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BAY-LOGI

BAY-LOGI. Safety-Relibility and Risk of Engineering Plants and Components, Second Hungarian-Ukrainian Joint Conference, Kyiv, Ukraine, 19-21. September 2007. Assessment of crack like defect in dissimilar welded joint by analytical and finite element methods. Szabolcs Szávai Róbert Beleznai

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  1. BAY-LOGI Safety-Relibility and Risk of Engineering Plants and Components, Second Hungarian-Ukrainian Joint Conference, Kyiv, Ukraine, 19-21. September 2007. Assessment of crack like defect in dissimilar welded joint by analytical and finite element methods SzabolcsSzávai Róbert Beleznai Tibor Köves

  2. Introduction • Fracture mechanical analysis is evident in case of nuclear pressure vessels during in-service inspection • Reliable and verified methods are required for analyzing nuclear pressure vessel and its welds • For NDT of welds a minimum defect size - to be detected- is required • Fracture mechanical solutions of the codes are developed for simple geometries like pipes or shell like components

  3. Introduction • There are several dissimilar metal welds at critical points • There is no valid solution for DMW • Critical points usually have complex 3D geometry and loading • Verified method is needed for DMW

  4. Objectives • Assess the applicability of the analytical KI solutions of the ASME BPVC for • complex geometry of VVER’sDMW • mismatch materials like DMW • mechanical and transient thermal loads

  5. Bay-Logi Activities • Comparison of KI values determined by ASME BPVC XI H4221 and A3300, R6 (FITNET) and FEM for pipe-like geometries under tension and bending loading • Calculation of KI and JI values for real 3D geometries with DMW under mechanical and transient thermal loading by FEM • Applicability of the ASME BPVC A3300 for a given 3D geometries

  6. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • Loading • tension (100 MPa) • bending (100 MPa) • Dimensions • Internal radius of the DMW for both case: 548 mm • R/t: 0,136 → shell like according ASME • Crack size • a/w: 0,25; 0,5; 0,75 • : 11,25°; 22,5°; 45°

  7. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI determination according to ASME XI H4221 • for pipes under bending and tension • circumferential defect • simple equation • wide range applicability

  8. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI determination according to ASME XI A3300 • for shell under through wall stress distribution • polynomial stress approximation • parameters from tables of ASME • wide range applicability(developed for plates but applicable for cylinders as well)

  9. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI determination according to R6 • for pipes under through wall axisymetric stress distribution and global bending • polynomial stress approximation • parameters from tables, but values only for R/t=5-10

  10. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI determination according to R6 • for plates under through wall stress • polynomial stress approximation • parameters from tables

  11. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI determination by FEM • Real 3D crack geometry • Linear elastic material model • J integral calculation/post–processing at the surface and deepest point of the cracks • KI calculation from J:

  12. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI determination by FEM a=55,875 =45° a=18,625 =11,25° a=37,25 =22,5° • MSC.MARC 2005r2 • 3D-s 20 nodes hexagonal elements

  13. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI and J values for 100 MPa maximal tension stress

  14. Applicability of the ASME BPVC for the given 3D geometries =22,5° a/t=0,5

  15. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • KI and J values for 100 MPa maximal bending stress

  16. Applicability of the ASME BPVC for the given 3D geometries =22,5° a/t=0,5 mm

  17. Applicability of the ASME BPVC for the given 3D geometries • What is the reason of the conservatism of ASME XI App A3300? • Is ASME conservative itself? • Can this appendix be applied for this problem at all? • Are the parameters out of the validity ranges? • Any other reason?

  18. Applicability of the ASME BPVC for the given 3D geometries • ASME XI App A3300 has quite wide applicability range - but parameters are given in a coarse grid for a nonlinear function a/t a/2c

  19. Applicability of the ASME BPVC for the given 3D geometries • Linear approximation is required for a real crack size • Polynomial approximation may give more realistic parameter values • Difference can be significant between linear and polynomial approximation =11,25° =22,5° =45° Tabular values

  20. Applicability of the ASME BPVC for the given 3D geometries • Relative difference between polynomial, linear approximations and the calculated KI values q=11,25° q=22,5° q=45° a/t=0,5

  21. Comparison ofASME BPVC XI H4221 and A3300, R6 and FEM • Conclusion • ASME appendix H shows good correlation with the FEM calculations for shallow cracks, but is becoming conservative for deep cracks • ASME appendix A has good correlation with the FEM results for shallow crack. The longer the crack is, the more conservative values can be obtained due to the linear parameter approximation • R6 gives the closest results to FEM, but the values are smaller than the numerically calculated ones - not conservative!

  22. Calculation of KI and JI values for real 3D geometries with DMW • DMW in VVER plants: at steam generator connecting the primary and secondary circuit pressure boundary connection

  23. Calculation of KI and JI values for real 3D geometries with DMW • Analyzed part Rigid ring Vessel Weld Buttering • Crack size • a/w: 0,25; 0,5; 0,75 • : 11,25°; 22,5°; 45° Austenitic part

  24. Calculation of KI and JI values for real 3D geometries with DMW • Loading • From the connected pipes, • Internal pressure • Transient thermal loads

  25. Calculation of KI and JI values for real 3D geometries with DMW • Loads from connected pipes • Tension and bending load from the limit load of connected pipes (extremely high)

  26. Calculation of KI and JI values for real 3D geometries with DMW • Loading from internal pressure • 10 MPa pressure in the primary circuit

  27. Calculation of KI and JI values for real 3D geometries with DMW • Loading internal pressure • 10 MPa pressure in the secondary circuit

  28. Calculation of KI and JI values for real 3D geometries with DMW • Thermal loading • 30°C/h cooling in the secondary circuit • Total loss of main steam pipe • 100°C thermal shock in the secondary circuit

  29. Calculation of KI and JI values for real 3D geometries with DMW • Thermal loading • 20 °C/h heating in the primary circuit, • 100°C thermal shock in the primary circuit

  30. Applicability of the ASME BPVC for the given 3D geometries • Stress distribution on the wall Bending Tension

  31. Applicability of the ASME BPVC for the given 3D geometries a/t=0,5 =22,5°

  32. Applicability of the ASME BPVC for the given 3D geometries =22,5° a/t=0,5 mm

  33. Calculation results for transient thermal loading inerside x outerside Stress distribution for 30°C/h cool as a function of time

  34. Calculation results for transient thermal loading 30°C/h cooling in the secondary circuit a=18,625 mm =11,25°

  35. Calculation results for transient thermal loading 100°C thermal shock in the secondary circuit a=18,625 mm f=11,25°

  36. BAY-LOGI Conclusions • The stress distribution on the wall is significantly different from the tension and bending of a straight pipe • The ASME BPVC XI H appendix can not be applied for the analyzed geometries since it gives non-conservative values. • The ASME BPVC XI A appendix gives conservative approximation, however it can not be recommended for more extended cracks without checking the parameter’ approximations • Thermal loads can be handled as a through wall bending, so ASME BPVC XI A appendix can be applied • Cooling does not have significant effect on the crack propagation above a/t=0,5 • However R6 seems to be applicable, but further numerical verification is needed with other FEM software

  37. Thank you forattention!

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