1. Twisted Racetrack Analysis Update

2. Twisted Racetrack Model
“real” clamp added to the model
Geometry restrictions unique to the twisted racetrack coil prevent the use of 1/8” shim plates at “severe” turn/twist areas. Pseudo clamps left off at these locations

3. Restraints and loads
- Contact surfaces are used between the clamp winding and the tee.
Thermal growth is imposed on the winding by utilizing the cte property and by applying a known strain over a given temperature change.
Example: strain = -800με , arbitrary temp difference = 72 F. Therefore,
Winging cte = -800με /72 F = = 1.11E-5 /F
Tee cte = 0
Winding is broken into regions (between blue lines) on which the magnetic pressure loads are applied.
Pseudo clamps are restrained in their respective normal directions to simulate real clamp behavior

4. Clamp modeling
Wave spring in clamp pocket
Modulus of washers is tailored to represent the spring constant of the belleville washers. Example: k = 26,000 lb/in, Awasher = 0.81in2, Depthwasher = 0.15 in2. Therefore: E= k*depth/A = 4814 psi
The cte of the washer is used to impose a preload on the clamp and winding. Assume 0.1 in/in stain Therefore: cte = 0.1 / -72 F = /F and preload for “hard” springs is 2600 lbs, and 1000 for “soft” springs
All washers have the same spring constant but have different modulus values.
The clamp is fixed to the tee by a stud at the top of the clamp and a representative bolt head on the lower end.
Fixed to tee
Contact Surfaces
Backside of washer is fixed to tee bolt
Contact Surfaces are used between the clamp and the winding.

5. Arriving at a viable clamp design
Winding deflection and strain are driving forces behind parameter selection.

6. Overall Deformation Case 2 Case 1 Case 3 Points:
Winding form more flexible than shell
Relative deformation between winding and form depends on springs and winding stiffness
Case 2
Model fixed here
Case 1
Case 3

7. Von Mises Stress
Case 2
Case 1
Case 3

8. Tee and Winding Stress (Case 1) (stresses high due to hard springs)
Peak Stress Caused by bolts
Peak Stress Caused by clamp pads
Red > 10,000 psi

9. Clamp Analysis Case 1
Deformation
Von Mises Stress

10. Clamp Analysis Cases 2, 3
(stresses lower with softer springs, case 3 shown)
Deformation
Von Mises Stress

11. Closure
The upgrade to wildfire has opened some avenues with mechanica that were previously closed. I.e.) modeling multiple contact surfaces (clamps) and exporting deformed shape of the winding?
Current Model accounts for Belleville washers, clamps with various material properties and the shrinkage off the tee.
More clamps may be added to the model if needed (limit?) and the pseudo clamps may slowly be replaced.
Analysis Procedure can be applied to the NCSX modular coils.