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MKIR Optics Finite Element Analysis

MKIR Optics Finite Element Analysis. Model, Results, and Recommendations. Overall FEM Summary. Comprehensive finite element model (FEM) generated for entire experiment 133,600 nodes 65,700 elements (parabolic formulation) All critical components explicitly modeled where possible

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MKIR Optics Finite Element Analysis

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  1. MKIR Optics Finite Element Analysis Model, Results, and Recommendations

  2. Overall FEM Summary • Comprehensive finite element model (FEM) generated for entire experiment • 133,600 nodes • 65,700 elements (parabolic formulation) • All critical components explicitly modeled where possible • Some components represented using lumped masses and rigid elements

  3. Overall FEM

  4. Boundary Conditions • Model is grounded at top of ISS/VJ Interface • One G gravity load applied in three directions • Vertical (+Z direction) • 70 degrees towards +X axis • 70 degrees towards +Y axis • All components attached directly where appropriate

  5. AO Bench Model

  6. AO Bench Open on WFS Side

  7. AO Bench Open on AO Side

  8. AO Bench Optics • Not explicitly modeled • Used lumped mass and rigid elements • Newport bench modeled explicitly with orthotropic core

  9. Vacuum Jacket FEM

  10. Cold Shield FEM

  11. Cryostat Unit Inside Vacuum Jacket

  12. Cryostat Assembly FEM

  13. Mechanism Box Without Cover

  14. Mechanism Box With Diachroic

  15. Mechanism Box With All Components

  16. Cold Block With Covers Removed

  17. Detailed FEMs of Components • Most major components are explicitly modeled • Some simplifications made • Holes in wheels neglected; density adjusted • Some bearings modeled as equivalent material • Some bearings modeled with springs • Bolted interfaces not explicitly modeled • Assumed that bolt margins are sufficient • Assume proper bolted design yields ‘continuous’ interface

  18. Focal Plane Mask FEM

  19. Spider Assembly FEM

  20. Pupil Wheel Assembly FEM

  21. Diachroic Wheel Assembly FEM

  22. Red Wheel Assembly FEM

  23. Blue Wheel Assembly FEM

  24. Pupil Imager FEM

  25. Cameras Modeled With Detail • Mounts are explicitly modeled

  26. Camera Mounts Without Cover

  27. Camera FEM Detail • Flexures modeled explicitly • Key component

  28. Generated Data • Translations and rotations recovered at critical locations • All components in AO Bench • Focal plane mask • Spider wheel • Pupil wheel • Diachroic • Red and Blue wheels, fold mirrors, OAP mirrors and detectors

  29. Displacements Generated • Typical displacement data • 70 degree X case

  30. Stresses Recovered in Model • Stress in all components recovered • Margin against gravity load show no problems • MoS > 10 for stress • Problem is stiffness driven • Examination of vacuum jacket under pressure not conducted • Design sizing presumed sufficient

  31. Y Direction Loading Stress in Blue Camera • Flexures show highest stress

  32. X Direction Loading Stress in Blue Camera Camera mount show highest stress

  33. Modal Frequencies Calculated • Modes calculated for entire structure to 100 Hz • First mode at 23.8 Hz for focal plane mask (torsion) • May be low due to some modeling assumptions • May warrant further examination • Second and third modes at 43.1 and 43.5 Hz FPM bending modes

  34. Conclusions • FEM of total model indicates structure is stiffness driven • Stresses all low • High Margins • First mode is in focal plane mask • No one component responsible for majority of displacements

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