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Mechanical Design & Analysis

Mechanical Design & Analysis . Igor Novitski. Outlines. Electromagnetic Forces in the Magnet Goals of Finite Element Analysis Mechanical Concept Description FEA Models Material Properties Magnet Components at Different Loads End Plate Stress and Deformation Summary.

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Mechanical Design & Analysis

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  1. Mechanical Design & Analysis Igor Novitski

  2. Outlines • Electromagnetic Forces in the Magnet • Goals of Finite Element Analysis • Mechanical Concept Description • FEA Models • Material Properties • Magnet Components at Different Loads • End Plate Stress and Deformation • Summary Mechanical Design & Analysis

  3. Electromagnetic Forcesin the Magnet To reduce the probability of spontaneous quenches due to turn motion and stabilize the magnet field harmonics, it is necessary to ensure the mechanical stability of turns. Turn mechanical stability is achieved by applying the prestress to the coil during magnet assembly and supporting the compressed coil during operation with a rigid support structure. The required prestress value is determined by magnet design, nominal operating field and mechanical properties of structural materials. Mechanical Design & Analysis

  4. Goals of Finite Element Analysis • ANSYS finite element (FE) 2D parametric models been created to analyze the mechanical characteristics of the dipole design at several magnet stages: • magnet assembly (collaring, yoking and skinning), • cool-down to operation temperature, and • excitation to the nominal current of 11.85 kA. • The mechanical structure was optimized to keep coil under compression up to the maximum design field of 12 T and to maintain the coil stress below 160 MPaat all times, which is considered a safe level for brittle Nb3Sn coils. • Stresses in all structural materials should be less than yield stress limit. Mechanical Design & Analysis

  5. Mechanical Concepts B A C The 30-mm horizontal collar width is virtually the maximum possible in the available space between the two coils in the double-aperture configuration with two independent collared coils. The 20-mm width is the minimal collar width determined by stress limits in the collar and key materials. Mechanical Design & Analysis

  6. Magnet Mechanical Concept Stainless Steel Skin Coil mechanical support is provided by stainless collars, vertically split iron yoke, aluminium clamp and welded stainless steel skin. Strong collars and iron yoke create the “rigidity belt” around Nb3Sn coil for conductor protection. Coil midplane shims generate initial coil azimuthal prestress at collaring stage. Skin and clamp tensions deform the iron, reduce the vertical collars spring-back and finalized coil compression. Collar-yoke-clamp-skin interferences support horizontal LF action. Stainless Steel Collars AL Clamp controls Outer Yoke Gap Iron Yoke Nb3Sn Coil Shims for interference Uniform MP Shims Phosphor Bronze Key CS-Bump controls Inner Yoke Gap Titanium Poles with stress-relive slot Aluminum Clamp Mechanical Design & Analysis

  7. Magnet Body FE Model • The 2D ANSYS parametric model of the dipole includes the coil, the two layers of collars (front and lock-leg ), the key, the iron yoke, the clamp and the skin. • The model has a quarter-symmetry. • The coil inner and outer layers, and interlayer insulation are glued together. • The Ti coil poles freely separates from the coil. • The coil is surrounded by two layers of stainless steel collars • Front and leg collars have symmetric boundariesalong X-axis (CP and CE equations simulate line motion). • The phosphor bronze keylocks collar laminations fixing the coil azimuthal prestress. • Clamped iron yoke supports the collars, andthe welded stainless steel skin restrains the iron yoke from outside. The design components are represented with 4-node plane quadrilateral elements (PLANE 42). Material interfaces are modelled with contact elements (CONTACT 169-172). Mechanical Design & Analysis

  8. End Plate FE Model • 3D ANSYSmodel for the end plate consists of a 50-mm thick end plate welded to a 12.7-mm thick skin, with the skin length extended back to the 2D lead end cross section. • One quarter symmetry is used in the model. • The end plate consists of two mechanically connected concentric rings with a central round hole for the magnet beam pipe and four holes for the instrumented bullets in the innermost ring, and four round cooling holes in the ring attached to the skin. • The Lorenz force in one quadrant was applied in the location of the bullet hole. The design components are represented with 8-node elements (SOLID 95) with contact elements (CONTACT 170-174). Mechanical Design & Analysis

  9. Material Properties Coil data from HFM dipole programs Cyclic Loading Tests Load-Unload-Reload Tests 44GPa Mechanical Design & Analysis

