The impact of residual technological stresses on the opening and stability of through cracks in pipeline elements

The impact of residual stresses in a DN850 pipe (steel 10GN2MFA) with austenitic cladding, welding stresses in the mounting annular seam of the pipeline, and residual stresses arising in a curvilinear branch DN350 (steel 08Kh18N10T) during manufacture by plastic deformation on the opening and stability of through cracks is considered. Calculations of residual stresses are performed using the finite element method (FEM). It is shown that residual stresses cause a change in the size and shape of the outflow channel, the coolant flow rate, and the value of the J-integral at the crack tip. In case of short cracks and relatively low operating stresses, the crack edges can close on the inside of the pipe wall due to the action of residual stresses thus leading to a decrease or cessation of the leak. A reversed effect of residual stresses on extended cracks is observed at rather high operating stresses: change in the shape of the outflow channel (an increase in the opening of the crack edges on the outer surface of the pipe) leads to a decrease in the friction of the coolant flow against the crack edges and, hence, to an increase in the leak volume. The results of testing full-scale models of elements of a straight section of the pipeline with a welded seam and a curvilinear branch DN350 with artificially created defects by internal pressure and bending moment are presented. It is shown that local through cracks develop from initial defects, which remain stable at maximum design loads (normal operating conditions plus maximum design earthquake) which matches the calculation results and meets the requirements of the applicability of the concept of «leak before break».

1. Getman A. F. Safety concept «Leak before destruction» for vessels and pipelines of NPP pressure. — Moscow: Énergoatomizdat, 1999. — 258 p. [in Russian].

2. Kiselev V. A., Rivkin E. Yu. Application of the concept of leak before destruction in the analysis of NPP safety / Atom. Énerg. 1993. Vol. 75. N 6. P. 426 – 430 [in Russian].

3. Makhutov N. A., Moskvichev V. V., Morozov E. M., Gol’dshtein R. V. Modern problems mechanics of destruction and mechanics of catastrophes / Zavod. Lab. Diagn. Mater. 2017. Vol. 83. N 10. P. 55 – 64 [in Russian]. DOI: 10.26896/1028-6861-2017-83-41-54

4. Lepikhin A. M., Morozov E. M., Makhutov N. A., Leshchenko V. V. Assessment of failure probabilities and the allowable size of defects in structural elements using the criteria of fracture mechanics / Zavod. Lab. Diagn. Mater. 2022. Vol. 88. N 3. P. 41 – 50 [in Russian]. DOI: 10.26896/1028-6861-2022-88-3-41-50

5. Silva G. F., Andrade A. H., Monteiro W. A. Leak-before break methodology applied to different piping materials: performance evaluation / Frattura ed Integrita Strutturale. 2019. Vol. 50. P. 46 – 53. DOI: 10.3221/igf-esis.50.06

6. Yoo Y. S., Ando K. Plastic collapse and LBB behavior of statically indeterminate piping system subjected to a static load / Nucl. Eng. Design. 2001. Vol. 207. P. 341 – 350.

7. Brickstad B., Sattari I. Crack shape developments for LBB applications / Eng. Fract. Mech. 2000. Vol. 67(6). P. 625 – 646.

8. Sharples J., Clayton A. A leak-before-break assessment method for pressure vessels and some current unresolved issues / Int. J. Press. Vessels Piping. 1990. Vol. 43. P. 317 – 327.

9. Kuzmin D. A. Investigation of the effect of austenitic steel surfacing on the crack opening area in the DN850 pearlite steel pipeline / Tyazh. Mashinostr. 2016. N 5. P. 7 – 10 [in Russian].

10. Matvienko Yu. G., Kuzmin D. A. Generalized equation for opening a through annular crack in a thick-walled clad pipeline / Probl. Mashinostr. Nadezhn. Mashin. 2018. N 5. P. 41 – 48 [in Russian].

11. Kazantsev A. G., Petrov O. M. The effect of residual stresses after surfacing in the Dn850 pipeline on the opening of a through crack / Tyazh. Mashinostr. 2018. N 10. P. 2 – 6 [in Russian].

12. Takahashi Y. Evaluation of leak-before-break assessment methodology for pipes with a circumferential through-wall crack. Part III: estimation of crack opening area / Int. J. Press. Vessels Piping. 2002. Vol. 79. P. 525 – 536.

13. Terasaki T., Akiyama T., Ishimura T. New Method for Estimating Residual Stresses in Pipe Made by Surfacing Weld / ASME J. Eng. Ind. 1995. Vol. 117(3). P. 365 – 371.

14. Li L., Mengjia H., Zhipeng C., et al. Residual stresses after on-line surfacing welding repairs on the flange surface of a nuclear grade pipe end / J. Tsinghua Univ. (Sci. Technol.). 2020. Vol. 60(1). P. 89 – 94.

15. Kiselev S. N., Kiselev A. S., Kurkin A. S., et al. Modern aspects of computer modeling of thermal, deformation processes and structure formation in welding and related technologies / Svar. Proizv. 1998. N 10. P. 16 – 24 [in Russian].

16. Galperin A. I. Machines and equipment for the manufacture of curved sections of the pipeline. — Moscow: Nedra, 1983. — 203 p. [in Russian].