Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
권호 표지
DOI QR코드

DOI QR Code

Fatigue Failure Behavior of Pipe Bends with Local Wall-Thinning Under Cyclic Bending Condition

반복굽힘 조건에서 감육 곡관의 피로손상 거동

  • Received : 2012.02.27
  • Accepted : 2012.07.23
  • Published : 2012.10.01
Download PDF
⟨ Previous Next ⟩

Abstract

In this study, fatigue tests were carried out using real-scale pipe bend specimens with wall-thinning defects under a cyclic bending load together with a constant internal pressure of 10 MPa. The wall-thinning defect was located at the extrados and the intrados of the pipe bend specimens. A fully reversed cyclic in-plane bending displacement was applied to the specimens. For the pipe bends with wall thinning at the extrados, an axial crack occurred at the crown of the pipe bend rather than at the extrados where the defect was located. In addition, the fatigue life was longer than that of a sound pipe bend predicted from the design fatigue curve in ASME Sec.III, and it was less dependent on the axial length of the wall-thinning defect. For the pipe bends with wall thinning at the intrados, a circumferential crack occurred at the intrados. In this case, the fatigue life was much shorter than that of a sound pipe bend predicted from the design fatigue curve, and it clearly decreased with decreasing axial length of the wall-thinning defect.

본 연구에서는 감육결함이 가공된 실배관 곡관 시편을 대상으로 10 MPa의 내압과 반복 굽힘하중 조건에서 피로 시험을 수행하였다. 시험에는 감육결함이 곡관의 외호부와 내호부에 존재하는 경우를 고려하였으며, 반복 하중으로는 완전 역방향의 변위제어 형태로 작용되는 In-plane 상의 굽힘하중이 고려되었다. 실험 결과, 감육결함이 곡관의 외호부에 존재하는 경우에는 결함부가 아닌 곡관의 측면에서 축방향 균열이 생성되었다. 또한, ASME Sec.III의 설계 피로곡선에서 예측된 건전 곡관의 피로수명보다 긴 피로수명을 보였으며, 피로수명이 결함 길이에 크게 영향을 받지 않았다. 반면, 결함이 내호부에 존재하는 곡관은 내호부에서 원주방향 균열이 발생하였으며, 피로수명은 ASME Sec.III의 설계 피로곡선에서 예측한 건전 곡관의 피로수명보다 짧은 값을 보였다. 또한, 내호부 감육 곡관의 피로수명은 결함 길이가 감소함에 따라 뚜렷이 감소하였다.

Keywords

References

  1. Shalaby, M.A. and Younan, M.Y.A., 1999, "Limits Loads for Pipe Elbows Subjected to In-Plane Opening Moments and Internal Pressure," J. of Press. Ves. Tech., Vol. 121, pp.17-23. https://doi.org/10.1115/1.2883661
  2. Chexal, B., Horowitz, J,. Dooley, B., Millett P., Wood, C. and Jones, R., 1998, "Flow-Accelerated Corrosion in Power Plant," EPRI/TR-106611-R2.
  3. Michel, F., Reck, H., and Schulz, H., 2001, "Experience with Piping in German NPPs with Respect to Ageing-Related Aspects." Nucl. Eng. & Design, Vol. 207, pp. 307-316. https://doi.org/10.1016/S0029-5493(01)00339-9
  4. NRC Information Notice 2006-08: Secondary Piping Rupture at the Mihama Power Station in Japan, May 16, 2006.
  5. Virginia Eletric and power Co., 1989, "Surry Unit 2 Reactor Trip and Feedwater Pipe Failure Report."
  6. Kim, Y.J. and Son, B.G., 2004, "Finite Element Based Stress Concentration Fators for Pipes with Local Wall Thinning," Int. J. Pres. Ves. & Piping, Vol. 81, pp.897-907. https://doi.org/10.1016/j.ijpvp.2004.06.002
  7. American Society of Mechanical Engineer, ASME B&PV Sec.XI, Div.1, ASME Code Case N-597 rev.2, "Requirement for Analytical Evaluation of Pipe Wall Thinning," 2003ed.
  8. Hasegawa, K., Sakata, K., Miyazaki, K., and Kanno, S., 2002, "Fatigue Strengths for Pipes with Allowable Flaws and Design Fatigue Curve," Int. J. Pres. Ves. & Piping, Vol. 79, pp.37-44. https://doi.org/10.1016/S0308-0161(01)00129-6
  9. Kim, J.W. and Park, C.Y., 2006, "Experimental Investigation of the Failure Behavior of Notched Wall-Thinned Pipes," Nucl. Eng. & Design, Vol. 236, pp.1838-1846. https://doi.org/10.1016/j.nucengdes.2006.02.005
  10. Hasegawa, K., Miyazaki, K., and Nakamura, I., 2008, "Failure Mode and Failure Strengths for Wall Thinning Straight Pipes and Elbows Subjected to Seismic Loading," J. of Press. Ves. Tech., Vol. 130, pp.011404-1-8. https://doi.org/10.1115/1.2826425
  11. Takahasi, K., Watanabe, S., Ando, K., Urabe, Y., Hasatune, M., Miyazaki, K., 2009, "Low Cycle Fatigue Behaviors of Elbows Subjected to Seismic Loading," Nucl. Eng. & Design, Vol. 239, pp.2719-2727. https://doi.org/10.1016/j.nucengdes.2009.09.011
  12. Urabe, Y., K., Takahashi, K. and Ando, K., 2011, "Low Cycle Fatigue and Seismic Assessment for Elbow Pipe Having Local Wall Thinning," Submitted to J. of Press. Ves. Tech.
  13. American Society of Mechanical Engineer, ASME B&PV Code Sec. III, "Nuclear Components," 1998ed.