NSTX TF Flag Joint Torque Collar Chit Review C Neumeyer 9113

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NSTX TF Flag JointTorque Collar Chit ReviewC
Neumeyer9/11/3
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BACKGROUND

• Four chits from the August 7 review expressed
  concern regarding the torque collar design
• TITUS
• The shear capacity of wet lay-up is based on test
  and a fine mesh model. Either Irv
• should have a local model with a similar fine
  mesh or the 1.6 factor from the
• test FEM should be ignored.
• NELSON
• Concern about welding ears to torque collar
  distortion, heating, etc. Suggest
• mock-up to confirm feasibility.
• NELSON
• Concern is shear lag at gaps. Recommend analysis
  of current design and
• continuous design, thicker bond line, more gaps,
  etc.
• ANDERSON
• Build mock-up of collar and test for shear
  failure due to temperature and torsion.

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• Initiated FEA of collar
• discovered problems not only with shear lag at
  gaps but also stress concentrations and excessive
  variations in compression due to lack of vertical
  symmetry

FEA Model of August 7 Collar Design
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• Pursued several variants before arriving at a
  design which.
• fits in the available space
• can be installed despite the limited access
• allows access to the box bolts
• limits shear in wet lay-up to acceptable values
• - analysis and testing not yet finalized

Inconel Struts
Threaded Connectors
Keys for torsion, free for vertical and Radial
motion
Anchor Bushings
Anchor Pins
Latest Design
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• In parallel, FEA cases have been run for
  collar-less design
• no significant structural impact in removing
  collar
• changes in joint pressure and resistance pattern
  result in a shift in the current distribution,
  but temperature impact is not severe
• peak temperature at joint 10oC higher than
  cases with collar
• Review of original FEA indicates that collar
  benefit to turn-turn insulation shear is not
  required to meet allowable
• collar reduces peak insulation shear by 17
• Peak shear under worst case conditions without
  collar would increase from 2.2 to 2.7ksi
• Allowable is 2.9ksi which includes a safety
  factor of 2 against RD tests at 600psi
  compression

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• Advantages of Collar
• 10oC peak temperature benefit
• 17 turn-turn shear stress benefit
• Restraint against clocking of bundle, in
  addition to friction
• Disadvantages of Collar
• Additional complexity of assembly
• Reduced access to box bolts
• Thermal induced stresses
• Potential cost/schedule risk

Analysis shows that collar-less design meets all
requirements
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• NEW STRATEGY
• Continue design/analysis/test of collar and bring
  to closure
• Do not implement collar initially, except for
  anchor pins
• Perform measurements during next run to confirm
  analysis
• Operations to be initiated at low Bt ( 3kG)
• Level to be increased only as justified by
  measurements
• Implement collar in future if measurements are
  not favorable

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PURPOSE OF REVIEW

• Obtain critique of collar-less strategy
• Preview new collar design but defer review to a
  later date
• if necessary

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ANALYSIS OF SOFT COLLAR-LESS CASE
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PRESSURE RESISTIVITY WITH COLLAR
Note Data interpolated from uniform pressure
during rampup to SOFT and during Flattop, then
held fixed at EOFT values thru EOP
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PRESSURE RESISTIVITY W/O COLLAR
SOFT assumption is conservative
Note Data interpolated from uniform pressure
during rampup to SOFT, then held fixed
at SOFT values thru EOP
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Add 15oC For Bolt Hole Effect, Tmax 117.5oC
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CURRENT REDISTRIBUTION
With Collar
Without Collar

• Current finds path of
• least resistance
• Much of joint is inactive

Note Contour values not equal
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SUMMARY

• Design meets allowables without collar
• Conservativism still remains
• All PF coils at max current for full time
  duration
• 0.7 sec flat top
• T120oC
• Collar increases margins, but adds risk and
  complexity

Strategy to defer collar is the best to pursue
at this time
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NEW COLLAR STATUS

• Design is in-hand
• Fabrication drawings being generated from Pro-E
  CAD model
• Analysis is essentially complete
• - SOFT, EOFT, EOP cases
• - Safety factor calculation based on
  extrapolation up to 8ksi of shear strength from
  prior database with compression up to 2ksi
• Testing is underway to determine wet lay-up
  shear at high compression

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NEW COLLAR DESIGN
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FEA OF NEW COLLAR DESIGN
angular motion fixed
3-total applied Torque 0.25M lb-inch
Scotchply CTD
angular motion fixed
Hysol Insulation
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TYPICAL FEA RESULT (SOFT)
Twist Shear (Torque)
Compression
Combined Shear
Axial Shear (Thermal)
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SAFETY FACTOR CALCULATION

• Shear_VectorSum (Shear_angular)2
  (Shear_long)20.5
• Shear_Allowable 28MPa(4ksi)
  1.3Compression
• Safety_Factor Shear_Allowable /
  Shear_VectorSum

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FEA SUMMARY TABLE