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Fatigue calculations on benchmark tasks according to ASME code, experiences, results

Bay Zoltán Foundation for Applied Research VEIKI Power Research Institute. Fatigue calculations on benchmark tasks according to ASME code, experiences, results. Szávai Szabolcs Pálfi Tamás Tóth László. Benchmark tasks for the Paks License Renewal Project.

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Fatigue calculations on benchmark tasks according to ASME code, experiences, results

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  1. Bay Zoltán Foundation for Applied Research VEIKI Power Research Institute Fatigue calculations on benchmark tasks according to ASME code, experiences, results Szávai Szabolcs Pálfi Tamás Tóth László

  2. Benchmark tasksfor the Paks License Renewal Project • Created by Mechanical Components Scientific Committee • Solution made by different research institutes, solution methodology accepted by MC-SC • Conflict the ASME interpretation of different experts • Compare the result of different solution methods and tools • Develop verification cases for the applied methodologies of the project • Create a general solution method which can also be used for more complicated problems

  3. Benchmark tasks for the Paks License Renewal Project • Analysis of pipeline and its elements • Evaluation of flange for structural integrity, stiffness, and leak tightness • Structural and fatigue analysis of a thick walled pressure vessel with openings

  4. Applied codes and regulations • ASME BPV CODE SECTION. III. (2001) • Procedure for actions related to the life time extension of equipment operating in nuclear plants • Directives for structural analysis of pressure vessels. OAH NBI 3.3

  5. Benchmark tasks for the Paks License Renewal Project • Simple problems require mainly numerical methods (e.g. FEM) however analytical solutions are also acceptable • ASME based, PNAE material properties • Class I. components • Design and operational conditions • Coupled thermo-mechanical static and cyclic analysis

  6. Benchmark tasks

  7. Analysis types

  8. T [˚C] p [MPa] T [˚C] p [MPa] 16 130 130 19,5 B. Cycle (2x) A. Cycle (1x) 0,1 60 60 0,1 t [h] t [h] 1,65 3,4 1,4 1,4 3,4 0 0 1,65 T [˚C] p [MPa] p [MPa] T [˚C] 12 300 12 300 2 month C. Cycle (5x) D. Cycle (5x) t [min] 60 0,1 290 11 t [h] 1454 1446 6 0 10 40 0 60 Loadcases • Cyclic load: • Design Load: p=13,7 MPaT=325ºC • Test pressure: p=16,4 MPa, T=140ºC • Load on the nozzle:N=300kN, M=200kNm T=100kNm

  9. Structural and fatigue analysis of a pressure vessel • Structural analysis for design conditions • Critical points (2. and 3.) • Nozzle • Fatigue evaluation at 3. • Thermal stress calculation in the cylindrical wall

  10. Structural analysisof the nozzle • Material properties based on PNAE • Analysis of the nozzle based on WRC107

  11. Structural analysisof pressure vessel • Axysymmetrical FEM model to get sufficient results for the critical points. • Derive the primary, secondary and peak stresses from the calculated stress distribution • Determination of the membrane and membrane+bending stresses • Fatigue evaluation • Calculation of the stress intensities • Rainflow analysis for determining the stress cycles • FSRF determination for the analyzed points • CUF calculation • Critical point evaluation

  12. Results, Experiences • Calculations were done by 2 independent research institutes • VEIKI Rt., Budapest • BAY-LOGI and Univ. of Miskolc, Miskolc • Good agreement between the stresses and the location of critical elements • WRC107: COADE interpolated and „manual” diagram reading of the parameters caused different results in the nozzle

  13. Results, Experiences

  14. Wall temperature distributions Cycle „A” Cycle „C”

  15. Fatigue analysis • Stress differences were calculated considering varying principal stress directions: • At the principal stress calculation the difference of each stress components in the two time steps was used

  16. Analysis of pipeline and its elements • Structural analysis • Design condition • Level A • Pressure test • Fatigue analyses • Primary, secondary and thermal stresses

  17. Required steps for analysisof pipeline and its elements • Material properties • based on PNAE • CAEPIPE model for • Stiffness calculation • Determination of the Moments for each element • ASME Class 1 stress indexes • Pipes, welds, curved pipes, branch connections, welded transitions • Structural analysis • Fatigue analysis • Determination of the stress amplitudes • CUF calculation

  18. Finite element solution • Stresses were calculated also using shell elements in Msc Nastran4W • In each cross-section: • Stress transformations needed to determine stresses in the local coordinate system • Parametric calculations needed to calculate the highest bending stress

  19. Finite element solution • Results using finite element solution was in good agreement with the results using CAEPIPE model and ASME stress indexes • Large deformation calculation needed, because the pressure caused deformation at the curved sections essentially affects stiffness • Special spring elements had to be used to model the support

  20. Analysis of flange joint for structural integrity, stiffness and leak tightness • Structural analysis for: • Level A • Pressure test • Leak tightness evaluation • seating load • stiffness • Fatigue analysis of bolts and threads

  21. Analysis of flange joint for structural integrity, stiffness and leak tightness • Material properties: • based on PNAE • Elastic model including: • bolts • sealing

  22. Analysis of flange joint for structural integrity, stiffness and leak tightness Required steps of the evaluation • Required bolt area verification • Analysis of bolts for level A condition • Stiffness calculation of the joint • Determination of the displacements • Examination of the leak tightness

  23. Analysis of flange joint for structural integrity, stiffness and leak tightness Required steps of the evaluation: • Analysis of the bolts for test pressure • Calculation of the gasket force • Examination of the thread • Fatigue analysis for bolts and threads

  24. The finite element model • Spring elements were used to model the seal and the bolts • Rigid elements were used for the washers • The active bolt length=unconstrained length+2x3 threads

  25. Results • Calculations were done in 2 independent research institutes • VEIKI Rt., Budapest: • Finite element model including bolts and sealing • BUTE, Budapest • Finite element model for the flanges + semi analytical model for stiffness calculations • Good agreement between the stiffness values and the stresses

  26. Results • Some of the stress calculations were done also by using analytical methods , and got higher stresses then by FEM calculations, because more complex analytical model required

  27. Check points for future participants

  28. Summary and conclusions The developed benchmark tasks are suitable for: • Demonstrating the ASME methodology in accordance with the Hungarian directives • Comparing the result of different solution methods and tools • Providing verification points for the applied methodologies • Act as a general solution method, can also be used for more complex problems

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