1. NCSX Modular Coil Joint Load/Stress Calculation By Leonard Myatt Myatt Consulting, Inc.

2. 29 January 2007MC Joint Analysis2 The Big Picture Estimates of Bolt Loads with Bonded Flange Interfaces need to be checked. MC Global model already quite big. Need to develop a simple bolt model with properties (shear & tensile stiffness) similar to the reference joint designs. Apply approximation to MC Global model to determine bolt load distribution.

3. 29 January 2007MC Joint Analysis3 Process Overview Import Joint Models from ORNL into ANSYS: “Joint1” (Double nut on Stud) “Joint2” (Bolt & tapped flange hole) Apply symmetry, add 30 mil Stycast gap, add general contact at flange-shim interface Loading: Impose lateral deformation (parallel to flange face) Impose axial deformation (parallel to bolt axis) Response: Lateral force and joint stiffness v. imposed deflection. Axial joint stiffness (single-value per joint configuration).

4. 29 January 2007MC Joint Analysis4 Process Overview, cont’d FYI: Report stresses for 25 k-lb lateral load. Develop simplistic equivalent bolt model for Global MC simulations. Incorporate simplistic bolted connection model into Global MC simulation. Analysis Units: Bolted Joints use English units. Global MC uses SI units.

5. 29 January 2007MC Joint Analysis5 Reference Design (Courtesy D. Williamson) Joint1 Joint2 Expected 30 mil Annular Gap at Flange Through-Hole Not Shown

6. 29 January 2007MC Joint Analysis6 Set Preload to ~73 k-lb f NASA Technical Memorandum 106943 used to define Preload Spec http://gltrs.grc.nasa.gov/reports/1995/TM-106943.pdf

7. 29 January 2007MC Joint Analysis7 ANSYS Model, Joint1

8. 29 January 2007MC Joint Analysis8 ANSYS Model, Joint2

9. 29 January 2007MC Joint Analysis9 Joint1 Bolt Preload Nominal Preload ~50 ksi

10. 29 January 2007MC Joint Analysis10 Joint2 Bolt Preload Nominal Preload ~50 ksi

11. 29 January 2007MC Joint Analysis11 Joint1 Force, Deflection & Stiffness Preload + Transverse Motion

12. 29 January 2007MC Joint Analysis12 Joint2 Force, Deflection & Stiffness Preload + Transverse Motion

13. 29 January 2007MC Joint Analysis13 Joint1 Contact Stress (S3) G11 & Stycast Insulating Parts Stress & Force Vectors, 25000 lb Shear Load

14. 29 January 2007MC Joint Analysis14 Joint1 Bolt Tension Stress (S1) Stress from 25000 lb Shear Load

15. 29 January 2007MC Joint Analysis15 Joint2 Contact Stress (S3) G11 & Stycast Insulating Parts Stress & Force Vectors, 25000 lb Shear Load

16. 29 January 2007MC Joint Analysis16 Joint2 Bolt Tension Stress (S1) Stress from 25000 lb Shear Load

17. 29 January 2007MC Joint Analysis17 Tensile Stiffness of Joints 1&2 Apply axial loading where bolt hardware interfaces with flange face. Calculate tensile stiffness of each joint. Stiffness values to be used as basis for developing simplistic joint model for more precise Global simulation of MC structure.

18. 29 January 2007MC Joint Analysis18 Joint1 Tensile Stiffness ~5.4 M-lb/in Check: k(bolt)=AE/L~(1.48in 2 )(27.6Msi)/6”~7 M-lb/in

19. 29 January 2007MC Joint Analysis19 Joint2 Tensile Stiffness ~8.8 M-lb/in Check: k(bolt)=AE/L~(1.48in 2 )(27.6Msi)/3.5”~12 M-lb/in

20. 29 January 2007MC Joint Analysis20 Simple Model of Bolted Joint1 for Equivalent Stiffness Approx. Stiffness Match Achieved with 2.9” diameter Bolt

21. 29 January 2007MC Joint Analysis21 Simple Model of Bolted Joint2a for Equivalent Stiffness Approx. Stiffness Match Achieved with 2.75” diameter Bolt

22. 29 January 2007MC Joint Analysis22 A-B Joint Bolt Definition Bolt layout drawing shows 26 bolts at this A-B flange.

23. 29 January 2007MC Joint Analysis23 A-B Bolt Types (M. Cole FP-STUDS.PPT)

24. 29 January 2007MC Joint Analysis24 Bolts 1-9 Defined by Project (M. Cole FP-STUDS.PPT)

25. 29 January 2007MC Joint Analysis25 Bolts 10-15 Defined by Project (M. Cole FP-STUDS.PPT)

26. 29 January 2007MC Joint Analysis26 Bolts 16-18 Defined by Project (M. Cole FP-STUDS.PPT)

27. 29 January 2007MC Joint Analysis27 Bolts 19-26 Defined by Project (M. Cole FP-STUDS.PPT)

28. 29 January 2007MC Joint Analysis28 Application of Equivalent Stiffness Bolted Joints to Global Model at A-B Flange Solid PIPE16 elements, with dimensions to match calc’d Joint stiffness, are added to each A-B Bolted connection.

