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Component Testing

Component Testing. Test Setup TapLok Insert Shear Key Copper Threads Friction Tests Collar Shear Tests. NSTX TF FLAG JOINT REVIEW 8/7/03. Michael Kalish. TapLok Threaded Inserts. A “TapLok” 3/8-16 “Medium Length” insert is used (OD into copper is .50” (OD = .562”, length = .562”) )

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Component Testing

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  1. Component Testing • Test Setup • TapLok Insert • Shear Key Copper Threads • Friction Tests • Collar Shear Tests NSTX TF FLAG JOINT REVIEW 8/7/03 Michael Kalish

  2. TapLok Threaded Inserts • A “TapLok” 3/8-16 “Medium Length” insert is used (OD into copper is .50” (OD = .562”, length = .562”)) • Loading: • The stud preload of 5,000 lbf results in 11,800 psi (10,069 psi) in shear at the outer threads of the insert into the copper. • Thermal + Mechanical loading adds a cyclic load of 1,800 psi • Per the inspection certification the Cu Tensile strength = 38 kpsi and Yield strength = 36 kpsi. Material: C10700 Silver Bearing Copper , Hard Drawn (50% Cold Worked) • Values of 34 kpsi used for yield to account for observation of slight degradation to hardness after thermal cycling

  3. Cyclic Testing, TapLok • Using same test setup medium length (.562”)Tap Lok inserts were cycled then pulled • Test sample was heated to 100 C during cycling • Six test pieces were cycled at 5,000 to 6,000 lbf for 50,000 cycles or greater • Test levels reflect the 1,000 cycle thermal loading case • Cycled with 1 Hz Sine Wave • Two samples were cycled at 5,000 to 7,360 lbf to test at the 2x Stress at design life condition • After cycling static pull tests determined if pull out strength had degraded

  4. TapLok Static Pull Test Results • Average pullout force for .562” TapLok was 12,700 lbf corresponding to a calculated ultimate shear stress of 29.9 KPSI (25.6 KPSI) • This value derived from the test data is 36% (17%) higher than the assumed ultimate strength in the fatigue analysis and twice the design load

  5. Results Cyclic Pull Tests for TapLok • No Failure of any sample including two samples cycled at 2x Stress and 50,000 cycles (5,000 lbf to 7,360 lbf) • Pull out strength relatively unchanged for samples cycled at design loads • Yield strength values averaged 82% of Tensile strength • Samples cycled at temperature did not vary from unheated samples

  6. Flag Stud Loading & Stress Summary • With the 5,000 lbf preload and the thermal loading applied the stud sees a max stress of 74.7 ksi • The ultimate tensile strength for the Inconel 718 stud is 210 ksi and the yield strength is 185 ksi

  7. Fasteners / Joint Design Michael Kalish NSTX TF FLAG JOINT REVIEW 8/7/03

  8. Modified Goodman Diagram for Insert in Copper Conductor

  9. Flag Stud Loading • A preload of 5,000 lbf is applied with an equivalent stress of 64,900 psi • Thermal loading after ratcheting of the flag temperature applies an enforced deflection of .0043 inches • Thermal ratcheting +mechanical loading adds 9,800 psi

  10. Modified Goodman Diagram For Stud

  11. Stud Preload • Maintaining the preload on the stud is critical for maintaining contact pressure and contact resistance • Using a long narrow stud results in a much higher stud elasticity relative to the flag • Stud elasticity keeps fatigue loading for the stud and insert low relative to the applied loading

  12. Minimum Contact Pressure 5.00 in 11.00 in Width - W = .79 in; Bolt Hole Dia. = .406 in Contact Area - AC = .79 in x 5.00 in – 4 (π x (.406 in)2)/ 4 = 3.434 in2 Bolt Pretension Force – FPRE = 4 x 5000 lbf = 20000 lbf Minimum Force - FMIN = 4 x 3300 lbf = 13,200 lbf Pretension Contact Pressure – PPRE = FPRE/ AC = 5843 psi Minimum Contact Pressure - PMIN = FMIN/ AC = 3846 psi (without Belleville washers)

  13. Leverage Previous Design Experience • Flag Material: C10700 H002, Silver Bearing Copper, Half Hard. Keep copper thread shear stress below 11,800 psi to eliminate need for retesting. • Tap-lok inserts: Use longest insert possible for given size. • Stud Material: Inconel 718. Pretension much less than .75 yield strength (copper thread shear stress dominates). • Use Belleville washers and/ or Direct Tension Indicating (DTI) washers to monitor bolt pretension, reduce cyclic stress amplitude, and maintain bolt tension with thermal cycling and creep. • Bolts loaded in tension only: separate shear load and compression load functions (rely on friction or separate feature to take shear load). • Monitor joint electrical contact resistance.

  14. NSTX Update Design Tap-Lok Inserts

  15. NSTX Update Design Tap-Lok Inserts

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