  10. Coil Stress Distribution After Collaring After Skin Welding After Cooling Down, 300-2K 41 59 86 89 Avg.=28MPa 91 118 148 Max Seqv. =77MPa 53 26 49 85 66 99 23 35 144 146 2 12 After 12T, 2K After 11T, 2K 113 129 124 135 Mechanical Design & Analysis

  11. Coil Stress The expected prestress variation with respect to the nominal coil prestressat the 50 m azimuthal coil size variation is within 10 MPa in the inner layer and within 23 MPa in the outer layer. Analysis shows that at the maximum design field of 12 T the minimal coil prestress in pole regions is 2-23 MPa. The maximum coil prestress at room temperature does not exceed 160 MPa, which is acceptable for the Nb3Sn cable and coil insulation. Mechanical Design & Analysis

  12. Poles Stress After Collaring After Skin Welding After Cooling Down, 300-2K Max Seqv. =133MPa 510 588 128 136 After 12T, 2K After 11T, 2K Mechanical Design & Analysis

  13. Collar Stress Front Collar Lock and Leg Collars After Collaring Max Seqv. =527MPa 490 413 After Skin Welding 339 Mechanical Design & Analysis

  14. Collar Stress Front Collar Lock and Leg Collars 469 After Cooling Down, 300-2K Max Seqv. =562MPa After 11T, 2K 476 397 Mechanical Design & Analysis

  15. Collar Stress Front Collar Lock and Leg Collars After 12T, 2K Max Seqv. =494MPa 401 Mechanical Design & Analysis

  16. Key Stress After Collaring After Skin Welding After Cooling Down, 300-2K Max Seqv. =362MPa 133 124 After 12T, 2K After 11T, 2K 185 202 Mechanical Design & Analysis

  17. Iron Yoke Stress After Skin Welding After Cooling Down, 300-2K Max Seqv. =351MPa 455 After 11T, 2K After 12T, 2K 362 387 Mechanical Design & Analysis

  18. Clamp Stress After Skin Welding After Cooling Down, 300-2K Max Seqv. =261MPa 287 After 11T, 2K After 12T, 2K 282 281 Mechanical Design & Analysis

  19. Skin Stress Max Seqv. =365MPa 489 Avg.=170MPa 266 After Skin Welding After Cooling Down, 300-2K 498 499 269 270 After 11T, 2K After 12T, 2K Mechanical Design & Analysis

  20. Structure Maximum Stress • The maximum stress in the collars and compression in the iron yoke achieves the material yield stress in small regions near key grooves and iron yoke corner (model singularities, mesh size). • To minimize the stress concentrations, the key grooves and iron corners have been rounded. All stress values are below yield stress of correspondingmaterials. Mechanical Design & Analysis

  21. Skin Welding Mechanical Design & Analysis

  22. Cooling Down and LF action Mechanical Design & Analysis

  23. Coil IR deflections Magnet cross-section is deformed due to the coil prestress, cool-down and Lorentz forces action. Bore deflections from the warm unstressed round geometry (magnetic design) calculated for the above mentioned effects at room and helium temperatures in the dipole straight section are summarized below: As it follows from the above data, at the nominal operating current of 11.85 kA the radial cross-section deflection from the magnetic design in the magnet midplane is ~165 m. Mechanical Design & Analysis

  24. End PlateDeformation and Stress • The 50-mm end plate deflection and coil end motion under the nominal LF is about 75 m. • The maximum stress in the end plate is 160 MPa. • Taking into account that usually only 20% of the Lorentz force is transferred to magnet end plates, the coil end motion is even smaller. Mechanical Design & Analysis

  25. End Plate Load Mechanical Design & Analysis

  26. Summary • ANSYS analysis of the mechanical structure of the demonstrator dipole model shows: • chosen mechanical design providesthe coil prestress required for the operating current range with sufficient margin; • design reliably restricts turn radial, azimuthal and longitudinal motion under the Lorentz forces up to 12T; • the maximal mechanical stresses in the major elements of coil support structure are below the limits for the materials used. • The mechanical design, structural materials and components, coil collaring and cold mass assembly procedures will be experimentally studied and further optimized using instrumented mechanical models. The results of experimental studies of mechanical models and measurements during demonstrator dipole test will be compared with the described ANSYS analysis. Mechanical Design & Analysis

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