29. 29 January 2007MC Joint Analysis29 Top 15 A-B Bolts

30. 29 January 2007MC Joint Analysis30 Bottom 11 A-B Bolts

31. 29 January 2007MC Joint Analysis31 Analysis Notes A significant effort was made to simulate both zero and finite friction at the A-B flange. Bolt Preload Load-Step converged OK. But excessive computer run-time (4+ days for 4% of EM load) has lead to an alternative approach: The AB interface is modeled as sliding and always in contact (KEYOPT(12)=4) with  =0.2 friction.

32. 29 January 2007MC Joint Analysis32 Analysis Notes, cont’d The model converges nicely, even with friction. This approach (sliding without separation) does not report accurate tensile loads on the bolts. We may ultimately need to find a way to run the model with friction and open/closed contact behavior (keyopt(12)=0) to confirm preload levels and bolt stresses. (This requires more thought.)

33. 29 January 2007MC Joint Analysis33 Global Model Results Various Contour Plots of A-B Flange Results: Bolt Preload [k-lb or kip] Bolt Shear Force Range [k-lb or kip] produced by EM Load cycle. Non-zero value indicates that the joint is not completely isolated with preload & modest friction. Slippage produced by EM Load cycle (~1/2 mm scuffing at inboard leg)

34. 29 January 2007MC Joint Analysis34 Preload [kip] in A-B Flange Bolts (67 min.<78 Average<81 max.) Falls within design goal of 52-86 kip

35. 29 January 2007MC Joint Analysis35 Shear Force Range in A-B Flange Bolts from EM Loads (  =0.2, 78 kip Preload) Max Shear Loads: 1.5 & 2.5 kip, Bolts 25 & 26)

36. 29 January 2007MC Joint Analysis36 Contact Slippage [m] at A-B Flange From EM Loading (  =0.2, 78 kip Preload) In Region of Bolts OnlyEntire A-B Flange Interface

37. 29 January 2007MC Joint Analysis37 Response of AB Flange to EM Loading (double-click to play AVI)

38. 29 January 2007MC Joint Analysis38 Observations: A-B Flange An analysis with A-B bolt preload at the 78 kip reference design value and  =0.2 shows: Slippage of ~3 mils at AB Bolt #26 produces a 2500 lb shear load from EM forces. Stresses of 4.5 ksi in the Stycast and 12 ksi (range) in the #26 bolt can be inferred from earlier contour plots with 25 kip unit loads. These seem OK. A Hybrid joint design (Friction + Collar) seems to be necessary (consistent with Reiersen recommendation). Scuffing at the inboard leg of order ½ mm from EM loads. High-cycle operation may dictate the use of more robust shear transfer mechanism (keys).

39. 29 January 2007MC Joint Analysis39 Observations: A-B The shortfall in A-B joint bolt #26 frictional capacity is ~2.5 kip based on an 80 kip preload and a friction coefficient of 0.2. The theoretical friction capacity is 16 kips The 2.5 kip shortfall can be made up by: Increasing  to 0.23, or Increasing the preload to 93 kip, or Increasing  to 0.25 and the preload to 74 kip

40. 29 January 2007MC Joint Analysis40 Analysis of B-C Bolted Flange A similar analysis of the B-C flange is performed.

41. 29 January 2007MC Joint Analysis41 Global Model Results, B-C Various Contour Plots of B-C Flange Results: Bolt Preload [k-lb or kip] Bolt Shear Force Range [k-lb or kip] produced by EM Load cycle. Non-zero value indicates that the joint is not completely isolated with preload & modest friction. Slippage produced by EM Load cycle (~0.8 mm scuffing at inboard leg)

42. 29 January 2007MC Joint Analysis42 Preload [kip] in B-C Flange Bolts (61 min.<78 Average<85 max.) Falls within design goal of 52-86 kip

43. 29 January 2007MC Joint Analysis43 Shear Force Range in B-C Flange Bolts from EM Loads (  =0.2, 78 kip Preload) Max Shear Loads: 3.1, 8.7 & 6.9 kip, on Bolts 27, 28 & 29)

44. 29 January 2007MC Joint Analysis44 Contact Slippage [m] at B-C Flange From EM Loading (  =0.2, 78 kip Preload) In Region of Bolts OnlyEntire B-C Flange Interface

45. 29 January 2007MC Joint Analysis45 Observations: B-C The shortfall in A-B joint bolt #28 frictional capacity is ~8.7 kip based on an 61 kip preload and a friction coefficient of 0.2. The theoretical friction capacity is 12 kips The 8.7 kip shortfall can be made up by: Increasing  to 0.34, or Increasing the preload to 105 kip, or Increasing  to 0.25 and the preload to 84 kip

46. 29 January 2007MC Joint Analysis46 Future Work A more thorough analysis of the interface still requires a traditional contact analysis where flange separation can occur. Analyses by others indicate that A-A may be a more heavily-loaded connection, and therefore should be evaluated ASAP [although this is more complex to implement and still being pondered].