• Title/Summary/Keyword: API 2W Gr.50

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Fatigue Behavior of Large Scale Tubular Joint for API 2W Gr. 50 Steel (API 2W Gr.50 강재를 이용한 대형 Tubular Joint 피로성능평가)

  • Im, Sung-Woo;Chang, In-Hwa;Jo, Chul-Hee;Park, Kwan-Kyu
    • Journal of Ocean Engineering and Technology
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    • v.19 no.3
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    • pp.54-58
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    • 2005
  • Large-scale model tests of welded tubular K-joints were carried out to observe the fatigue behavior of API 2W Gr.50 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 were 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 obtaine.

A Study on the Fatigue Life of Large-Scale Tubular K-joints (대형 Tubular K-Joint의 피로수명에 관한 연구)

  • Im, Sung-Woo;Chang, In-Hwa
    • Journal of Ocean Engineering and Technology
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    • v.22 no.2
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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.

Characteristics of HAZ Toughness and Cold Crack Susceptibility of Heavy Thickness API 2W Gr. 50 Steel for Offshore Structures (해양구조물용 극후물 API 2W Gr. 50강의 HAZ 인성 및 저온균열 감수성)

  • 홍현욱;김충명
    • Proceedings of the KWS Conference
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    • 2003.05a
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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.

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Assessment of Fatigue Strength Characteristics of Tendon Porch in Offshore Platforms for API 2W Gr. 50 Steel (API 2W Gr.50 강재를 이용한 해양구조물 Tendon Porch의 피로성능 평가)

  • Im, Sung-Woo;Lee, Joo-Sung
    • Journal of Ocean Engineering and Technology
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    • v.20 no.5 s.72
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    • pp.82-88
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    • 2006
  • This assessment is concerned with the fatigue strength of the tendon porch found in TLP. Lorge-scale fatigue tests with models constructed at 30% the size of the real structures have been carried out to investigate the fatigue behavior of the API 2W Grade 50 steel recently produced by POSCO. The fatigue life for the present test models was obtained based on the concept of nominal stress. A comparison of the present test results with those obtained by a numerical approach based on the structural analysis results has showngood agreement. The present results were also compared with the design curves in DnV RP-C203.

Effect of Weld Improvement on the Corroded Fatigue Life of Welded Structures (용접구조물의 부식피로수명에 미치는 용접부 개선처리 효과)

  • Im, Sung-Woo;Chang, In-Hwa;Kim, Sang-Shik;Song, Ha-Cheol
    • Journal of Ocean Engineering and Technology
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    • v.22 no.2
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    • pp.50-57
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    • 2008
  • The effect of weld improvement on the corroded fatigue life of welded structures was investigated. Toe grinding, TIG dressing and weld profiling were used as the geometric improvement methods. Fatigue tests under the corroded condition in artificial seawater were carried out to investigate the corrosion fatigue behavior of API 2W Gr.50T steel plate produced by POSCO. The test results in weld improved conditions were compared with those in as-welded condition. The test results were also compared with the design curves in UK DEn Class F. Corroded fatigue life of weld improved specimens was longer than that of as-welded specimen. Especially, the corroded fatigue life exceeded the mean SN curve in air of UK DEn Class F.

Variability of Fatigue Crack Initiation Life in Flux Cored Arc Welded API 2W Gr.50 Steel Joints

  • Sohn, Hye-Jeong;Kim, Seon-Jin
    • International Journal of Ocean System Engineering
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    • v.2 no.3
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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.

Fatigue Strength Assessment of TLP Tendon Porch Using API 2W Gr.50 Steel

  • Im, Sung-Woo;Seo, Young-Seok;Lee, Joo-Sung
    • Journal of Ship and Ocean Technology
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    • v.11 no.1
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    • pp.25-35
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    • 2007
  • This paper is concerned with the fatigue strength assessment of tendon porch found which is categorized as the special structural member in TLP. Large-scale tendon porch specimens have been designed and fabricated with API 2W Gr.50 steel recently produced by POSCO. Fatigue test has been carried out for three tendon porch specimens under various load level. Fatigue strength has been evaluated based on the nominal stress range and the results are compared with the fatigue design curve of DnV RP-C203. From the present experimental study, it has been found that the porch specimens satisfy the fatigue design rule although test was carried out under the positive stress ratio. It can be, therefore, said that the API 2W steel produced by POSCO possess sufficient fatigue strength.

Fatigue Behavior of Offshore Topside Structure (상부 해양 요소 접합부의 피로 평가)

  • Im, Sung-Woo;Park, Kwan-Kyu;Park, Ro-Sik;Cho, Won-Chul;Jo, Chul-Hee
    • Journal of Ocean Engineering and Technology
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    • v.20 no.6 s.73
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    • pp.88-92
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    • 2006
  • Large-scale model tests of welded topside joints were carried out to observe the fatigue behavior of API 2W Gr.50 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 AWS D1.1 and DnV RP-C203 design curves. The large-scale experiment models were fabricated, based on the actual operating east area fixed platform. The dimensions of the models were slightly modified to accommodate the test facilities and capacities. The fatigue test was carried out having ${\Delta}Q$ of T1=705.6kN, T2=749.7kN and T3=793.8kN. The three specimens were statically loaded 20 times, with various loadings of about 50kN intervalsbetween the maximum and minimum loads required in the fatigue tests. This loading removed the residual stress in the specimen before the fatigue tests. The topside joint crack was initiated from the brace heel, where the maximum tensile stress occurred. The API 2W Gr.50 steel satisfied the AWS D1.1 detail category C and DnV RP-C203 detail category F ${\Delta}S-N$ curve.

Marco and Microscopic Observations of Fatigue Crack Growth Behavior in API 2W Gr. 50 Steel Joints (API 2W Gr. 50 강재 용접부의 피로균열전파거동의 거시적 및 미시적 관찰)

  • Sohn, Hye-Jeong;Kim, Seon-Jin
    • Journal of Ocean Engineering and Technology
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    • v.26 no.5
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    • pp.73-80
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    • 2012
  • It is well known that a considerable amount of scatter is shown in experimental results relating to fatigue crack growth even under identical and constant amplitude cyclic loading conditions. Moreover, flux cored arc welding (FCAW) is a common method used 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 macro- and microscopic observations of the fatigue crack growth (FCG) behavior of the FCAWed API 2W Gr. 50 steel joints typically applied for offshore structures. In order to clearly understand the randomness of the fatigue crack growth behavior in the materials of three different zones, the weld metal (WM), heat affected zone (HAZ), and base metal (BM), experimental fatigue crack growth tests for each of five specimens were performed on ASTM standard compact tension (CT) specimens under constant amplitude cyclic loading. Special focus was placed on the fatigued fracture surfaces. As a result, a different behavior was observed at the macro-level, depending on the type of material property: BM, HAZ, or WM. The variability in the fatigue crack growth rate for WM was higher than that of BM and HAZ.

Numerical Analysis of Welding Residual Stresses for Ultra-thick Plate of EH40 TM and API 2W Gr.50 Steel Joined by Flux Core Arc Welding (EH40과 API2W강재의 극 후판재 다층 FCAW 버트 접합부 잔류응력해석)

  • Hwang, Se-Yun;Lee, Jang-Hyun;Yang, Young-Sik;Lee, Sung-Je;Kim, Byung-Jong
    • Journal of Welding and Joining
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    • v.28 no.3
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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.