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

  • Received : 2012.08.06
  • Accepted : 2012.10.25
  • Published : 2012.10.31


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.


Flux Core Arc Welding;Fatigue Crack Growth;Constant Amplitude Cyclic Loading;Scanning Electron Microscopy


  1. Virkler, D.A., Hillberry, B.M. and Goal, P.K. (1979). "The Statistical Nature of Fatigue Crack Propagation", J. Engineering Materials and Technology, ASME, Vol 101, pp 148-153.
  2. Wu, W.F. and Ni, C.C. (2007). "Statistical Aspects of Some Fatigue Crack Growth Data", Engineering Fracture Mechanics, Vol 74, pp 2951-2963.
  3. ASTM (2008). "Standard test Method for Measurement of Fatigue Crack Growth Rates", American Society for Testing and Materials, ASTM E647-08.
  4. Itagaki, H., Ishizuka, D. and Huang, P. (1993). "Experimental Estimation of the Probability Distribution of Fatigue Crack Growth Lives", Probabilistic Engineering Mechanics, Vol 8, No 1, pp 25-34.
  5. Kazuyuki, S. and Takeshi, S. (2003). "Welding Consumables for Offshore Structures", Technical Paper of Kobe Steel, Vol 53, No 2, pp 85-89.
  6. Ortiz, K. and Kiremidjian, A.S. (1986). "Time Series Analysis of fatigue Crack Growth Rate Data", Engineering Fracture Mechanics, Vol 25, No 4, pp 657-668.
  7. Paris, P.C. and Erdogan, F. (1963). "A Critical Analysis of Fatigue Crack Propagation Laws", ASME J. Basic Engineering, Vol 56, pp 528-534.
  8. 손상훈, 공유식, 김선진 (2009). "피로균열전파의 확률모델과 통계적 양상", 2009년도 한국해양공학회 추계학술대회논문집, pp 573-576.
  9. 손혜정, 공유식, 김선진 (2011) "다층 플럭스코아드아크 용접한 API 2W Gr.50 강재의 피로균열전파의 시험편간 변동", 2011년 도 한국해양과학기술협의회 공동학술대회 논문집, pp 1616-1619.
  10. 임성우, 이주성 (2006). "API 2W Gr.50 강재를 이용한 대형 Tubular Joint 피로성능평가", 한국해양공학회지, 제19권, 제3호, pp 54-58.
  11. 임성우, 장인화, 조철희, 박관규 (2005). "API 2W Gr.50 강재를 이용한 해양구조물 Tendon Porch의 피로성능평가", 한국해양공학회지, 제20권, 제5호, pp 92-88.
  12. 황세윤, 이장현, 양용식, 이성제, 김병종 (2010). "EH40과 API2W 강재의 극 후판재 다층 FCAW 버트 용접부 잔류응력해석", 대한용접접학학회지, 제28권 제3호, pp. 293-300.
  13. Ashok, S. and Hudak, S.J. (1978). "Review and Extension of Compliance Information for Common Crack Growth Specimens", International Journal of Fracture, Vol 14, No 5, pp 453-461.
  14. 김선진 (2003). "일정 응력확대계수 제어하의 피로균열전파 수명 분포의 파라메터 특성", 한국해양공학회지, 제17권, 제2호, pp 54-59.
  15. 박희선, 김현수, 고민성, 박창수, 방한서 (2008). "조선용 극후물 강재 EH36 FCAW 용접부의 역학적 특성 고찰", 한국용접학회 2008년도 추계학술대회 발표 초록, p. 123.
  16. 김선진 (1999). "피로균열전파저항의 변동성에 의한 균열전파율의 해석", 대한기계학회논문집, 제23권, 제7호, pp 1139-1146.

Cited by

  1. Prediction of Reliability of Fatigue Limit of S34MnV Steel for Marine Diesel Engine Crank Throw Components vol.40, pp.8, 2016,