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NEEP 541 – Material Properties

NEEP 541 – Material Properties. Fall 2003 Jake Blanchard. Outline. Materials in Reactors Fission Fusion Material Properties Tensile tests Impact tests Creep tests. Materials in Reactors. Fission Fuel Cladding Moderator Core structure Reflector Control rods Coolant

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NEEP 541 – Material Properties

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  1. NEEP 541 – Material Properties Fall 2003 Jake Blanchard

  2. Outline • Materials in Reactors • Fission • Fusion • Material Properties • Tensile tests • Impact tests • Creep tests

  3. Materials in Reactors • Fission • Fuel • Cladding • Moderator • Core structure • Reflector • Control rods • Coolant • Pressure vessel • shielding • Fusion • Fuel • Structure • Tritium breeder • Coolant • insulators • shielding

  4. Fission • Primary radiation damage is in fuel and cladding • Cladding: • Adequate strength (T, fluence) • Corrosion resistance • Thermal conductivity • Neutronics (low absorption) • Available resources • Fabricability • Inexpensive

  5. Cladding Materials • Low thermal absorption cross section • Al • Mg • Zr • Be • High thermal absorption cross section • Nb • Mo • Ta • V • Ti • Steel

  6. Some Numbers

  7. Fusion Structure Requirements • Same as fission plus… • Low swelling • Low embrittlement • Typical Materials • Austenitic steel (316 SS) • Ferritic steel (lately ODS FS) • Refractory alloys • composites

  8. Radiation Effects • Radiation hardening (increase in strength) • Embrittlement (decrease in ductility) • Swelling (volume increase due to voids) • Irradiation creep

  9. Tests • Tensile tests (modulus, ductility, strength) • Tube burst tests (creep) • Impact tests (ductility, fracture toughness)

  10. Tensile Tests

  11. Understanding the Tensile Test • A0=cross sectional area before test (in test section) • A=cross sectional area during test (load=P) • L0=section length before test • L=section length during test

  12. Tensile Tests • Engineering stress=eng=P/A0 • True Stress=true=P/A • Before necking, A~A0 • Engineering strain==(L-L0)/L0 • True strain=

  13. Stress-Strain Curve

  14. True Stress – True Strain

  15. Combined

  16. When does necking start? • Plastic Instability (dP=0) Volume is conserved

  17. Plastic Instability Necking occurs when slope of true stress-true strain curve=true stress

  18. Plastic Instability • suppose

  19. Hardening

  20. Impact Testing • Test for ductility • Measure energy absorbed during fracture

  21. Typical Results • DBTT=ductile to brittle transition temperature Upper shelf Lower shelf E (J) irradiated 40 T DBTT

  22. Creep Tests • Apply load and measure deformation as a function of time primary secondary tertiary Creep strain time

  23. Study creep rupture with a tube burst test 2R L p

  24. Burst Test Analysis Slice cylinder vertically p

  25. Burst Test Analysis Slice cylinder horizontally (picture is shown cut away vertically as well)

  26. Burst Test Analysis • Uniaxial (1-D tensile test) • Constant stress

  27. Burst Test Analysis

  28. Burst Test Analysis

  29. Burst Test Analysis

  30. Burst Test Analysis

  31. Burst Test Analysis • Negative radial strain means that wall gets thinner • Zero axial strain means length doesn’t change • Positive hoop strain means radius increases • Analysis assumes small strain, constant stress • For large strain, wall thins and stress increases, leading to rupture

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