A Study on the Fracture Behavior of a Two Dimensional Crack in Gas Pipelines Considering Constraint Effects

구속효과를 구려한 가스배관 결함의 2차원적 파괴거동 해석에 관한 연구

  • Published : 2001.01.01


EFP(Fitness For Purpose) type defect assessment methodologies based on ECA(Engineering Critical Analysis) have been established and are in use for the structural integrity evaluation of gas pipelines. ECA usually includes the fracture mechanics analysis, and it is assumed that the J-integral uniquely characterizes the crack-tip stress-strain field. However, it has been proven that the J-integral alone can not be sufficient to characterize the crack-tip field under low levels of constraint with a single parameter. Since pipeline structures are made of ductile material, locally loaded in tension, cracks may experience low level of constraint, and therefore, J-dominance will be lost. For this reason, the level of constraint must be quantified to establish a precise assessment procedure for pipeline defects. The objective of this paper is to investigate the fracture behavior of a crack in gas pipeline(KS D 3507) by quantifying the level of constraint. For this purpose, tensile tests and CTOD tests were performed at room temperature(24$\^{C}$) and low temperature(-40$\^{C}$) to obtain the material properties. J-Q analyses were performed for SENB and SENT specimens based on 2-D finite element analyses, in order to investigate the in-plane constraint effects on pipeline defects. For precise assessment of cracks, especially shallow cracks, in KS D 3507 pipeline, constraint effect must be considered.


CTOD;J-integral;Constraint Effects;J-Q Analysis;Finite Element Analysis;SENB Specimen;SENT Specimen


  1. McMeeking, R.M., 1989, 'Numerical Calculations for Problems of Ductile Fracture,' Advances in Fracture Research, Vol. 3, pp. 1971-1998
  2. Hutchinson, J.W., 1968, 'Singular Behavior at End of a Tensile Crack Tip in a Hardening Material,' Journal of the Mechanics and Physics of Solids, Vol. 16, pp. 13-31
  3. Rice, J.R. and Rosengren, G.F., 1968, 'Plane Strain Deformation near a Crack Tip in a Power-Law Hardening Material,' Journal of the Mechanics and Physics of Solids, Vol. 16, pp. 1-12
  4. ASTM E8, 1995, 'Standard Test Method for Tension Testing of Metallic Materials,' 1995 Annual Book of ASTM Standards, Vol. 3.01, pp. 56-76
  5. 1991, Method for Determination of $K_{IC}$, Critical CTOD and Critical J Values of Metallic Materials, BSI 7448 Part1, British Standards Institution, London
  6. ABAQUS User's Manual, 1998, Hibbitt, Karlsson & Sorensen, Inc
  7. O'Dowd, N.P., and Shih, C.F., 1992, 'Family of Crack Tip Fields Characterized by A Triaxiality Parameter-II. Fracture Applications,' Journal of Mechanics and Physics of Solids, Vol. 40, No. 5, pp. 939-963
  8. 이형일, 함종호, 김윤재, 1999, '수정된 경계층법에 의한 변형경화 이종접합재의 계면균열선단 구속 상태 및 J-적분 고찰,' 대한기계학회논문집 A권, 제23권 제9호, pp. 1525-1535
  9. 서헌, 한태수, 이형일, 1999, '구속상태를 고려한 반타원 표면균열의 파손평가선도,' 대한기계학회논문집 A권, 제23권 제11호, pp. 2022-2032
  10. Nyhus, B., 1998, 'Oseberg Hyperbaric Welding Procedure Development. Fracture Mechanics Testing and ECA Analysis,' SINTEF Report
  11. 최재붕, 1997, 'Constraint를 고려한 Pipeline Steel의 파괴해석,' 대한기계학회 1997년도 추계학술대회논문집 A, pp. 173-178
  12. 1987, Specifications for Field Welding of Carbon Steel Pipelines, BS 4515, Appendix H, British Standards Institution, London
  13. 1996, Standards of Acceptability for Circumferential Pipe Butt Welds Based on Fracture Mechanics Principles, CSA Z662, Appendix K
  14. 1991 , Guidance on Some Methods for the Derivation of Acceptable Levels of Defects in Fusion Welded Joints, BSI PD6493, British Standards Institution, London
  15. Kumar, V., German, M.D., Wilkening, W.W., Andrews, W.R., deLorenzi, H.G., and Mowbray, D.F., 1984, 'Advances in Elastic-Plastic Fracture Analysis,' EPRI Report NP-3607, Electric Power Research Institute, Palo Alto, CA
  16. Betegon, C. and Hancock, J., 1991, 'Two-Parameter Characterization of Elastic-plastic Crack-Tip Fields,' Journal of Applied Mechanics, Vol. 58, pp. 104-110
  17. O'Dowd, N.P., and Shih, C.F., 1991, 'Family of Crack Tip Fields Characterized by A Triaxiality Parameter-I. Structure of Fields,' Journal of Mechanics and Physics of Solid5, Vol. 39, No. 8, pp. 989-1015
  18. 1998, The American Petroleum Institute API Standard 1104, Appendix A, Standard for Field Welding Pipe Lines and Related Facilities