in fatigue crack growth life from the notch root of a compact tension specimen. Offshore structural steel (API 2W Gr.50) plates (60-mm thick) were used to fabricate multi-path flux core arc welded butt welded joints to clearly consider fatigue fractures at the weld zone from the notch. Fatigue tests were performed under a constant amplitude cyclic loading of R = 0.4. The mean fatigue crack initiation life of the HAZ specimen was the highest among the base metal (BM), weld metal (WM), and heat affected zone (HAZ). In addition, the coefficient of variation was the highest in the WMl specimen. The variability of the short fatigue crack growth rates from the notch tips in the WM and HAZ specimens was higher than in BM.

• Journal of Welding and Joining
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• 제28권3호
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• pp.65-72
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• 2010

Some structural members of large-scale marine vessels such as large-scale offshore structures and very large container ships are assembled by very thick plates of which thickness exceeds 60mm. Also, high-tensile steels have been selected to meet the required structural strength and fatigue strength. Generally, multi-pass welding method such as FCA(Flux-Core Arc) welding has been used to join the thick plates. Considering the welding residual stresses, fatigue strength of the welded joints of thick plates should be assured since the residual stress influences the fatigue strength. This paper presents a numerical procedure to investigate the residual stress of structure joined by multi-pass FCA welding so that it can be incorporated into the fatigue strength assessment considering the effect of welding residual stress. The residual stress distribution is also measured by X-Ray diffraction method. The residual stress obtained by the computational model also has been compared with that of experiment. The results of FEA are in very good agreement with the experimental measurements.

• Journal of Welding and Joining
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• 제26권3호
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• pp.51-60
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• 2008

This paper is to evaluate fracture characteristics of API 2W Gr.50 TMCP steel weldment typically applied for offshore structures, with the focus on the influence of heat input arising from flux cored arc welding. Based on the results and insights developed from this study, it is found that the toughness for both CTOD and impact exhibits a tendency to decrease as the weld heat input increases. The reheated zone of weldmetal exhibit lower hardness than solidified zone and microstructure that are liable to affect the toughness are acicular ferrite and martensite-austenite constituents (M-A). In particular, M-A is a more effective micro-phase for CTOD toughness than impact toughness.