# Presentation: 373045

## NSTX TF Flag JointDesign ReviewSUMMARYC Neumeyer8/7/3

## Topics

- Performance
- Design Margins
- Design Improvement Summary
- Conclusions

## PERFORMANCE

- FEA Element Pressures and Resistivities

*Red cells > 1****-in**2*

## Temperatures Well Below Limit of 120oC

- Contact Region

- Max Temperature of 94oC Occurs Just After EOFT

-  Tflat = 0.7sec (vs. 0.6 req’t)
-  Bolt Holes not exactly modeled (+10oC)
-  OH constant at max current (-TBDoC)
-  Insignificant change from constant resistivity simulation

## OFF-NORMAL CASE: 3000lbf PRELOAD

*Normal*

-  Peak Temperature ≈ 3oC Higher
-  Temperature Distribution Different
-  Current Redistribution Beneficial

- Notes:
- Held SOFT pressure conditions after SOFT due to lack of EOFT data
- Color scales different

*Off-Normal*

## DESIGN MARGIN METHODOLOGY

- State Safety Factor against Yield (as applicable) and against Failure
- Flag bolts, Collar bolts, Box bolts
- Compare load to _published material data_ for yield and ultimate tensile
- Threaded inserts and Shear Shoe bolts
- Compare load to yield and failure data* from _pullout tests_
- Failure data based on _3____ statistics_
- Yield based on stress/strain test curves , average yield/failure ratio
- Wet lay-up
- Compare load to failure data* from _shear tests at 1ksi compression_
- Failure data based on _3____ statistics_
- FEA-derived loads
- Use worst load from all “nominal” cases:  =0.2,0.4, T= SOFT,EOFT,EOP
- *Note: Data from uncycled samples

## SHEAR TEST DATA INTERPRETATION

## TEST DATA

## DESIGN MARGINS

## DESIGN IMPROVEMENTS

| Feature | Old Design  | New Design |
| --- | --- | --- |
| Hub Stiffness | Not adequate; lacking stiff linkages between disks because flags could slide w.r.t. disks | Very stiff. Boxes form webs with disks like  |
| Bolts/Studs | Shoulder engagement was too small  | Shear Shoe using two 3/8” dia bolts |
|  | 5/16” Bolt thread necked down too far, shank not necked down, not compliant for thermal cycling | 3/8” Studs necked down to root diameter, belleville washers |
|  | Torsion in long bolts during tightening, inaccurate tensioning | Studs with nuts used in place of long bolts, stud tensioner |
|  | Dual purpose bolts, combined tension and shear functions, tolerance issues, torque(tension) uncertainty | Loose fitting clearance holes for studs, separate shear shoes |
|  | Four 5/16" bolts @ 2500#, marginal friction to carry shear  | Four 3/8" studs @ 5000#, doubling of preload  |
|  | Thin washers under bolt heads at tee-ends | 1/4" thick washer plate over Belleville washers at tee-ends |

## All defects contributing to original failure have been addressed

*All defects contributing to original failure have been addressed*

| Feature | Old Design  | New Design |
| --- | --- | --- |
| Inserts | Keensert type, marginal thread engagement | Taplok type, thread engagement > 0.5" |
| Shimming | Manually selected and inserted G10 shim stock
 | Hysol/glass tape potting in boxes, mold released to permit thermal growth |
| Out-of-Plane Load Path | Wedged G10 blocks with pusher bolts | Flags potted in boxes, boxes bolted to hub disks |
| Torque Collar | Two piece collar bolted directly to hub. Wet lay-up 0.25” thick Hysol RE2039 & HD3561. Holes in collar for epoxy outflow to enhance adhesion.  | Three piece collar with sliding contact with hub for torsion-only connection. Wet lay-up 0.180” thick Hysol E-120HP (improved adhesive strength). Serrations in collar to enhance adhesion. |
| Joint Resistance Measurement | 10A Biddle measurement via connection to two half flags on disassembled joint, 1μΩ resolution | 200A precision measurement using voltage taps in situ, ≈ 20x enhanced resolution |

## CONCLUSIONS

- New Design Corrects All Defects Associated with Original Design
- New Design Has Sufficient Margins at 6kG
-  Follow-on Activities Will Increase Confidence
-  Mechanical Prototype Testing
-  Electrical Prototype Testing
-  Instrumentation During Commissioning and Operations
- - voltage drop (200A maintenance and real-time) system
- - other (temperature, strain, displacement)