Component Testing

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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
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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

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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

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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

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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

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Fasteners / Joint Design
Michael Kalish
NSTX TF FLAG JOINT REVIEW 8/7/03
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Modified Goodman Diagram for Insert in Copper
Conductor
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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

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Modified Goodman Diagram For Stud
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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

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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 (p
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)
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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.

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NSTX Update Design Tap-Lok Inserts
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NSTX Update Design Tap-Lok Inserts
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