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 120 o C Contact Region Max Temperature of 94 o C Occurs Just After EOFT Tflat = 0.7sec (vs. 0.6 req’t) Bolt Holes not exactly modeled (+10 o C) OH constant at max current (-TBD o C) Insignificant change from constant resistivity simulation

OFF-NORMAL CASE: 3000lbf PRELOAD Normal Peak Temperature ≈ 3 o C Higher Temperature Distribution Different Current Redistribution Beneficial Notes: 1)Held SOFT pressure conditions after SOFT due to lack of EOFT data 2)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 FEA peak/avg = 1.65

TEST DATA

DESIGN MARGINS

DESIGN IMPROVEMENTS FeatureOld DesignNew Design Hub StiffnessNot adequate; lacking stiff linkages between disks because flags could slide w.r.t. disks Very stiff. Boxes form webs with disks like Bolts/StudsShoulder engagement was too smallShear 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" 2500#, marginal friction to carry shear Four 3/8" 5000#, doubling of preload Thin washers under bolt heads at tee-ends1/4" thick washer plate over Belleville washers at tee-ends

All defects contributing to original failure have been addressed FeatureOld DesignNew Design InsertsKeensert type, marginal thread engagementTaplok type, thread engagement > 0.5" ShimmingManually selected and inserted G10 shim stockHysol/glass tape potting in boxes, mold released to permit thermal growth Out-of-Plane Load Path Wedged G10 blocks with pusher boltsFlags potted in boxes, boxes bolted to hub disks Torque CollarTwo 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)