1. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Assessment of crack like defect in dissimilar welded joint by analytical and finite element methods BAY-LOGI Safety-Relibility and Risk of Engineering Plants and Components, Second Hungarian-Ukrainian Joint Conference, Kyiv, Ukraine, 19-21. September 2007. Szabolcs Szávai Róbert Beleznai Tibor Köves

2. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Objectives  Assess the applicability of the analytical K I solutions of the ASME BPVC for  complex geometry of VVER’s DMW  mismatch materials like DMW  mechanical and transient thermal loads

5. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Bay-Logi Activities  Comparison of K I values determined by ASME BPVC XI H4221 and A3300, R6 (FITNET) and FEM for pipe-like geometries under tension and bending loading  Calculation of K I and J I 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM  K I determination according to ASME XI H4221 –for pipes under bending and tension –circumferential defect –simple equation –wide range applicability

8. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM  K I 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM  K I 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM  K I determination according to R6 –for plates under through wall stress –polynomial stress approximation –parameters from tables

11. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI  K I 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 –K I calculation from J: Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM

12. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI a=55,875  =45° a=37,25  =22,5° a=18,625  =11,25° Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM MSC.MARC 2005r2 3D-s 20 nodes hexagonal elements  K I determination by FEM

13. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM  K I and J values for 100 MPa maximal tension stress

14. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI a/t=0,5  =22,5° Applicability of the ASME BPVC for the given 3D geometries

15. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME BPVC XI H4221 and A3300, R6 and FEM  K I and J values for 100 MPa maximal bending stress

16. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI a/t=0,5 mm  =22,5° Applicability of the ASME BPVC for the given 3D geometries

17. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI 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  =45°  =22,5°  =11,25° Tabular values

20. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Applicability of the ASME BPVC for the given 3D geometries  Relative difference between polynomial, linear approximations and the calculated K I values a/t=0,5  11,25°  22,5°  45°

21. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Comparison of ASME 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I values for real 3D geometries with DMW  DMW in VVER plants: at steam generator connecting the primary and secondary circuit pressure boundary connection

23. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I values for real 3D geometries with DMW  Analyzed part Austenitic part Rigid ring Vessel Weld Buttering  Crack size –a/w: 0,25; 0,5; 0,75 –  : 11,25°; 22,5°; 45°

24. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I values for real 3D geometries with DMW  Loading –From the connected pipes, –Internal pressure –Transient thermal loads

25. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I values for real 3D geometries with DMW  Loading from internal pressure –10 MPa pressure in the primary circuit

27. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I values for real 3D geometries with DMW  Loading internal pressure –10 MPa pressure in the secondary circuit

28. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation of K I and J I 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. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Applicability of the ASME BPVC for the given 3D geometries  Stress distribution on the wall Tension Bending

31. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI a/t=0,5  =22,5° Applicability of the ASME BPVC for the given 3D geometries

32. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI a/t=0,5 mm  =22,5° Applicability of the ASME BPVC for the given 3D geometries

33. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Stress distribution for 30°C/h cool as a function of time Calculation results for transient thermal loading x inerside outerside

34. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI 30°C/h cooling in the secondary circuit a=18,625 mm  =11,25° Calculation results for transient thermal loading

35. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Calculation results for transient thermal loading 100°C thermal shock in the secondary circuit a=18,625 mm  =11,25°

36. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems 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 BAY-LOGI

37. Bay Zoltán Foundation for Applied Reseach Institute for Logistics and Production Systems BAY-LOGI Thank you for attention!