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Finite element analysis of DECam May 11 C1 corrector lens – gravity and thermal load cases

Finite element analysis of DECam May 11 C1 corrector lens – gravity and thermal load cases. Bruce C. Bigelow, Physics Department, University of Michigan 6-7 July 2005 . FEA of May 11 C1 element. This talk: Conceptual design for an athermal elastomeric lens mount (RTV)

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Finite element analysis of DECam May 11 C1 corrector lens – gravity and thermal load cases

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  1. Finite element analysis of DECam May 11 C1 corrector lens – gravity and thermal load cases Bruce C. Bigelow, Physics Department, University of Michigan 6-7 July 2005 B. C. Bigelow - UM Physics

  2. FEA of May 11 C1 element • This talk: • Conceptual design for an athermal elastomeric lens mount (RTV) • Description of objectives, model, and load cases • Deflection and stress results B. C. Bigelow - UM Physics

  3. FEA of May 11 C1 element • Objectives: • Determine deflections of C1 under gravity loads for RTV mount • Determine stresses in C1, elastomer, and cell for -20C temp swing • Models: • 1/2 geometry model • 3mm RTV elastomeric bond (radial and axial directions) • Invar cell, FS lens • Assume a perfectly rigid barrel • Load cases: • gravity along optical axis • gravity across optical axis • steady-state temperature change of -20C B. C. Bigelow - UM Physics

  4. FEA of May 11 C1 element 3d solid (“brick”) elements B. C. Bigelow - UM Physics

  5. FEA of May 11 C1 element Detail of elastomer bond line B. C. Bigelow - UM Physics

  6. FEA of May 11 C1 element Symmetry boundary conditions and constraints B. C. Bigelow - UM Physics

  7. FEA of May 11 C1 element B. C. Bigelow - UM Physics

  8. FEA of May 11 C1 element Gravity across optical axis, deflections across optical axis in meters (2 microns at center) B. C. Bigelow - UM Physics

  9. FEA of May 11 C1 element Gravity across optical axis, deflections along optical axis, in meters (+/- 2 microns) B. C. Bigelow - UM Physics

  10. FEA of May 11 C1 element Gravity along optical axis, deflections along optical axis in meters (7.6 microns) B. C. Bigelow - UM Physics

  11. FEA of May 11 C1 element -20C temp change, max. stresses in Pa (1450 PSI max) B. C. Bigelow - UM Physics

  12. FEA of May 11 C1 element Stresses in cell in Pa (1450 PSI max) B. C. Bigelow - UM Physics

  13. FEA of May 11 C1 element Stresses in RTV in Pa (12 PSI max) B. C. Bigelow - UM Physics

  14. FEA of May 11 C1 element Stresses in lens in Pa (217 PSI) B. C. Bigelow - UM Physics

  15. FEA of May 11 C1 element • Conclusions: • Gravity deflections seen here are probably negligible • Thermal stresses are very low relative to yield for all three materials • The RTV mount provides stiff yet thermally compensating support • This FEA model is readily adapted to other geometry and materials • Although 90mm central thickness of C1 appears to be OK for mounting and thermal loads, it will very difficult to fabricate and test. The RTV mount can easily accommodate a thicker lens. B. C. Bigelow - UM Physics

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