Dark Energy Camera - PowerPoint

Document Sample
Dark Energy Camera - PowerPoint Powered By Docstoc
					                   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




6-7 July 2005            B. C. Bigelow - UM Physics   1
                             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




6-7 July 2005                            B. C. Bigelow - UM Physics                2
                          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

6-7 July 2005                             B. C. Bigelow - UM Physics                  3
                FEA of May 11 C1 element




                    3d solid (“brick”) elements
6-7 July 2005             B. C. Bigelow - UM Physics   4
                FEA of May 11 C1 element




                   Detail of elastomer bond line

6-7 July 2005              B. C. Bigelow - UM Physics   5
                  FEA of May 11 C1 element




                Symmetry boundary conditions and constraints
6-7 July 2005                    B. C. Bigelow - UM Physics    6
                FEA of May 11 C1 element




6-7 July 2005          B. C. Bigelow - UM Physics   7
                FEA of May 11 C1 element




                Gravity across optical axis, deflections across
                optical axis in meters (2 microns at center)
6-7 July 2005                 B. C. Bigelow - UM Physics          8
                FEA of May 11 C1 element




                Gravity across optical axis, deflections along
                optical axis, in meters (+/- 2 microns)
6-7 July 2005                 B. C. Bigelow - UM Physics         9
                FEA of May 11 C1 element




                Gravity along optical axis, deflections along
                optical axis in meters (7.6 microns)
6-7 July 2005                 B. C. Bigelow - UM Physics        10
                     FEA of May 11 C1 element




                -20C temp change, max. stresses in Pa (1450 PSI max)
6-7 July 2005                      B. C. Bigelow - UM Physics          11
                FEA of May 11 C1 element




                   Stresses in cell in Pa (1450 PSI max)

6-7 July 2005              B. C. Bigelow - UM Physics      12
                FEA of May 11 C1 element




                   Stresses in RTV in Pa (12 PSI max)

6-7 July 2005             B. C. Bigelow - UM Physics    13
                FEA of May 11 C1 element




                   Stresses in lens in Pa (217 PSI)

6-7 July 2005              B. C. Bigelow - UM Physics   14
                          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.




6-7 July 2005                             B. C. Bigelow - UM Physics                        15

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:5
posted:2/20/2010
language:English
pages:15