tearing. Following the formation of a bounding defect of a low aspect ratio the major crack advance by tearing occurs near the free surface, in contrast to the fatigue where consistent crack advance along the crack front towards a stable aspect ratio was observed [12]. Codified recharacterisation procedure [1,2] for defects with re-entrant sectors recommends the evaluation for a bounding semi-elliptical defect. The conservatism of such procedure has been demonstrated for both, fatigue and ductile tearing. The coalescence phase amounts to the significant fatigue life of the component before the bounding profile develops. Although replacing the re-entrant crack with a bounding crack may incur premature repairs and expenses, the process is inherently conservative. Applying the recharacterisation procedure to cracks with re-entrant sectors in bending dominated ductile tearing is also conservative, since tearing starts in the re-entrant sector and the defect develops to the bounding shape of a recharacterised defect. For re-entrant cracks subject to conditions near the ductile-brittle transition regime a low fracture toughness was found [6] and a potentially non-conservative situation exists, when applying the codified recharacterisation procedure to such defects failing on the lower shelf. ACKNOWLEDGEMENTS The authors are thankful to Hibbitt, Karlsson and Sorensen for access to ABAQUS under Academic License. The support of British Energy Generation plc and discussions with Dr. R.A. Ainsworth is gratefully acknowledged. REFERENCES 1. ASME, (1992), Boiler and pressure vessel design code, Section XI , American Society of Mechanical Engineers, Philadelphia, Pa. 2. BS7910:1999, Guide on methods for assessing the acceptability of flaws in metallic structures, British Standard Institution, London, 1999 3. Twaddle, B.R. and Hancock, J.W., (1986), Fatigue of Offshore Structures, EMAS 4. Leek, T.H. and Howard, I.C., (1996), Int. J. Press. Ves. and Pip., 68, p: 181 5. Lin, X.B. and Smith, R.A., (1997), Int. J. Fract., 85, p: 283 6. Bezensek, B. and Hancock J.W., (2001), Proc. ASME PVP2001, Atlanta, Ga. 7. Betegón, C. and Hancock, J.W., (1991), J. Appl. Mech.-T ASME, 58, p:104 8. Hancock, J.W., Reuter, W.A. and Parks, D.M., (1993), Constraint effects in fracture, ASTM STP 1171, American Society for Testing and Materials, Philadelphia, p: 121 9. Rice, J.R. and Levy, N., (1972), J. Appl. Mech.-T ASME, 39, p: 185 10. Parks, D.M. and White, C.S., (1982), J. Press. Vess. – T ASME, 104, p: 287 11. HKS, (1998), ABAQUS/Standard Theory Manual, V 5.8, Hibbitt, Karlsson and Sorensen, inc, Providence, Rhoad Island 12. Scott, P.M. and Thorpe, T.W., (1981), Report R-10104, Atomic Energy Research Establishment, Harwell, UK
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