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FATIGUE CONSIDERATIONS FOR ITER IVC COILS Jun Feng INTERIM DESIGN REVIEW OF ITER IN-VESSEL COILS (IVC) PPPL, July 26-July 28, 2010 PSFC, MIT. Contents. Goal Method of Analysis VS Coils - Material – Cu - Total fatigue life - Fatigue crack growth life ELM Coils - Material – CuCrZr

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  1. FATIGUE CONSIDERATIONSFOR ITER IVC COILSJun FengINTERIM DESIGN REVIEW OF ITER IN-VESSEL COILS (IVC)PPPL, July 26-July 28, 2010 PSFC, MIT

  2. Contents • Goal • Method of Analysis • VS Coils - Material – Cu - Total fatigue life - Fatigue crack growth life • ELM Coils - Material – CuCrZr - Total fatigue life - Fatigue crack growth life • Conclusions • Issues and Resolution Plan

  3. Goal • Review analysis method, material, loading, and operation environment. • Evaluate total fatigue life and fatigue crack growth life for both VS and ELM coils. • Propose problems and resolutions.

  4. Analysis Method – Total Fatigue Life • Coffin-Manson Law (S-N Curve): • Goodman relation (Mean stress effect) • Miner rule: (Multi-stress fatigue)

  5. Assumptions – Total Fatigue Life • The safety factor of the total fatigue life is 20; • The effect of higher temperature (120C–130C) and radiation are covered by the safety factor; • Residual tension is removed by annealing; • There is no defect on the surface or sub-surface, fatigue crack initiates from the smooth surface of the conductor.

  6. Analysis Method – Fatigue Crack Growth Life • Paris Law: • Stress Intensity Factor • Walker equation (Mean stress effect) • Miner rule: (Multi-stress fatigue)

  7. Assumptions – Fatigue Crack Growth Life a. An elliptical sub-surface crack of aspect ratio 0.1 (equivalent surface crack of aspect ratio of 0.2), b. The safety factor: 2 for crack size, 1.5 for fracture toughness, and 2 for crack growth life. c. The effect of higher temperature and radiation are included in the safety factor. d. Any residual tension is removed by annealing.

  8. VS Coil – Pure Copper

  9. VS Coil – Total Fatigue Life

  10. VS Coil - Fatigue Crack Growth Life

  11. ELM Coil – CuCrZr Alloy

  12. ELM Coil – Total Fatigue Life

  13. ELM Coil – Fatigue Crack Growth Life

  14. N ~30,000 x2 as initial crack size ~ 17mm^2 (~1.5mm in depth)

  15. Conclusions • The total fatigue life of VS coil is much greater than the design life 30,000 x20 since the applied stress is around the endurance limits. • The fatigue crack growth life of VS coil is controlled by the 1st peak stress. For any visible crack up to ~5 mm in depth, the life is greater than the designed life of 30,000 x 2 due to the applied low tensile stress. • The total fatigue life of ELM coil made of intermediate or high strength CuCrZr is much beyond the designed life 30,000 cycles x20. However, the low strength CuCrZr would induce severe plastic strain during operation, and therefore, can not generate required fatigue life. • d. Any visible cracks up to depth ~1.5 mm in ELM coils are allowed for the designed machine cycle of 30,000 x 2.

  16. Issues and Resolution Plan

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