# Presentation: 451801

## NSTX TF Flag JointTorque Collar Chit ReviewC Neumeyer9/11/3

## 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.*

##   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*

##   Pursued several variants before arriving at a design which....

-   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

*Latest Design*

- Keys for torsion,
- free for vertical and
- Radial motion

- Inconel Struts

- Threaded Connectors

- Anchor Bushings

- Anchor Pins

## 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 R&D tests at 600psi compression

## Analysis shows that collar-less design meets all requirements

- 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

## 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

## PURPOSE OF REVIEW

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

## ANALYSIS OF SOFT COLLAR-LESS CASE

| Case | lost contact area
 | <1000 psi contact pressure |
| --- | --- | --- |
| 6kG w/collar | 4% | 9%
 |
| 6kG w/o collar | 15.6%	 | 21.3%
 |

## 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

## PRESSURE & RESISTIVITY W/O COLLAR

- Note: Data interpolated from uniform pressure during rampup to SOFT,
-           then held fixed at SOFT values thru EOP

- SOFT assumption is conservative

## Add 15oC 

- Add 15oC
- For Bolt Hole
- Effect, Tmax = 117.5oC

## CURRENT REDISTRIBUTION

- With Collar

- Without Collar

*Note: Contour values not equal*

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

## SUMMARY

-  Design meets allowables without collar
- Conservativism still remains
- All PF coils at max current for full time duration
- 0.7 sec flat top
- T=120oC
-  Collar increases margins, but adds risk and complexity

* **Strategy to defer collar is the best to pursue at this time*

## 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

## NEW COLLAR DESIGN

## FEA OF NEW COLLAR DESIGN

**Scotchply & CTD**

**Hysol Insulation**

**3-total applied Torque =0.25M lb-inch**

**angular motion fixed**

**angular motion fixed**

## TYPICAL FEA RESULT (SOFT)

- Compression

- Twist Shear (Torque)

- Axial Shear (Thermal)

- Combined Shear

## SAFETY FACTOR CALCULATION

- 	Shear_VectorSum = {(Shear_angular)2 + (Shear_long)2}0.5
- 	Shear_Allowable = 28MPa(4ksi) + 1.3*|Compression|
- 	Safety_Factor = Shear_Allowable / Shear_VectorSum

## FEA SUMMARY TABLE

|  | Pressure on insulation | angular shear on insulation | z-direction shear on insulation | Safety factor with compress. |
| --- | --- | --- | --- | --- |
| dT=17 degree
with Torque
0.25M[lb-inch] | 4~57MPa
(0.6~8.1ksi)
ave. ~25MPa | 15MPa
(2.1ksi) | 5MPa
(0.7ksi) | 2.6 |
| dT=54 degree
with Torque
0.25M[lb-inch] | 9~52MPa
(1.3~7.4ksi)
ave. ~25MPa | 29MPa
(4.1ksi) | 14MPa
(2.0ksi) | 1.8 |
| dT=72 degree
without Torque | 11~45MPa
(1.6~6.4ksi)
ave. ~25MPa | 28MPa
(4ksi) | 18MPa
(2.6ksi) | 1.9 |